Current state of ENT radiology

TEMPORAL BONE

BASIC ANATOMY The (adult) temporal bone consists of five portions. The squamous portion forms most of the lateral wall of the middle cranial fossa, its convex lateral surface serving as origin of the temporalis muscle. The anteriorly directed zygomatic process arises from its lower aspect, and the articular subdivision of the mandibular fossa is another component. The mastoid portion is characterized by the mastoid process, which is largely pneumatized. The numerous air cells are of variable size and communicate with the middle ear. On the inner surface of the mastoid portion, the sigmoid sinus causes a wide sulcus. The tympanic portion forms the anterior, inferior, and lower posterior aspect of the bony external auditory canal, the remainder being formed by the squamous portion. Medially it serves as attachment of the tympanic membrane. It is separated from the squamous, petrous, and mastoid portions of the temporal bone by the petrotympanic and tympanomastoid fissures, respectively. The petrous portion, the largest and most important component of the temporal bone, has roughly the shape of a (lying) four-sided pyramid. Its posterolaterally directed base is fused to the squamous as well as mastoid portions, and its apex points anteromedially toward the foramen lacerum, the long axis forming an angle of approximately 45 degrees with the midsagittal plane. The anterosuperior wall represents a considerable proportion of the middle cranial fossa. An elevation near its midportion is caused by the underlying superior semicircular canal. Anterolateral to this lies the tegmen tympani, the thin roof of the middle ear. A shallow depression at the apex lodges the trigeminal ganglion. The petrous ridge serves as attachment of the tentorium and has a groove for the superior petrosal sinus. The steeper posterior pyramidal wall is part of the posterior fossa and characterized by the centrally located internal auditory canal. The third wall appears on the inferior side of the skull. Major features are the jugular fossa and anterior to this, the carotid canal. The styloid process arises from the undersurface of the temporal bone just posterior to the external auditory canal and anteromedial to the mastoid process; it marks the exit of the 7th cranial nerve. The external auditory canal has cartilaginous walls laterally and osseous walls medially. Its anteroinferior wall is 5 to 6 mm longer than its posterosuperior wall, which causes a double tilt of the tympanic membrane. The tympanic cavity or middle ear is a relatively narrow, airfilled space with three floors (Figs 1 and 2). The cleft-like hypotympanic recess lies more or less below the level of the external auditory canal and is posteriorly separated from the jugular fossa by a thin plate of bone. The part opposite the tympanic 7

Fig 1.--Normal anatomy: medial wall of tympanic cavity. Tegmen tympani (1), epitympanic recess (2), prominence of lateral semicircular canal (3), oval window (4), pyramidal eminence arising from prominence of facial canal (5), promontory (6), grooves caused by tympanic plexus (7), jugular wall (8), subiculum of promontory and round window (9). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.)

membrane (mesotympanum) communicates anteriorly with the nasopharynx via the Eustachian tube. The comparatively wide epitympanic recess (attic) extends above the level of the external auditory canal and contains the articulating portion of the malleus and incus with the head of the malleus in front of the body of the incus. This space communicates posteriorly with the antrum, leading directly to the mastoid air cell system. The medial (labyrinthine) wall of the tympanic cavity is characterized by bulges, depressions, and openings. The anteriorly located promontory is caused by the basal turn of the cochlea. Posterior to this structure lies the oval window receiving the foot plate of the stapes. The round window has a somewhat hidden location on the posteroinferior aspect of the promontory. Two prominences above and behind the oval window niche, at the junction between labyrinthine and mastoid walls of the tympanic cavity, are caused by the lateral semicircular canal and the second portion of the facial nerve canal. The pyramidal eminence, housing the stapedius muscle, arises from the latter. The entire middle ear cavity including ossicles, tendons, and chorda tympani is covered by a thin mucosal membrane which continues into the mastoid air cells as well as into the Eustachian tube. The three components of the bony labyrinth are (from front to back) cochlea, vestibule, and semicircular canals. Of these inter8

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Fig 2.--Normal anatomy: posterior half of tympanic cavity. Posterior ligament of incus (1), superior ligament of incus (2), superior ligament of malleus (3), body of incus (4), head of malleus (5), handle of malleus (6), tendon of tensor tympani muscle (7), lateral ligament of malleus (8), scutum (9). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.)

communicating structures the cochlea is the most medial one, its base abutting on the internal auditory canal and roughly paralleling the posterior surface of the pyramid. The posterolaterally adjacent vestibule which holds parts of the vestibular sense organ continues into the semicircular canals. The orientation of the three (anterior/posterior/lateral) semicircular canals relative to each other and relative to the petrous pyramid is shown in Figure 3. The lateral semicircular canal is not exactly horizontal but has a slight posterior inclination. The oval and round windows open into the perilymphatic space. The cochlear aqueduct, arising from the basal t u r n of the cochlea, is a narrow channel t h a t terminates just anteromedial to the jugular fossa. It serves as a communication between perilymphatic and subarachnoid spaces. The larger vestibular aqueduct carries endolymph from the vestibule and terminates about halfway between internal auditory canal and sigmoid sulcus on the back of the pyramid. The internal auditory canal is nearly perpendicular to the sagittal plane and, because of the oblique orientation of the pos9

Fig &--Normal anatomy: topography of labyrinth. terior surface of the pyramid, has a shorter posterior t h a n anterior wall. Its central portion m a y be slightly wider t h a n its medial or lateral portions. Close to its fundus, the falciform crest incompletely divides the canal into an inferior and a (smaller) superior component, with a vertical bony ridge dividing it further. The two posterior subcompartments serve as passageways for the vestibular nerve. Anteriorly the facial nerve together with the nervus intermedius courses through the superior compartment, and the cochlear nerve runs through the inferior one. While the 8th cranial nerve terminates (or rather originates) within the cochlea and at the various macular regions, the 7th cranial nerve continues through the perforated lateral end of the internal auditory canal and turns rather abruptly forward (labyrinthine portion). J u s t above the cochlea, the nervus intermedius forms the geniculate ganglion and gives off the greater petrosal nerve. The facial nerve then courses sharply backwards (genu) and continues posteriorly below the lateral semicircular canal, but above the promontory and oval window, separated from the middle ear only by a thin shell of bone (tympanic portion). It then turns downward, lateral to the pyramidal eminence and stapedius muscle. After a vertical course of 15 to 20 mm through bone (vertical portion of facial or Fallopian canal), it leaves the skull via the stylomastoid foramen (Fig 4). On the undersurface of the petrous pyramid, the entrance into the carotid canal is anterior to the j u g u l a r fossa. Its first (vertical) portion lies in about the same coronal plane as the cochlea. 10

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Fig 4.--Normal anatomy: course of facial nerve through temporal bone. Facial nerve (1), genu of facial nerve (2), geniculate ganglion (3), greater petrosal nerve (4), stapedial nerve (5), chorda tympani (6), connection with tympanic plexus (7), digastric branch (8), connection with glossopharyngeal nerve (9), stylohyoid branch (10). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.)

Its second (horizontal) portion runs anteromedially and ends above the foramen lacerum. The thin bony plate separating the carotid canal from the middle ear forms a large part of the anterior wall of the tympanic cavity (carotid wall). The jugular foramen is divided into a smaller anteromedial pars nervosa, transmitting the glossopharyngeal nerve as well as the inferior petrosal sinus, and a posterior pars vascularis containing the jugular bulb along with the vagus and spinal accessory nerves. 1 IMAGING TECHNIQUES

Plain film radiography has lost much of its previous significance. Nevertheless, in this era of cost containment it behooves the radiologist to remain familiar with the time-honored projections. Among the relatively few t h a t gained wide acceptance, the transorbital view of the petrous pyramids "is the single most valuable plain film view for delineating the internal acoustic canal, cochlea, vestibule, and semicircular canals. ''2 Also quite well seen are the middle ear structures and most of the petrous ridge. The Towne view demonstrates the petrous ridge even better and allows a comparison of the mastoids. Particularly well shown is the antrum. The axial or submentovertex view has its main usefulness when larger erosive or destructive bony lesions 11

are suspected. The Schueller view, including its modifications, primarily allows evaluation of the mastoid. It also affords a look at both the anterior and posterior surfaces of the petrous pyramid. The Stenvers view is unique in that it presents the pyramid as a whole with little geometric distortion. The internal auditory canal is somewhat foreshortened though. Conventional tomography with pluridirectional blurring motion or complex motion tomography has for many years held the position as the most advanced imaging technique, only recently being challenged by high resolution computed tomography (HRCT). In our opinion it is far from being totally outmoded, as thin section CT is not always and everywhere available. Also CT m a y not be feasible in the plane best suited for the evaluation of certain structures, for example, the tympanic and vertical portions of the facial canal. Linear tomography, to be sure, plays no role in state-of-the-art imaging of the temporal bone. How should tomography of the temporal bone be performed? The most important sections are the ones in the coronal plane, preferably obtained from one side at a time. For some purposes, e.g., optimal visualization of posterior portions of the tympanic cavity, inclined coronal sections with 15-degree head rotation toward the side of interest (Guillen projection) m a y be employed instead. In the majority of situations it seems sufficient to cover the region from the carotid canal in front to the jugular fossa in back, however fully including these structures. Good collimation of the x-ray beam is essential for high image quality. The decision to include lateral (sagittal) tomography depends upon what the coronal images show; the study of one side frequently suffices. Two-millimeter contiguous slices are acceptable in most cases, however 1-mm incrementation m a y be necessary to demonstrate structures like the vestibular aqueduct. How far lateral or medial the study should be carried depends on the individual case. Sectioning planes other than the coronal or lateral ones m a y be chosen by experienced otoradiologists. Computed tomography calls for rather sophisticated equipment and meticulous positioning, if it is to be beneficial. It has two significant advantages over conventional tomography: (1) there are no "ghost shadows" from structures outside the plane of interest, and (2) soft tissue even within narrow bony confines is well depicted. 3 Furthermore, the radiation dose is considerably lower. Unfortunately, there are also some drawbacks. For example, with scanners that have a relatively small effective gantry aperture, persistent high-quality imaging in other than axial planes is at best difficult. On the other hand, van Waes et al. 4 have demonstrated that with ultrawide aperture machines, scanning in practically all otoradiologic planes is indeed possible (Fig 5). Axial scans of the temporal bones obtained in planes parallel to the orbitomeatal line represent a good compromise, although 12

Fig 5.--Normal anatomy: non-axial CT scans of temporal bone. Top, sagittal section at level of medial-most portion of external auditory canal shows ossicles within epitympanic recess (malleus in front of incus = "molar tooth-appearance"), tegmen tympani (curved arrow), lateral semicircular canal (straight arrow), and vertical portion of facial nerve canal (arrowhead). Bottom, axiopetrosal section at level of middle and inner ear demonstrates entire malleus within tympanic cavity (not labelled), promontory (white arrow), oval window (arrowhead), and anterior or superior semicircular canal (arrow). (Courtesy Paul F.G.M. van Waes, M.D. and Frans W. Zonneveld, M.Sc., Utrecht/Einthoven.) occasionally slightly different planes, inclined in either direction, m a y be preferable (Figs 6 and 7). The image volume should encompass the region from the tip of the mastoid to a level just above the petrous pyramid. Whenever disease appears to extend beyond these limits, the study has to be expanded. A slice thickness of 1.0 to 1.5 mm is probably best, but for practical purposes 2 mm are satisfactory. Above and below the temporal bone, thicker slices should be chosen (4 to 5 mm). No overlapping is needed either in the temporal bone or in the regions above and below. Coronal scans are usually easiest with the patient in prone position. Again, the slice thickness should not exceed 2 mm, and table incrementation is non-overlapping. The region covered is identical to the one in coronal (frontal) complex motion tomography. Sagittal scans are difficult to obtain directly 13

Fig &--Normal anatomy: axial CT scans of temporal bone (different cases). A, section at level of mastoid process shows well-developed and normally aerated air cells; styloid process (arrowhead). B, section at level of external auditory canal shows tympanic membrane (white arrow), vertical portion of facial canal (arrowhead), horizontal portion of carotid canal (c), upper portion of jugular fossa containing jugular bulb (/), and cochlear aqueduct (black arrow); in this case mastoid portion of temporal bone is hypoaerated. and usually necessitate an ultrawide aperture scanner. Reformatted images seem to represent an acceptable substitute in a number of cases of bone destruction or fracture (see Fig 13). Indispensable for good imaging results is special software providing reconstruction with zoom factors between 4 and 6. A 512 x 512 matrix is preferred over a 256 x 256 matrix, and an extended gray scale with a window width up to 4000 H is used for display of bone detail. In m a n y clinical situations, contrast enhancement is not required; for instance, in suspected congenital malformation, acute trauma, or otosclerosis. However, w h e n tumor is a possibility, intravenous or intrathecal administration of suitable contrast media may prove extremely beneficial. Specifically, intravenous enhancement is needed to rule out intracranial or cervical extension of larger masses as well as possible encroachment on major vessels at the base of the skull. Intrathecal e n h a n c e m e n t either with a water-soluble medium, e,g., metrizamide (4 to 6 ml, 170 to 190 mg I/ml), or with gas (preferably CO2, 5 to 7 ml) is particularly helpful in the evaluation of the cerebellopontine angle (CT-cisternography). Despite their invasive nature, both studies can be done on an outpatient basis when certain provisions are made. Intravenous enhancement is also necessary whenever intracranial complications of inflammatory middle ear or mastoid disease are suspected. In addition, i t helps in detecting surgically important vascular anomalies, Instructive articles on the normal CT a n a t o m y in various planes have been pub14

Fig 7.--Normal anatomy:axial CT scans of temporal bone. A and B, contiguous sections at level of external auditory canal and tympanic cavity (t) show eustachian tube (white arrow) anterolateral to carotid canal (black arrow). C, section at level of internal auditory canal and epityrnpanic recess with ossicles (branched white arrow) shows antrum (a), cochlea (curved black arrow), vestibule with lateral semicircular canal (open arrow), and posterior semicircular canal (arrowhead). D, next section above C shows proximal portion of facial canal with genu and geniculate ganglion (curved arrow), posterior semicircular canal (arrowhead), and upper level of internal auditory canal (straight arrow).

lished by Virapongse et al., 5 Chakeres and Spiegel, 6 and Daniels et al. 1 Nuclear medicine plays a minor role in temporal bone imaging. Occasionally, Tc-99m bone scans and Ga-67 scans may be helpful in evaluating possible inflammatory or neoplastic diseases. Magnetic resonance imaging (MRI), being free of bone-induced artifacts, presents a valuable new diagnostic tool where soft tissue structures adjacent to the temporal bone are concerned (Fig 8). This imaging modality is capable of detecting small tumors within the internal auditory canal and m a y well eventually sup15

Fig 8.--Primary cholesteatoma (epidermoid) arising from petrous portion of left temporal bone; 33-year-old man. A, T1/T2-balanced coronal MR tomogram at level of upper pons (p) shows mass (m) having signal intensity similar to brain tissue. B, corresponding T2-weighted image shows lesion much more clearly despite increase in noise.

plant CT-cisternography since preliminary results are rather promising (see Fig 15). 7 By the same token, visualization of normal or abnormal "intrinsic" temporal bone soft tissue, ordinarily obscured by bone, is not out of reach, s Angiography is rarely part of the workup of patients with suspected temporal bone disease. In a few instances, however, information concerning vascular structures provided by contrast CT is inadequate. If only the petrous segment of the internal carotid artery or the sigmoid sinus-internal jugular vein complex are to be evaluated, digital venous angiography (DVA) may be sufficient. 9 More detailed evaluation, indispensable in lesions like glomus tumors or dural arteriovenous malformations (AVMs), requires selective arteriography. A thorough discussion of this matter including normal and pathological arterial anatomy can be found in the classical monograph by Djindjian and Merland. 1° RADIOLOGIC PATHOLOGY

Developmental Anomalies and Malformations In these disorders, plain film radiography is of limited value. For detailed diagnosis, HR-CT rivals complex motion tomography as the method of choice. However, in our opinion, CT m a y fully supplant conventional tomography only if an ultrawide aperture scanner is available. Otherwise the two methods should be regarded as complementary, at least in more complex cases. The single most valuable projection in conventional tomography 16

is the coronal plane, whereas with CT, axial-transverse slices are preferred initially. Examination in additional planes is often necessary. Because of their common embryologic origin, the middle and external ear frequently exhibit malformative changes at the same time. Conversely, anomalies of the inner ear (with its independent development) are almost never associated with such changes involving other parts of the ear. Exceptions to this rule have been seen primarily in cases of thalidomide-induced anomalies, though sporadically without this specific etiology. In patients with middle and/or external ear involvement, it is the radiologist's responsibility to determine the thickness of bone between tympanic cavity and auricle, the degree of development of the middle ear, and the status of the labyrinth. According to Frey (cited by Jensen and Rovsing 11) the tomographic findings can be classified as follows: I. Solitary malformations of ossicles. II. Diminished or atretic external meatus, thin atresia plate, normal-sized tympanic cavity, and as a rule, malformed ossicles. III. Diminished or atretic external meatus, moderately thick atresia plate, partially atretic tympanic cavity, malformed ossicles. IV. Completely atretic external meatus, thick atresia plate, partial or complete atresia of tympanic cavity, and as a rule, no visible ossicles. V. Atypical malformations (Fig 9). Inner ear findings m a y be classified after Terrahe12: I. Dysplasic or aplasia of lateral semicircular canal (by far the most frequent); m a y be associated with deformity of cochlea. II. Dysplasic or aplasia of lateral and anterior, or rarely posterior, semicircular canals; usually with deformity of cochlea. III. Total

Fig 9.--Congenital malformation of left external and middle ear; 11-year-old boy. A, axial CT scan at level of external auditory canal and mesotympanum shows normal structures on right. B, corresponding image on side of lesion reveals type IV changes with completely atretic external meatus, thick atresia plate, and partial obliteration of tympanic cavity; there were no ossicles visible. 17

aplasia of semicircular canals; with or without deformity of cochlea. IV. Total aplasia of labyrinth (so:called Michel defect if bilateral). The relatively common Mondini malformation involves only the cochlea, which then has 1 to 11/2 turns instead of the normal 21/2 to 23/4. This condition is usually bilateral and accompanied by neurosensory hearing loss. Of greater therapeutic importance are changes involving the o v a l window (atresia or aplasia) because they m a y be amenable to surgical correction. Malformations of the internal auditory canal are frequent in all major forms of dysplasia b u t m a y also occur as isolated findings; the same can be said of the facial nerve canal. Occasionally the internal auditory canal is unilaterally dilated without the presence of a mass. Important for reasons of differential diagnosis and as entities of their own are two vascular anomalies, the lateral position of the internal carotid artery and the high-lying jugular bulb. In both instances the vessel involved presents in the middle ear, the bone normally separating it from the latter cavity being dehiscent. In order to demonstrate this abnormality, angiography m a y not be necessary if CT is unequivocal. Occasionally aneurysms of the petrous carotid, carotidobasilar anastomoses, and diverticuli of the j u g u l a r bulb present in a similar manner. Traumatic Disorders

In patients with hemotympanum, conductive or neurosensory hearing loss, or facial nerve paralysis after significant head injury, temporal bone fractures are extremely frequent. Since plain film sensitivity in such cases is rather low, complex motion tomography with its higher yield of positive findings was the preferred radiodiagnostic modality for years. Recently, HR-CT as an alternative procedure has found an increasing number of advocates (Fig 10). Bergeron 2 refers to CT as "now probably the technology of choice." There are many clinical situations where CT is unquestionably superior to conventional tomography. On the other hand, the need for high resolution coronal or lateral images may arise during the evaluation of patients who cannot, or should not, hyperextend their necks. Under such circumstances conventional tomography m a y still be the best choice. CT is particularly useful in localizing bone fragments (or foreign bodies) and demonstrating soft tissue changes. It is quite possible to determine the status of the ossicular chain on axial cuts alone.13, 14 Also, intravenous contrast CT allows an assessment of the internal carotid artery concerning possible traumatic aneurysm or occlusion in fractures crossing the carotid canal. About 70% to 80% of the petrous pyramid fractures are longitudinal, and only 10% to 20% transverse or vertical. The few remaining fractures are complex, frequently of the comminuted type. The longitudinal fractures can be further subdivided into anterior and posterior ones. Fractures of the anterior type begin 18

Fig "fO.--Transverse fracture of petrous portion of temporal bone; 30-year-old man. A, axial CT scan at level of lower portion of internal auditory canal shows fracture extending into vestibule; hemotympanum and opacification of mastoid air cells are also present. B, scan at level of upper portion of internal auditory canal demonstrates fracture continuing through cochlea (arrow) into region of genu of facial canal. Ossicles appear intact. in the temporoparietal region of the cranial vault and course through the tegmen tympani toward the labyrinth. Fractures of the posterior type pass through the mastoid to eventually also converge on the labyrinth. The semicircular canals may be crossed but the vestibule and cochlea are rarely involved. Damage to the facial nerve most frequently results from fracture through the vertical portion of the facial canal. The best w a y to demonstrate this kind of bony injury is lateral (sagittal) tomography. Axial and coronal images are excellent for revealing transverse fractures of the petrous pyramid, which frequently cross the labyrinth as well as the more proximal portions of the facial canal (Fig 10). Complex fractures m a y necessitate multiple views and tomography or CT in multiple planes. Gross disruption of the ossicular chain m a y be equally well demonstrated with conventional lateral tomography and high resolution axialtransverse CT; minor changes are difficult to visualize with any method.

Inflammatory Disorders Acute infections of the ear are diagnosed clinically. In the few cases where the radiologist is called upon to rule out advancing disease, plain films m a y be sufficient. If the infection appears to be recurrent, chronic-progressive or complicated, detailed radiographic imaging of the temporal bone is a highly valuable addition to the various otologic tests. There is a growing opinion that HR-CT represents the superior technique in most cases (Fig 11).15, 16 The role of MRI has yet to be defined. Malignant external otitis is a severe necrotizing inflammation caused in almost all cases by Pseudomonas aeruginosa that develops in elderly diabetics. If progressive despite antibiotic 19

Fig 11.--Mastoiditis; 57-year-old woman. A, axial CT scan at level of external auditory canal and temporomandibular joint (TMJ) shows opacification of most mastoid air cells with bony septae preserved. B, corresponding image scan of normal side for comparison.

treatment, it may lead to extensive osteomyelitis at the base of the skull and widespread involvement of adjacent soft tissues. Multiple cranial nerve symptoms (7th, 9th to 12th), meningitis, sepsis, and eventually death (in up to 50% of patients) m a y result. A similar disease unrelated to diabetic microangiopathy is seen in immunosuppressed patients. CT shows the bony and soft tissue changes to best advantage but radionuclide studies such as bone scans and especially gallium scans are more sensitive and better suited for initial diagnosis and follow-up. 1~ Acute mastoiditis, radiographically characterized by clouding of air cells with normal appearing bony septae can be reliably diagnosed with plain films alone. In coalescent mastoiditis with progressive lysis of septae, CT is probably not indispensable but certainly extremely valuable. However, when intracranial complications are suspected, CT should be utilized without hesitation. HR-CT then must be complemented by a regular CT with intravenous contrast covering the entire neurocranium. Recurrent or chronic otitis media with mastoiditis manifests itself in sclerosis of the temporal bone. In cases where the ear infection began early in childhood, pneumatization is more or less absent. Both changes, sclerosis and lack of pneumatization, are of similar appearance and readily seen on plain films. The condition of the middle ear is best evaluated by CT. is Cholesteatomas are almost always of the aquired, postinflammatory type. Typically they occupy the epitympanic recess (attic) and adjacent spaces or portions thereof; their tendency to become infected is high. The diagnosis is usually made by otoscopy, but radiologic examinations are extremely valuable for surgical planning. Complex motion tomography is more informative than plain film radiography, but a number of authors consider HR-CT the method of choice. 15 With growing size and extension into the mastoid antrum, cholesteatomas destroy the 20

lateral attic wall including the so-called scutum. Medial extension m a y cause erosion of the lateral semicircular canal. Some lesions extend into the mesotympanum and displace or destroy the ossicles; normally, on axial cuts, the ossicular chain is equidistant from medial and lateral walls of the epitympanic recess. 16 The bony defect, which also can affect the facial canal, is usually well defined. On CT, cholesteatomas usually appear homogenous although nonspecific as to Hounsfield numbers (Fig 12). Following surgery it m a y be extremely difficult if not impossible to differentiate recurrent cholesteatoma from ~[ranulation or scar tissue, postoperative deformity, and tumor. 1° Therefore, Swartz et al. 19 recommend a baseline HR-CT scan approximately three months after the operation. They also describe and illustrate the CT appearance of various types of surgery including reconstructive procedures.

Neoplastic Disorders In patients suspected of harboring a tumor of the temporal bone region, HR-CT with and without intravenous contrast is almost always the method of choice. Plain films are not sensitive enough and conventional tomograms notoriously lead to underestimation of the size of larger lesions. 2° The most frequent benign tumors of the external auditory canal are osteomas, sometimes simulated by the exostoses occurring in cold-water swimmers. Adenomas and keratomas are quite rare and usually diagnosed clinically. P r i m a r y malignant tumors are commonly basal cell carcinomas when their origin is

Fig 12.--Recurrent cholesteatoma; 21-year-old woman. A, axial CT scan at level of lateral or horizontal semicircular canal (straight arrow) shows large defect, partially the result of previous surgery, involving entire tympanic cavity and mastoid antrum; defect is filled with soft tissue and extends into facial canal anteriorly (curved arrow); ossicles are absent; sigmoid sulcus (s). B, scan at level of anterior (arrowhead) and posterior (open arrow) semicircular canals shows upper extent of lesion; considerable swelling of external soft tissues is present. 21

the pinna, or squamous cell carcinomas when they arise in the external auditory canal (Fig 13). Adenocystic or adenocarcinomas arising from sweat glands are less frequent. Metastatic carcinoma may have a similar radiographic appearance, with varying degrees of bone destruction (or occasionally sclerosis) and soft tissue involvement. In the middle ear, glomus tumors (paragangliomas) are the most common benign neoplasms. Glomus tympanicum tumors arise from chemoreceptor cells related to the tympanic plexus on the promontory (9th cranial nerve). Clinically they present as reddish or purplish masses behind the eardrum, and the patients complain of pulsating tinnitus. Initially there is no bony erosion, which explains why conventional tomograms may be negative. On HR-CT these tumors are readily detected, making selective arteriography, until recently considered the mainstay of radiological diagnosis, "no longer necessary in their routine preoperative evaluation. ''21 As mentioned above, lateral position of the petrous carotid and aberrant jugular bulb should be considered in the differential diagnosis. Primary malignant tumors include squamous cell and adenocystic carcinomas, rhabdomyosarcomas (almost exclusively in children), and rarely lymphoma, all eventually causing massive bone destruction, multiple cranial nerve deficits, and possible intracranial extension. 2 Glomus jugulare tumors arise from chemoreceptor cells in the jugular fossa and are frequently discovered when already quite large. These rather vascular neoplasms grow aggressively in various directions, yet usually follow the path of least resistance with erosive expansion of the jugular foramen first. Eventually they may have intratympanic as well as intracranial (posterior fossa) and extracranial (parapharyngeal) extensions, oftentimes accompanied by neoplastic occlusion of the jugular vein (Fig 14). Clinical findings then include hearing loss, foramen jugulare syndrome, and cerebellar dysfunction. Generally, all information essential for planning the operative therapy is provided by

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Fig 14.--Glomus jugulare tumor; 33-year-old woman. A, axial CT scan at level of external auditory canals after intravenous contrast administration shows expansile enhancing mass (T) involving left jugular foramen and extending into middle ear cavity (white arrow). B, scan at level of occipital condyles reveals cervical extension of tumor (small arrows) medial to styloid process (large arrow), obliterating internal jugular vein on right (j). axial HR-CT; angiography is felt necessary only in particularly large or atypical masses. 22 Foramen jugulare neuromas arising from cranial nerves 9 to 11 can closely mimic glomus jugulare tumors, clinically as well as radiologically. Also to be considered in the differential diagnosis are meningiomas, epidermoid cysts, chondrosarcomas, metastases, and components of (usually malignant) neighboring mass lesions. The diagnosis of small acoustic neuromas, i.e., purely intracanalicular tumors or tumors with only little cisternal extension, is presently best achieved with gas HR-CT cisternography. 23 However, care should be t a k e n to introduce enough gas into the cerebellopontine angle cistern, as an insufficient amount m a y simulate pathology. The normal internal auditory canal fills completely, outlinging the neurovascutar bundle. Neuromas practically always appear as soft tissue masses with a convex r a t h e r t h a n a flat medial contour (Fig 15,A), the latter being more indicative of postinflammatory arachnoid changes. 23 Preliminary results have already shown t h a t minimal enlargement of the nerves within the internal auditory canal m a y be revealed by MRI (Fig 15,B). 7 The differential diagnosis of intracanalicular neuroma includes meningioma, facial neuroma, and metastasis, though these rarely originate within the internal auditory canal. Outside the internal auditory canal, facial neuromas seem to have a predilection for the geniculate region and for the distal facial nerve segment. In typical Bell's palsy, a tumor is rarely found to be the cause, whereas with gradual onset of facial nerve paralysis, tumors are more likely and include malignancies of the subtemporal region. 23

Fig 15.--Small acoustic neuroma; 66-year-old man. A, CT air cisternogram shows soft tissue mass filling left internal auditory canal (arrow) and extending slightly into cerebellopontine angle cistern. B, T1/T2-balanced coronal MR tomogram clearly depicts lesion (arrow) which has signal intensity similar to brain tissue. Miscellaneous Disorders Otosclerosis, a peculiar but not infrequent disease, is characterized by replacement of portions of the otic capsule by spongy new bone that later becomes even denser than the original bone. The end result is hearing loss, usually of the conductive type. In the vast majority of cases, the process involves the region of the oval window (fenestral otosclerosis), and hearing can often be restored by surgery. Provided there is optimal technique and a large enough osseous plaque, the condition can be diagnosed radiographically either with coronal complex motion tomography or axial HR-CT. 24 Paget s disease, fibrous dysplasia, and histiocytosis X m a y also involve the temporal bone, the latter condition being characterized by bone destruction instead of hyperostosis and sclerosis. In M~ni~re's disease the endolymphatic vestibular aqueduct appears to be of reduced size. Radiologically this" structure can be visualized, at least in its terminale~portion, with lateral or off-lateral complex motion tomography. NASAL

CAVITY AND

PARANASAL

SINUSES

BASIC ANATOMY The two nasal cavities, separated from each other only by a relatively thin midline septum, are components of the upper airways as well as of the olfactory system. Their narrow external openings are called the anterior nares. Posteriorly they communicate with the nasopharynx via the choanae or posterior nares. The smooth medial wall of the main chamber of each cavity is 24

formed by the septum which is largely osseous except for its cartilagenous anterior portion. The floor is identical with the hard palate: The major part of the roof consists of the cribriform plate of the ethmoid bone. Posteriorly, the body of the sphenoid bone and anteriorly, the nasal cartilage, nasal bone, and a portion of the frontal bone are the components. The lateral wall, without prominent features anteriorly, is rather complex posteriorly where it separates the nasal cavity from the maxillary sinus and ethmoid air cell system. The structural elements responsible for this are the three conchae which protrude medially, thereby narrowing and incompletely compartmentalizing the nasal cavity (Fig 16,A). The inferior concha is a separate bone whereas the somewhat smaller middle concha and the tiny superior concha are parts of the ethmoid. The inferior nasal meatus runs below the inferior concha into which the nasolacrimal duct opens anteriorly. The middle meatus, bordered by the inferior and middle nasal concha, is the site of drainage for most of the paranasal sinuses. The superior meatus, running on top of the middle nasal concha, is comparatively insignificant. Above and posterior to the superior conchae, just anterior to the sphenoid sinus, lies the sphenoethmoid recess. The entire surface of the nasal cavity is lined by well-vascularized respiratory mucosa (ciliated pseudostratified epithelium) which is rather thick in places, specifically where covering the conchae (turbinates). A specialized mucosa exists, however, in the olfactory region below the cribriform plate. The maxillary sinus is usually the largest of the paranasal

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10

Fig 16.--Normal anatomy: lateral wall of nasal cavity. A, atrium of middle nasal meatus (1), olfactory region (2), sphenoethmoid recess (3), sphenoid sinus (4), superior nasal meatus (5), middle nasal turbinate (6), middle nasal meatus (7), inferior nasal turbinate (8), nasopharyngeal meatus (9), inferior nasal meatus (10). B, same, after removal of middle nasal turbinate; sphenoid sinus (4), superior nasal meatus (5), inferior nasal turbinate (8), inferior nasal meatus (10), frontal sinus (11), ethmoid bulla (12), superior nasal turbinate (13), ethmoid infundibulum (14), semilunar hiatus (15). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.) 25

sinuses. Its posterolateral wall is often rather thin, and even thinner is its roof (the floor of the orbit). When well developed, the sinus extends down into the alveolar process of the maxilla to form the alveolar recess. Posteriorly it borders on the pterygopalatine fossa and canal. The main, central part of the sinus opens medially into the semilunar hiatus of the middle nasal meatus; it is frequently called the maxillary antrum. The size of the frontal sinus is highly variable. In cases of prominent pneumatization, the sinus extends high into the squama of the frontal bone as well as posteriorly into the orbital roofs (orbital recesses). Like the maxillary, the frontal sinus opens into the middle nasal meatus or, to be more exact, into the anterosuperior portion of the semilunar hiatus (Fig 16,B). The ethmoid sinus consists of multiple anterior, middle, and posterior air cells. Of these, the anterior and middle cells drain as a group into the middle nasal meatus, whereas the posterior cells open into the superior meatus. The paired ethmoid sinuses are separated from each other by the nasal septum and the slitlike nasal cavity (nasal vault). Posteriorly, they border on the sphenoid sinuses and superiorly they are related to the anterior cranial fossa. Laterally they make up the medial wall of the orbit (lamina papyracea). The sphenoid sinus occupies variable portions of the body of the sphenoid bone and is therefore related to t h e anterior and middle cranial fossae as well as the sella. Occasionally, it extends into the anterior clinoid processes and also the dorsum sellae. Prominent lateral recesses are often present, pneumatizing the greater sphenoid wing, the floor of the middle fossa, or the upper pterygoid bone. The two sinus cavities m a y be of different size because of an off-midline or oblique position of the septum. Drainage occurs into the superior nasal meatus through an ostium that lies relatively high on the anterior wall. All paranasal sinuses are lined by respiratory epithelium. The pterygopalatine or sphenomaxillary fossa is located between the posterior wall of the maxillary a n t r u m and the pterygoid process. Being much wider above than below, this retromaxillary space has a V-shape when looked at from the side. Laterally it communicates with the infratemporal fossa via the sphenomaxillary fissure, medially with the nasal cavity via the sphenopalatine foramen, and anterosuperiorly with the orbit via the inferior orbital fissure. Inferiorly, the pterygopalatine fossa, the site of terminal branching of the m a x i l l a r y artery and passageway for numerous other vascular and neural structures, continues into the palatine canals and finally the oral cavity. IMAGING TECHNIQUES

Plain film radiography, i.e., the "sinus series," is still the most commonly used radiodiagnostic technique in suspected sinus dis26

ease or disease involving the nasal cavity. It can be rapidly performed and provides excellent and comparatively inexpensive overall information. The Caldwell view shows the frontal sinuses and the ethmoid labyrinth r a t h e r well, whereas the maxillary sinuses a r e obscured by the petrous pyramids. The Waters view shows the maxillary sinuses to best advantage and the frontal sinuses are also well demonstrated (although somewhat distorted). However, only the anterior ethmoid cells are seen free of superimposition. In the base view, the maxillary sinuses and orbits are superimposed. Evaluation of the ethmoid air cell system is usually possible, and the sphenoid sinus is also seen. Also a good view of the sphenoid sinus is the lateral projection. In this view, which is probably best t a k e n slightly off-lateral, the right and left ethmoid sinuses are superimposed upon each other as are the two maxillary sinuses, frontal sinuses, and pterygopalatine fossae. The hard palate is relatively well seen. Conventional tomography is capable of eliminating confusing superimposed detail. As in other anatomic regions of high complexity, pluridirectional (complex motion) tomography is much more effective: t h a n tomography with a simple linear blurring motion. W h a t makes this technique still valuable is the ease w i t h which direct frontal (coronal) and lateral (sagittal) sections can be made. Axial (transverse) views, in contradistinction, are rather difficult to obtain while axial (transverse) CT sections are standard. The main disadvantage of conventional tomography as compared with CT is the limitation of soft tissue visualization and differentiation. Computed tomography, with its capability of depicting bony structures and soft tissues equally well, is presently the single most valuable radiodiagnostic technique. In order to demonstrate the entire nasal cavity and all paranasal sinuses, the examination needs to cover a region t h a t extends from the level of the alveolar process of the maxilla below to a level just above the frontal sinuses. Axial scanning is performed parallel to the hard palate, a structure easily identified on a scanner-produced lateral digital radiograph. For practical purposes, slice thicknesses of 4 to 5 m m are often satisfactory. Thinner slices (1 to 2 mm) are less contrasty but give a better resolution of bony detail and allow image reformation in coronal, sagittal, or oblique planes, as well as three-dimensional reconstruction (Fig 17). 2~ Direct coronal scanning permits optimal evaluation of bony structures such as the hard palate, floor of orbit, and floor of anterior cranial fossa. In most cases the scan angle will be somewhat less t h a n the ideal 90 degrees, with reference to Reid's baseline, either because the patient is unable to extend his neck enough or because avoidance of dental work calls for a specific slant in order to eliminate or minimize artifacts. The study m a y be carried out i n prone or supine position. Intravenous contrast 27

Fig 17.--Three-dimensional frontal CT surface reconstruction of facial bones in 60-year-old woman treated by extended maxillectomy for squamous cell carcinoma of right maxillary sinus. Arrow points to undisturbed right pterygoid process. (Courtesy Michael Vannier, M.D. and Jeffrey Marsh, MD., St. Louis.)

enhancement is not routinely necessary. Detailed descriptions of the normal CT anatomy of nasal cavity, paranasal sinuses, pterygopalatine fossae, and adjacent spaces (Fig 18) are given by Hesselink et a l . y Daniels et al., 2s Unger and Chintapalli, 29 and Som. 3° Nuclear medicine is seldom used in the radiodiagnostic workup of patients with nasal or paranasal sinus disease except in cases of suspected cerebrospinal fluid (CSF) leak. Occasionally bone scans m a y assist in detecting and differentiating osseous lesions. In a series of 25 cases, patients with carcinoma of the maxillary sinus all had positive gallium scans, whereas patients with chronic maxillary sinusitis had either negative or only weakly positive scans. 31 Magnetic resonance imaging, because of its high sensitivity for differences in soft tissue composition, has the potential for distinction between neoplastic and inflammatory disease. On T2weighted images the signal from tumor is usually much less than the signal from inflamed mucosa or retained mucus (Fig 19). As in contrast enhanced CT imaging, MRI is helpful in the evaluation of possible intracranial spread of inflammatory or neoplastic processes originating in the nose or paranasa] sinuses. On the other hand, the poor and indirect demonstration of bony detail is clearly a disadvantage, s Angiography is seldom indicated b u t m a y help in determining the extent, degree, and source of vascularity and likely tissue type of some tumors, e.g., angiofibromas and rhabdomyosarcomas. It m a y also become necessary in primarily intracranial masses that only later involve the nose and sinuses, such as meningiomas, giant aneurysms, and carotid cavernous fistulas. Another indication for angiography is rhinocerebral fungal dis28

Fig 18.--Normal anatomy: reformatted coronal and oblique CT images of nasal cavity and paranasal sinuses (axial scans with planes of reconstruction above). A, coronal section at level of anterior portion of maxillary and ethmoid sinuses; lateral wall of nasal cavity = medial wall of maxillary sinus (curved arrow), turbinates (t), infraorbital sulcus (straight white arrow), cribriform plate (black arrow), medial rectus muscle (arrowhead). B, coronal section at level of posterior portion of maxillary and ethmoid sinuses; temporalis muscle (tm), zygomatic arch (arrow). C, coronal section at level of sphenoid sinus; lateral plate of pterygoid process (curved arrow), vomer (V), contrast-enhanced cavernous sinus (arrowheads). D, oblique section through left maxillary and sphenoid sinuses; pterygopalatine fossa (curved arrow), inferior rectus muscle (arrowheads).

ease with possible encasement or invasion of major arteries at the base of the skull. High-quality DVA m a y be sufficient in most of these rare cases. Interventional c a t h e t e r techniques are employed to stop otherwise u n m a n a g e a b l e epistaxis, devascularize vascular tumors before surgery, and occlude arteriovenous communications.I° 29

Fig 19.--Axial MR tomogram in 38-year-old man with acinic cell carcinoma of nasal cavity. A, T1/T2-balanced image at level of maxillary antra shows tumor (T) having similar signal intensity as brain tissue. B, T2-weighted image at level of inferior tumor pole (T) reveals high signal area within lower portion of adjacent maxillary sinus consistent with mucosal thickening or retained mucus; signal intensity of mass remains low.

P

Fig 20.--Comminuted fracture of right maxillary sinus walls; 36-year-old man. In this axial CT scan at level of antrum, only fractures involving medial and (postero-) lateral walls are clearly seen. Opacification of sinus lumen with air-fluid level presumably caused by blood.

30

RADIOLOGIC PATHOLOGY

Developmental Anomalies and Malformations Most minor anomalies, such as hypoplasia and aplasia of one or more paranasal sinuses, are easily detected and satisfactorily delineated on plain films. Major anomalies, however, require either complex motion tomography or HR-CT. CT is generally to be preferred because of its versatility, superior soft tissue resolution, and low radiation dose. Sincipital (anterior) encephaloceles m a y involve the nasal cavity and paranasal sinuses, sometimes appearing as a "polyp" clinically. Not uncommonly, they go totally unnoticed on plain films. The bony defect accompanying these soft tissue herniations at the base of the skull is often rather obvious on axial CT scans, b u t m a y be inconspicuous on conventional coronal or lateral tomograms. CT is preferable to demonstrate unilateral or bilateral choanal atresia. A detailed description of the numerous and often complex craniofacial anomalies is beyond the scope of this monograph. Suffice it to say that in the radiodiagnostic workup, HR-CT is the method of choice. Recently, sophisticated techniques with three-dimensional reconstruction of bony and soft tissue surfaces have markedly improved the understanding of such deformities and have facilitated surgical planning and evaluation of postoperative results: 26 Traumatic Disorders Commonly, the first radiotogic examination in a patient with facial injury is routine p l a i n film sinus or facial bone radiography. Although m a n y fractures can be detected in this way, tomography is frequently necessary for a more detailed evaluation. In the past, conventional complex motion tomography has been the mainstay of definitive diagnosis; more recently, CT has gained importance (Fig 20). Zilkha 32 performed plain film radiography, conventional tomography, and CT on 30 patients with facial t r a u m a and found CT to be the superior diagnostic modality. He suggested that CT follow plain film radiography in such cases because it demonstrated bone and soft tissue involvement. In another efficacy analysis, Kreipke et al. s3 reached the conclusion that in combination with plain films, CT was better than conventional tomography when two projections (axial and direct coronal) were utilized. However, when only one projection from each modality was used (axial CT and coronal or frontal conventional tomography, respectively), conventional tomography surpassed CT. Diagnostic failures occurred when the plane of section was not sufficiently perpendicular to the plane of the fractured bony structure. In order not to overlook significant bony injury, imaging in two planes is therefore a necessity with conventional tomography as well as with CT. With HR-CT, however, coronal views need not always be obtained in a direct fashion (Fig 21), since thin axial slices (1.5 to 2.0 mm) allow suffi31

Fig 21.--Complicated LeFort II fracture; 27-year-old man. A, coronal CT scan at level of bridge of nose reveals comminuted fracture of nasal processes and adjacent portions of frontal bone; also present are small amount of intracranial air (curved arrow) and emphysema of left lower lid (arrowheads). B, scan at level of bodies of zygomatic bones (z) shows multiple fractures involving lateral walls of maxillary sinuses, orbital floors, medial orbital walls, and cribriform region with adjacent portions of orbital roofs; arrow points to depressed left cribriform plate; opacification of maxillary and ethmoid sinuses secondary to hemorrhage and mucosal swelling; intact frontozygomatic sutures. C, on scan at level of posterior portion of maxillary sinuses, displaced fragments of lateral sinus walls (arrows) are seen as well as air in soft tissue on right; additional fractures involve greater sphenoid wing (sw), temporal squama, and zygomatic arch on left. D, scan further posterior demonstrates bilateral fractures of pterygoid processes and lateral walls of nasal cavity (arrows); there is almost total opacification of sphenoid sinus.

ciently informative computer reformations in many cases (compare with Fig 18). An added advantage of CT is the visualization of brain and eye injury. Blowout fractures of the orbit, with or without simultaneous involvement of the inferior orbital rim, are best evaluated by reformatted views in the oblique sagittal plane. Limited inferior rectus muscle mobility causing diplopia on upward gaze may be the result of muscle kinking secondary to orbital fat pad pro32

lapse into the maxillary sinus, rather t h a n muscle entrapment between bone fragments. 34 Both are demonstrable by CT but may not be by conventional tomography. Depressed fractures of the medial orbital wall (lamina papyracea) with prolapse of orbital tissue into the ethmoid labyrinth are best seen on axial cuts (Fig 22). Orbital emphysema is also readily recognized on CT scans, as is intraorbital hematoma. Posttraumatic opacification of the sinuses can have a number of causes including mucosal edema, submucosal and i n t r a l u m i n a l hemorrhage, CSF leakage, or simply blocked drainage of normal secretions. For a detailed description of the radiographic appearance of the classical Le Fort I ("floating palate"), Le Fort II ("floating maxilla"), and Le Fort III ("floating face") fractures, as well as the various isolated zygomatic fractures, the reader is referred to S o m . 3°

CSF rhinorrhea, in most cases, is the result of t r a u m a (77% in the series of Manelfe et alY). Although the majority of leaks stop within a week or so, some leaks persist and may cause recurrent or late meningitis. Accurate localization of the site of leakage has been accomplished with either radionuclide cisternography or metrizamide CT cisternography. The yield of both procedures is highest in the presence of active rhinorrhea at the time of the study. HR-CT, if successful, may show the leak and

Fig 22.--Depressed fracture of medial wall or lamina papyracea of orbit; 43-yearold man. Axial CT scan at level of optic nerves (n) shows prolapse of orbital fat and medial rectus muscle into ethmoid labyrinth on right; fracture of orbital floor was also present. Patient had been hit by softball. 33

the bony discontinuity at the same time, but more often those procedures provide only proof of leak and lateralizing information.

Inflammatory Disorders In acute viral rhinosinusitis, radiographic findings are scanty as long as no bacterial superinfection exists. At best, mild mucosal thickening and some swelling of the turbinates m a y be noted. In the absence of recent t r a u m a or antral lavage, an airfluid level in one of the maxillary sinuses usually denotes acute bacterial infection. Air-fluid levels m a y also be seen in acute frontal sinusitis or infection of the ethmoid labyrinth, although the latter probably only on CT. In the sphenoid sinus, on the other hand, an air fluid level m a y simply occur as result of poor drainage of normal secretion. In fact, of all paranasal sinuses the sphenoid sinus is least often affected by inflammatory disease, although potentially seriously. The sinuses most often affected are the maxillary antra, followed by the ethmoid sinuses. 3° Allergic sinusitis, a rather common disease, manifests itself in a more or less symmetric fashion, and also leads to pansinusitis considerably more often t h a n bacterial infection. Polypoid mucosal hypertrophy is the h a l l m a r k of chronic sinusitis. Unless the entire sinus i s opacified, these changes are rather obvious on conventional radiographs and even more so on CT scans. Total sinus opacification m a y result either from mucosal swelling alone or, more commonly, from a combination of such changes with mucus retention. Reactive sclerosing osteitis involving sinus walls and adjacent bony structures, not at all rare in the pre-antibiotic era but now an infrequent finding, suggests long-standing chronic disease. Among the minor sequelae of rhinosinusitis are mucous retention cysts, which result from obstruction of the excretory duct of single or several seromucinous glands. On plain films, conventional tomograms, and CT scans, they appear as smoothly marginated, homogenous soft tissue masses projecting into the sinus lumen. On T2-weighted MR images, they exhibit a very high signal intensity (long T2). As tong as they are small, a more or less spherical shape prevails. With increasing size, they tend to mold to the wall of the sinus but do not completely fill the cavity. Conventional tomograms and particularly CT scans show a thin rim of air, separating even large cysts from the sinus walls. These cysts m a y be seen in all paranasal sinuses but are most frequent in the maxillary sinuses. There they usually occupy the inferior portions of the antrum. For the most part, differentiation from mucoceles which totally opacify the sinus is not difficult. Conversely, mucoceles result from obstruction of the drainage opening (ostium) of a sinus. Their tendency to expand the cavity of origin and eventually erode through its walls is remarkable. 34

In addition, they m a y become infected and then are called pyoceles. About 65% of paranasal mucoceles involve the frontal sinuses. Next in frequency are mucoceles of the ethmoid labyrinth (about 25%), followed by lesions of the maxillary sinuses (5% to 10%). Sphenoid mucoceles, although uncommon, should always be included in the differential diagnosis of atypical mass lesions involving the pituitary fossa and sphenoid sinus, even in children. Initially, a mucocele presents with clouding of the sinus, b u t later, expansion causes thinning of its walls and the overall result then m a y be a lesion that appears lucent despite the replacement of air by fluid. Although the diagnosis usually can be made on plain films or conventional tomograms, CT is preferred. Probably the most significant reason is the importance of evaluating extension of a mucocele into adjacent spaces. Frontal mucoceles, for instance, m a y break through the sinus wall into the intracranial cavity. Ethmoid mucoceles tend to involve the orbit (Fig 23). A classification of ethmoid mucoceles based on CT appearances has been advanced by Som and Shugar. 3~ Loss of the normal intrinsic bony architecture is a characteristic feature. In certain rare instances, nearly all septae are preserved, however, and the ethmoid labyrinth is expanded in its entirety. This entity, "polypoid mucocele," actually represents a conglomerate of numerous small ethmoidal mucoceles;

Fig 23.--Ethmoid mucocele; 11-year-old girl. Axial CT scan at level of optic nerves reveals homogeneous expansile mass involving anterior ethmoid air cells on right; lesion bulges into orbit and encroaches on globe, widening space between medial rectus muscle and lamina papyracea posteriorly. Compare with normal anatomic relationship between these structures on opposite side (arrowheads). 35

its appearance on CT is highly characteristic (Fig 24). Sphenoid mucoceles may lead to intrasellar extension with superior displacement of the pituitary gland. Such an event, fortunately rare, is probably best clarified by sagittal and coronal MR imaging. The sinus content with its very high signal intensity particularly on T2-weighted images, is then clearly seen to extend beyond the eroded sellar floor. On CT scans obtained after intravenous contrast administration, mucoceles do not enhance though peripheral enhancement occasionally can be observed in pyoceles. In cases of delayed or unsuccessful antibiotic treatment of acute bacterial sinusitis, the inflammatory process m a y spread beyond the sinus, a very serious complication with a potentially grave prognosis. For anatomic reasons, involvement of the orbit is to be expected most often. Again, CT is by far the best method to determine the presence and extent of orbital cellulitis or subperiosteal orbital abscess. The latter occurrence, an ophthalmologic emergency, most commonly arises from ethmoid sinusitis. Characteristically, a soft tissue mass bulges into the orbit next to the lamina papyracea, effacing the fat plane which normally separates this structure from the medial rectus muscle. Along with findings of sinusitis and orbital edema, there is usually proptosis (Fig 25). At this point, it should be remembered that

Fig 24.--So-called polypoid ethmoid mucocele; 37-year-old woman. On this axial CT scan the entire ethmoid labyrinth is widened as well as inhomogeneously opacified, Curved arrow points to bony erosion at frontoethmoid junction; arrowheads denote areas of erosive thinning of medial orbital wall on left; fat planes between medial rectus muscle and lamina papyracea bilaterally retained. 36

Fig 25.--Acute orbital inflammation; 17-year-old boy. Axial CT scan at level of superior orbital fissures (curved arrows) demonstrates mucosal thickening of ethmoid air cells, particularly on left, as well as evidence of subperiosteal abscess and periorbital ceilulitis of left orbit; there is considerable proptosis. Abscess (asterisk) obliterates fat plane between lamina papyracea and medial rectus muscle posteriorly and contains air, presumably from adjacent sinus, anteriorly (open arrow). In this case, infection arose from maxillary sinus. orbital infection carries the risk of septic thrombophlebitis and cavernous sinus thrombosis, complications which are still associated with a high mortality rate, especially if unrecognized. Another dangerous complication of bacterial frontal sinusitis is the formation of an epidural abscess. On CT, the fluid accumulation (exudate) appears hypodense, and the dura, which i s stripped away from the inner table of the skull, undergoes intense enhancement (Fig 26). Bone window images m a y show evidence of osteomyelitis. Subdural empyema and brain abscess are the ultimate complication if spread of infection is unchecked. Fungal and infectious granulomatous diseases including tuberculosis and actinomycosis occasionally affect the nasal cavity or paranasal sinuses. They m a y be radiographically indistinguishable from malignancies. Rhinocerebral mucormycosis occurs especially in patients with poorly controlled diabetes mellitus and in immunosuppressed individuals. The CT findings include "patchy" sinusitis, bone destruction, and orbital involvement. Also, there is a tendency of intracranial spread.

Neoplastic Disorders Radiological procedures play a decisive role in the diagnostic evaluation of patients suspected of harboring a tumor of the na37

Fig 26.--Frontal epidural abscess; 19-year-old woman. Axial CT scan after intravenous contrast administration shows densely enhancing dura (arrowheads) stripped away from inner table of skull and displaced posteriorly. Intracranial infection resulted from acute bacterial frontal sinusitis clearly evident in this section; additional inflammatory changes involve extracranial soft tissues and include small accumulation of air (arrow).

sal cavity or paranasal sinuses. At present, the method of choice is CT37; although if CT is not available, plain film radiography and particularly conventional tomography are certainly capable of answering m a n y important questions. MRI seems to have a potential of separating neoplastic tissue from edematous mucosa or inspissated secretions, and both CT and MRI can demonstrate orbital and intracranial tumor spread (Figs 27 and 28). Also, posterior extension of maxillary malignancies into the pterygopalatine and subtemporal fossae can be directly visualized. With CT, intravenous contrast enhancement m a y help in delineating vascular masses or evaluating the carotid artery and jugular vein. Benign tumors are comparatively rare. Among the few benign neoplasms of ectodermal origin, inverting papillomas stand out as the most common lesions. In contradistinction to the exophytic (simple) papillomas, these unusual tumors proliferate internal to the mucosa and grow toward the underlying stroma. Their potential to destroy bone is significant, and recurrences after incomplete resection are almost the rule. Especially after multiple recurrences, malignant transformation is a possibility. The need for exact preoperative determination of extent is therefore obvious. Initially an inverting papilloma presents as a nonspecific polyp within the nasal cavity, nearly always arising from the lateral wall. Untreated, it continues to grow, eventually expanding the nasal fossa and, after destruction of the lat38

Fig 27.--Undifferentiated carcinoma of nasal cavity; 64-year-old man. A, T1weighted coronal MR tomogram at level of maxillary antra clearly separates neoplastic tissue (T) from retained mucus (asterisk); tumor invades, in addition to orbit (arrow), ethmoid and maxillary sinuses on right. B, on axial CT scan, tumor (7-) and tumor-induced right maxillary mucocele have same density.

Fig 28.--Extensive nasal carcinoma with orbital and intracranial spread as well as invasion of sinuses; 40-year-old-man. A, on T1/'r2-balanced parasagittal MR tomogram, delimitation of tumor is difficult; note middle cerebral artery at posterior aspect of intrecranial component of mass (curved arrow) and destruction of orbital floor posteriorly (open arrow). B, correspondng T2-weighted image clearly depicts entire tumor extent (7-) and separates neoplastic tissue from retained secretions within maxillary and frontal sinuses; body of lateral ventricle (v).

39

eral wall, extending into the adjacent maxillary sinus (Fig 29). In advanced cases, the lesion breaks through the other sinus walls and also m a y invade the orbit, the ethmoid labyrinth, and finally the intracranial space. 3s Despite their histologically benign nature, inverting papillomas thus resemble malignant lesions. On radiologic grounds alone, the diagnosis can only be suspected since the signs described are not specific. In cases with a mass in the nose, opacification of the maxillary sinus and destruction of intervening bone, carcinomas, and lymphoma are more likely. The common benign polyps of allergic or inflammatory origin, which sometimes cause extensive radiographic changes as a result of expansion and obstruction, may present a similar or identical appearance but do not proceed to orbital or intracranial involvement. Though frequently recurrent, they do not become malignant. Neurogenic tumors rarely occur within the nasal cavity or paranasal sinuses but are not infrequent in adjacent spaces. The growth pattern is expansile, and most of these well-circumscribed lesions exhibit marked, albeit inhomogeneous, enhancement on CT. For the most part the occasional meningiomas are extensions from intracranial tumors. 3° The juvenile angiofibromas which may affect the nasal cavity and paranasal sinuses will be dealt with in the following section.

|

Fig 29.--Inverting papilloma; 69-year-old woman. Axial CT scan at level of maxillary antra shows soft tissue mass filling right maxillary sinus and portion of nasal cavity with destruction of intervening bony wall. 40

Of all benign fibro-osseous tumors, osteomas are by far the most common, the majority being seen in the frontoethmoid region. Obstruction of ostia with development of a mucocele is possible. Large frontal osteomas more or less conform to the sinus, leaving its normally scalloped contour intact. Most of the time the radiographic appearance is quite characteristic. Ossifying fibromas are less dense t h a n osteomas and also less homogenous. They occur mainly in the maxilla with secondary encroachment on the sinus; the differentiation from fibrous dysplasia may be difficult. Osteoblastomas, chondromas, and true giant cell tumors are rare. Chordoma represents an extension of an intracranial lesion and is even more rare. The most common malignant tumors of the nasal cavity and paranasal sinuses are the squamous cell carcinomas (80% to 90%). The majority of these tumors, which tend to afflict older people, originate within the maxillary sinus; only 10% to 30% begin in the nose (Fig 30). The ethmoid labyrinth is the primary origin in about 10% to 20% (Fig 31), and cases of squamous cell carcinomas arising in the frontal or sphenoid sinuses are exceptional. As with osteomas, neoplastic obstruction of the sinus ostium m a y induce formation of a mucocele, which could, at least temporarily, mask the real underlying pathology. 39 On the other hand, in the ethmoid sinus, "simple" mucoceles are so much more common t h a t carcinoma would hardly be considered. Squamous cell carcinoma is very aggressive and clear bone destruc-

Fig 30.--Squamous cell carcinoma of maxillary sinus; 52-year-old woman. Axial CT scan at level of antra reveals almost total destruction of medial and (postero-) lateral sinus walls with invasion of nasal cavity, pterygopalatine fossa (straight arrow), and subtemporal region (asterisk); tumor also grows through anterior sinus wall into subcutaneous soft tissue (curved arrow); pterygoid process undisturbed. 41

Fig 31.--Squamous cell carcinoma of ethmoid labyrinth; 71-year-old man. This "semi-coronal" scan provides excellent information on overall tumor extent including bone destruction; note invasion of both maxillary sinuses, left more than right, as well as invasion of left orbit (arrow).

tion rather t h a n sinus expansion is an early radiographic finding occurring in more t h a n three fourths of cases. The next most common epithelial malignancies are undifferentiated carcinomas and adenocarcinomas, including adenoid cystic carcinomas which arise from minor salivary glands (cyclindromas) (Fig 32). Acinic cell carcinomas represent a rare form ofadenocarcinoma. Esthesioneuroblastoma is an unusual tumor of neuroectodermal origin arising from the olfactory neurosensory tissue in the nasal vault and cribriform region. It tends to afflict older children and adolescents. The biological behavior varies from relatively benign to markedly aggressive. In the latter case, intracranial spread results in the appearance on CT of an enhancing mass in the anterior cranial fossa. Similar changes m a y be seen in metastatic neuroblastoma. Only a relatively small fraction of nasal and p a r a n a s a l malig_nancies (probably less t h a n 15%) are of mesodermal origin. Malignant lymphomas, specifically lymphosarcomas, dominate in this group. Early recognition is of great importance as these tumors are curable by radiation therapy. Compared with the findings in carcinomas, bone destruction is not such a prominent feature. For example, soft tissue masses m a y be present on either side of a sinus wall t h a t radiographically looks intact. Indeed, permeation of bone without destruction seems to be a mode of propagation of m a l i g n a n t lymph cells. 4° Sinus expansion and 42

Fig 32.--Adenoid cystic carcinoma involving ethmoid sinus; 55-year-old woman. Axial CT scan reveals destruction of lamina papyracea anteriorly on right with neoplastic invasion of orbit, causing lateral displacement of medial rectus muscle (arrowheads) and mild proptosis; mass represents recurrence of maxillary sinus tumor about two years after surgery and radiation therapy. bony displacement of erosion m a y also occur. P r i m a r y malignant melanomas stem from ectopic melanocytes. Radiographically they appear as either soft tissue masses with clear-cut destruction of bone, or they combine such ominous signs with features of expansion. 3° Embryonal rhabdomyosarcomas should be considered in young patients with clinical signs and symptoms of nasal or paranasal malignancy, especially below the age of 10. When first evaluated radiologically most of these tumors have already caused at least some bone destruction, and even evidence of intraorbital and intracranial spread may be present (Fig 33). Unfortunately, histological confusion with other mesenchymal malignancies can occur. Most fibrosarcomas grow slowly and by expansion rather t h a n destruction, thus resembling more benign lesions~ Chondrosarcomas show a similar behavior but are usually partially calcified. Osteogenic sarcomas characteristically have the so-called "sunburst" appearance secondary to a specific periosteal reaction, which is best seen on conventional films. Metastases from a primary tumor below the head and neck region most commonly stem from renal cell carcinoma and are rather vascular. 3° Other t u m o r s t h a t m a y metastasize to the nasal cavity and paranasal sinuses are breast and lung cancers. Although, as mentioned above, bone destruction is the most 43

Fig 33.--Embryonal rhabdomyosarcoma of nasal cavity with invasion of adjacent spaces; 15-year-old boy. On axial CT scan after intravenous contrast enhancement at level of optic nerves (above), tumor is seen to extend through ethmoid sinus into right orbit (asterisk). Midsagittal reformation of same study (below) reveals degree of intracranial extension (arrows); tumor (T) enhances moderately and blocks drainage of sphenoid sinus (s).

reliable sign of malignancy, some highly aggressive tumors m a y initially show only expansion of a sinus. The reason for this is either production of a mucocele, often by squamous cell carcinoma, or an invasive direct tumor enlargement as sometimes seen in adenocarcinoma, rhabdomyosarcoma, esthesioneuroblastoma, and melanoma. 39 Malignant tissue can reach areas apparently remote from the primary tumors by growing along nerves. In tumors of the palate, sinuses, and face, this type of spread usually involves the maxillary division of the trigeminal nerve. On CT, obliteration of the fatty tissue normally seen in the pterygopalatine fossa suggests pathology. 41 Miscellaneous Disorders The following rare and, in many respects, poorly understood entities are mentioned primarily because they either mimic neoplastic disease or, in fact, develop into frankly malignant tumors. The latter event, for instance, is known to occur in perhaps 2% to 5% of cases with Paget's disease of the maxillary bone, resulting in osteogenic sarcoma. Simultaneous evidence of osteitis deformans of the calvarium (sclerotic stage) is the rule. Fibrous dysplasia, a sometimes disfiguring disease (Fig 34), rarely m a y become malignant, particularly following irradiation. 44

Fig 34,--Fibrous dysplasia involving maxillary sinus; 18-year-old man. A, axial CT scan at level of antra demonstrates enlarged right maxilla with obliteration of entire sinus lumen; a r r o w points to infraorbital foramen. B, three-dimensional CT surface reconstruction of facial bones generated from set of 64 non-overlapping, 2mm scans provides excellent information on degree of bony distortion; note narrowing of right orbit and additional involvement of right mandible, (Courtesy Michael Vannier, M.D. and Jeffrey Marsh, M.D., St. Louis.) Wegener's granulomatosis, probably an autoimmune disease, begins in the nose but may manifest itself in the paranasal sinuses and nasopharynx. The disease is not uniformly fatal, especially since chemotherapy has proved to be effective. The maxillary antra are involved most frequently, and chronic bacterial sinusitis is often superimposed. Gradual obliteration of the sinus lumen is not rare, and destruction of nasal turbinates or loss of the septum are also quite frequent. These changes, as well as invasion of the cavernous sinus in the absence of gross bony destruction, can all be demonstrated by CT. Idiopathic midline granuloma, probably related to lymphoma, 3° radiologically shows some resemblence to Wegener's granulomatosis. The granulomas in sarcoidosis are non-caseating but otherwise similar to the ones seen in tuberculosis and other granulomatous diseases of known infectious origin. Systemic disease is always present. The lesions are relatively small and usually located on turbinates and septum. An overview on the radiographic appearance of various surgical procedures performed in diseases of the nasal cavity and paranasal sinuses (Fig 35) is given by Som. 3° NASOPHARYNX

AND

ADJACENT

SPACES

BASIC ANATOMY The nasopharynx represents the upper portion of the pharyngeal cavity, has relatively thin muscular walls, and is lined by mucosa (Fig 36). As part of the upper airway system, it communicates anteriorly, via the choanae, with the nasal cavity. A 45

Fig 35.--Status after left partial maxillectomy and radiation for leiomyosarcoma of maxillary sinus; 72-year-old woman. Axial CT scan shows slightly nodular soft tissue mass (asterisk) suggestive of tumor recurrence adjacent to hyperostotic lateral sinus wall.

variable amount of lymphoid tissue is found in its roof, particularly in children. The superior boundaries of the nasopharynx are formed by the sphenoid sinus and upper clivus, the posterior ones by the lower clivus and upper cervical spine. Interposed between the posterior nasopharyngeal wall and these bony structures are the longus capitis and colli muscles as well as some fascial membranes. In fact, patency of the nasopharynx is guaranteed by the pharyngobasilar fascia. The lateral wall is characterized by the torus tubarius, a mucosal prominence caused by the cartilagenous end of the Eustachian tube. The pharyngeal ostium of the Eustachian tube lies just anterior to this structure, and the fossa of Rosenmueller is the recess immediately behind and above it. Anteriorly, the lateral nasopharyngeal wall is bordered by the medial pterygoid plate, whereas posterolaterally only soft tissue boundaries exist. The inferior limit of the nasopharynx is the soft palate. The paranasopharyngeal space contains the pterygoid process with the levator and tensor muscles of the palatine velum anteriorly, and the carotid sheath, holding internal carotid artery, internal jugular vein, lymphatics, sympathetics, and cranial nerves 9 to 12 posterolaterally. The adjacent infratemporal fossa contains the medial and lateral pterygoid muscles as well as portions of the temporalis muscle. It is traversed by the maxillary artery and branches of the trigeminal nerve. Important 46

Fig 36.--Normal anatomy: lateral wall of nasopharynx. Pharyngeal ostium of eustachian tube (1), sphenoid sinus (2), pharyngeal recess of Rosenmueller (3), fossulae or pits (4) of pharyngeal tonsil (5), pharyngeal bursa (6), torus tubarius (7), salpingopharyngeal muscle (8), soft palate (9), prevertebral soft tissue including superior constrictor muscle of pharynx (10). (From Feneis H.: Pocket Atlas of Human .Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.)

structures that are more laterally located include the facial nerve passing through the parotid gland, the posterior belly of the digastric muscle, and the styloid process. The spaces in between are filled with connective tissue, fat, and a venous (pterygoid) plexus. The anatomy of the pterygopalatine fossa, located between the pterygoid process and the back of the maxillary antrum, has already been described above. IMAGING TECHNIQUES

Plain film radiography, if properly executed, is still of some value as an initial study. The most important projections are the lateral and the axial (submentovertex) views of the skull, the air-filled nasopharynx providing excellent outlining of the soft tissues. Unfortunately, pathologic changes t h a t leave the soft tissues essentially undistorted and do not (yet) significantly affect the bone go unnoticed. On the axial view, the nasopharyngeal "air shadow," which always remains medial to the ptery47

goid processes and anterior to the anterior arch of C1, must not be confused with the "shadows" or rather lucencies caused by oropharynx and piriform sinuses. Conventional tomography may supplement plain films by eliminating disturbing superimpositions, but the problem of contrast resolution limited to air, soft tissue, and bone basically remains the same. Computed tomography is presently the radiodiagnostic method of choice in suspected or known nasopharyngeal disease. 42' 43 There are two m a i n reasons: (1) The nasopharynx and adjacent spaces lend themselves exceptionally well to sectioning in axialtransverse planes; and (2) CT shows, in addition to bone and mucosal surfaces, the submucosal as well as the deep tissues. These latter soft tissue planes are not adequately accessible to palpation or fiberoptic inspection, which makes CT the complement par excellence to the clinical examination. The study should include the base of the skull and extend inferiorly beyond the hard palate. Not infrequently, even lower cuts or cuts encompassing a part or all of the intracranial cavity are necessary. The tailoring of the examination is greatly facilitated by digital radiographs. Normally, 4 to 5-mm thick contiguous slices provide adequate visualization of the nasopharynx and adjacent spaces. However, t h i n n e r sections, preferably generated with an algorithm t h a t emphasizes bone detail, m a y be needed for the base of the skull. This is particularly true when image reformation is contemplated. We usually scan in planes parallel to the orbitomeatal line, but moderate inclination of the g a n t r y in either direction does not adversely affect the results. ~° Significant lateral tilt of the patient's head should be avoided, however. Indications for intravenous enhancement include possible intracranial spread of neoplastic or inflammatory disease, determination of presence and extent of a vascular lesion, and evaluation of the topographic relationship between a known mass and the carotid sheath. With dynamic scanning, after a 50-ml bolus injection of contrast medium followed by rapid drip infusion, the necessity for DVA or conventional angiography can be reduced. 44 Direct coronal cuts as well as maneuvers t h a t help distend the upper airways during the scanning procedure (openmouth breathing, Valsalva) m a y be needed in certain cases for further evaluation and avoidance of misinterpretation. 42 Direct sagittal scans which can be obtained with machines having an ultrawide g a n t r y aperture are certainly not indispensable but may be helpful. The value of CT in reference to the infratemporal fossa and parapharyngeal space is discussed by Doubleday et al. 45 and by Unger and Chintapalli. 2~ These authors also give descriptions of the normal anatomy as seen on CT (Fig 37). Nuclear medicine plays no significant role in the radiodiagnos48

Fig 37.--Normal anatomy: Reformatted coronal CT image of nasopharynx and adjacent spaces. Sphenoid sinus (ss), clivus (cl), torus tubarius (t), paranasopharyngeal space (ps), stylopharyngeus, styloglossus, stylohyoid/digastric muscle group (asterisk), medial pterygoid muscle (pt), superior constrictor muscle of pharynx(c).

tic workup of patients with suspected nasopharyngeal disease. Nevertheless, occasionally a bone scan m a y be helpful if metastatic invasion of the clivus or nearby bony structures is a possibility. Conversely, a bone scan with abnormally high uptake in the roof of the nasopharynx m a y dictate the need for CT. Magnetic resonance imaging is just beginning to challenge CT. First published results 4~ as well as our own experience strongly suggest that the new technology may soon become the preferred method of visualizing the nasopharynx and adjacent spaces. The superior soft tissue discrimination afforded by spin echo images obtained with a TR of 1500 msec or above and multiple echos permits clear differentiation between mucosa, submucosa, fat, muscles, vessels, and lymph nodes (Fig 38,A). Another advantage of MRI is the ease with which direct coronal and sagittal sections are obtained (Fig 38,B). Disadvantageous, however, is the relatively poor depiction of the bony structures at the base of the skull. Angiography is important in some hypervascular masses either for purposes of further differentiation or for planning of therapy (see Fig 42). Occasionally, the surgeon needs to know the exact course of the carotid artery relative to a large tumor. Also, if sacrifice of the carotid artery is necessary for total resection, preoperative angiography with an evaluation of collateral circulation is indispensable. Some of these questions m a y be solved with DVA, but a more detailed study necessitates selective arteriography. Superselective arteriography of the nasopharynx is, in our opinion, necessary only in conjunction with therapeutic embolization. 49

Fic] 38.--Normal anatomy. A, T1/T2-balanced axial MR tomogram at level of nasopharynx. Fatty tissue adjacent to lateral wall of maxillary sinus (f), masseter muscle (m), lateral pterygoid muscle (pt), Iongus colli/capitis muscles (Ic), levator/tensor veli palatini muscles (curved arrow), torus tubarius (tiny white arrow), carotid sheath (arrowheads), mandibles (straight black arrows). B, Tl-weighted midsagittal MR tomogram of head and neck demonstrating nasopharynx, oropharynx, and hypopharynx. Sphenoid sinus (ss), clivus with bone marrow (curved arrow), hard palate (arrowhead), soft palate (sp), tongue (t), prevertebral soft tissues (black arrow), preepiglottic space (asterisk).

RADIOLOGIC PATHOLOGY Non-neoplastic lesions of the nasopharynx, except for hypertrophy of lymphoid tissue, are quite uncommon but need to be considered in the differential diagnosis.

Developmental Anomalies and Malformations In rare cases, a transsphenoidal encephalocele is the cause of a soft tissue mass in the pharyngeal fornix. The correct diagnosis is best made by HR-CT with coronal and lateral reformation, if necessary using intrathecal enhancement, but can be strongly suggested by plain films and the clinical examination. Occasionally, an amorphous calcification (most likely a r e m n a n t of the primitive notocord) m a y be seen in the otherwise normal soft tissue just posterior to the pharyngeal bursa.

Traumatic Disorders Fractures through the basisphenoid are rather uncommon lesions. Not so uncommon, however, are injuries to the upper cervical spine, some of which are unaccompanied by neurological deficit and easily overlooked on routine x-ray examinations. These lesions usually go along with significant soft tissue swelling at the posterior pharyngeal wall.

Inflammatory Disorders The pharyngeal tonsil (later in life becoming the bursa) as well as the lateral walls of the nasopharynx m a y be involved in 5o

a number of nonspecific inflammations, also in generalized sarcoidosis. Tuberculosis, which in an advanced stage closely mimics neoplastic disease, is rare now. More frequent is nasopharyngeal spread of rhinocerebral fungal disease in immunosuppressed patients or patients debilitated from various other causes. Mucormycosis is found in the majority of these cases, the differential diagnosis again being a malignancy.

Neoplastic Disorders Clinical symptoms and signs suggestive of tumor in the nasopharyngeal region include serous otitis media secondary to obstruction of the Eustachian tube, stuffiness of the nose especially with recurrent epistaxis, various neurological syndromes, and enlarged cervical lymph nodes. Benign lesions are the exception rather than the rule, and this applies to neoplasms originating within the nasopharynx proper as well as to neoplasms involving primarily the parapharyngeal space. Among the more common benign lesions, the juvenile angiofibroma is probably best known. This unusual neoplasm, seen almost exclusively in pubescent males, is very vascular and grows through preexisting canals, fissures and foramina at the base of the skull. It may also enter the paranasal sinuses, the orbits, and the intracranial space. As a rule, there is only bone displacement and not bone erosion. A characteristic, almost pathognomonic radiological sign, particularly well seen on axial CT images, is anterior bowing of the posterior wall of the maxillary sinus (Fig 39). This occurs when the tumor spreads from its presumed site of origin at the sphenopalatine foramen 47 into the infratemporal fossa. Occasionally, this "antral bowing sign" is seen in other (not always benign) slowly progressive mass lesions (Fig 40). If the tumor grows medially, it protrudes into the nasopharynx and may block one or both posterior nares. The

Fig 3g.--Antral bowing or anterior bowing of posterior wall of maxillary sinus, characteristic, but nonspecific sign of juvenile angiofibroma; 19-year-old man. A, axial CT scan at level of maxillary antra shows nasopharyngeal mass (T) extending into nasal cavity anteriorly and subtemporal fossa laterally; note widening of pterygopalatine fossa (arrow) due to bone displacement. B, conventional lateral tomogram corroborates CT findings; asterisk denotes widened pterygopalatine fossa. 51

Fig 40.--Embryonal rhabdomyosarcoma exhibiting antral bowing sign; 5-year-old boy. Axial CT scan at level of maxillary antra demonstrates large subtemporal mass of slightly lower density than muscle and normal adenoid tissue (ad). Posterior wall of left antrum is displaced anteriorly (arrowheads), suggesting slow growth of lesion, but simultaneous destruction of left pterygoid process is consistent with malignant process; undisturbed pterygoid process (pt) on right; area of calcification at lateral tumor border (arrow).

diagnosis is made clinically. However, CT in axial or coronal planes is presently the single most useful radiological method of investigation, indispensable for delimiting the exact tumor extent (Fig 41). The angioarchitecture of angiofibromas is quite typical, although today selective external and internal carotid angiography is needed mainly to determine the feeding vessels (Fig 42). Preoperative embolization is routinely used to prevent excessive blood loss during surgical resection. The differential diagnosis of angiofibromas includes angiomatous polyp, 4s lymphoma, rhabdomyosarcoma, and also nasopharyngeal carcinoma, which does occur in the second decade of l i f e 9 These lesions enhance less on CT and angiographically appear only moderately vascular. Other benign lesions arising in the parapharyngeal space secondarily bulge into the naso-oropharynx from the side. Among them are tumors, which originate within or extend into the carotid sheath. These are usually well circumscribed and enhance inhomogeneously (neuromas/neurofibromas) or homogeneously (glomus jugulare/glomus vagale tumors). 44 The rare lipomas, teratomas, dermoid cysts, and branchial cleft cysts are recognized on CT by virtue of their low density as well as other rela52

Fig 41.--Juvenile angiofibroma; 10-year-old boy. A, non-contrast axial CT scan at level of nasopharynx permits no differentiation between tumor and normal adenoid tissue. B, corresponding scan after intravenous contrast administration clearly delimits markedly enhancing mass. C, reformatted coronal section at level of pterygoid processes (pt) shows lesion wedged between these structures. D, reformatted midsagittal section reveals tumor (T) bulging into sphenoid sinus (closed arrows); open arrow points to spheno-occipital synchondrosis; asterisk denotes normal adenoid tissue. E, Tl-weighted midsagittal MR tomogram corroborates findings in D; tumor (I"); component protruding into sphenoid sinus (arrow). tively specific features. Even rarer are meningiomas, pituitary adenomas, craniopharyngiomas, chondromas, and chordomas growing into the region under discussion from above. Thornwaldt's cyst, a peculiar lesion involving the pharyngeal bursa, has a rather typical roundish-smooth appearance and is not uncommon. Benign neoplasms arising from the major and minor salivary glands are discussed in the respective section. The most important malignant tumor is the nasopharyngeal carcinoma, which must be considered whenever deep soft tissue infiltration into the parapharyngeal or retropharyngeal spaces is present (Fig 43,A). Normally these spaces appear perfectly symmetric and fat planes are well seen. Various types of squamous cell carcinomas including lymphoepitheliomas dominate the scene with adenocarcinomas representing only about one fifth of the lesions. The distinction between histological groups cannot be made radiographically. CT is particularly helpful when the clinical examination does not reveal an abnormality. Certain carcinomas that have already spread into the parapharyngeal or retropharyngeal spaces, leave the mucosal surface intact. 4~ In this respect, MRI seems to be even more sensitive, showing, on spin echo images, high-intensity lesions separable from the muscles, s' 48 Bone destruction, most frequent around the formen lacerum, may be well seen on axial CT scans but is 53

Fig 42.--Recurrent juvenile angiofibroma; 20-year-old man. In addition to main vascular supply from branches of external carotid artery (not shown), major feeding arteries derive from internal carotid artery. Arrow points to Vidian artery within Vidian (pterygoid) canal at base of pterygoid process; bulk of mass lodged in nasopharynx and pterygopalatine fossa.

Fig 43.--Nasopharyngeal carcinoma with orbital and possible intracranial spread; 40-year-old man. A, axial CT scan at level of nasopharynx is remarkable for asymmetry of prominent soft tissues appearing somewhat more bulky on left (asterisk) and partial obliteration of fat planes on same side. B, axial scan after intravenous contrast administration reveals marked enlargement of enhancing left cavernous sinus (cs) presumably secondary to soft tissue mass at orbital apex/superior orbital fissure (arrow), causing venous obstruction and direct tumor invasion.

54

usually better depicted on coronal cuts and sagittal reformations. The same applies to intracranial spread (Fig 43,B). With high resolution techniques and intravenous contrast enhancement, CT is probably superior to the clinical examination in detecting cervical lymph node metastases. The t r e a t m e n t for nasopharyngeal carcinoma and other malignancies involving the nasopharynx is generally not surgical (Fig 44). Malignant neoplasms originating in the parapharyngeal space are predominantly adenocystic, acinic cell, or mucoepidermoid carcinomas. They do not enhance to any significant degree. 5° Lymphomas and various kinds of sarcomas are comparatively rare (Fig 45). Atypical facial pain, gradual onset of peripheral 7th nerve palsy or possible hemifacial spasm, and Horner's syndrome with other symptoms and signs are indications for HRCT scanning or MR imaging of the nasopharynx (and oropharynx) and adjacent spaces. 51 If a mass is found b u t cannot be differentiated further, CT-guided thin needle biopsy may provide the answer. 52 Miscellaneous Disorders Hypertrophy of adenoids, sometimes complicated by inflammation, m a y be quite pronounced, particularly in children and adolescents. The question of tumor can be settled with CT or MRI which show absence of deep tissue infiltration and retained pliability of the mucosa (Fig 46). In an adult, especially over 40, direct inspection and even biopsy is indicated for the same soft tissue alteration. Unilateral atrophy leading to a s y m m e t r y of parapharyngeal structures with widening of lateral nasal pharyngeal recesses, wasting of muscles, and increased fat, m a y be seen in mandibular dysfunction of various origins. 43

Fig 44.--Squamous cell nasopharyngeal carcinoma: effect of radiation therapy; 71-year-old woman. A, axial CT scan shows prominent nasopharyngeal soft tissues with bulk on right (asterisk) and obliteration of fat planes; irregularity and lucency at pharyngeal aspect of clivus (arrow) suggests invasion of bone. B, axial scan at slightly higher level after radiation proves considerable reduction of size of mass with restoration of fat planes on left; clivus appears normal in this section.

55

Fig 45.--Fibrosarcoma of subtemporal fossa indirectly affecting nasopharynx; 58year-old man. Axial CT scan at level of maxillary antra demonstrates large mass on right bulging medially into nasopharynx and extending laterally into subcutaneous tissue of cheek; portions of mandibular ramus and pterygoid process have been destroyed. Note marked anterior antral bowing with opacification of sinus due to obstruction of ostium.

Fig 46.--Normal pharyngeal tonsil in 5-year-old girl. T1weighted midsagittal MR tomogram allows clear differentiation between brighterappearing adenoid tissue (arrow) and darker- to blackappearing subjacent muscles, membranes, and bony structures.

56

OROPHARYNX AND FLOOR OF THE MOUTH BASIC ANATOMY

The region discussed in this chapter includes the base of the tongue and can be defined as that portion of the upper aerodigestive tract extending from the hard palate to the valleculae and pharyngoepiglottic folds (Fig 47). The oropharynx is separated from the nasopharynx during swallowing by contraction of the sphincter-like Passavant's muscle (which on CT is seen as a Ushaped band of soft tissue density at the level of the hard palate). This structure is composed of several interdigitated muscles and lymphoid tissue, and its normal thickness can vary widely. The lateral walls of the oropharynx are formed by the faucial pillars with the palatine tonsils between them. The palatoglossus muscle and the palatopharyngeus muscle covered by mucosa form the anterior and posterior tonsilar pillars, respectively, and blend with the thin medial pharyngeal constrictor posteriorly. Further inferiorly, these soft tissue structures are continuous with the glossopharyngeal sulci and the tongue base. The tough pharyngobasilar fascia separates the superficial structures surrounding the airway from the deep fat-containing

Fig 47.--Normal anatomy: oropharynx. Upper arrow points to hard/soft palate as border between nasopharynx and oropharynx; lower arrow points to level of valleculae and pharyngoepiglottic folds as border between oropharynx and hypopharynx. (From Feneis, H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976, Used by permission.) 57

parapharyngeal spaces laterally and serves as an anatomic boundary which is disrupated only by aggressive inflammatory and neoplastic processes. 3 While the superficial mucosal soft tissue structures m a y be normally asymmetric, the paraoropharyngeal space is less so. Directly posterior to the oropharyngeal airway and also separated from it by the pharyngobasilar fascia" are the prevertebral muscles (longus colli/capitis). The contents of the carotid sheaths are usually easily identified at the oropharyngeal level and lie posterolateral to the prevertebral muscles. The sheath itself does not serve as a boundary to pathologic processes. In the fat between the carotid sheaths and the prevertebral muscles are retropharyngeal lymph nodes normally less than 5 mm in diameter, which serve as first-order drainage of the nasopharynx. 43 The tongue is composed of intrinsic and extrinsic muscles which create well-defined, deep tissue planes often visible in CT scans (Fig 48). The largest extrinsic muscles are the geniohyoid and the genioglossus, paired muscles originating from the genial tubercle on the inner aspect of the anterior mandible. They are separated by a low-density, midline fibrous lingual septum. The intrinsic muscles are of lower attenuation than the extrinsic muscles. The lingual tonsil is normally asymmetric and irregular; located on the base of the tongue, it m a y extend a variable distance into the intrinsic tongue musculature. The mucosa of the base of the tongue is continuous with the pharyngeal surface of the epiglottis at the valleculae which are paired, usually

Fig 48.--Normal anatomy: axial CT scans of oropharynx after intravenous contrast enhancement. A, section at level of tonsillar pillars (white arrows) shows fatcontaining parapharyngeal space (ps), parotid gland (pg), styloid process (s), masseter muscle (ma), mandibular ramus (mr), medial pterygoid muscle (pt), internal carotid artery (c), internal jugular vein (j), Iongus colli/capitis muscles (black arrows), and midline lingual septum (arrowhead). B, section at level of angle of mandible in another patient demonstrates asymptomatic stone (S) in submandibular duct. genioglossus muscle (g), mylohyeid muscle (m), hyogtossus muscle (h), lingual arteries (arrows), internal carotid artery (c), internal jugular vein (j); oval low-density area anterior to lingual tonsil (arrowheads) represents intrinsic tongue muscles. C, section at slightly lower level in same patient as B shows both submandibular glands (smg) with lower portion of stone on right side; anterior belly of digastric muscle (a) is inferior to mylohyoid muscle (m); posterior belly (p) is lateral to carotid sheath; asymmetric appearance of lingual tonsil (arrows); sternocleidomastoid muscle (st). 58

asymmetric spaces separated by the median glossoepiglottic fold. The tip of the epiglottis projects cephalad to the body of the hyoid bone, and paired pharyngoepiglottic folds course posterolaterally from the epiglottis to the walls of the pharynx. The submandibular glands lie partly in the floor of the mouth and partly in the upper neck and are seen external to the mylohyoid muscle at the level of the mandibular angle (also see section on salivary glands). The parapharyngeat space shrinks inferiorly as it merges with the submandibular space surrounding the submandibular gland; there is no fat plane between the gland and the base of the tongue. The floor of the mouth is a crescentic space limited by the mylohyoid and hyoglossus muscles. There are lateral fat planes between the mylohyoid and genioglossus muscles anteriorly and between the mylohyoid and hyoglossus muscles posteriorly. The submandibular duct and the hypoglossal and lingual nerves course in this fat, and the lingual artery runs medial to the hyoglossus and genioglossus muscles. Knowledge of the position of these structures is important as hemigtossectomy requires an intact lingual artery and hypoglossal nerve. Deep cervical nodes are present around the jugular vein. The jugulodigastric node is usually found at the level of the body of the hyoid bone between the angle of the mandible and the anterior border of the sternocleidomastoid muscle, and can be normally up to 1.5 cm in diameter. 53 All other normal nodes are smaller, ranging from 3 to 10 mm. IMAGING TECHNIQUES

Plain film radiography and conventional tomography show lesions that arise from the mucosal surfaces, the vast majority being squamous cell carcinomas with origin from tonsillar pillars, floor of the mouth, or base of the tongue. These tumors, however, are usually easily detectable by inspection. Conservation surgery and refined radiation therapy techniques require precise definition of the margins of such masses, often impossible by physical examination and certainly out of reach of conventional x-ray technique. Computed tomography is therefore presently the modality of choice (Fig 48). It is performed in a manner similar to that of the nasopharynx: For axial cuts, the patient is positioned in slight neck extension so that the hard palate is parallel to the scan plane. A lateral digital radiogram m a y be of value to plan gantry angulation when dental artifacts are a problem; direct coronal scanning is sometimes useful, too. Contiguous 4- to 5mm sections are obtained from above the hard palate to the body of the hyoid bone. The patient is asked to hold his breath and refrain from swallowing during scans to minimize motion artifact. Contrast enhancement m a y be useful to identify the lingual 59

arteries, distinguish carotid sheath vessels from masses, diagnose vascular lesions such as paragangl~omas, and in the differential diagnosis of lymphadenopathy. After the initial set of plain scans, 50 m l o f contrast medium are given as an intravenous bolus injection, the scans then being repeated during rapid drip infusion (150 ml total). Magnetic resonance imaging will be useful in this region because of multiplanar data acquisition and high soft tissue contrast (Figs 38,B and 49). 54 Lymph nodes can be differentiated from vessels without the use of parenterally administered contrast, and tumor has different signal intensity from muscle and inflammatory disease. Current units suffer from lack of spatial resolution, though, and widespread use of this technique will depend upon development of high resolution radiofrequency coils. Angiography is rarely employed in evaluation of the oropharynx and floor of the mouth b u t is necessary in the preoperative evaluation of paragangliomas.

Fig 49.--Normal anatomy: Tl-weighted MR tomogram at level of oropharynx. Mandible (m), tongue (t), posterior belly of digastric muscle (arrow), internal carotid artery (c), internal jugular vein (j), vertebral artery (v) passing through transverse foramen of C3 (asterisk), Iongus colli/capitis muscles (Ic), sternocleidomastoid muscle (st), external jugular vein (arrowhead). 60

RADIOLOGIC PATHOLOGY

Developmental Anomalies and Malformations Lingual thyroid tissue is readily distinguished from neoplasms (usually malignancies) as it contains iodine and therefore has a high density on plain CT. The ectopic tissue is seen as a mass at the base of the tongue that enhances considerably more than the surrounding musculature after intravenous contrast administration. Thyroglossal duct cysts are found in the anterior midline anywhere from the base of the tongue to the thyroid gland; they are non-enhancing, fluid density lesions. 43 The relationship of such a cyst to the body of the hyoid bone is important in surgical planning. Malformations of the tongue not associated with a mass are beyond the scope of this monograph.

Inflammatory Disorders Masses of infectious origin have a nonspecific appearance, but clinical symptoms usually prompt the correct diagnosis. There m a y be a history of dental or pharyngeal infection, tuberculosis, swallowed foreign body, or traumatic intubation. The presence of gas bubbles in the soft tissue mass makes the diagnosis more certain.

Neoplastic Disorders Benign masses in the oropharynx other than those of salivary gland origin (see following section) are unusual. Paragangliomas (glomus jugulare/vagale/caroticum tumors) and neuromas arise in the carotid sheath and have characteristic enhancement patterns. The glomus tumors will show intense

Fig 50.--Carotid sheath paraganglioma (carotid body tumor); 69-year-old man. A, non-contrast axial CT scan at low oropharyngeal level demonstrates tumor mass (T) bowing posterior belly of digastric muscle (p) laterally, and encroaching medially on oropharynx (arrow); submandibular gland (s). B, corresponding scan after intravenous contrast enhancement reveals marked, homogeneous increase in density of lesion; higher noise level is due to thinner section thickness (2 mm) than in A (4 mm). 61

homogeneous enhancement (Fig 50) while the neuromas often have peripheral rim enhancement and tow attenuation centers (necrosis). The most frequent indication for CT of the oropharynx is known or suspected squamous cell carcinoma. These tumors can arise from any mucosal surface and infiltrate locally, causing thickening of the soft tissues and loss of n o r m a l fat planes (Figs 51 and 52). The tumor m a y spread to lymph nodes or to adjacent regions of the upper aerodigestive tract, i.e., hase of tongue to supraglottic larynx. The degree of deep tumor infiltration and adenopathy m a y be impossible to assess clinically. The clinician needs to know if the tumor crosses the midline or if a base of tongue lesion invades both lingual arteries or hypoglossal nerves.55, 56 Trismus, pain, or hyperactive gag reflex m a y preclude adequate palpation in base of tongue lesions. Many oropharyngeal scans are performed to re-stage patients who have undergone surgery and radiation therapy for epidermoid carcinoma. Anatomic distortions then add difficulty to the interpretation; therefore, a baseline CT should be performed six weeks after completion of therapy. In this context, t h e noncon-

Fig 51.--Squamous cell carcinoma of base of tongue; 81-year-old man. A, axial CT scan at low oropharyngeal level demonstrates soft tissue mass in tongue base, more prominent on left; lack of invasion suggested by preservation of lateral fat plane (arrows) and intact submandibular space (arrowhead); submandibular gland (s), internal carotid artery (c), internal jugular vein (j). B, scan at slightly lower level, however, shows tumor (T) having obliterated valleculae. C, scan at level of body of hyoid bone reveals extension of tumor into preepiglottic space (arrowheads) and marked enlargement of left aryepiglottic fold (aef). 62

Fig 52.--Carcinoma of tonsil; 61-year-old woman..&, axial CT scan after intravenous contrast enhancement at level of tonsillar fossa shows large tumor on right invading alveolar ridge of maxilla (white arrow), and extending into buccomasseteric region (arrowheads); considerable neoplastic spread across midline posteriorly. Note asymmetry of parapharyngeal spaces; black arrow points to necrotic retropharyngeal lymph node metastasis; internal carotid artery (c), internal jugular vein (j). B, scan at somewhat higher level reveals tumor extending into nasopharyngeal region with probable bilateral retropharyngeal adenopathy; partial opacification of both maxillary sinuses; internal carotid artery (c), internal jugular vein (j). trast scans are omitted. 57 The deep tissue planes and lymph nodes are near normal if therapy has completely eradicated the tumor. A bulky mass should be considered evidence of residual or recurrent tumor, however. Obliteration of tissue planes alone, without a mass, is an unreliable sign of tumor. When patient m a n a g e m e n t depends upon equivocal CT findings, biopsy should be performed. 5e Adenopathy m a y be due to metastatic carcinoma, lymphoma, or inflammatory disease. Recent reports suggest a role of CT in evaluation of difficult cases. 5s' 59 Retropharyngeal nodes larger t h a n 1 cm are abnormal. Inflammatory nodes may show thick rim enhancement. 6e Mancuso et al. 53' 5s feel t h a t metastatic epidermoid carcinoma should be strongly suspected in nodes with rim enhancement and low attenuation (necrotic) centers. Although the n u m b e r of cases is small, metastatic adenocarcinoma and lymphoma produced neither necrosis nor rim enhancement in their series. Necrosis must be differentiated from focal fatty replacement within nodes, a relatively common normal variant. Normal lymph nodes do not enhance after intravenous contrast administration. SALIVARY

GLANDS

BASIC ANATOMY The three major salivary glands are the parotid, the submandibular, and the sublingual gland (Fig 53). Numerous additional 63

Fig 53.--Normal anatomy: salivary glands. Greater sublingual duct (1), lesser sublingual ducts (2), sublingual gland (3), submandibular gland (4), submandibular or Wharton's duct (5), parotid gland with superficial and deep portion (6), accessory parotid gland (7), parotid or Stensen's duct (8), masseter muscle (9). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/Georg Thieme Publishers, 1976. Used by permission.)

minor salivary glands rarely exceeding 1 to 2 mm in diameter are found in the submucosal tissue of the oral and pharyngeal cavities. Ectopic salivary tissue may be the origin of most of the extraparotid benign mixed tumors occurring in the parapharyngeal space. 44 The parotid gland is about twice the size of the submandibular gland. Its superficial portion has a sharp anterior border and covers the masseter muscle posteriorly as well as the angle of the mandible. Its smaller deep portion extends medially between the mandible in front and the external auditory canal and sternocleidomastoid muscle behind, eventually coming in contact with or close to the digastric muscle posteriorly, the medial pterygoid muscle anteriorly, and the styloid muscle group medially; the carotid sheath is abutted posteromedially. This division is a practical (serving surgical needs) rather than an anatomical one, the structure that separates the 64

two portions being the facial nerve. After its exit from the stylomastoid foramen, the 7th cranial nerve runs a short distance on the lateral surface of the posterior belly of the digastric muscle, then continues in the parotid gland. There it remains lateral to the retromandibular vein and external carotid artery before eventually ramifying. Stensen's duct with an overall length 5 to 6 cm originates at the anterior aspect of the gland, and after having crossed the anterior surface of the masseter, turns abruptly medially and pierces the buccinator muscle. It terminates on a mucosal papilla in the oral vestibule, just opposite the second upper molar. Rather frequently an accessory parotid gland is present next to the duct. The submandibular gland (also see foregoing section) occupies most of the submandibular trigone, inferiorly covered only by ptatysma and the superficial cervical fascia. Anteromedially, the gland abuts on the anterior belly of the digastric muscle, posteromedially on the posterior belly and on the stylohyoid muscle. Laterally it is bordered by the body of the mandible and the medial pterygoid muscle. The structure above is the mylohyoid muscle, b u t the gland also has an extension that continues around the posterior margin onto the upper surface of this muscle. Wharton's duct (length about 5 cm) originates within this "deep" portion, turns similarly around the mylohyoid muscle, and then runs anterosuperiorly in order to terminate on the sublingual papilla next to the frenulum. The sublingual gland is the smallest of the three major salivary glands and consists of a conglomerate of 10 to 20 small glands, each having its own short excretory duct at and posterior to the sublingual papilla. IMAGING TECHNIQUES

Plain film radiography has limited application but may be utilized to demonstrate dystrophic glandular calcifications, radiopaque stones, and possibly bony changes involving the mandible. It is therefore an important part of sialography (see below). Conventional tomography is rarely employed because the anatomic structures focused upon are not particularly comp~ex. It has been used, however, in conjunction with sialography. Computed tomography is presently the method of choice whenever neoplastic disease is suspected. It m a y also furnish important information in inflammatory disease and a number of other conditions. Furthermore, CT can be performed in conjunction with contrast filling of the ductal system, either as primary CTsialography, or as a supplement to conventional sialography. For axial imaging, sections parallel to Reid's baseline are suitable, though the presence of dental fillings m a y force the radiologist to select different planes. Slice thicknesses of 4 to 5 mm are usually sufficient. The examination should span the region from 65

about the external auditory canal to a level somewhat below the angle of the mandible. Coronal imaging i~s not indispensable, but can be helpful in a given case. Intravenous contrast enhancement (bolus technique) is necessary only if considerable parapharyngeal mass extension is present and the question of extraparotid origin arises. Contrast filling of the ductal system, either with aqueous or oily contrast material, is the basis of CT-sialography, a technique t h a t facilitates differentiation of intrinsic from extrinsic parotid mass. 62' 63 On plain CT scans, the normal parotid gland is less dense t h a n the surrounding muscles but more dense t h a n fat. After intravenous enhancement, the retromandibular vein and external carotid artery are easily recognized. The submandibular gland appears somewhat denser t h a n the parotid, approaching the attenuation values of muscle (see Fig 48,A)Y On CT sialograms, intrinsic masses cause filling defects, whereas extrinsic masses deform and/or displace the glands. Conventional sialography essentially remains reserved for cases with a history suggesting sialolithiasis, or chronic inflammatory disease and granulomatous or autoimmune disease. 64' 85 Its continuing value is based on the detailed demonstration of the ductal system. For anatomical as well as clinical reasons, only parotid and less frequently submandibular sialography is performed. Cannulation of Wharton's duct i s somewhat more difficult t h a n cannulation of Stensen's duct. Oily media remain longer within the ductal system t h a n water-soluble substances. This makes CT-sialography technically easier; however, small radiolucent calculi m a y be obscured by dense contrast. Contraindications for sialography are known patient sensitivity to the contrast medium and acute salivary gland inflammation. Nuclear medicine imaging techniques are infrequently used. The normal salivary glands accumulate Technetium-99m pertechnetate over a relatively short period of time after intravenous injection. Increased concentration m a y be seen in acute inflammatory and granulomatous disease. Reduced concentration is present in Sjoegren's syndrome and neoplastic lesions except Warthin's tumors which show extensive radionuclide uptake. Magnetic resonance imaging m a y soon become a serious competitor for CT. The important vascular structures, e.g., the retromandibular vein, are consistently demonstrated without the use of contrast media (Fig 54). Differentiation of intrinsic from extrinsic parotid masses seems to be easier, but the signal characteristics of the various pathologic entities have not been established yet. Angiography is needed only in the exceptional case of an unusually vascular mass including arteriovenous malformation, or when the carotid artery is threatened by surgery. Ultrasonography m a y be utilized occasionally to distinguish between cyst and solid tumor. 66

Fig 54.--Normal anatomy: Tl-weighted MR tomogram at level of parotid glands. Parotid gland (pg), posterior belly of digastric muscles (closed arrows), sternocleidomastoid muscle (st), retromandibular vein (open arrow), carotid sheath (sh), medial pterygoid muscle (pt), parapharyngeal space (ps), mandible (arrowhead). RADIOLOGIC PATHOLOGY

Developmental Anomalies and Malformations Agenesis, hypoplasia, and cystic malformation of t h e salivary gland are r a t h e r rare. The former group especially m a y be associated with other abnormalities, which usually involve the face. CT, as a supplement to the physical examination, is sufficient in most cases.

Traumatic Disorders T r a u m a most frequently involves the parotid gland and Stensen's duct. Contusion of the glandular parenchyma m a y result in intracapsular hematoma. Severe blunt t r a u m a or penetrating injury m a y lead to laceration, including laceration of the main duct. Another possibility is the formation of a sialocele or of a fistula. Sialography, if necessary and feasible at all, should be performed with water-soluble rather t h a n oily contrast media. Extravasation and splaying or non-filling of secondary ducts may be seen under such circumstances. 67

Inflammatory Disorders Diseases of this kind are usually in the chronic stage when they come to the attention of the radiologist. Chronic sialadenitis presents clinically as recurrent episodes of painful salivary gland swelling. The most informative diagnostic procedure is still conventional sialography 63' 6~ which reveals a variable degree of "pruning" of the peripheral ducts along with some central sialectasis and irregularity of ductal lumina. There is dilatation of terminal ducts and acini with retention of contrast medium after drainage. These scattered collections appear nonuniform and distinctly different from the pseudo-sialectatic lesions seen in autoimmune diseases. ~6 Sialodochitis is characterized by dilatation of the main duct, which also shows multiple areas of concentric focal narrowing. Chronic sialadenitis as well as sialodochitis more frequently involve the parotid t h a n the submandibular or sublingual glands.

Neoplastic Disorders Parotid tumors comprise about 80% of all salivary gland neoplasms. The second and third most common lesions are those involving the minor salivary and submandibular glands, respectively. Benign mixed tumors (pleomorphic adenomas) far outnumber all other epithelial or mesenchymal masses, benign and malignant. Next in frequency are adenolymphomas or Warthin's tumors which, too, are benign, but unlike mixed tumors develop exclusively within parotid tissue. They also tend to be multiple, either with several masses on one side or a single mass on either side. Among the malignancies, the mucoepidermoid tumors predominate, representing 6% to 9% of all salivary tumors and about 30% of the m a l i g n a n t ones. 64 Again, by far the most common location is the parotid gland itself. The remaining malignancies are divided among the acinic cell tumors, the various carcinomas including m a l i g n a n t mixed tumors, and a number of non-epithelial neoplasms. Primary lymphomas, by the way, are rather rare, as are metastases. With MRI not yet established as a generally available, routine examination, the radiologic evaluation of the salivary glands in suspected neoplastic disease presently rests largely on CT. Conventional sialography is still of value, though, particularly when the distinction between tumorous and non-tumorous, e.g., chronic inflammatory, gland swelling has to be made. In the latter situation, the ductal system frequently shows fairly characteristic changes, such as sialectasis with or without luminal irregularity, peripheral pruning, etc. Neoplasms, on the other hand, chiefly displace the secretory ducts. Unfortunately, rather often it is not possible to differentiate benign from m a l i g n a n t lesions. Furthermore, peripherally located lesions m a y have the same sialographic appearance as j u x t a g l a n d u l a r masses, and small tumors m a y go unnoticed. It is here t h a t CT-sialography 68

comes into play. This method shows even rather small masses and supplies important topographic information, for example, on superficial versus deep lobe involvement and on location of the facial nerve relative to the lesion (Fig 55). The differentiation of intrinsic and extrinsic masses is greatly improved, as is the definition of the overall extent of a presumably neoplastic process identified on the conventional sialogram. 61-G3 If multiple nodular masses are present, the differential diagnosis is mainly between sarcoid (involving intraparotid lymph nodes) and Warthin's tumors. ~7 Plain CT scans, if necessary supplemented by intravenously enhanced scans, may in fact be diagnostically sufficient in a large proportion of parotid neoplasms including the salivary gland tumors originating in the parapharyngeal space (Fig 56). 44, ~5 Miscellaneous Disorders The procedure of choice in suspected sialolithiasis (especially after negative plain films) is sialography which also shows the degree of concomitant inflammatory change. In the vast majority of cases, the submandibular gland is involved, and the filling defect caused by the calculus will be seen in Wharton's duct. Salivary gland stones not visualized on conventional radiographs may, however, be quite conspicuous on CT scans. Unilat-

Fig 55.--Pleomorphic adenoma or benign mixed tumor or parotid gland; 57-yearold woman. Axial CT scan after contrasting right parotid gland with oily medium (CTsialogram) shows filling defect caused by tumor (T); lesion involves superficial portion of gland; small contrast-free area behind mandibular ramus (asterisk) contains retromandibular vein and external carotid artery (compare with left side, arrows). 69

Fig 56.--Pleomorphic adenoma or benign mixed tumor of parotid gland; 36-yearold woman. Axial CT scan demonstrates smoothly marginated, homogeneous mass (T) with significantly higher density than surrounding tissue; lesion confined to superficial portion of gland.

Fig 57.--Autoimmune pseudosialectasis of parotid gland; 29-year-old woman. A, lateral sialogram shows multiple small collections of contrast medium uniform in size and distribution, absence of most peripheral ducts, and moderate irregularity of lumen of Stensen's duct; overall caliber of Stensen's duct is within normal limits; arrow points to metallic tip of Rabinov catheter. B, lateral post-evacuation film reveals contrast collections to remain within the gland.

70

eral or bilateral hypertrophy of the masseter muscle, readily diagnosed by CT, is a rare disorder but, nevertheless, should be included in the differential diagnosis of masses of the parotid region. Sialosis or sialoadenosis primarily refers to the dystrophic changes of the parotid gland occurring in some of the major chronic metabolic or endocrine disorders. A pertinent feature is enlargement of the glands secondary to interstitial edema and fatty infiltration. Among the granulomatous diseases, sarcoid is the most likely to involve the salivary glands. Usually it presents with multiple nodules, which then have to be differentiated from Warthin's tumors. ~7 The so-called autoimmune diseases cause weakening of the ducta] walls, leading to variable degrees of what has been termed pseudo-sialectasis. 6~ The sialographic appearance is fairly characteristic with diffusely distributed, uniform "punctate" or globular extravasations of contrast material. Following drainage, these contrast collections remain within the gland (Fig 57). This disease m a y progress to "cavitary" and eventually "destructive" pseudo-sialectasis.

HYPOPHARYNX, LARYNX, AND ADJACENT STRUCTURES BASIC ANATOMY The neck extends from the mylohyoid muscle to the thoracic inlet and m a y be divided into four c o m p a r t m e n t s Y The visceral compartment contains the hypopharynx, larynx, trachea, esophagus, thyroid, and parathyroid glands. The two lateral compartments are the carotid sheaths and their contents. The jugular vein is posterior to the carotid artery high in the neck and courses gradually anterior to it at the thoracic inlet. The right jugular vein is usually larger than the left, and m a y be mistaken for an enlarged lymph node on non-contrast CT scans. The posterior compartment is the largest and contains the cervical spine and its flexor and extensor muscles. The larynx is a complex fibromuscular organ supported by a delicate cartilaginous skeleton and suspended by muscles and ligaments from various surrounding structures (Fig 58). The hyoid bone and the epiglottic, thyroid, arytenoid, and cricoid cartilages comprise the laryngeal skeleton. There is a large degree of variability in the mineralization of these structures. The hyoid bone, which surrounds the epiglottis, is composed of a thick anterior body and thinner lateral cornua. The normal separation between the parts of the hyoid bone should not be mistaken for fracture. The valleculae lie posterior to the hyoid bone and anterior to the epiglottis. They are frequently asymmetric in size. The epiglottis, a thin band of elastic cartilage which infrequently calcifies, is wider superiorly and tapers to a point (pe71

Fig 58.--Normal anatomy: frontal section of larynx (posterior view). Epiglottis (1), aryepiglottic fold (2), thyroid cartilage (3), false vocal cord (4), true vocal cord (5), thyroarythenoid muscle (6), cricothyroid muscle (7), cricoid cartilage (8), vocal muscle (9), rima vestibuli--cleft between false vocal cords (10). (From Feneis H.: Pocket Atlas of Human Anatomy. Chicago, Year Book Medical Publishers/ Georg Thieme Publishers, 1976. Used by permission.)

tiole) inferiorly. The epiglottis is attached anteriorly to the tongue by the median glossoepiglottic fold, which separates the air-containing valleculae, and posterolaterally to the pharynx by the bilateral pharyngoepiglottic folds (Fig 59). The thyroid cartilage is composed of paired alae which frequently calcify and may even contain a marrow cavity. The degree of mineralization m a y vary from side to side and simulate fracture or invasion by tumor. On CT scans, the V-shaped anterosuperior thyroid notch should not be mistaken for cartilaginous destruction or fracture (Fig 60,A). The infrahyoid strap muscles appear as a band of soft tissue density anterior and parallel to the thyroid alae. The paired arytenoid cartilages are pyramidal in shape and are situated just superior and slightly lateral to the top of the cricoid lamina (Fig 60). The vocal processes project anteriorly to attach to the vocalis muscle and define the true vocal cord level. At the false vocal cord level, the foot processes point superiorly and the muscular processes project posterolaterally. The arytenoid cartilages adduct and rotate toward the midline during phonation. The cricoid cartilage is the only complete ring of cartilage, and 72

Fig 59.--Normal anatomy: axial CT scans of hypopharynx after intravenous contrast enhancement. A, section at level of hyoid bone demonstrates valleculae (v) separated from each other by midline glossoepiglottic fold (arrow), and from vestibule (ve) by pharyngoepiglottic folds; arrowhead points to tip of epiglottis; external carotid artery (e), internal carotid artery (i), internal jugular vein (j). B, section 8-mm inferior to A shows fat-containing preepiglottic space (open arrow), continuing laterally into paralaryngeal space (closed arrow) and aryepiglottic fold (arrowhead); piriform sinus (p).

is the most important supporting structure of the larynx (Fig 61). It has a thin anterior arch and a taller posterior lamina. There is close apposition of the thyroid and cricoid cartilages at the cricothyroid joint, which should appear bilaterally symmetric. No detectable soft tissue should be visible on CT between the airway and inner border of the cricoid ring.

Fig 60.--Normal anatomy: axial CT scans of larynx. A, section at level of false vocal cords (arrows) shows thyroid notch (arrowhead) and irregular mineralization of thyroid cartilage, which should not be mistaken for fracture or destruction; foot processes of arytenoid cartilages (f), sternocleidomastoid muscle (st), internal jugular vein (j), common carotid artery (c). B, section at level of true vocal cords (white arrowhead) demonstrates vocal processes (white arrow) of arytenoid cartilages (a) extending anteriorly; arytenoid cartilages located at superior aspect of cricoid lamina (black arrows); anterior commissure (black arrowhead) should be less than 2 mm in thickness. (From Glazer H.S., Sagel S.S.: The larynx and hypopharynx, in Carter B.D. (ed.): Computed Tomography of the Head and Neck. New York, Churchill Livingstone, Inc., 1985. (Used by permission,) 73

Fig 61.--Normal anatomy: axial CT scan of larynx at subglottic level. Note airway closely apposed to cricoid ring (black arrowheads) which is complete 4 mm below this level (not shown); inferior cornua (arrow) of thyroid cartilage articulate with cricoid; cricothyroid membrane (white arrowhead).

The intrinsic laryngeal soft tissue structures include the aryepiglottic folds, false vocal cords, and true vocal cords. The aryepiglottic (AE) folds are thin, paired structures that thicken as they course inferolaterally from the epiglottis to the arytenoid cartilages. The AE folds separate the piriform sinuses from the supraglottic airway (vestibule) and are continuous with the fatcontaining paralaryngeal and preepiglottic spaces inferior to the valleculae. The piriform sinuses, which are frequently asymmetric in size, are air-containing lateral recesses of the hypopharynx bordered by the AE folds medially and the thyroid alae laterally. The false vocal cords are visualized on CT as a thick band of soft tissue at the level of the foot processes of the arytenoids (Fig 60,A). There normally m a y be soft tissue thickening internal to the anterior aspect of the thyroid cartilage at the insertion of the thyroepiglottic ligament. The true vocal cords are triangular shaped structures, wider posteriorly than anteriorly (Fig 60,B). They are abducted during slow inspiration and there is normally only 1 to 2 mm of soft tissue density at the anterior commissure (where the vocal ligaments attach to the thyroid cartilage) or the posterior commissure (between the vocal processes of the arytenoid cartilages). If the true vocal cords are adducted, these areas m a y appear falsely thickened. 74

The soft tissue deep to the endolarynx consists primarily of fat and is therefore well visualized on CT. The fat-containing preepiglottic space extends inferiorly from the hyoid bone to the anterior commissure. It is bordered anteriorly by the thyrohyoid membrane and posteriorly by the epiglottis (Figs 59 and 60). The low density paralaryngeal space is contiguous with the preepiglottic space. It is bordered by the thyroid cartilage laterally, aryepiglottic folds medially, and piriform sinuses posteriorly. On cross section, the supraglottic portion of the laryngeal airway (laryngeal vestibule) is elliptical in shape. At the level of the true vocal cords, the anteroposterior diameter of the airway increases, while in the subglottic region, the airway is more circular with a flat posterior border at the level of the trachea (Figs 60 and 61). IMAGING TECHNIQUES

Plain film radiography and conventional tomography, utilizing film-screen and xerographic techniques, have previously enabled radiologists to localize lesions of the neck. Additional information was supplied from contrast laryngography and barium examinations (see below). Since the application of CT, the importance of these procedures has decreased. Computed tomography has greatly improved the evaluation of patients with t r a u m a and tumors of the hypopharynx and larynx.69, 70 In most centers it has completely replaced contrast laryngography in the evaluation of laryngeal carcinoma. The CT examination of t h e hypopharynx and larynx is performed with the patient supine with the neck mildly hyperextended in order to make the larynx perpendicular to the scanning plane. Contiguous 4- to 5-ram scans are performed from above the hyoid bone to the subglottic region. The sections are obtained during slow inspiration because less than adequate distention of the airway m a y cause the endotaryngeal soft tissues to appear falsely thickened. If there is a question of abnormality in the piriform sinus region, additional scans m a y be performed during phonation or modified Valsalva maneuver to distend the pyriform sinuses and optimize visualization of the aryepiglottic folds. In selected cases, intravenous administration of iodinated contrast medium may be helpful to improve separation of vessels from adjacent masses (Fig 59). Barium examination, when employed with air-contrast views and motion recording techniques, is still useful in evaluation of both structural and functional abnormalities. 71-73 Although it usually adds little to the complete clinical examination coupled with CT, the barium swallow can define the inferior margin of a mass when trismus, pain, o r bulky tumor preclude optimal direct visualization. It is also a good method to screen patients 75

referred by the non-ENT physician and can detect a second prim a r y in the esophagus. Fistulous tracts due to t r a u m a can be defined with water-soluble contrast. Magnetic resonance imaging is likely to become an important technique for radiologic examination of the neck. However, considerably further experience is necessary as is improvement in spatial resolution. Compared with CT, tumors and lymph nodes are more easily differentiated from musculature and adjacent blood vessels (see Fig 68,B and C). Unfortunately, some overlap of signal characteristics exists for a variety of neoplastic and inflammatory conditions. 54' 74, 75 Ultrasonography is useful in the evaluation of cystic neck masses and vascular abnormalities, e.g., jugular vein thrombosis. Some authors have also successfully used this imaging technique to evaluate cervical lymphadenopathy.7~ Angiography is still occasionally required to assess vascular tumors such as paragangliomas and to predict morbidity should sacrifice of a carotid artery become necessary in surgical removal of neck masses. RADIOLOGIC PATHOLOGY

Developmental Anomalies and Malformations A laryngocele is an abnormal enlargement of the saccule of the laryngeal ventricle (Fig 62). It may be confined to the paralaryngeal space (internal laryngocele) but sometimes extends through the thyrohyoid membrane into the neck (external laryngocele). External components of laryngoceles may present as a neck mass. Laryngoceles often communicate with the ventricle and are air-filled but m a y contain mucoid or purulent material and be more difficult to differentiate from tumor. On CT, fluidfilled laryngoceles m a y measure near water density, or they may measure soft tissue density if they contain mucoid or purulent material. The location, smooth border, and normal mucosa at laryngoscopy should suggest laryngocele. 77 Branchial cleft anomalies may occur as any combination of sinus, fistula, or cyst, and frequently do not present until young adulthood. 7s Those anomalies t h a t are not associated with a neck mass are probably best evaluated by injection of the tract with water-soluble contrast. The cystic lesions are usually second branchial cleft derivatives and m a y occur anywhere from the angle of the mandible to the clavicular head. The usual CT appearance is a round, fluid-density mass anteromedial to the sternocleidomastoid muscle, anterolateral to the carotid sheath, and posterior to the submandibular gland (Fig 63). 7s If the cyst is inflamed, there may be a thick, contrast-enhancing rim with surrounding edema. Cystic hygroma (lymphangioma) results from an abnormal development of lymphatic tissue and usually presents as an 76

Fig 62.--Air-filled internal laryngocele; 73-year-old woman. Axial CT scan at level of hyoid bone (h) reveals laryngocele (L) compressing and distorting the vestibule (v). (From Glazer H.S., Siegel M.: Radiology of the larynx, in Cummings C.W. et al. (eds.): Otolaryngology--Head and Neck Surgery. St. Louis, C.V. Mosby Co., in press. Used by permission.)

Fig 63.--Branchial cleft cyst; 39-year-old man. Axial CT scan after intravenous contrast administration reveals large nonenhancing mass of fluid density with smooth borders; location of lesion is anteromedial to sternocleidomastoid muscle (st); carotid artery (c), internal jugular vein (j). 77

asymptomatic mass in the posterior triangle of the neck. 79 The typical CT appearance is a well defined, fluid-density mass posterior to the sternocleidomastoid muscle. CT m a y also be helpful in showing extension of the mass into the mediastinum.

Traumatic Disorders Because of its cross-sectional display, CT is an excellent w a y to evaluate the airway after blunt t r a u m a to the neck. 7°' so, sl In particular, CT is helpful in patients with marked supraglottic swelling, which m a y compromise adequate laryngoscopic evaluation. CT expedites determination of the extent of cartilaginous damage, hematoma, and edema, as well as of the amount of airway compromise (Fig 64). Transverse or vertical fractures of thyroid or cricoid cartilages, dislocation of the arytenoid cartilage at the cricoarytenoid joint, separation of the cricothyroid joint, as well as avulsion of the base of the epiglottis can all be demonstrated by CT. Inflammatory Disorders Inflammatory lesions of the larynx are relatively common in children and can usually be evaluated with plain film radiography. In complicated problems, however, CT may be helpful in showing small gas bubbles not apparent on conventional radiography. CT can also detect spread of inflammatory masses into the mediastinum. Neoplastic Disorders CT has become an important complementary imaging procedure to laryngoscopy in the evaluation of patients with laryngeal carcinoma. The clinical decision between radiation therapy,

Fig 64.--Laryngeal trauma: 23-year-old man. A, axial CT scan at level of thyroid notch is remarkable for enlargement of right aryepiglottic fold (a) and paralaryngeal space with obliteration of right piriform sinus secondary to hemorrhage and/or edema; air in soft tissue of neck caused by emergency tracheostomy. B, scan at lower level reveals fracture of posterolateral cricoid lamina (arrow) as well as swelling of right true vocal cord (arrowhead). (From Glazer H.S., Sagel S.S.: The larynx and hypopharynx, in Carter B.L. (ed.): Computed Tomography of the Head and Neck. New York, Churchill Livingstone, Inc., 1985. Used by permission.) 78

conservation surgery, or total laryn~ectomy requires an accurate demonstration of tumor extent, s~ While contrast laryngography and plain film radiography give similar information to laryngoscopy, CT may show deep extension of tumor and cartilaginous invasion not suspected clinically. Laryngoscopy remains the best procedure for detecting mucosat abnormalities and glottic function. Neoplasm is seen on CT as an abnormal area of soft tissue density that m a y result in laryngeal a s y m m e t r y (Figs 65 and 66). These findings, however, are nonspecific and m a y be secondary to hemorrhage, fibrosis, edema, or inflammation. Therefore, CT findings must be correlated with the clinical history. In order to prevent confusion with hemorrhage or edema, the examination should be performed prior to biopsy or at least 48 hours after biopsy. Supraglottic tumors arise at or above the false vocal cord level. Carcinoma of the epiglottis m a y result in thickening of the borders of the epiglottis or a large soft tissue mass. CT is helpful in demonstrating extension into the fat-containing preepiglottic or paralaryngeal spaces, frequently a difficult problem clinically. CT can also show deep spread of neoplasm to the anterior commissure. Supraglottic laryngectomy usually requires a 3- to 5mm free margin above the anterior commissure, s2 CT scans performed during phonation or modified Valsalva maneuver are helpful in demonstrating tumors of the aryepiglottic fold. Piriform sinus carcinomas are locally aggressive and metastasize to lymph nodes more frequently than other supraglottic neoplasms. There is also a high incidence of thyroid cartilage invasion with these tumors. Unilateral obliteration of the piriform sinus, ipsilateral widening of the cricothyroid joint, and

Fig 65.--Carcinoma of piriform sinus with transglottic extension; 61-year-old man. A, axial CT scan at level of thyroid notch demonstrates large tumor arising in left piriform sinus and compressing laryngeal vestibule (v). B, scan at somewhat lower level reveals tumor (T) involving left true vocal cord and characteristically widening thyroarytenoid joint (arrow). (From Glazer H.S., Siegel M.: Radiology of the larynx, in Cummings C.W. et al. (eds.): Otolaryngology--Head and Neck Surgery. St. Louis, C.V. Mosby Co., in press. Used by permission.) 79

Fig 66.--Carcinoma of true vocal cord with subglottic extension; 53-year-old man. A, axial CT scan at level of vocal cords shows thickening of anterior commissure (arrowhead) and tumor of left vocal cord extending posteromedially toward posterior commissure (arrows). 13, scan at subglottic level reveals inferior extension of tumor with thickening of soft tissue medial to cricoid cartilage on teft (arrows). (From Sagel S.S.: Larynx, in Lee J.K.T., Sagel S.S., Stanley R.J. (eds.): Computed Body Tomography. New York, Raven Press, 1983. Used by permission.)

extralaryngeal spread are characteristic of piriform sinus tumors (Fig 65). s3 If vocal cord carcinoma is confined to a normal mobile cord, it m a y be t r e a t e d with radiation t h e r a p y or partial laryngectomy. s2 In such patients, the CT examination m a y be normal or

Fig 67.--Laryngeal carcinoma with destruction of thyroid cartilage; 62-year-old man. Axial CT scan at level of cricoid lamina (open black arrows) reveals large defect of anterior aspect of both thyroid laminae and tumor invading extralaryngeal soft tissue (white arrows). 80

only demonstrate focal or diffuse thickening of the vocal cord. The primary role of CT in patients with true vocal cord tumors is in the evaluation of the anterior and posterior commissures, the subglottic space, and the thyroid and cricoid cartilages (Fig 66). An increase in thickness of the anterior commissure greater than 2 mm is abnormal and should be considered suspicious for tumor extension. Tumor that extends to the posterior commissure will result in thickening of the soft tissues over the arytenoid cartilages. The relationship between the tumor and the cricoid cartilage is important in determining subglottic extension of tumor. On CT there should not be any measurable soft tissue thickness between the airway and the cricoid cartilage. It is important not to mistake the undersurface of the true vocal cord for subglottic extension of tumor. Although CT can demonstrate cartilaginous invasion, there are limitations. The thyroid cartilage normally may have an irregular pattern of mineralization. Therefore, neoplastic involvement can only be confidently diagnosed when it is advanced (Fig 67). If the CT findings are equivocal, biopsy is necessary to substantiate the need for radical surgery. Transglottic tumors involve the supraglottic, glottic, and often subglottic regions of the larynx. They have a high incidence of cartilage involvement and extralaryngeal spread that m a y not be appreciated on physical examination, s4 CT m a y occasionally demonstrate enlarged lymph nodes that are not palpable on physical examination. 6s The relationship of enlarged nodes to adjacent vessels can be shown especially with the use of intravenous contrast. MRI can provide comparable information without the need for intravenous contrast (Fig 68). Recent reports suggest that CT m a y be helpful in evaluating patients who have undergone prior laryngeal surgery as it can

Fig 68.--Cervical lymphadenopathy in patient with unknown primary tumor; 52year-old man. A, axial CT scan after intravenous contrast enhancement at level of hyoid bone (h) demonstrates lymph node mass (T) on right, displacing adjacent vessels; sternocleidomastoid muscle (st), submandibular gland (smg). B, Tl-weighted MR tomogram at same level permits separation of tumor mass (T) from surrounding fat (f) and displaced vessels (arrows). C, corresponding TJT2-balanced image is useful for separating tumor (T) from adjacent sternocleidomastoid muscle (arrow). 81

demonstrate the normal anat om y of t he postoperative l arynx and clinically occult recurrences. SUMMARY AND OUTLOOK In cu r r en t E N T radiology, the single most valuable diagnostic method is, no doubt, high resolution CT. Although in daily practice, plain film r ad i ogr a phy m a y still be useful and entirely satisfactory in a n u m b e r of clinical situations, e.g., uncomplicated sinus disease, one could question w h e t h e r it is needed in cases complex enough to necessitate CT. Conventional tomography, too, has lost most of its previous importance. However, if facial or temporal bone structures are to be examined in planes unaccessible to CT for clinical or technical reasons, it remains the method of choice. Radionuclide studies have few indications but nevertheless m a y be more sensitive (as in m a l i g n a n t external otitis) or more specific (as in Wharthin's tumors of the parotid gland) t h a n CT. Ultrasonic imaging techniques are essentially limited to the eva l ua t i on of the major cervical vessels in neoplastic disease, and to the separation of cystic from solid neck masses. Angiography m a y no longer be m a n d a t o r y to diagnose confidently such lesions as juvenile angiofibromas or paragangliomas (glomus tumors) but is still needed, at least in the form e r neoplasms, prior to surgery and certainly before interventional occlusive procedures. The role of MRI has yet to be defined. This new noninvasive method with its lack of bone-induced artifacts and its great potential for soft tissue discrimination and vascular imaging unquestionably represents a big challenge for CT and may, in fact, supersede CT in several diagnostic areas. This seems to be r a t h e r likely, for example, in the evaluation of the cerebellopontine angle where invasive procedures such as air CT-cisternography are still unavoidable to rule out small mass lesions. Other areas m i ght be the nasopharynx with adjacent spaces, the oropharynx, and the salivary glands. How the m a i n weakness of MRI, i.e., its poor capability of visualizing bone, could be overcome, r em a ins to be seen. REFERENCES 1. Daniels D.L., Williams I.L., Haughton V.M.: Jugular foramen: Anatomic and computed tomographic study. A.J.N.R. 4:1227, 1983. 2. Bergeron R.T.: The temporal bone, in Bergeron R.T., Osborn AoG.,Som P.M. (eds.): Head and Neck Imaging; Excluding the Brain. St. Louis, C.V. Mosby Co., 1984. 3. Lufkin R., Barni J.J., Glen W., et al.: Comparison of computed tomography and pluridirectional tomography of the temporal bone. Radiology 143:715, 1982. 4. van Waes P.F.G.M., ZonneveldF.W., Damsma H., et al.: Direct multiplanar CT of the petrous bone. Exhibit, 9th International Congress of Radiology of Otorhinolaryngology,Fontevraud Abbey, France, 1982 (published by Philips Medical Systems). 82

5. Virapongse C., Rothman S.L.G., Kier E.L., et al.: Computed tomographic anatomy of the temporal bone. A.J.N.R. 3:379, 1982. 6. Chakeres D.W., Spiegel P.K.: A systematic technique for comprehensive evaluation of the temporal bone by computed tomography. Radiology 146:97, 1983. 7. Daniels D.L., Herfkins R., Koehler P.R., et al.: Magnetic resonance imaging of the internal auditory canal. Radiology 151:105, 1984. 8. Han J.S., Huss R.G, Benson J.E., et al.: MR imaging of the skull base. J. Comput. Assist. Tomogr. 8:944, 1984. 9. Modic M.T., Weinstein M.A., Chilcote W.A., et al.: Digital subtraction angiography of the intracranial vascular system: Comparative study in 55 patients. A.J.N.R. 2:527, 1981. 10. Djindjian R., Merland J.J.: Super-Selective Arteriography of the External Carotid Artery. New York, Springer-Verlag, 1978. 11. Jensen J., Rovsing H.: Tomography in congenital malformations of the middle ear. Radiology 90:268, 1968. 12. Terrahe K.: Diagnostik der Missbildungen des Ohres und des Ohrschaedels. Arch. klin. exp. Ohr-Nas-u. Kehlk. Heilk. 202:85, 1972. 13. Virapongse C., Rothman S.L.G., Sasaki C., et al.: The role of high resolution computed tomography in evaluating disease of the middle ear. J. Comput. Assist. Tomogr. 6:711, 1982. 14. Johnson D.W., Hasso A.N., Stewart C.E., et al.: Temporal bone trauma: high resolution computed tomographic evaluation. Radiology 151:411, 1984. 15. Mafee M.F., Kumar A., Yannias D.A., et al.: Computed tomography of the middle ear in the evaluation of cholesteatomas and other soft tissue masses: Comparison with pluridirectional tomography. Radiology 148:465, 1983. 16. Johnson D.W., Voorhees R.L., Lufkin R.B., et al.: Cholesteatomasof the temporal bone: role of computed tomography. Radiology 148:733, 1983. 17. Mendelson D.S., Som P.M., Mendelson M.H., et al.: Malignant external otitis: The role of computed tomography and radionuclides in evaluation. Radiology 149:745, 1983. 18. Swartz J.D., Goodman R.S., Russell K.B., et al.: High-resolution computed tomography of the middle ear and mastoid: Part II. Tubotympanic disease. Radiology 148:455, 1983. 19. Swartz J.D., Goodman R.S., Russell K.B., et al.: High-resolution computed tomography of the middle ear and mastoid: Part III. Surgically altered anatomy and pathology. Radiology 148:461, 1983. 20. Bird C.R., Hasso A.N., Stewart C.E., et al.: Malignant primary neoplasms of the ear and temporal bone studied by high-resolution computed tomography. Radiology 149:171, 1983. 21. Som P.M., Reede D.L., Bergeron R.T., et al.: Computed tomography of glomus tympanicum tumors. J. Comput. Assist. Tomogr. 7:14, 1983. 22. Lo W.W.M., Solti-Bohman L.G., Lambert P.R.: High-resolution CT in the evaluation of glomus tumors of the temporal bone. Radiology 150:737, 1984. 23. Solti-Bohman L.G., Magaram D.L., Lo W.W.M.: Gas-CT cisternography for detection of small acoustic nerve tumors. Radiology 150:403, 1984. 24. Swartz J.D., Faerber E.N., Wolfson R.J., et al.: Fenestral otosclerosis: significance of preoperative CT evaluation. Radiology 151:703, 1984. 25. Gado M.H., Arenberg I.K.: Radiological visualization of the vestibular aqueduct. Radiology 117:621, 1975. 26. Vannier M.W, Marsh J.L., Warren J.O.: Three-dimensional CT reconstruction images for craniofacial surgical planning and evaluation. Radiology 150:179, 1984. 27. Hesselink J.R., New P.F.J., Davis K.R., et al.: Computed tomography of the paranasal sinuses and face: Part I. Normal anatomy. J. Comput. Assist. Tornogr. 2:559, 1978. 28. Daniels D.L, Rauschning W., Lovas J., et al.: Pterygopalatine fossa: computed tomographic studies. Radiology 149:511, 1983. 29. Unger J.M., Chintapalli K.N.: Computed tomography of the parapharyngeal space. J. Comput. Assist. Tomogr. 7:605, 1983. 83

30. Som P.M.: The paranasal sinuses, in Bergeron R.T., Osborn A.G., Som P.M. (eds.): Head and Neck Imaging; Excluding the Brain. St. Louis, C.V. Mosby Co., 1984. 31. Higashi T., Aoyama W., Mori Y., et al.: Gallium-67 scanning in the differentiation of maxillary sinus carcinoma from chronic maxillary sinusitis. Radiology 123:117, 1977. 32. Zilkha A.: Computed tomography in facial trauma. Radiology 144:545, 1982. 33. Kreipke D.L., Moss J.J., Franco J.M., eta].: Computed tomography and thinsection tomography in facial trauma. A.J.N.R. 5:185, 1984. 34. Hammerschlag S.B., Hughes S., O'Reilly GN., et al.: Blow-out fractures of the orbit: A comparison of computed tomography and conventional radiography with anatomical correlation. Radiology 143:487, 1982. 35. Manelfe C., CeUerier P., Sobel D., et al.: Cerebrospinal fluid rhinorrhea: evaluation with metrizamide cisternography. A.J.N.R. 3:25, 1982. 36. Som P.M., Shugar J.M.A.: The CT classification of ethmoid mucoceles. J. Comput. Assist. Tomogr. 4:199, 1980. 37. Parsons C., Hodson N.: Computed tomography of paranasal sinus tumors. Radiology 132:641, 1979. 38. Momose K.J., Weber A.L., Goodman M., et al.: Radiological aspects of inverted papilloma. Radiology 134:73, 1980. 39. Som P.M., Shugar J.M.A.: The significance of bone expansion associated with the diagnosis of malignant tumors of the paranasal sinuses. Radiology 136:97, 1980. 40. Kondo M., Hashimoto T:, Shiga H., et al.: Computed tomography of sinonasal non-Hodgkin lymphoma. J. Comput. Assist. Tomogr. 8:216, 1984. 41. Curtin H.D., Williams R., Johnson J.: CT of perineural tumor extension: Pterygopalatine fossa. A.J.N.R. 5:731, 1984. 42. Mancuso A.A., Bohman L., Hanafee W., et al.: Computed tomography of the nasopharynx: Normal and variants of normal. Radiology 137:113, 1980. 43. Mancuso A.A., Som P.M.: The upper aerodigestive tract (nasopharynx, oropharynx, and floor of the mouth), in Bergeron R.T., Osborn A.G., Som P.M. (eds): Head and Neck Imaging: Excluding the Brain. St. Louis, C.V. Mosby Co., 1984. 44. Som P.M., Bitler H.F., Lawson W., et al.: Parapharyngeal space masses: an updated protocol based upon 104 cases. Radiology 153:149, 1984. 45. Doubleday L.C., Jing B-S, Wallace S.: Computed tomography of the infratemporal fossa. Radiology 138:619, 1981. 46. Dillon W.P., Mills C.M., Kjos B., et al.: Magnetic resonance imaging of the nasopharynx. Radiology 152:731, 1984. 47. Bryan R.N., Sessions R.B., Horowitz B.L.: Radiographic management of juvenile angiofibromas. A.J.N.R. 2:157, 1981. 48. Som P.M., Cohen B,A., Sacher M., et al.: The angiomatous polyp and the angiofibroma: Two different lesions. Radiology 144:329, 1982. 49. Vita H.C., Mendiondo O.A., Shaw D.L:, et al.: Nasopharyngeal carcinoma in the second decade of life. Radiology 148:253, 1983. 50. Sore P.M.: The parapharyngeal space, in Bergeron R.T., Osborn A.G., Som P.M. (eds.): Head and Neck Imaging; Excluding the Brain. St. Louis, C.V. Mosby Co., 1984. 51. Kalovidouris A., Mancuso A.A., Dillon W.: A CT-clinical approach to patients with symptoms related to the V, VII, IX-XII cranial nerves and cervical sympathetics. Radiology 151:671, 1984. 52. Gatenby R.A., Mulhern C.B. Jr., Richter M.P., et al.: CT-guided biopsy for the detection and staging of tumors of the head and neck. A.J.N.R. 5:287, 1984. 53. Mancuso A.A., Harnsberger H.R., Muraki A.S., et al.: Computed tomography of the cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head and neck cancer. Radiology 148:709, 1983. 54. Lufkin R.B., Larsson S.G., Hanafee W.N.: Work in progress: NMR anatomy of the larynx and tongue base. Radiology 148:173, 1983. 84

55. Larsson S.G., Mancuso A., Hanafee W.: Computed tomography of the tongue and floor of the mouth. Radiology 143:493, 1982. 56. Muraki A.S., Mancuso A.A., Harnsberger H.R., et al.: CT of the oropharynx, tongue base, and floor of the mouth: Normal anatomy and range of variations, and applications in staging carcinoma. Radiology 148:725, 1983. 57. Harnsberger H.R., Mancuso A.A., Muraki A.S., et al.: The upper aerodigestive tract and neck: CT evaluation of recurrent tumors. Radiology 149:503, 1983. 58. Mancuso A., Harnsberger H.R., Muraki A.S., et at.: Computed tomography of cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head and neck cancer. Part II. Pathology. Radiology 148:715, 1983. 59. Muraki A.S., Mancuso A.A., Harnsberger H.R.: Metastatic cervical adenopathy from tumors of unknown origin: The role of CT. Radiology 152:749, 1984. 60. Reade D.L., Whelan M.A., Bergeron R.T.: Computed tomography of the infrahyoid neck. Part II. Pathology. Radiology 145:397, 1982. 61. Carter B.L., Karmody C.S., Blickman J.R., et al.: Computed tomography and sialography: I. Normal anatomy. J. Comput. Assist. Tomogr. 5:42, 1981. 62. Som P.M., Biller H.F.: The combined CT-sialogram. Radiology 135:387, 1980. 63. Stone D.N, Mancuso A.A., Rice D., et al.: Parotid CT sialography. Radiology I38:393, 1981. 64. Som P.M, Sanders D.E.: The salivary glands, in Bergeron R.T., Osborn A.G., Som P.M. (eds.): Head and Neck Imaging; Excluding the Brain. St. Louis, C:V. Mosby Co., 1984. 65. McGahan J.P., Walter J.P., Bernstein L.: Evaluation of the parotid gland. Comparison of sialography, non-contrast computed tomography, and CT sialography. Radiology 152:453, 1984. 66. Som P.M., Shugar J.M.A., Train J.S., et al.: Manifestations of parotid gland enlargements: Radiographic, pathologic, and clinical correlations. Part I. The autoimmune pseudosialectasias. Radiology 141:415, 1981. 67. Som P.M., Shugar J.M.A., Train J.S., et al.: Manifestations of parotid gland enlargement: Radiographic, pathologic, and clinical correlation. Part II. The diseases Of Miculicz syndrome. Radiology 141:421, 1981. 68. Mancuso A.A.: Computed tomography of the neck, in Moss A.A., Gamsu G., Genant H.K. (eds.): Computed Tomography of the Body. Philadelphia, W.B. Saunders Co., 1983. 69. Sagel S.S., AufderHeide J.F., Aronberg D.J., et al.: High resolution computed tomography in the staging of carcinoma of the larynx. Laryngoscope 91:292, 1981. 70. Gamsu G.: Computed tomography of the larynx and piriform sinuses, in Moss A.A., Gamsu G., Genant H.K. (eds.): Computed Tomography of the Body. Philadelphia, W.B. Saunders Co., 1983. 71. Donner M.W.: Swallowing mechanism and neuromuscular disorders. Semin.Roentgenol. 9:273, 1974. 72. Balfe D,M, Koehler R.E., Setzen M., et al.: Barium examination of the esophagus after total laryngectomy. Radiology 143:501, 1982. 73. Ekberg O., Nylander G.: Pharyngeal dysfunction after treatment for pharyngeal cancer with surgery and radiotherapy. Gastrointest. Radiol. 8:97, 1983. 74. Stark D.D., Moss A.A., Gamsu G., et al.: Magnetic resonance imaging of the neck. Part I. Normal anatomy. Radiology 150:447, 1984. 75. Stark D.D., Moss A.A., Gamsu G., et al.: Magnetic resonance imaging of the neck: Part g. Pathologic findings. Radiology 150:455, 1984. 78. Bruneton J.N., Roux P., Caramella E., et al.: Ear, nose, and throat cancer: ultrasound diagnosis of metastasis to cervical lymph nodes. Radiology 152:771, 1984. 77. Glazer H.S., Mauro M.A., Aronberg D.J., et al.: Computed tomography of laryngoceles. A.J.R. 140:549, 1983. 78. Harnsberger H.R., Mancuso A.A., Muraki A.S., et at.: Brachial cleft anom85

79. 80. 81. 82. 83. 84. 85.

alies and their mimics: Computed tomographic evaluation. Radiology 152:739, 1984. Silverman P.M., Korobkin M., Moore A.V.: Computed tomography of cystic neck masses. J. Comput. Assist. Tomogr. 7:498, 1983. Mancuso A.A., Hanafee W.N.: Computed tomography of the injured larynx. Radiology 133:139, 1979. Sagel S.S.: Larynx, in Lee J.K.T., Sagel S.S., Stanley R.J. (eds.): Computed Body Tomography. New York, Raven Press, 1983. Ogura J.H., Heeneman H.: Conservation surgery of the larynx and hypopharynx--selection of patients and results. J. Otolaryngol. 2:11, 1973. Larsson S., Mancuso A., Hoover L., et al.: Differentiation of piriform sinus cancer from supraglottic laryngeal cancer by computed tomography. Radiology 141:427, 1981. Tucker G.F.: The anatomy of laryngeal cancer. J. Otolaryngol. 3:417, 1974. DiSantis D.J., Balfe D.M., Hayden R., et al.: The neck after vertical hemilaryngectomy: computed tomographic study. Radiology 151:683, 1984.

SELF-ASSESSMENT ANSWERS A n s w e r s can be f o u n d on the following pages: 1. 12 10. 41 2. 14 11. 43 3. 19-20 12. 52 4. 20 13. 63 5. 23 14. 64 6. 2 5 15. 66 7. 2 7 16. 68 8. 2 8 17. 71 9. 34-35 18. 74 19. 79-80

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