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Sinusitis: Postoperative changes and surgical complications
Sinusitis: Postoperative Changes and Surgical Complications Barbara Zeifer Functional endoscopic sinus surgery (FESS) is the standard of care for the surgical management of sinonasal inflammatory disease. This group of procedures focuses on the sinus outflow tract, and is designed to improve sinus function by restoring sinonasal physiology. Use of the monocular endoscope is associated with a range of unique surgical complications that often require cross-sectional imaging. Many patients considering sinus surgery today have had surgical procedures in the past that were directed at removing diseased mucosa, rather than improving sinus drainage, and have a different appearance on CT. This report addresses the spectrum of surgical changes found on postoperative imaging of the paranasal sinuses, and the surgical complications that may occur during endoscopic sinus surgery. Copyright 2002, Elsevier Science (USA). All rights reserved,
oday, sinus surgery is nearly synonymous with functional endoscopic sinus surgery, or FESS. Diagnostic and surgical endoscopy was pioneered and developed by Messerklinger in Germany in the 1960s and 1970s. I It was later popu= larized in this country by Kennedy. 2 FESS is the standard of care for the treatment of uncomplicated inflammatory sinus disease. Experienced otolaryngologists use this technique to treat many complicated sinonasal conditions such as mucocele, allergic fungal sinusitis, as well as localized neoplasia such as inverted papilloma. FESS employs a set of rigid, fiberoptic endoscopes to examine the nose and sinus cavities. The tips of these endoscopes vary in angulation from 0 to 70 degrees so that any area of the sinonasal cavity can be visualized. Specialized instruments (forceps, cutting instruments, suction devices, probes, and most recently, high-speed drills, or micro-debriders) are inserted along with the viewing endoscope to perform the intended surgical procedure. Treatment of sinusitis, whether medical or surgical, intends to restore sinus health. There are 4 basic components of sinus health: the medical and immunological condition of the patient; the quality and quantity of secretions; the status of ciliary function; and the patency of the sinus outflow tracts. When conservative therapy fails, the otolaryngologist is called upon to evaluate the condition of the sinus outflow tracts and the mucociliary clearance mechanism that propels mucous into and through the drainage pathways. Mucociliary clearance proceeds in a specific, genetically determined pathway that cannot be altered by any means. In fact, the direction and pattern of mucociliary clearance has been studied and defined for each of the sinus cavities. 1"3 Maintenance of ciliary function through the drainage pathway of a sinus cavity
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depends on adequate spacing between the apposing mucosal surfaces allowing room for both the sol phase of mucous in which the cilia beat, and the superficial gel phase that transports debris. Optimal clearance through these narrow channels is achieved when the superficial gel phase of the mucous blanket contacts that of the opposite mucosal surface. In this case, both sets of cilia can affect movement of the gel phase and enhance clearance. This is even more efficient at a sinus ostium, where a 360 degree ring of cilia propels the gel out of the sinus lumen) Any disease process or anatomical configuration that results in crowding of the cilia at the outflow tract will disrupt ciliary motion and cause mechanical or functional obstruction. If this situation persists, mucociliary dysfunction spreads proximally, secretions accumulate, and intrasinus pressure, temperature, and pH are altered. 3 Negative intraluminal pressures may result in aspiration of bacteria from the nose into the sinus cavity through the natural or accessory ostium. Sinusitis will then develop. This sequence of events identifies the central drainage pathways of the siuonasal cavity as the pathological unit and the source of the problem. Therefore, effective imaging 4 and treatment must address the 3 functional units of the sinonasal cavity: the frontal recess (FR) draining the frontal sinus; the ostiomeatal unit (OMU) draining the
From the Department of Radiology, Northwestern Memorial Hospital, Chicago, 1L. Address reprint requests to Northwestern University, Department of Radiology, 676 North Saint Clair, Suite 800, Chicago, 1L 60611. Copyright 2002, Elsevier Science (USA). All rights reserved. 0887-2171/02/2306-0001535.00/0 doi :l O.1053/sult.2002.34016
Seminars in Ultrasound, CT, and MR/, Vol 23, No 6 (December), 2002: pp 475-491
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frontal recess, anterior ethmoid air cells, and maxillary sinus; and the sphenoethmoid recess (SER) draining the sphenoid sinus and posterior ethmoid air cells. FESS was developed as a method to surgically enhance ventilation and drainage through the sinus outflow tracts using a transnasal approach, taking advantage of the directionality of mucociliary clearance. Older surgical techniques were replaced by FESS because of significant reduction in morbidity with better or equal outcomes. Initially, procedures performed with endoscopic techniques were extensive, involving removal of all components of the outflow tract. Less extensive resection is now the standard of care. Outflow tracts are enlarged by removing as little bone as possible, minimizing damage to the adjacent mucosal surfaces. THE POSTOPERATIVE SINUS CT
Patients are referred for routine postoperative imaging when symptoms fail to resolve or recur. Bear in mind that sinus surgery cannot 'cure' chronic sinusitis. Instead, the treatment goal is to substantially reduce the number of sinus infections the patient experiences each year and to improve quality of life. Therefore, recurrent sinusitis does not necessarily imply that the surgery was ineffecfive. The scan is ordered to establish an etiology for the ongoing or recurrent sinus disease, to define remnants of drainage anatomy that continue to prevent adequate mucociliary clearance, and to identify potential sites for revision surgery. Interpretation of the postoperative sinus CT must involve a precise analysis of the central drainage pathways. The key questions to answer are: (1) What was the intended surgical procedure? (2) What structures were removed? (3) Were they completely or partially removed? (4) What is the current status of the natural sinus ostium and outflow tract? (5) If the outflow tract is opacified, is it because of bone or soft tissue material? (6) Are the sinuses that depend on that outflow tract diseased, suggesting physiologic obstruction? As with the preoperative CT, defining postoperative anatomy helps the surgeon select the proper course of treatment. Irrigation fluid, mucosal edema, and packing material will be present in the immediate postoperative period. Irritation, edema, crusting, and formarion of debris may persist for 6 to 8 weeks. Therefore, sinus CT within this time period is of no
value in assessment of mucosal disease and the evaluation focuses on alteration of bony anatomy. Ostiomeatal Unit FESS
Initial descriptions of endoscopic techniques were focused on the OMU and to a lesser extent, on the SER l'z because these anatomic areas were accessible to the early endoscopes and instruments. Early proponents of FESS sought to dramatically widen the drainage pathway of the maxillary sinus and anterior ethmoid labyrinth. The standard procedure therefore included a complete uncinectomy, a wide middle meatal autrostomy contiguous with the natural maxillary sinus ostium, a middle turbinectomy, and a total anterior ethmoidectomy (Fig 1). This was considered a 'definitive' procedure, with removal of as much of the anatomy as possible. As time went on and outcomes were observed, it became clear that more was not necessarily better. These procedures did not always improve the patient's quality of life; in particular, patients with extensive turbinectomies did not feel well. Despite the fact that their nasal cavity was empty, they felt that they had difficulty breathing (Fig 2). Today, the emphasis is on performing the most limited procedure that will still result in adequate
Fig 1. "Standard" FESS. Coronal CT. There have been complete uncinectomies, anterior ethmoidectomies, middle meatal antrostomies, middle turbinate head reductions, and a septoplasty.
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ventilation and drainage of the sinus cavities. The pendulum has now swung towards performing less extensive surgeries. Limited or minimally invasive FESS became feasible when powered instrumentation became available. 5 Powered drills, or microdebriders, enable sculpting of the bony anatomy and precise removal of tissue without damaging adjacent mucosa. This permits small surgical openings to heal properly, without synechia formation and ostial closure, eliminating the requirement for a large opening. A minimal procedure typically includes a complete uncinectomy taken into the maxillary ostium, possibly a small middle meatal antrostomy, and a limited anterior ethmoidectomy involving either simple opening of the ethmoidal bulla or removal of a few septations (Fig 3). Proponents of even less invasive surgery recommend opening the infundibulum (infundibulotomy), excision of polyps and redundant tissue, leaving the ostium untouched. 6 More extensive anterior ethmoidectomies (subtotal or total) are indicated for more severe refractory ethmoid disease. In these cases, more of the septations will be taken down. During the surgery,
Fig 2. 'Extensive" FESS. Coronal CT. There have been complete uncinectomies, anterior ethmoidectomies, wide middle meatal antrostomies, middle and inferior turbinate excisions, and a septoplasty. This patient complained bitterly of nasal obstruction. Note the persistence of antral fluid collections that, in the absence of recent antral lavage, are because of poor mucociiiary clearance through the OMU and functional outlet obstruction.
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Fig 3. "Minimal FESS'. Coronal CT. There has been a left uncinectomy and excision of the inferior lamella of the ethmoidal bulla. The left middle and inferior turbinate heads are thin compared to the right, either because of the nasal cycle or decongestion. Note the prominent ethmoidal bulla on the right (*) with paradoxical curvature of the middle turbinate head (t). u, intact right uncinate plate.
if mucosa is stripped from a septation, the lamina papyracea, or the ethmoid roof, a reactive osteitis develops. Within months, this produces sclerosis and thickening of the bone plate. This is an incidental surgical change, and is rarely, if ever, associated with postoperative pain. However, if this proliferative process extends into the frontal or maxillary sinus ostium it will cause persistent outlet obstruction and sinus disease (Fig 4). A bulky middle turbinate will interfere with surgical access and visualization of the OMU or FR, and partial excision (turbinate head reduction) may be required. 7 If a large concha bullosa is present, its lateral lamella may be taken down; some surgeons suture the resultant middle turbinate remnant to the septum after reduction to prevent it from swinging laterally and scarring to the lateral nasal wall (Fig 5). Surgery of the inferior turbinate is performed to address persistent nasal obstruction because of irreversible turbinate hypertrophy (see Fig 7). Partial conservative resection has been shown to have the best long-term results. 8 Septal deviation and septal spur frequently contribute to nasal obstruction and poor ventilation of the OMU. Septal deviations are generally more
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Fig 4. Post-FESS osteitic reaction and surgical failure with missed ostium. Coronal CT. A, through OMU; B, 6mm posterior to A. There is marked asymptomatic osteitic thickening of the left ethmoid roof and lamina papyracea (arrows) 3 years after FESS. There has been a septoplasty complicated by a perforation (arrow heads), through which a conchal neck air cell protrudes (*), There is a small uncinate base remnant anteriorly in A with fracture and lateralization of the posterior uncinate in B (open arrows), leaving the diseased inner maxillary ostium untouched and obstructed, Note the antral fluid collection because of persistent outlet obstruction. Posterior to B was a patent middle meatal antrostomy (not shown) that did not protect the patient from developing postoperative sinus disease because it was not a physiological opening. This patient went on to have successful revision surgery with removal of the uncinate remnant and fibrous tissue, and extension of the antrostomy to join the natural ostium.
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Fig 5. Coronal CT. A, preoperative; B, postoperative. In A, there is a right concha bullosa cell (c) and paradoxical curvature of the left middle turbinate head (t) crowding the middle meati bilaterally. In B, the lateral lamella of the concha bullosa was removed, and the medial lamella was sutured to the septum to prevent deviation. The paradoxical middle turbihate on the left was reduced (arrowhead). In addition there was a left uncinectomy and limited anterior ethmoidectomy with opening of the ethmoidal bulla from below, asterisk, ethmoidal bulla.
pronounced on nasal endoscopy than they appear on the CT scan, and are most significant when they contact an opposing surface such as the inferior turbinate, the lateral nasal wall, and particularly, the middle turbinate head. Submucosal resection of
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Fig 6. Septopiasty. Coronal CT. A, preoperative; B, postoperative. In A, there is a left septal deviation with a septal spur that bridges the nasal meatus; the middle turbinate is hypoplastic as a result. In B, there has been resection of the central bone plate and spur. The septum is now midline and lacks a bony plate.
the septum at the outset of FESS eases access to and visualization of the OMU. The perpendicular ethmoid plate and vomer will be partially excised with loss of the dense bony plate (Fig 6). Postoperative necrosis may complicate a septoplasty and result in a septal perforation (see Fig 4). Concomitant rhinoplasty may be performed at the same time in many patients. 9
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Fig 7. CaldwelI-Luc procedure. A, coronal CT; B, axial CT. There are wide anterior antrostomy defects (arrowheads). The lateral nasal walls have been resected from the nasal floor to the inferior turbinate necks producing wide nasoantral windows (arrows). Middle turbinate resections were performed as well, In B, there is posterior maxillary wall thickening (curved arrows) and anterior wall retraction, markedly reducing antral volume; the concave opacification of the antral lumen (m) represents fibrous tissue. This reactive process is secondary to a mucosal stripping procedure many years earlier. More recently, there has been a limited endoscopic anterior ethmoidectomy on the right (*). Note the prominence of the inferior turbinate mucosa (t) that, if persistent and irreversible, would represent turbinate hypertrophy.
Caldwell-Luc Antrostomy Before FESS, the Caldwell-Luc procedure was the standard of care for the surgical treatment of refractory maxillary and ethmoid sinus disease,
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initially described by Caldwell in 1893, and Luc in 1894. lO A wide antrostomy was performed through a transoral/sub-labial approach at the canine fossa for direct visualization of the maxillary lumen utilizing a binocular operating microscope. This provided access to the nose and anterior ethmoid air cells. Polyps and mncosa were removed (mucosal stripping), and an inferior antrostomy (nasoantral window) was performed for gravity dependent drainage. A transantral ethmoidectomy could be performed if necessary. At the end of the procedure, the anterior antrostomy defect was closed. Limited success and a range of postoperative sequelae made this a controversial procedure in recent years. 11 The Caldwell-Luc procedure is now reserved for surgical access to the pterygopalatine fossa, management of selected midface fractures and tumors, foreign body and sinolith retrieval, and oroantral fistula repair, a° Mucosal stripping is no longer performed. The Caldwell-Luc procedure may be recognized by the presence of the anterior antrostomy defect and the nasoantral window (Fig 7). The most remarkable imaging feature of the post-CaldwellLuc antrostomy patient is exuberant bone proliferation and retraction of the antral walls, initiated by stripping of the mucosal lining. This reduces the volume of the antral lumen, and may cause facial deformity because of the acquired hypoplasia. Formation of synechia may compartmentalize the antrum and result in formation of a postCaldwell-Luc mucocele (Fig 8). The nasolacrimal duct may be obliterated or damaged during this procedure. Frequently, the retracting maxilla adheres to the duct orifice in the inferior nasal meatus. In these cases, ductal occlusion results in epiphora and potentially, dacryocystitis. A dacryocystorhinostomy is often required to reestablish a drainage pathway for tears from the lacrimal sac to the nasal cavity.
Surgical Failure: FESS The patient with chronic sinusitis will inevitably experience episodes of sinusitis even after a successful FESS. The CT scan will demonstrate the surgical changes, varying degrees of outflow tract opacification, and mucosal thickening. The radiologist must critically assess the remnant anatomy and identify structural features that may predispose toward continued sinus disease.
BARBARA ZEIFER
Fig 8. CaldwelI-Luc procedure with mucocele. Coronal CT. The anterior antrostomy defects are not seen on this slice. The nasoantral windows are small (arrows). There is marked proliferative bone formation on the right, almost completely obliterating the sinus lumen. Rounded densities with expansile features in the left maxillary sinus lumen and outflow tract are postoperative mucoceles (m} requiring revision surgery for drainage.
The most common etiology for surgical failure is an incomplete resection of the uncinate plate. An uncinate base remnant protects the inner maxillary sinus ostium and the proximal infundibulum. If the cause of the sinus disease was impaired mucociliary clearance through this outlet channel, then the problem was not addressed and disease will persist in the face of the incomplete surgery. This problem has been called the 'missed ostium sequence' (Fig 4). 12 Ostial obstruction may be inflammatory, fibrous, or osseous. Remember that mucociliary clearance direction is genetically determined and cannot be altered under any circumstance, including sinonasal surgery. 3 Ciliary action will continue to propel mucous and debris towards an obstructed ostium and sinus drainage will be inadequate even if there is a wide, patent antrostomy. An extensive middle turbinate head reduction may destabilize the turbinate neck anteriorly and superiorly at the skull base. The turbinate neck can then migrate laterally and overlie the frontal recess. Postoperative frontal sinusitis will ensue even though the frontal sinus outflow tract was not addressed by the surgery (Fig 9). 7'13
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Fig 9. Surgical failure: lateralized middle turbinate neck. Coronal CT. A, frontal recess; B, frontal sinus lumen, anterior to A, There was complete resection of both middle turbinate heads 8 months earlier. In A, the right middle turbinate neck is retracted laterally (arrows), closing over and obstructing the frontal recess. Note the normal position of the left turbinate neck (arrowhead), anchored by an ethmoid septation. Persistent mucosal disease and retained secretions are seen in B because of outflow tract obstruction. This necessitated revision surgery with frontal sinusotomy and temporary stent placement to maintain patency of the ostium.
Surgical Complications Complications of FESS can be divided into local, orbital, skull base, and intracranial events. Local complications including bleeding and synechia formation do not require imaging. The most common orbital complication is vio-
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lation of the lamina papyracea producing a bone defect. If periorbita was disrupted as well, orbital fat will bulge through this defect into the adjacent ethmoid air cell. This is because of infracturing of the orbital plate and alone is of no clinical significance. If forceps or biting instruments actually penetrate the orbit proper, edema may develop in or around the medial rectus muscle. This may be asymptomatic or may result in postoperative diplopia that usually resolves (Fig 10). The anterior ethmoid artery arises from the ophthalmic artery in the orbit, and enters the ethmoid cavity through the anterior ethmoid foramen. The artery traverses the ethmoid roof running an anterior-medial course, and penetrates the lateral lamella of the cribriform plate to enter the (intracranial) olfactory fossa (Fig 11). 14 During its ethmoid course, the artery may be completely covered in a bony canal, may be submucosal and unprotected, or rarely may hang down on a mesentery. In the latter 2 cases, the artery is at risk for injury during an ethmoidectomy. Laceration of the anterior ethmoidal artery results in profuse bleeding that requires cauterization, packing, and termination of the surgical procedure. If transected, the proximal end of the artery may retract into the orbit and produce an orbital hematoma requiring canthotomy for pressure release. The newer powered instruments, so useful in the sinus cavities, can produce devastating and immediate intraorbital damage before the surgeon is aware of the situation. The medial rectus muscle, lying in close proximity to the lamina papyracea can be macerated by a penetrating microdebrider (Fig 12). The drill can even protrude into the muscle cone, and injure the central retinal branch of the ophthalmic artery along its intraconal course between the optic nerve and the lateral rectus muscle, causing immediate blindness (Fig 13). The central retinal artery first encircles the perioptic sheath, then pierces it 1.0 to 1.5cm behind the optic nerve head to supply the retina and portions of the optic nerve. 15 Clearly the optic nerve is also at risk in this situation. Intra-operative or postoperative cerebrospinal fluid (CSF) rhinorrhea is a well-known complication of FESS, occurring in .5% of patients. 16 Frequently recognized during the procedure, the leak can be immediately addressed and sealed from below. 17 Although the cribriform plate is thin and delicate, the lateral lamella of the cribriform plate
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defect cannot be seen and CSF rhinorrhea persists, then a CT cisternogram may demonstrate the site of the leak. Pneumocephalus may accompany the skull base defect, especially with nose blowing after the packing material is removed. If the bone defect is particularly wide, brain and meninges may herniate inferiorly into the nasal cavity (Fig 15). Intracranial instrumentation is obviously a serious complication of FESS. That this occurs at all is a testament to the technical difficulty of endoscopic surgery, and the lack of orientation and depth perception for the operator of a monocular viewing endoscope. 19 Potential intracranial injuries include extraaxial, parenchymal, and intraventricular hemorrhage (Fig 16). If vessels are lacerated, subarachnoid hemorrhage will occur2° and a pseudoaneurysm may develop. FRONTAL SINUS AND THE FRONTAL SINUS OUTFLOW TRACT FESS
Development of endoscopic techniques for the frontal sinus outflow tract initially lagged behind those of the ostiomeatal unit. The reasons for this included the lower frequency of refractory frontal sinusitis, the fact that frontal sinus disease often resolves after FESS performed on the OMU, 21 and
Fig 10. Orbital fat herniation. A, intra-operative endoscopic view. B, coronal CT. This 'standard FESS' procedure went smoothly, and the surgeon took intra-operative pictures for teaching purposes. On reviewing this slide 3 days later, he noticed a small globule of orbital fat herniating through the lamina papyracea into the ethmoid cavity, prompting the CT scan. The scan demonstrated the bony defect of the orbital plate as expected (arrows), as well as thickening and slight distortion of the medial rectus muscle belly (arrowhead), unexpected in this asymptomatic patient. The maxillary and ethmoid sinus opacification represents edema and irrigation fluid in this immediate postoperative study, f, fat herniation; LP, lamina papyracea.
is the weakest component of the anterior skull base 18 and the most common location for intraoperative fracture, usually because of manipulation of the middle turbinate neck. The postoperative CT scan will almost always demonstrate an anterior skull base defect that can vary from tiny and barely detectable to surprisingly wide (Fig 14). If the bone
Fig 11. Anterior ethmoidal artery. Coronal CT. In this patient, the artery runs through the ethmoid bone within a discrete canal (arrows) from the orbit to the olfactory fossa. Surrounding reactive bone from a subtotal anterior ethmoidectomy enhances the appearance of the canal on the left. Forked line: cribriform plate, medial; lateral lamella, lateral; c, crista galli.
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but other terms include the Draf III,25 the frontal sinus drill Out, 24 and the transeptal frontal sinusotomy. 28 The original external Lothrop procedure was developed in 1914, and intended to produce as large a frontal-nasal opening that the anatomy would allow. 21 Today, the endoscopic derivative remains technically demanding, with an unmistak-
Fig 12. Medial rectus muscle injury post-FESS with microdebrider. Coronal Tl-weighted MRI, 3-inch surface coil over left orbit. The fracture of the left orbital plate is not well seen, but orbital contents are tethered towards the bone defect because of the suctioning effect of the instrument (arrow). The medial rectus muscle has been severely damaged: the cross-sectional area is markedly reduced, and function was limited. The patient was managed by the orthoptics service. mr, medial rectus muscle; so, superior oblique muscle, straight segment; stub, superior muscle bundle; Ir, lateral rectus muscle; it, inferior rectus muscle; on, optic nerve.
the complex anatomy of this region. 22 As understanding of frontal recess anatomy expanded, techniques and instrumentation were refined, and with time, the frontal sinus drainage pathways could be approached with the endoscope. 23 Several authors have described techniques for endoscopic frontal sinus surgery, also known as frontal sinusotomy. All systems are based on stepwise incremental extension of the procedure proportional to the severity of disease. 24-27 The most limited of these procedures involves an uncinectomy and possibly a middle turbinate head reduction, ie, a routine FESS that addresses the inferior frontal recess. This can be extended to include an anterior ethmoidectomy with specific removal of those air cells that directly impinge on the frontal recess, such as the agger nasi and frontal bulla cells. 4 The next more extensive procedure requires excision of the frontal sinus floor from the middle turbinate neck to the lamina papyracea, often referred to as the Draf IIB procedure (Fig 17). The most definitive endoscopic procedure performed on the frontal sinus is widely known as an endoscopic modification of the Lothrop procedure,
Fig 13. Medial rectus muscle injury and central retinal artery occlusion with microdebrider. A, axial CT immediate after surgery; B, axial T2-weighted MRI with 3 inch surface coil over each orbit, 2 weeks later. The mid lamina papyracea is disrupted (*), at which point there is an abrupt change in caliber of the medial rectus muscle belly (arrow). This location corresponds to the course of the central retinal branch of the ophthalmic artery. Initially, there was proptosis because of minimal hemorrhage and post-traumatic edema with stranding of the orbital fat. By the time of the MRI, the edema subsided, and mild enophthalmos developed because of tissue loss. Lateral deviation of the globe (exotropia) is because of complete loss of medial rectus function and unopposed lateral rectus (Ir) action, with contraction of the muscle belly. The optic nerve is thick with high "1"2 signal (arrowheads) because of central retinal artery laceration and occlusion. The patient had "no light perception' as a result.
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nal drainage catheter. The anterior osteotomy is often visible on the CT scan as a smooth bone defect, 3 to 5 mm in diameter (Fig 19).
Osteoplastic Flap
Fig 14. Anterior skull base injury. Coronal CT, immediately after surgery. There is a wide defect in the right skull base (arrowheads), predominantly involving the lateral lamella and the ethmoid roof. Most of the cribriform plate remains in place. The ethmoid and nasal cavities are filled with packing material (p); the maxillary sinuses contain irrigation fluid. Forked line on normal side: cribriform plate, medial; lateral lamella, lateral.
The osteoplastic flap procedure, first reported in 1894, was popularized in the 1960s 31 and is still performed today to eradicate frontal sinusitis. The osteoplastic flap is an acceptable alternative to the endoscopic approach in many circumstances. Indications for this external procedure include lateral location of significant sinus disease or mucocele, fracture and CSF fistula repair, and tumor excision. 25 It is the 'salvage' procedure performed in the face of failed endoscopic surgery. Before the surgery, the patient has a 6 foot Caldwell radiograph, and the contour of the frontal sinus is physicalIy cut out of the film, sterilized, and used as a template to approximate the contour of the sinus lumen on the frontal bone. In centers where image-guided surgery systems are used, the outline of the frontal sinus can be localized and marked on the frontal bone. Once the osteotomy is performed, the anterior table of the frontal sinus is detached superiorly, and hinged inferiofly, so that the entire frontal sinus lumen is visualized. The mucosa is
able appearance on CT. There is a complete anterior ethmoidectomy, excision of the anterior segment of the perpendicular ethmoid plate and the intersinus frontal septation, and excision of the frontal sinus floor extending the full width between the lacrimal bones (Fig 18). Despite the tremendous advances made in frontal sinus surgery, re-stenosis of the outflow tract remains a vexing problem, particularly when the surgical ostium is less than 5ram in diameter. 29 Temporary stent placement is the standard procedure for many of these endoscopic frontal sinus procedures. The stents are removed after healing has occurred, usually between 4 and 8 weeks after the surgery 3° and are rarely imaged.
Frontal Sinus Trephination Frontal sinus trephination is an external procedure indicated for rapid drainage and irrigation of an acutely infected frontal sinus. It may be used in conjunction with an endoscopic procedure to identify the frontal ostium from below by irrigation from above. The trephine is an anterior-inferiormedial frontal sinus wail puncture just below the eyebrow for irrigation and placement of an exter-
Fig 15. latrogenic cephalocele. Coronal T2-weighted MRI, 2 years after extensive FESS. There are wide defects in the anterior skull base bilaterally through which dura, cerebrospinal fluid, and gyrus rectus herniate. The patient complained of recurrent sinus inflammatory symptoms, and the cephaloceles were noted on routine office nasal endoscopy.
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Fig 16. Intracranial instrumentation during FESS, A, coronal sinus CT and B, axial head CT immediately after the procedure. C, coronal CT 2 years later. Towards the end of a 'routine' FESS, the surgeon noted sudden L orbital proptosis. The FESS was terminated and the nose was packed (p). Immediate CT scan demonstrated penetration of the skull base through the posterior cribriform plate and its lateral lamella, and an instrument track through the frontal lobe with hemorrhage and air (arrows). A superior lamina papyracea defect (arrowhead) was seen without orbital hematoma. Axial head CT demonstrated epidural air and intraventricular air with hemorrhage. Postoperative diplopia resolved after a few weeks, and the patient recovered without symptomatic sequelae, but had a pseudostrabismus. Two years later, her sinus symptoms recurred. The CT scan demonstrated the encephalomalacic frontal lobe track (arrows) and concave fibrosis of the ethmoid cavity (e) with an adhesion to a rounded medial rectus muscle (m) accounting for her clinical appearance. The antrum was now completely opacified because of recurrent outflow tract obstruction.
completely removed and the sinus cavity and ostium are packed most commonly by abdominal fat, but bone graft and hydroxyapatite materials have been used as well. The anterior table is then placed back into position, and is closed. 21'32
Both CT and MRI will demonstrate the integrity of the bone flap and the fatty contents of the autograft. Animal studies have shown that even in the absence of infection, there is variable fat resorption and replacement by soft tissue with time,
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Fig 17. Frontal sinusotomy, Draf liB. Coronal CT. There has been a complete anterior ethmoidectomy and excision of the middle turbinate neck. This produces a wide communication between the frontal sinus lumen and the nasal cavity {arrow).
BARBARA ZEIFER
Fig 19. Frontal sinus trephination, Coronal CT, many years after surgery. There is a smooth bone defect {arrows) along the anterior-inferior-medial wall of the frontal sinus.
ranging from 0 to 70% 33,34 A range of normal CT density and MRI signal intensity will reflect this phenomenonY '36 The sinus lumen should be completely filled by the graft material, without residual
Fig 18. Modified endoscopic Lothrop procedure. Coronal CT. Excision of all the anterior ethmoidal septations, the intersinus frontal septation, the middle turbinate necks, and the anterior segment of the nasal septum have created the ultimate frontal sinusotomy. Courtesy of Dr. Michelle Smith, Medical College of Wisconsin,
Fig 20. Osteoplastic flap. Axial CT 6 weeks post-op. The anterior table of this large frontal sinus has been detached, the mucosa removed, and the lumen packed with fatty tissue. The bone flap fractured but lies in anatomical position {arrows). The fat of the graft (f) is clear and abuts the inner cortex; the patient had no frontal sinus symptoms and the graft was not felt to be infected. Inadvertent disruption of the posterior table on the left is noted, with protrusion of the fat graft into the anterior cranial fossa (arrowheads).
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air or evidence of graft retraction, and the cortex of the bone flap should be intact (Figs 20 and 21).
Surgical Failure
Fig 21. Frontal sinus obliteration. Sagittal reformat. This patient had an infected osteoplastic flap that could not be salvaged, For revision, the frontal sinus lumen was obliterated with hydroxyapatite paste (h) that also served to reform the anterior table. A stent was placed in a supraorbital ethmold air cell (arrow) to maintain aeration.
Fig 22. Ostial stenosis. Frontal sinus, sagittal reformat. Manipulation of the frontal sinus ostium resulted in 360 ° reactive bone formation and severe stenosis (arrows). Thick mucoid secretions cannot clear out and layer posteriorly in the frontal sinus. Note the complete anterior ethmoidectomy cavity (e). p, posterior ethmoid; s, sphenoid sinus; f, frontal sinus.
The frontal ostium is particularly sensitive to manipulation. Mucosal disruption during FESS dramatically raises the probability of developing postoperative ostial stenosis. The stenosis may be fibrous and therefore soft tissue in density, or calcified because of an osteitic reaction (Fig 22). Persistent frontal sinusitis following frontal sinusotomy requires revision to the next level of frontal sinusotomy or an osteoplastic flap. The osteoplastic flap procedure may fail if the mucosal surface is not completely eradicated. In this situation, epithelial regeneration occurs, and secretion continues into the surgically obstructed sinus cavity. The end result will be the develop-
Fig 23. Infected osteopiastic flap. Coronal CT. Three years earlier, the patient had an osteoplastic flap procedure with subsequent bouts of graft infection. On the current scan obtained while symptomatic there is partial replacement of the autologous fat graft (f) by soft tissue material (s). This finding can be nonspecific, but when compared to prior scans, the soft tissue component was larger and more rounded. An old trephination defect had widened laterally (arrowheads), because of osteomyelitis and necrosis of the bone plate.
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Fig 24. Trephination complication. A, anterior and B, posterior, contiguous coronal CT scans; C, axial CT. This 9-year-old child presented with acute frontal sinusitis and a superior subperiosteal orbital abscess. A frontal trephination procedure was performed, but the osteotomy was too lateral, and the trocar penetrated both anterior (A) and posterior (B) frontal sinus tables; the drainage catheter was inserted into the frontal lobe. Note the subperiosteal drain in the superior-temporal orbital quadrant (arrowhead). Irrigation resulted in epidural empyema (e), frontal lobe cerebritis (c) later developing into a frank abscess, and subgaleal phlegmon (g). The patient eventually recovered completely. Arrows, drainage catheter.
ment of a frontal sinus mucocele or pyocele. Postoperative infection of the graft may occur and is difficult to medically eradicate. Imaging studies will show replacement of the fatty graft material by soft tissue material that is often difficult to distin-
guish from normal graft evolution34 although a rounded density within the fatty tissue suggests infection (Fig 23). The clinical status of the patient is therefore as important as the imaging findings in diagnosing an infected osteoplastic graft.
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event, because of the accessibility of the SER and the ability to produce large openings that tend to remain patent. Surgical C o m p l i c a t i o n s The sphenoid sinus has complex neurovascular relationships, with proximity to the cavernous sinus, carotid artery, optic canal, tbramen rotundum,
Fig 25. Posterior FESS, bilateral. Axial CT. All ethmoidal septations have been removed, including the basal lamella, creating one large ethmoidal cavity (e). The anterior wall of the sphenoid sinus has been opened creating the anterior sphenoidotomy (arrows). s, sphenoid sinus.
Surgical C o m p l i c a t i o n s Complications of frontal sinusotomy and the modified endoscopic Lothrop procedure include laceration of the anterior ethmoidal artery in the ethmoid roof, damage to the cribriform plate and olfactory apparatus, and inadvertent instrumentation of the anterior cranial fossa or orbit. Even the relatively safe and simple frontal trephination can be complicated by penetration of the posterior frontal table with subsequent introduction of irrigation fluid and infectious material into the anterior cranial fossa (Fig 24).
SPHENOETHMOID RECESS Endoscopic surgery of the posterior ethmoid and sphenoid sinuses is directed at the sphenoethmoid recess, the common drainage pathway of this region. The typical posterior FESS includes a posterior ethmoidectomy and anterior sphenoidotomy, best evaluated in the axial scan plane (Fig 25). The minimal procedure would involve removal of polyps and redundant mucosa from the recess alone, without manipulating the sphenoid ostium.
Surgical Failure Failed posterior surgery is caused by stenosis of, or recurrent disease in, the sphenoid ostium or sphenoethmoid recess. This is an uncommon
Fig 26. Onodi cell. A, coronal CT; B, oblique-sagittal reformat. In A, an air cell is seen above the sphenoid sinus, bordering the optic canal. This could represent an Onodi cell, or a septated sphenoid sinus. The sagittal reformat confirms this cell to be of posterior ethmoid (p) origin. Asterisk, Onodi cell; arrow, optic canal; s, sphenoid sinus.
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and the vidian canal. The thickness of the sphenoid sinus wall is variable. Areas of the sphenoid sinus wall can measure as little as .5 mm in thickness, and foci of bony dehiscence are common. 36 When these areas of extreme thinning or dehiscence are found at critical neurovascular structures, instrumentation of the sinus cavity can potential result in an untoward event, such as injury to the cavernous carotid artery or optic nerve. Therefore, the surgeon follows a medial and inferior course with the endoscope, along the intersinus septation, should entry into the sphenoid sinus be required. An Onodi cell is an anatomic variant of the posterior ethmoid labyrinth. The Onodi cell is produced by posterior pneumatization of the posterior ethmoid air cell into the sphenoid bone, cephalad to the sphenoid sinus lumen. This developmental variation places a posterior ethmoid air at
the optic canal, an unexpected anatomic relationship. In this situation, the optic nerve is at risk for instrumentation and injury during the course of an endoscopic posterior ethmoidectomy. Clearly, preoperative knowledge of an Onodi cell is critical in preventing a devastating complication (Fig 26). CONCLUSION
Today, radiologists see more and more CT scans following a wide variety of sinus surgeries. Changes of the transnasal endoscopic procedures and the older external surgical procedures will inevitably be encountered. Reviewing the spectrum of these procedures and their anatomical alterations is helpful to the radiologist in providing a dynamic and useful CT report to the referring otolaryngologist.
REFERENCES 1. Messerklinger W: Endoscopy of the Nose. BaltimoreMunich, Urban & Schwarzenberg, 1978 2. Kennedy DW, Zinreich SJ, Rosenbaarn AE, et al: Functional endoscopic sinus surgery. Arch Otolaryngol 111:576582, 1985 3. Stammberger H: Secretion transportation, in Stammberger H: Functional Endoscopic Sinus Surgery. Philadelphia, PA, B. D. Decker, 1991, pp 17-48 4. Zeifer B: Update on sinonasal imaging. Neuroimaging Clin North Am 8:607-630, 1998 5. Setliff RC III, Parsons DS: The 'hummer': New instrumentation for functional endoscopic sinus surgery. Am J Rhinol 8:275-278, 1994 6. Setliff RC 1II: The small-hole technique in endoscopic sinus surgery. Otolaryngol Clin North Am 30:341-354, 1997 7. Giacchi 1Ll, Lebowitz RA, Jacobs JB: Middle mrbinate resection: Issues and controversies. Am J Rhinolo 14:193-197, 2000 8. Passali D, Lauriello M, Anselmi M, et al: Treatment of hypertrophy of the inferior turbinate: Long-term results. Ann Otol Rhinol Laryngol 108:569-575, 1999 9. Risk SS, Edelstein DR, Matarasso A: Concurrent functional endoscopic sinus surgery and rhinoplasty. Ann Plast Surg 38:323-329, 1997 10. Blitzer A, Lawson W: The Caldwell-Luc procedure in 1991. Otolaryngol Head Neck Surg 105:717-722, 1991 11. Unger JM, Dennison BF, Duncavage JA, et al: The radiologic appearance of the post-Caldwell-Luc maxillary sinus. Clin Radiol 37:77-81, 1986 12. Parsons DS, Stivers FE, Talbot AR: The missed ostium sequence and the surgical approach to revision functional endoscopic sinus surgery. Otolaryngol Clin North Am 29:169183, 1996 13. Saidi IS, Biedlingmaler JF, Rothman MI: Pre- and postoperative imaging analysis for frontal sinus disease following
conservative partial middle turbinate resection. Ear, Nose & Throat J 44:326-330, 1998 14. Chung SK, Dhong HJ, Kim HY: Computed tomography anatomy of the anterior ethmoid canal. Am J Rhinol 15:77-81, 2001 15. Janfaza P, Rubin PAD, Azar N. Orbit, in Janfaza P, et al (eds): Surgical Anatomy of the Head and Neck. Philadelphia, PA, Lippincott Williams & Wilkins, 2001, pp 149-221 16. May M, Levine HL, Mester SJ, et al: Complications of endoscopic sinus surgery: Analysis of 2108 patients-incidence and prevention. Laryngoscope 104:1080-1083, 1994 17. Wax MK, Ramadan I-1H, Ortiz O, et al: Contemporary management of cerebrospinal fluid rhino?rhea. Otolaryngol Head Neck Surg 116:442-449, 1997 18. Kainz J, Starnmberger H: The roof of the anterior ethmoid: A place of least resistance in the skull base. Am J Rhinol 4:191-199, 1990 19. Lucente FE, Shoenfeld PS: Calibrated approach to endoscopic sinus surgery. Ann Otol Rhinol Laryngo199:1-4, 1990 20. Berenholz L, Kessler A, Sarfaty S, at al: Subarachnoid hemorrhage: A complication of endoscopic sinus surgery using powered instrumentation. Otolaryngol Head Neck Surg 121: 665-667, 1999 21. Gross CW: Clinical Challenges in Otolaryngology: Surgical treatments for symptomatic chronic frontal sinusitis: Arch Otolaryngol Head Neck Surg 126:101-102, 2000 22. Nguyen QA Leopold DA: Current concepts in the surgical management of chronic frontal sinusitis. Otolaryngol Clin North Am 30:355-370, 1997 23. Kuhn FA: Chronic frontal sinusitis: The endoscopic approach. Operative Tech Otolaryngol--Head Neck Surg 7:222229, 1996 24. Metson R, Glildich RE: Clinical outcome of endoscopic sinus surgery for frontal sinusitis. Arch Otolaryngol Head Neck Surg 124:1090-1096, 1998
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25. Weber R, Draf W, Kratzsch B, et al: Modem concepts of frontal sinus surgery. Laryngoscope 111:137-146, 2001 26. May M, Schaitldn B: Frontal sinus surgery: Endoscopic drainage instead of an external osteoplastic approach. Operative Tech Otolaryngol---Head Neck Surg 6:184-192, 1995 27. Kuhn FA, Javer AR: Primary endoscopic management of the frontal sinus. Otolaryngol Clin North Am 34:59-75, 2001 28. Lanza DC, McLaughlin RB, Hwang PH: The five-year experience with endoscopic trans-septal frontal sinusotomy. Otolaryngol Clin North Am 34:139-152, 2001 29. Hoseman W, Kuhnel TH, Held P, et al: Endonasal frontal sinusotomy in surgical management of chronic sinusitis: A critical evaluation. Am J Rhinol 11:1-19, 1997 30. Rains BM III: Frontal sinus stenting. Otolaryngol Clin North Am 34:101-110, 2001 31. Montgomery WW: Osteoplastic frontal sinus operation: Coronal incision. Ann Otol Rhinol Laryngol 74:821-830, 1965
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32. Montgomery WW, Lazor JB: Controversies in surgery for chronic frontal sinusitis, in Bailey BJ (ed): Head and Neck Surgery---Otolaryngology, vol 1 (ed 2). Philadelphia, PA, Lippincott-Raven, 1998, pp 837-849 33. Montgomery WW, Pierce DL: Anterior osteoplastic fat obliteration for frontal sinus: Clinical experience and animal studies. Trans Am Ophthalmol Otolaryngol 67:46-57, 1963 34. Montgomery WW: The fate of adipose tissue in a body cavity. Laryngoscope 74:816-827, 1964 35. Catalano PJ, Lawson W, Som P, et al: Radiographic evaluation and diagnosis of the failed frontal osteoplastic flap with fat obliteration. Otolaryngol Head Neck Surg 104:225234, 1991 36. Loevner LA, Yousem DM, Lanza DC, et al: MR evaluation of frontal sinus osteoplastic flaps with autogenous fat grafts. Am J Neuroradiol 16:1721-1726, 1995 37. Fujii K, Chamber SM, Rhoton AL: Neurovascular relationships of the sphenoid sinus. J Neurosurg 50:31-39, 1979
oday, sinus surgery is nearly synonymous with functional endoscopic sinus surgery, or FESS. Diagnostic and surgical endoscopy was pioneered and developed by Messerklinger in Germany in the 1960s and 1970s. I It was later popu= larized in this country by Kennedy. 2 FESS is the standard of care for the treatment of uncomplicated inflammatory sinus disease. Experienced otolaryngologists use this technique to treat many complicated sinonasal conditions such as mucocele, allergic fungal sinusitis, as well as localized neoplasia such as inverted papilloma. FESS employs a set of rigid, fiberoptic endoscopes to examine the nose and sinus cavities. The tips of these endoscopes vary in angulation from 0 to 70 degrees so that any area of the sinonasal cavity can be visualized. Specialized instruments (forceps, cutting instruments, suction devices, probes, and most recently, high-speed drills, or micro-debriders) are inserted along with the viewing endoscope to perform the intended surgical procedure. Treatment of sinusitis, whether medical or surgical, intends to restore sinus health. There are 4 basic components of sinus health: the medical and immunological condition of the patient; the quality and quantity of secretions; the status of ciliary function; and the patency of the sinus outflow tracts. When conservative therapy fails, the otolaryngologist is called upon to evaluate the condition of the sinus outflow tracts and the mucociliary clearance mechanism that propels mucous into and through the drainage pathways. Mucociliary clearance proceeds in a specific, genetically determined pathway that cannot be altered by any means. In fact, the direction and pattern of mucociliary clearance has been studied and defined for each of the sinus cavities. 1"3 Maintenance of ciliary function through the drainage pathway of a sinus cavity
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depends on adequate spacing between the apposing mucosal surfaces allowing room for both the sol phase of mucous in which the cilia beat, and the superficial gel phase that transports debris. Optimal clearance through these narrow channels is achieved when the superficial gel phase of the mucous blanket contacts that of the opposite mucosal surface. In this case, both sets of cilia can affect movement of the gel phase and enhance clearance. This is even more efficient at a sinus ostium, where a 360 degree ring of cilia propels the gel out of the sinus lumen) Any disease process or anatomical configuration that results in crowding of the cilia at the outflow tract will disrupt ciliary motion and cause mechanical or functional obstruction. If this situation persists, mucociliary dysfunction spreads proximally, secretions accumulate, and intrasinus pressure, temperature, and pH are altered. 3 Negative intraluminal pressures may result in aspiration of bacteria from the nose into the sinus cavity through the natural or accessory ostium. Sinusitis will then develop. This sequence of events identifies the central drainage pathways of the siuonasal cavity as the pathological unit and the source of the problem. Therefore, effective imaging 4 and treatment must address the 3 functional units of the sinonasal cavity: the frontal recess (FR) draining the frontal sinus; the ostiomeatal unit (OMU) draining the
From the Department of Radiology, Northwestern Memorial Hospital, Chicago, 1L. Address reprint requests to Northwestern University, Department of Radiology, 676 North Saint Clair, Suite 800, Chicago, 1L 60611. Copyright 2002, Elsevier Science (USA). All rights reserved. 0887-2171/02/2306-0001535.00/0 doi :l O.1053/sult.2002.34016
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frontal recess, anterior ethmoid air cells, and maxillary sinus; and the sphenoethmoid recess (SER) draining the sphenoid sinus and posterior ethmoid air cells. FESS was developed as a method to surgically enhance ventilation and drainage through the sinus outflow tracts using a transnasal approach, taking advantage of the directionality of mucociliary clearance. Older surgical techniques were replaced by FESS because of significant reduction in morbidity with better or equal outcomes. Initially, procedures performed with endoscopic techniques were extensive, involving removal of all components of the outflow tract. Less extensive resection is now the standard of care. Outflow tracts are enlarged by removing as little bone as possible, minimizing damage to the adjacent mucosal surfaces. THE POSTOPERATIVE SINUS CT
Patients are referred for routine postoperative imaging when symptoms fail to resolve or recur. Bear in mind that sinus surgery cannot 'cure' chronic sinusitis. Instead, the treatment goal is to substantially reduce the number of sinus infections the patient experiences each year and to improve quality of life. Therefore, recurrent sinusitis does not necessarily imply that the surgery was ineffecfive. The scan is ordered to establish an etiology for the ongoing or recurrent sinus disease, to define remnants of drainage anatomy that continue to prevent adequate mucociliary clearance, and to identify potential sites for revision surgery. Interpretation of the postoperative sinus CT must involve a precise analysis of the central drainage pathways. The key questions to answer are: (1) What was the intended surgical procedure? (2) What structures were removed? (3) Were they completely or partially removed? (4) What is the current status of the natural sinus ostium and outflow tract? (5) If the outflow tract is opacified, is it because of bone or soft tissue material? (6) Are the sinuses that depend on that outflow tract diseased, suggesting physiologic obstruction? As with the preoperative CT, defining postoperative anatomy helps the surgeon select the proper course of treatment. Irrigation fluid, mucosal edema, and packing material will be present in the immediate postoperative period. Irritation, edema, crusting, and formarion of debris may persist for 6 to 8 weeks. Therefore, sinus CT within this time period is of no
value in assessment of mucosal disease and the evaluation focuses on alteration of bony anatomy. Ostiomeatal Unit FESS
Initial descriptions of endoscopic techniques were focused on the OMU and to a lesser extent, on the SER l'z because these anatomic areas were accessible to the early endoscopes and instruments. Early proponents of FESS sought to dramatically widen the drainage pathway of the maxillary sinus and anterior ethmoid labyrinth. The standard procedure therefore included a complete uncinectomy, a wide middle meatal autrostomy contiguous with the natural maxillary sinus ostium, a middle turbinectomy, and a total anterior ethmoidectomy (Fig 1). This was considered a 'definitive' procedure, with removal of as much of the anatomy as possible. As time went on and outcomes were observed, it became clear that more was not necessarily better. These procedures did not always improve the patient's quality of life; in particular, patients with extensive turbinectomies did not feel well. Despite the fact that their nasal cavity was empty, they felt that they had difficulty breathing (Fig 2). Today, the emphasis is on performing the most limited procedure that will still result in adequate
Fig 1. "Standard" FESS. Coronal CT. There have been complete uncinectomies, anterior ethmoidectomies, middle meatal antrostomies, middle turbinate head reductions, and a septoplasty.
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ventilation and drainage of the sinus cavities. The pendulum has now swung towards performing less extensive surgeries. Limited or minimally invasive FESS became feasible when powered instrumentation became available. 5 Powered drills, or microdebriders, enable sculpting of the bony anatomy and precise removal of tissue without damaging adjacent mucosa. This permits small surgical openings to heal properly, without synechia formation and ostial closure, eliminating the requirement for a large opening. A minimal procedure typically includes a complete uncinectomy taken into the maxillary ostium, possibly a small middle meatal antrostomy, and a limited anterior ethmoidectomy involving either simple opening of the ethmoidal bulla or removal of a few septations (Fig 3). Proponents of even less invasive surgery recommend opening the infundibulum (infundibulotomy), excision of polyps and redundant tissue, leaving the ostium untouched. 6 More extensive anterior ethmoidectomies (subtotal or total) are indicated for more severe refractory ethmoid disease. In these cases, more of the septations will be taken down. During the surgery,
Fig 2. 'Extensive" FESS. Coronal CT. There have been complete uncinectomies, anterior ethmoidectomies, wide middle meatal antrostomies, middle and inferior turbinate excisions, and a septoplasty. This patient complained bitterly of nasal obstruction. Note the persistence of antral fluid collections that, in the absence of recent antral lavage, are because of poor mucociiiary clearance through the OMU and functional outlet obstruction.
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Fig 3. "Minimal FESS'. Coronal CT. There has been a left uncinectomy and excision of the inferior lamella of the ethmoidal bulla. The left middle and inferior turbinate heads are thin compared to the right, either because of the nasal cycle or decongestion. Note the prominent ethmoidal bulla on the right (*) with paradoxical curvature of the middle turbinate head (t). u, intact right uncinate plate.
if mucosa is stripped from a septation, the lamina papyracea, or the ethmoid roof, a reactive osteitis develops. Within months, this produces sclerosis and thickening of the bone plate. This is an incidental surgical change, and is rarely, if ever, associated with postoperative pain. However, if this proliferative process extends into the frontal or maxillary sinus ostium it will cause persistent outlet obstruction and sinus disease (Fig 4). A bulky middle turbinate will interfere with surgical access and visualization of the OMU or FR, and partial excision (turbinate head reduction) may be required. 7 If a large concha bullosa is present, its lateral lamella may be taken down; some surgeons suture the resultant middle turbinate remnant to the septum after reduction to prevent it from swinging laterally and scarring to the lateral nasal wall (Fig 5). Surgery of the inferior turbinate is performed to address persistent nasal obstruction because of irreversible turbinate hypertrophy (see Fig 7). Partial conservative resection has been shown to have the best long-term results. 8 Septal deviation and septal spur frequently contribute to nasal obstruction and poor ventilation of the OMU. Septal deviations are generally more
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Fig 4. Post-FESS osteitic reaction and surgical failure with missed ostium. Coronal CT. A, through OMU; B, 6mm posterior to A. There is marked asymptomatic osteitic thickening of the left ethmoid roof and lamina papyracea (arrows) 3 years after FESS. There has been a septoplasty complicated by a perforation (arrow heads), through which a conchal neck air cell protrudes (*), There is a small uncinate base remnant anteriorly in A with fracture and lateralization of the posterior uncinate in B (open arrows), leaving the diseased inner maxillary ostium untouched and obstructed, Note the antral fluid collection because of persistent outlet obstruction. Posterior to B was a patent middle meatal antrostomy (not shown) that did not protect the patient from developing postoperative sinus disease because it was not a physiological opening. This patient went on to have successful revision surgery with removal of the uncinate remnant and fibrous tissue, and extension of the antrostomy to join the natural ostium.
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Fig 5. Coronal CT. A, preoperative; B, postoperative. In A, there is a right concha bullosa cell (c) and paradoxical curvature of the left middle turbinate head (t) crowding the middle meati bilaterally. In B, the lateral lamella of the concha bullosa was removed, and the medial lamella was sutured to the septum to prevent deviation. The paradoxical middle turbihate on the left was reduced (arrowhead). In addition there was a left uncinectomy and limited anterior ethmoidectomy with opening of the ethmoidal bulla from below, asterisk, ethmoidal bulla.
pronounced on nasal endoscopy than they appear on the CT scan, and are most significant when they contact an opposing surface such as the inferior turbinate, the lateral nasal wall, and particularly, the middle turbinate head. Submucosal resection of
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Fig 6. Septopiasty. Coronal CT. A, preoperative; B, postoperative. In A, there is a left septal deviation with a septal spur that bridges the nasal meatus; the middle turbinate is hypoplastic as a result. In B, there has been resection of the central bone plate and spur. The septum is now midline and lacks a bony plate.
the septum at the outset of FESS eases access to and visualization of the OMU. The perpendicular ethmoid plate and vomer will be partially excised with loss of the dense bony plate (Fig 6). Postoperative necrosis may complicate a septoplasty and result in a septal perforation (see Fig 4). Concomitant rhinoplasty may be performed at the same time in many patients. 9
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Fig 7. CaldwelI-Luc procedure. A, coronal CT; B, axial CT. There are wide anterior antrostomy defects (arrowheads). The lateral nasal walls have been resected from the nasal floor to the inferior turbinate necks producing wide nasoantral windows (arrows). Middle turbinate resections were performed as well, In B, there is posterior maxillary wall thickening (curved arrows) and anterior wall retraction, markedly reducing antral volume; the concave opacification of the antral lumen (m) represents fibrous tissue. This reactive process is secondary to a mucosal stripping procedure many years earlier. More recently, there has been a limited endoscopic anterior ethmoidectomy on the right (*). Note the prominence of the inferior turbinate mucosa (t) that, if persistent and irreversible, would represent turbinate hypertrophy.
Caldwell-Luc Antrostomy Before FESS, the Caldwell-Luc procedure was the standard of care for the surgical treatment of refractory maxillary and ethmoid sinus disease,
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initially described by Caldwell in 1893, and Luc in 1894. lO A wide antrostomy was performed through a transoral/sub-labial approach at the canine fossa for direct visualization of the maxillary lumen utilizing a binocular operating microscope. This provided access to the nose and anterior ethmoid air cells. Polyps and mncosa were removed (mucosal stripping), and an inferior antrostomy (nasoantral window) was performed for gravity dependent drainage. A transantral ethmoidectomy could be performed if necessary. At the end of the procedure, the anterior antrostomy defect was closed. Limited success and a range of postoperative sequelae made this a controversial procedure in recent years. 11 The Caldwell-Luc procedure is now reserved for surgical access to the pterygopalatine fossa, management of selected midface fractures and tumors, foreign body and sinolith retrieval, and oroantral fistula repair, a° Mucosal stripping is no longer performed. The Caldwell-Luc procedure may be recognized by the presence of the anterior antrostomy defect and the nasoantral window (Fig 7). The most remarkable imaging feature of the post-CaldwellLuc antrostomy patient is exuberant bone proliferation and retraction of the antral walls, initiated by stripping of the mucosal lining. This reduces the volume of the antral lumen, and may cause facial deformity because of the acquired hypoplasia. Formation of synechia may compartmentalize the antrum and result in formation of a postCaldwell-Luc mucocele (Fig 8). The nasolacrimal duct may be obliterated or damaged during this procedure. Frequently, the retracting maxilla adheres to the duct orifice in the inferior nasal meatus. In these cases, ductal occlusion results in epiphora and potentially, dacryocystitis. A dacryocystorhinostomy is often required to reestablish a drainage pathway for tears from the lacrimal sac to the nasal cavity.
Surgical Failure: FESS The patient with chronic sinusitis will inevitably experience episodes of sinusitis even after a successful FESS. The CT scan will demonstrate the surgical changes, varying degrees of outflow tract opacification, and mucosal thickening. The radiologist must critically assess the remnant anatomy and identify structural features that may predispose toward continued sinus disease.
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Fig 8. CaldwelI-Luc procedure with mucocele. Coronal CT. The anterior antrostomy defects are not seen on this slice. The nasoantral windows are small (arrows). There is marked proliferative bone formation on the right, almost completely obliterating the sinus lumen. Rounded densities with expansile features in the left maxillary sinus lumen and outflow tract are postoperative mucoceles (m} requiring revision surgery for drainage.
The most common etiology for surgical failure is an incomplete resection of the uncinate plate. An uncinate base remnant protects the inner maxillary sinus ostium and the proximal infundibulum. If the cause of the sinus disease was impaired mucociliary clearance through this outlet channel, then the problem was not addressed and disease will persist in the face of the incomplete surgery. This problem has been called the 'missed ostium sequence' (Fig 4). 12 Ostial obstruction may be inflammatory, fibrous, or osseous. Remember that mucociliary clearance direction is genetically determined and cannot be altered under any circumstance, including sinonasal surgery. 3 Ciliary action will continue to propel mucous and debris towards an obstructed ostium and sinus drainage will be inadequate even if there is a wide, patent antrostomy. An extensive middle turbinate head reduction may destabilize the turbinate neck anteriorly and superiorly at the skull base. The turbinate neck can then migrate laterally and overlie the frontal recess. Postoperative frontal sinusitis will ensue even though the frontal sinus outflow tract was not addressed by the surgery (Fig 9). 7'13
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Fig 9. Surgical failure: lateralized middle turbinate neck. Coronal CT. A, frontal recess; B, frontal sinus lumen, anterior to A, There was complete resection of both middle turbinate heads 8 months earlier. In A, the right middle turbinate neck is retracted laterally (arrows), closing over and obstructing the frontal recess. Note the normal position of the left turbinate neck (arrowhead), anchored by an ethmoid septation. Persistent mucosal disease and retained secretions are seen in B because of outflow tract obstruction. This necessitated revision surgery with frontal sinusotomy and temporary stent placement to maintain patency of the ostium.
Surgical Complications Complications of FESS can be divided into local, orbital, skull base, and intracranial events. Local complications including bleeding and synechia formation do not require imaging. The most common orbital complication is vio-
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lation of the lamina papyracea producing a bone defect. If periorbita was disrupted as well, orbital fat will bulge through this defect into the adjacent ethmoid air cell. This is because of infracturing of the orbital plate and alone is of no clinical significance. If forceps or biting instruments actually penetrate the orbit proper, edema may develop in or around the medial rectus muscle. This may be asymptomatic or may result in postoperative diplopia that usually resolves (Fig 10). The anterior ethmoid artery arises from the ophthalmic artery in the orbit, and enters the ethmoid cavity through the anterior ethmoid foramen. The artery traverses the ethmoid roof running an anterior-medial course, and penetrates the lateral lamella of the cribriform plate to enter the (intracranial) olfactory fossa (Fig 11). 14 During its ethmoid course, the artery may be completely covered in a bony canal, may be submucosal and unprotected, or rarely may hang down on a mesentery. In the latter 2 cases, the artery is at risk for injury during an ethmoidectomy. Laceration of the anterior ethmoidal artery results in profuse bleeding that requires cauterization, packing, and termination of the surgical procedure. If transected, the proximal end of the artery may retract into the orbit and produce an orbital hematoma requiring canthotomy for pressure release. The newer powered instruments, so useful in the sinus cavities, can produce devastating and immediate intraorbital damage before the surgeon is aware of the situation. The medial rectus muscle, lying in close proximity to the lamina papyracea can be macerated by a penetrating microdebrider (Fig 12). The drill can even protrude into the muscle cone, and injure the central retinal branch of the ophthalmic artery along its intraconal course between the optic nerve and the lateral rectus muscle, causing immediate blindness (Fig 13). The central retinal artery first encircles the perioptic sheath, then pierces it 1.0 to 1.5cm behind the optic nerve head to supply the retina and portions of the optic nerve. 15 Clearly the optic nerve is also at risk in this situation. Intra-operative or postoperative cerebrospinal fluid (CSF) rhinorrhea is a well-known complication of FESS, occurring in .5% of patients. 16 Frequently recognized during the procedure, the leak can be immediately addressed and sealed from below. 17 Although the cribriform plate is thin and delicate, the lateral lamella of the cribriform plate
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defect cannot be seen and CSF rhinorrhea persists, then a CT cisternogram may demonstrate the site of the leak. Pneumocephalus may accompany the skull base defect, especially with nose blowing after the packing material is removed. If the bone defect is particularly wide, brain and meninges may herniate inferiorly into the nasal cavity (Fig 15). Intracranial instrumentation is obviously a serious complication of FESS. That this occurs at all is a testament to the technical difficulty of endoscopic surgery, and the lack of orientation and depth perception for the operator of a monocular viewing endoscope. 19 Potential intracranial injuries include extraaxial, parenchymal, and intraventricular hemorrhage (Fig 16). If vessels are lacerated, subarachnoid hemorrhage will occur2° and a pseudoaneurysm may develop. FRONTAL SINUS AND THE FRONTAL SINUS OUTFLOW TRACT FESS
Development of endoscopic techniques for the frontal sinus outflow tract initially lagged behind those of the ostiomeatal unit. The reasons for this included the lower frequency of refractory frontal sinusitis, the fact that frontal sinus disease often resolves after FESS performed on the OMU, 21 and
Fig 10. Orbital fat herniation. A, intra-operative endoscopic view. B, coronal CT. This 'standard FESS' procedure went smoothly, and the surgeon took intra-operative pictures for teaching purposes. On reviewing this slide 3 days later, he noticed a small globule of orbital fat herniating through the lamina papyracea into the ethmoid cavity, prompting the CT scan. The scan demonstrated the bony defect of the orbital plate as expected (arrows), as well as thickening and slight distortion of the medial rectus muscle belly (arrowhead), unexpected in this asymptomatic patient. The maxillary and ethmoid sinus opacification represents edema and irrigation fluid in this immediate postoperative study, f, fat herniation; LP, lamina papyracea.
is the weakest component of the anterior skull base 18 and the most common location for intraoperative fracture, usually because of manipulation of the middle turbinate neck. The postoperative CT scan will almost always demonstrate an anterior skull base defect that can vary from tiny and barely detectable to surprisingly wide (Fig 14). If the bone
Fig 11. Anterior ethmoidal artery. Coronal CT. In this patient, the artery runs through the ethmoid bone within a discrete canal (arrows) from the orbit to the olfactory fossa. Surrounding reactive bone from a subtotal anterior ethmoidectomy enhances the appearance of the canal on the left. Forked line: cribriform plate, medial; lateral lamella, lateral; c, crista galli.
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but other terms include the Draf III,25 the frontal sinus drill Out, 24 and the transeptal frontal sinusotomy. 28 The original external Lothrop procedure was developed in 1914, and intended to produce as large a frontal-nasal opening that the anatomy would allow. 21 Today, the endoscopic derivative remains technically demanding, with an unmistak-
Fig 12. Medial rectus muscle injury post-FESS with microdebrider. Coronal Tl-weighted MRI, 3-inch surface coil over left orbit. The fracture of the left orbital plate is not well seen, but orbital contents are tethered towards the bone defect because of the suctioning effect of the instrument (arrow). The medial rectus muscle has been severely damaged: the cross-sectional area is markedly reduced, and function was limited. The patient was managed by the orthoptics service. mr, medial rectus muscle; so, superior oblique muscle, straight segment; stub, superior muscle bundle; Ir, lateral rectus muscle; it, inferior rectus muscle; on, optic nerve.
the complex anatomy of this region. 22 As understanding of frontal recess anatomy expanded, techniques and instrumentation were refined, and with time, the frontal sinus drainage pathways could be approached with the endoscope. 23 Several authors have described techniques for endoscopic frontal sinus surgery, also known as frontal sinusotomy. All systems are based on stepwise incremental extension of the procedure proportional to the severity of disease. 24-27 The most limited of these procedures involves an uncinectomy and possibly a middle turbinate head reduction, ie, a routine FESS that addresses the inferior frontal recess. This can be extended to include an anterior ethmoidectomy with specific removal of those air cells that directly impinge on the frontal recess, such as the agger nasi and frontal bulla cells. 4 The next more extensive procedure requires excision of the frontal sinus floor from the middle turbinate neck to the lamina papyracea, often referred to as the Draf IIB procedure (Fig 17). The most definitive endoscopic procedure performed on the frontal sinus is widely known as an endoscopic modification of the Lothrop procedure,
Fig 13. Medial rectus muscle injury and central retinal artery occlusion with microdebrider. A, axial CT immediate after surgery; B, axial T2-weighted MRI with 3 inch surface coil over each orbit, 2 weeks later. The mid lamina papyracea is disrupted (*), at which point there is an abrupt change in caliber of the medial rectus muscle belly (arrow). This location corresponds to the course of the central retinal branch of the ophthalmic artery. Initially, there was proptosis because of minimal hemorrhage and post-traumatic edema with stranding of the orbital fat. By the time of the MRI, the edema subsided, and mild enophthalmos developed because of tissue loss. Lateral deviation of the globe (exotropia) is because of complete loss of medial rectus function and unopposed lateral rectus (Ir) action, with contraction of the muscle belly. The optic nerve is thick with high "1"2 signal (arrowheads) because of central retinal artery laceration and occlusion. The patient had "no light perception' as a result.
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nal drainage catheter. The anterior osteotomy is often visible on the CT scan as a smooth bone defect, 3 to 5 mm in diameter (Fig 19).
Osteoplastic Flap
Fig 14. Anterior skull base injury. Coronal CT, immediately after surgery. There is a wide defect in the right skull base (arrowheads), predominantly involving the lateral lamella and the ethmoid roof. Most of the cribriform plate remains in place. The ethmoid and nasal cavities are filled with packing material (p); the maxillary sinuses contain irrigation fluid. Forked line on normal side: cribriform plate, medial; lateral lamella, lateral.
The osteoplastic flap procedure, first reported in 1894, was popularized in the 1960s 31 and is still performed today to eradicate frontal sinusitis. The osteoplastic flap is an acceptable alternative to the endoscopic approach in many circumstances. Indications for this external procedure include lateral location of significant sinus disease or mucocele, fracture and CSF fistula repair, and tumor excision. 25 It is the 'salvage' procedure performed in the face of failed endoscopic surgery. Before the surgery, the patient has a 6 foot Caldwell radiograph, and the contour of the frontal sinus is physicalIy cut out of the film, sterilized, and used as a template to approximate the contour of the sinus lumen on the frontal bone. In centers where image-guided surgery systems are used, the outline of the frontal sinus can be localized and marked on the frontal bone. Once the osteotomy is performed, the anterior table of the frontal sinus is detached superiorly, and hinged inferiofly, so that the entire frontal sinus lumen is visualized. The mucosa is
able appearance on CT. There is a complete anterior ethmoidectomy, excision of the anterior segment of the perpendicular ethmoid plate and the intersinus frontal septation, and excision of the frontal sinus floor extending the full width between the lacrimal bones (Fig 18). Despite the tremendous advances made in frontal sinus surgery, re-stenosis of the outflow tract remains a vexing problem, particularly when the surgical ostium is less than 5ram in diameter. 29 Temporary stent placement is the standard procedure for many of these endoscopic frontal sinus procedures. The stents are removed after healing has occurred, usually between 4 and 8 weeks after the surgery 3° and are rarely imaged.
Frontal Sinus Trephination Frontal sinus trephination is an external procedure indicated for rapid drainage and irrigation of an acutely infected frontal sinus. It may be used in conjunction with an endoscopic procedure to identify the frontal ostium from below by irrigation from above. The trephine is an anterior-inferiormedial frontal sinus wail puncture just below the eyebrow for irrigation and placement of an exter-
Fig 15. latrogenic cephalocele. Coronal T2-weighted MRI, 2 years after extensive FESS. There are wide defects in the anterior skull base bilaterally through which dura, cerebrospinal fluid, and gyrus rectus herniate. The patient complained of recurrent sinus inflammatory symptoms, and the cephaloceles were noted on routine office nasal endoscopy.
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Fig 16. Intracranial instrumentation during FESS, A, coronal sinus CT and B, axial head CT immediately after the procedure. C, coronal CT 2 years later. Towards the end of a 'routine' FESS, the surgeon noted sudden L orbital proptosis. The FESS was terminated and the nose was packed (p). Immediate CT scan demonstrated penetration of the skull base through the posterior cribriform plate and its lateral lamella, and an instrument track through the frontal lobe with hemorrhage and air (arrows). A superior lamina papyracea defect (arrowhead) was seen without orbital hematoma. Axial head CT demonstrated epidural air and intraventricular air with hemorrhage. Postoperative diplopia resolved after a few weeks, and the patient recovered without symptomatic sequelae, but had a pseudostrabismus. Two years later, her sinus symptoms recurred. The CT scan demonstrated the encephalomalacic frontal lobe track (arrows) and concave fibrosis of the ethmoid cavity (e) with an adhesion to a rounded medial rectus muscle (m) accounting for her clinical appearance. The antrum was now completely opacified because of recurrent outflow tract obstruction.
completely removed and the sinus cavity and ostium are packed most commonly by abdominal fat, but bone graft and hydroxyapatite materials have been used as well. The anterior table is then placed back into position, and is closed. 21'32
Both CT and MRI will demonstrate the integrity of the bone flap and the fatty contents of the autograft. Animal studies have shown that even in the absence of infection, there is variable fat resorption and replacement by soft tissue with time,
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Fig 17. Frontal sinusotomy, Draf liB. Coronal CT. There has been a complete anterior ethmoidectomy and excision of the middle turbinate neck. This produces a wide communication between the frontal sinus lumen and the nasal cavity {arrow).
BARBARA ZEIFER
Fig 19. Frontal sinus trephination, Coronal CT, many years after surgery. There is a smooth bone defect {arrows) along the anterior-inferior-medial wall of the frontal sinus.
ranging from 0 to 70% 33,34 A range of normal CT density and MRI signal intensity will reflect this phenomenonY '36 The sinus lumen should be completely filled by the graft material, without residual
Fig 18. Modified endoscopic Lothrop procedure. Coronal CT. Excision of all the anterior ethmoidal septations, the intersinus frontal septation, the middle turbinate necks, and the anterior segment of the nasal septum have created the ultimate frontal sinusotomy. Courtesy of Dr. Michelle Smith, Medical College of Wisconsin,
Fig 20. Osteoplastic flap. Axial CT 6 weeks post-op. The anterior table of this large frontal sinus has been detached, the mucosa removed, and the lumen packed with fatty tissue. The bone flap fractured but lies in anatomical position {arrows). The fat of the graft (f) is clear and abuts the inner cortex; the patient had no frontal sinus symptoms and the graft was not felt to be infected. Inadvertent disruption of the posterior table on the left is noted, with protrusion of the fat graft into the anterior cranial fossa (arrowheads).
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air or evidence of graft retraction, and the cortex of the bone flap should be intact (Figs 20 and 21).
Surgical Failure
Fig 21. Frontal sinus obliteration. Sagittal reformat. This patient had an infected osteoplastic flap that could not be salvaged, For revision, the frontal sinus lumen was obliterated with hydroxyapatite paste (h) that also served to reform the anterior table. A stent was placed in a supraorbital ethmold air cell (arrow) to maintain aeration.
Fig 22. Ostial stenosis. Frontal sinus, sagittal reformat. Manipulation of the frontal sinus ostium resulted in 360 ° reactive bone formation and severe stenosis (arrows). Thick mucoid secretions cannot clear out and layer posteriorly in the frontal sinus. Note the complete anterior ethmoidectomy cavity (e). p, posterior ethmoid; s, sphenoid sinus; f, frontal sinus.
The frontal ostium is particularly sensitive to manipulation. Mucosal disruption during FESS dramatically raises the probability of developing postoperative ostial stenosis. The stenosis may be fibrous and therefore soft tissue in density, or calcified because of an osteitic reaction (Fig 22). Persistent frontal sinusitis following frontal sinusotomy requires revision to the next level of frontal sinusotomy or an osteoplastic flap. The osteoplastic flap procedure may fail if the mucosal surface is not completely eradicated. In this situation, epithelial regeneration occurs, and secretion continues into the surgically obstructed sinus cavity. The end result will be the develop-
Fig 23. Infected osteopiastic flap. Coronal CT. Three years earlier, the patient had an osteoplastic flap procedure with subsequent bouts of graft infection. On the current scan obtained while symptomatic there is partial replacement of the autologous fat graft (f) by soft tissue material (s). This finding can be nonspecific, but when compared to prior scans, the soft tissue component was larger and more rounded. An old trephination defect had widened laterally (arrowheads), because of osteomyelitis and necrosis of the bone plate.
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Fig 24. Trephination complication. A, anterior and B, posterior, contiguous coronal CT scans; C, axial CT. This 9-year-old child presented with acute frontal sinusitis and a superior subperiosteal orbital abscess. A frontal trephination procedure was performed, but the osteotomy was too lateral, and the trocar penetrated both anterior (A) and posterior (B) frontal sinus tables; the drainage catheter was inserted into the frontal lobe. Note the subperiosteal drain in the superior-temporal orbital quadrant (arrowhead). Irrigation resulted in epidural empyema (e), frontal lobe cerebritis (c) later developing into a frank abscess, and subgaleal phlegmon (g). The patient eventually recovered completely. Arrows, drainage catheter.
ment of a frontal sinus mucocele or pyocele. Postoperative infection of the graft may occur and is difficult to medically eradicate. Imaging studies will show replacement of the fatty graft material by soft tissue material that is often difficult to distin-
guish from normal graft evolution34 although a rounded density within the fatty tissue suggests infection (Fig 23). The clinical status of the patient is therefore as important as the imaging findings in diagnosing an infected osteoplastic graft.
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event, because of the accessibility of the SER and the ability to produce large openings that tend to remain patent. Surgical C o m p l i c a t i o n s The sphenoid sinus has complex neurovascular relationships, with proximity to the cavernous sinus, carotid artery, optic canal, tbramen rotundum,
Fig 25. Posterior FESS, bilateral. Axial CT. All ethmoidal septations have been removed, including the basal lamella, creating one large ethmoidal cavity (e). The anterior wall of the sphenoid sinus has been opened creating the anterior sphenoidotomy (arrows). s, sphenoid sinus.
Surgical C o m p l i c a t i o n s Complications of frontal sinusotomy and the modified endoscopic Lothrop procedure include laceration of the anterior ethmoidal artery in the ethmoid roof, damage to the cribriform plate and olfactory apparatus, and inadvertent instrumentation of the anterior cranial fossa or orbit. Even the relatively safe and simple frontal trephination can be complicated by penetration of the posterior frontal table with subsequent introduction of irrigation fluid and infectious material into the anterior cranial fossa (Fig 24).
SPHENOETHMOID RECESS Endoscopic surgery of the posterior ethmoid and sphenoid sinuses is directed at the sphenoethmoid recess, the common drainage pathway of this region. The typical posterior FESS includes a posterior ethmoidectomy and anterior sphenoidotomy, best evaluated in the axial scan plane (Fig 25). The minimal procedure would involve removal of polyps and redundant mucosa from the recess alone, without manipulating the sphenoid ostium.
Surgical Failure Failed posterior surgery is caused by stenosis of, or recurrent disease in, the sphenoid ostium or sphenoethmoid recess. This is an uncommon
Fig 26. Onodi cell. A, coronal CT; B, oblique-sagittal reformat. In A, an air cell is seen above the sphenoid sinus, bordering the optic canal. This could represent an Onodi cell, or a septated sphenoid sinus. The sagittal reformat confirms this cell to be of posterior ethmoid (p) origin. Asterisk, Onodi cell; arrow, optic canal; s, sphenoid sinus.
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and the vidian canal. The thickness of the sphenoid sinus wall is variable. Areas of the sphenoid sinus wall can measure as little as .5 mm in thickness, and foci of bony dehiscence are common. 36 When these areas of extreme thinning or dehiscence are found at critical neurovascular structures, instrumentation of the sinus cavity can potential result in an untoward event, such as injury to the cavernous carotid artery or optic nerve. Therefore, the surgeon follows a medial and inferior course with the endoscope, along the intersinus septation, should entry into the sphenoid sinus be required. An Onodi cell is an anatomic variant of the posterior ethmoid labyrinth. The Onodi cell is produced by posterior pneumatization of the posterior ethmoid air cell into the sphenoid bone, cephalad to the sphenoid sinus lumen. This developmental variation places a posterior ethmoid air at
the optic canal, an unexpected anatomic relationship. In this situation, the optic nerve is at risk for instrumentation and injury during the course of an endoscopic posterior ethmoidectomy. Clearly, preoperative knowledge of an Onodi cell is critical in preventing a devastating complication (Fig 26). CONCLUSION
Today, radiologists see more and more CT scans following a wide variety of sinus surgeries. Changes of the transnasal endoscopic procedures and the older external surgical procedures will inevitably be encountered. Reviewing the spectrum of these procedures and their anatomical alterations is helpful to the radiologist in providing a dynamic and useful CT report to the referring otolaryngologist.
REFERENCES 1. Messerklinger W: Endoscopy of the Nose. BaltimoreMunich, Urban & Schwarzenberg, 1978 2. Kennedy DW, Zinreich SJ, Rosenbaarn AE, et al: Functional endoscopic sinus surgery. Arch Otolaryngol 111:576582, 1985 3. Stammberger H: Secretion transportation, in Stammberger H: Functional Endoscopic Sinus Surgery. Philadelphia, PA, B. D. Decker, 1991, pp 17-48 4. Zeifer B: Update on sinonasal imaging. Neuroimaging Clin North Am 8:607-630, 1998 5. Setliff RC III, Parsons DS: The 'hummer': New instrumentation for functional endoscopic sinus surgery. Am J Rhinol 8:275-278, 1994 6. Setliff RC 1II: The small-hole technique in endoscopic sinus surgery. Otolaryngol Clin North Am 30:341-354, 1997 7. Giacchi 1Ll, Lebowitz RA, Jacobs JB: Middle mrbinate resection: Issues and controversies. Am J Rhinolo 14:193-197, 2000 8. Passali D, Lauriello M, Anselmi M, et al: Treatment of hypertrophy of the inferior turbinate: Long-term results. Ann Otol Rhinol Laryngol 108:569-575, 1999 9. Risk SS, Edelstein DR, Matarasso A: Concurrent functional endoscopic sinus surgery and rhinoplasty. Ann Plast Surg 38:323-329, 1997 10. Blitzer A, Lawson W: The Caldwell-Luc procedure in 1991. Otolaryngol Head Neck Surg 105:717-722, 1991 11. Unger JM, Dennison BF, Duncavage JA, et al: The radiologic appearance of the post-Caldwell-Luc maxillary sinus. Clin Radiol 37:77-81, 1986 12. Parsons DS, Stivers FE, Talbot AR: The missed ostium sequence and the surgical approach to revision functional endoscopic sinus surgery. Otolaryngol Clin North Am 29:169183, 1996 13. Saidi IS, Biedlingmaler JF, Rothman MI: Pre- and postoperative imaging analysis for frontal sinus disease following
conservative partial middle turbinate resection. Ear, Nose & Throat J 44:326-330, 1998 14. Chung SK, Dhong HJ, Kim HY: Computed tomography anatomy of the anterior ethmoid canal. Am J Rhinol 15:77-81, 2001 15. Janfaza P, Rubin PAD, Azar N. Orbit, in Janfaza P, et al (eds): Surgical Anatomy of the Head and Neck. Philadelphia, PA, Lippincott Williams & Wilkins, 2001, pp 149-221 16. May M, Levine HL, Mester SJ, et al: Complications of endoscopic sinus surgery: Analysis of 2108 patients-incidence and prevention. Laryngoscope 104:1080-1083, 1994 17. Wax MK, Ramadan I-1H, Ortiz O, et al: Contemporary management of cerebrospinal fluid rhino?rhea. Otolaryngol Head Neck Surg 116:442-449, 1997 18. Kainz J, Starnmberger H: The roof of the anterior ethmoid: A place of least resistance in the skull base. Am J Rhinol 4:191-199, 1990 19. Lucente FE, Shoenfeld PS: Calibrated approach to endoscopic sinus surgery. Ann Otol Rhinol Laryngo199:1-4, 1990 20. Berenholz L, Kessler A, Sarfaty S, at al: Subarachnoid hemorrhage: A complication of endoscopic sinus surgery using powered instrumentation. Otolaryngol Head Neck Surg 121: 665-667, 1999 21. Gross CW: Clinical Challenges in Otolaryngology: Surgical treatments for symptomatic chronic frontal sinusitis: Arch Otolaryngol Head Neck Surg 126:101-102, 2000 22. Nguyen QA Leopold DA: Current concepts in the surgical management of chronic frontal sinusitis. Otolaryngol Clin North Am 30:355-370, 1997 23. Kuhn FA: Chronic frontal sinusitis: The endoscopic approach. Operative Tech Otolaryngol--Head Neck Surg 7:222229, 1996 24. Metson R, Glildich RE: Clinical outcome of endoscopic sinus surgery for frontal sinusitis. Arch Otolaryngol Head Neck Surg 124:1090-1096, 1998
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25. Weber R, Draf W, Kratzsch B, et al: Modem concepts of frontal sinus surgery. Laryngoscope 111:137-146, 2001 26. May M, Schaitldn B: Frontal sinus surgery: Endoscopic drainage instead of an external osteoplastic approach. Operative Tech Otolaryngol---Head Neck Surg 6:184-192, 1995 27. Kuhn FA, Javer AR: Primary endoscopic management of the frontal sinus. Otolaryngol Clin North Am 34:59-75, 2001 28. Lanza DC, McLaughlin RB, Hwang PH: The five-year experience with endoscopic trans-septal frontal sinusotomy. Otolaryngol Clin North Am 34:139-152, 2001 29. Hoseman W, Kuhnel TH, Held P, et al: Endonasal frontal sinusotomy in surgical management of chronic sinusitis: A critical evaluation. Am J Rhinol 11:1-19, 1997 30. Rains BM III: Frontal sinus stenting. Otolaryngol Clin North Am 34:101-110, 2001 31. Montgomery WW: Osteoplastic frontal sinus operation: Coronal incision. Ann Otol Rhinol Laryngol 74:821-830, 1965
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32. Montgomery WW, Lazor JB: Controversies in surgery for chronic frontal sinusitis, in Bailey BJ (ed): Head and Neck Surgery---Otolaryngology, vol 1 (ed 2). Philadelphia, PA, Lippincott-Raven, 1998, pp 837-849 33. Montgomery WW, Pierce DL: Anterior osteoplastic fat obliteration for frontal sinus: Clinical experience and animal studies. Trans Am Ophthalmol Otolaryngol 67:46-57, 1963 34. Montgomery WW: The fate of adipose tissue in a body cavity. Laryngoscope 74:816-827, 1964 35. Catalano PJ, Lawson W, Som P, et al: Radiographic evaluation and diagnosis of the failed frontal osteoplastic flap with fat obliteration. Otolaryngol Head Neck Surg 104:225234, 1991 36. Loevner LA, Yousem DM, Lanza DC, et al: MR evaluation of frontal sinus osteoplastic flaps with autogenous fat grafts. Am J Neuroradiol 16:1721-1726, 1995 37. Fujii K, Chamber SM, Rhoton AL: Neurovascular relationships of the sphenoid sinus. J Neurosurg 50:31-39, 1979