- Email: [email protected]
Orbital trauma
Orbital Trauma Michael Rothman The globe and orbit constitute a very small portion of the body; however, trauma to this region assumes critical importance due to the high value we place on vision. The evaluation of orbital trauma has progressed rapidly with the development and wide distribution of computer-assisted imaging. Plain radiography, angiography, computed tomography (CT}, and magnetic resonance imaging (MRI), may all be used in the evaluation of orbital trauma and the search for foreign bodies. Copyright © 1997 by W,B. Saunders Company
HE ORBIT MAY be injured directly or indirectly, with both blunt and penetrating trauma occurring with equal frequency. Soft tissue swelling often obscures direct clinical evaluation of the globe, limits ocular motion, and may limit clinical assessment of vision. Plain film evaluation of the orbit may accurately depict the presence of bony injury, as well as the presence of radiopaque and radiolucent foreign bodies. However, the lack of soft tissue detail limits its utility for treatment planning. CT shows both soft tissue and bony injury, and more clearly defines the location and orientation of displaced bony fragments, foreign bodies and air. MRI may be complementary to CT scanning in certain patients, particularly with injuries involving the globe or optic nerve, but is contraindicated in the presence of a metallic foreign body. The presence of orbital emphysema or penetrating trauma, enophthalmos/exophthalmos, palpable bony step-off, visual loss or extra-ocular muscle deficit on physical examination indicates the need for cross-sectional imaging evaluation. 1,2
T
TECHNIQUE
In many emergency rooms, plain film evaluation of the orbit remains the standard initial imaging modality. Standard plain film examination of the orbit includes anteroposterior or Caldwell, lateral, and Water's views of the face. Although supplementary views may be obtained (eg, Rhese view of the optic foramen), subtle and complex fractures are best evaluated by CT scanning. The ability to obtain an adequate plain film examination of the orbit may be limited in the presence of concurrent trauma elsewhere, particularly cervical injuries. Standard CT examination should include both axial and direct coronal imaging at slice thicknesses of 3 mm or less, with images presented in both soft tissue and bone windows (preferably using bone algorithm reconstruction). Imaging may be obtained with either conventional axial or spiral/ helical modes. Helically acquired data may be retrospectively reconstructed in thinner sections (1
to 1.5 ram), allowing for improved coronal reconstructions when direct coronal imaging is not possible, or is limited by streak artifact from dental materials. Obfique sagittal reconstructions along the course of the optic nerve may also be useful in selected circumstances. Three-dimensional presentation of data sets can be performed, allowing interactive review and display, although the effort and time required to do so may be prohibitive in an acute setting. Contrast administration is not necessary. The use of MRI in acute trauma has not been studied prospectively in large series. Injuries to the orbit may be well demonstrated on MR1, and it is useful in selected cases, once metal foreign bodies have been excluded. 3,4 Standard evaluation of the orbit may be performed with a standard head coil or with a dedicated surface coil, and should include both axial and coronal Tl-weighted sequences (see the article by Belden, same issue). Oblique sagittal sequences may be useful for evaluation of the optic nerve injuries, while T2-weighted sequences and post-contrast infusion fat-suppressed images delineate globe injuries well (see the article by Kubal, same issue). Dynamic evaluation of extra-ocular muscle function may be obtained in patients with entrapment syndrome with or without diplopia. FOREIGN BODIES
Foreign bodies may be deposited into the orbital soft tissues as a consequence of penetrating injury, and must be localized prior to surgical debridement. X-rays in orthogonal planes may provide sufficient information, but CT shows smaller fragments and their relationship to the globe and optic nerve5,6 (Fig 1). Wood is generally appreciated From the Department of Radiology, University of Maryland Medical Systems, Baltimore, MD. Address reprint requests to Michael Rothman, MD, Anna Gudelsky Magnetic Resonance Imaging Facility, University of Maryland Medical Systems 22 S Greene St, Baltimore, MD 21201. Copyright © 1997 by W.B. Saunders Company 0887-2171/97/1806-000455. 00/0
Seminars in Ultrasound, CT, andMRI, Vo118, No 6 (December), 1997: pp 437-447
437
438
MICHAEL ROTHMAN
Fig 1. Metal foreign bodies sip shotgun injury and repair. (A) Lateral CT Scout film. Multiple metal projectiles overlie the face and orbits. Metal mesh fixes orbit floor (arrow). (B) Axial CT, bone window: 2 metal BBs in right orbit, mesh plate is elevated above orbit floor (arrow). C) Axial CT above level of (B), soft tissue window. Displacement of optic nerve by elevated mesh plate (arrow) (subsequently re-operated and repaired).
emergently as linear air density, whereas glass is usually hyperdense (Fig 2). Plastics vary in their composition and thus, in their CT appearance. 7 Metals are hyperdense, and may cause streak artifact. Plain films or CT may be used with confidence to exclude the presence of ocular metallic foreign bodies before MRI. MRI may also be used to localize non-metallic foreign bodies, s Retained foreign bodies may lead to infection and abscess formation. ISOLATED ORBITAL FRACTURES Blow-out Fractures
"Blow-out" fractures occur when direct blunt force is applied to the globe and orbit, with disruption of an orbital wall and resultant decompression of orbital contents. 9 The inferior or medial wall is
most often damaged, with the superior and lateral walls less commonly involved, l° By definition, the orbital rim is intact ("pure" blow-out fracture) il (Fig 3, 4). Herniation of orbital fat and periorbita into the adjacent maxillary or ethmoid sinuses may occur, and is easily observed on both CT and MRI. These injuries may be associated with displacement of the rectus muscles or their connective tissue attachments and limitation of range of motion of the globe (entrapment syndrome). 1° Children have an increased incidence of "trap-door" fractures and resultant limitation of range of motion as compared with adults) 2 Contusion and laceration of the extraocular muscles may also produce a restriction of motion. Fractures may allow communication of air into the orbit, often with air-fluid levels demonstrated within adjacent paranasal sinuses (Fig 5).
ORBITAL TRAUMA
439
tion of gaze more frequently than with blow-out fractures, and surgical intervention is necessary is all cases.15 As with blow-out fractures, involvement of the orbital rim separates pure and impure blow-in fractures. Superior fractures are associated with more severe cranial injuries, especially epidural hematomas and frontal lobe contusions ~6(Fig 6). COMPLEX ORBITAL FRACTURES
Complex fractures of the midface/orbit are welldefined by CT, including zygomaticomaxillary complex fracture (ZMC) or "tripod" fractures (the zygomatic arch, orbit, maxillary sinus, and zygomaticofrontal process), " N O E " (naso-orbitalethmoid), Le Fort type 2 and 3 fractures (involvement of the pterygoid plates, nasal cavity, and orbit walls), and skull base fractures extending through the optic canal, MRI may be helpful acutely in directly evaluating the intracanalicular portion of the optic nerve. CT and MRI may also be helpful in the evaluation of chronic sequelae of orbital injuries, such as entrapment syndromes (Fig 7), exophthalmos/increased orbital volume (Fig 6), enophthalmos/decreased orbital volume, visual disturbances/ diplopia, and post-surgical complications (Fig 1).
Zygomaticomaxillary Complex Fracture
Fig 2. Wood foreign body. (A) Axial CT. Linear air density (arrow heads) represents wooden FB. (B) Axial CT, delayed f011ow-up. Linear increased density (arrow heads) represents fluid accumulating in interstices of wooden FB. Surrounding soft tissue indicates hematoma and inflammatory reaction. Note additional FB (arrow) poorly observed on (A).
Extension of the fracture plane to involve the rim ("impure" blow-out fracture) generally indicates a more severe traumatic injury. 1t Involvement of the superior rim is particularly significant, and is associated with a greater likelihood of associated cranial injuries, especially in children. 13 As children age and the paranasal sinuses pneumatize, the incidence of orbital floor fractures increases. 14
Blow-in Fractures "Blow-in" fractures are a result of the application of blunt force near the orbit, with decompression and displacement of fracture fragments into the orbit. Patients present with proptosis and restric-
ZMC fractures are usually the result of direct trauma to the malar eminence, resulting in depression of the cheek, dental malocclusion, or trismus. Facial anesthesia due to trauma of the infraorbital nerve is common. The complex includes fractures of the zygomatic arch, orbit floor and rim, anterior, lateral and posterior walls of the maxillary sinus, and zygomaticofrontal process (Figs 8, 9). Nondisplaced fractures are termed "simple." "Complex" fractures are associated with more significant vascular or airway injuries due to the medially displaced and rotated fracture fragments. ~7 Although plain films may delineate the fracture lines well, CT is
Fig 3. Concurrent inferior and medial blow-out fractures. (A, B, C, D) Plain film, Caldwell view; coronal CT, bone and soft tissue windows; coronal Tl-weighted MRI. Left orbit floor and medial wall are disrupted, with dependent soft tissue density representing herniated orbital contents (*), bone fragment (arrow), and partial opacification of maxillary sinus. Medial rectus muscle (arrow head) is tented toward the opacified left ethmoid air cells and medial blow-out fracture. Soft tissue streaky density within intraconal space represents hematoma. (E,F) Axial CT and Tl-weighted MRI. Medial blow-out fracture and medial rectus tenting (arrow head) are better seen. Intraconal hematoma and left globe hemorrhage with choroidal detachment (large arrowhead) are also noted.
440
MICHAEL ROTHMAN
Fig 3 (on previous page).
ORBITAL TRAUMA
441
Fig 6. Superior blow-in fracture. Coronal T1-weighted MRI. Right superior orbit encephalocele (arrow), old, due to prior superior blow-in fracture.
Fig 4. Superior blow-out fracture. (A) Coronal CT, bone window. Comminuted fracture of the orbital roof (arrow). CT of the brain shows a subfrontal hematoma and cortical contusion.
preferred for its ability to accurately define the degree of displacement of the fracture fragments.
Naso-Orbital-Ethmoid Complex Fracture The NOE fracture occurs due to direct trauma to the midface and nasal bones. Concurrent complex bilateral facial trauma and multisystem injuries are commonly observed when the trauma is due to
high-speed motor vehicle accidents, but simple fractures are more frequent when the injury is due to a direct blow as from a fist.18 Fractures may include avulsion of the fossa, comminution of the fossa or canal, and linear fractures of the canaP 9 (Fig 10). Transection of the nasolacrimal apparatus may occur, but is infrequent. Telecanthus, or widening of the interorbital distance, may be observed acutely and is due to avulsion of the medial canthal ligament. Epiphora or lacrimal mucocele due to blockage of the duct, and rhinorrhea secondary to cerebrospinal fluid leak from a concurrent cribi-
Fig 5. Medial blow-out fracture. (A,B) Axial and coronal CT, bone window. Extensive intra- and extra-conal orbital air from lamina papyrcea disruption/ethmoid sinus outlines intraorbital structures.
442
MICHAEL ROTHMAN
Fig 8. Zygomaticomaxillary complex fracture (ZMC). (A) Plain film, Water's view. Left ZMC fracture, including zygomatic arch (a), orbit floor and rim (b), anterior, lateral (c) and posterior walls of the maxillary sinus, and zygomaticofrontal process (d).
form plate or frontal sinus fracture, may occur in delayed presentation. Le Fort Fractures
These midface fractures occur along lines of structural weakness, as defined by Le Fort in 1901. Three types are classically described (in order of increasing severity): (1) transverse fracture through the maxilla above the level of the hard palate including the pterygoid plates, resulting in dissociation of the maxilla from the midface; (2) pyramidal fracture crossing the nasal bridge and septum, medial orbital walls and floors, maxillary antra, and pterygoid plates, resulting in dissociation of the midface from the cranium; (3) transverse fracture through the nasal bridge, and orbits, then diverging through the zygomaticofrontal processes and arches, and the maxilla and pterygoid plates, resulting in craniofacial dissociation (Fig 11). Although originally described as bilaterally symmetrical, pure c
Fig 7. Medial blow-out fracture, chronic. (A, B, C) Axial and coronal CT soft tissue window, coronal CT bone window. Tented and clinically entrapped left medial rectus muscle (arrow head), with herniation of medial rectus muscle, fat, and periorbita into ethmoid air cells, Lack of sinus fluid, and clinical history, confirm chronicity. Note persistent intraorbital air on coronal CT, indicating continuing communication of sinus cavity and orbit.
ORBITAL TRAUMA
443
Fig 9. Zygomaticomaxillary complex fracture. (A, B, C, D) Axial, coronal anterior, coronal posterior and 3D CT, bone window. Right ZMC fracture, including zygomatic arch(a), orbit floor and rim (b), anterior, lateral and posterior walls of the maxillary sinus (c), and zygomaticofrontal process (d). This patient also has a right naso-orbital-ethmoid fracture (arrow).
fracture patterns are rare, and combinations of complex midface fractures are usually observed: the "facial smash" 17 (Figs 10, 12). Complications due to this severe facial trauma are extremely common. Soft tissue hematomas resulting in airway compromise must be excluded during the evaluation process. Immediate and delayed cerebrospinal fluid leaks occur more often with these injuries than with other orbitofacial fractures. Coexistent remote trauma is also frequent due to the high-velocity impact that produces these injuries) 7
TRAUMATIC CRANIAL NEUROPATHIES
Diplopia occurring in the setting of orbital trauma is common and may be due to either injury or restriction of the extraocular muscles or cranial nerves. Cranial nerve injury may occur at the brainstem, in the cisterns, at the skull base or cavernous sinus, or at the orbital apex. CT scanning in axial and coronal planes evaluates the extracranial and skull base segments effectively, but MRI, with high-resolution thin section sequences, best visualizes the intracranial extent of the cranial
444
MICHAEL ROTHMAN
Fig 10. Naso-orbital-ethmoid fracture/facial smash. (A, B) Axial CT inferior and superior levels. Comminuted, impacted bilateral facial fractures with displacement and rotation of nasolacrimal sac/lacrimal bone and duct (arrow). (C) Anteroposterior dacrocystogram transecting and obstructing the nasolacrimal duct (arrow).
nerves. Cranial nerves 2, 3, 4, 5, and 6 (optic, ophthalmic, trochlear, trigeminal, and abducens) may all be injured following trauma. Optic nerve injury may result from direct penetrating trauma, or may be due to compression or transection in association with fractures of the orbital apex/optic canal? ° Loss of visual acuity or visual field deficits are noted by the patient or discovered on physical examination. The presence of post-septal soft tissue density in and around the optic nerve sheath is indicative of perineural hematoma (Fig 13). Bony fragments may also displace or contuse the nerve (Fig 14). Isolated ophthalmic nerve (CN 111) palsy due to
trauma is less common than CN III palsy from other causes? ~Patients present with a combination of diplopia, ptosis, and pupillary dilation. The presence of neck pain, Homer's syndrome, or bruit on physical examination should prompt further evaluation of the vascular tree for the possibility of internal carotid dissection. Trochlear (CN IV) nerve palsy occurs secondary to trauma more often than from any other cause. CN IV innervates the superior oblique muscle, and its deficit results in unopposed action of the inferior oblique muscle. Identification of a trochlear deficit clinically is difficult as a palsy results in hypertropea, mimicking a blow-out fracture on physical examination. 2a
ORBITAL TRAUMA
445
Fig 11. Le Fort fracture. (A, B, C, D) Axial CT from inferior to superior, 3D reconstruction. Bilateral Le Fort fractures: right Le Fort I, II, Left Le Fort I, II, II1. Pterygoid plates fractures (large arrow head) define this complex.
Fig 12. Facial smash. (A, B) Axial CT bone and soft tissue windows. Bilateral facial smash-highly comminuted and impacted crush facial injury. Left globe is ruptured and filled with hemorrhage.
446
M CHAEL ROTHMAN
Trigeminal (CN VI) nerve palsy results in facial anesthesia and absent corneal reflex. It is commonly injured in fractures of the orbit floor or roof, especially if the rim is involved. Fractures through the orbital apex/fissures may also produce Clinical symptoms. ~7 Abducens palsy (CN V1) is the most frequently encountered cranial neuropathy and results in lat-
Fig 14. Optic canal fracture and optic nerve compression. (A, B) Axial and coronal CT, bone window, Complex skull base fracture-extending through right optic canal; with inferior displacement and clockwise rotation of the fracture fragment (arrow). Right sphenoid sinus Iocule is opacified, right pterygold plates are fractured (open arrows); right superior Orbit rim is fractured (arrowhead). ,
Fig 13. Penetrating trauma, (A, B, C) Axial and coronal CT, sagittal reconstruction along the course of the optic nerve. Perineural hematoma (h) along optic nerve following stab injury to inferiomedial orbit with a pencil.
eral rectus palsy and limitation of lateral gaze. The ner+e's long intracranial course is thought to be responsible for its increased susceptibility to traumatic injury.23 Acute or delayed onset of post-traumatic dipl0pia associated ~ith proptosi s and chemosis, sugge;ts a diagfiosis Of direct carotid cavernous fistula (CCF! (Fig. 15)'. Direct CCF results from a tear of the cavernous internal carotid artery that allows arterial blood [0 enter the cavernous sinus, reversing tl~e flo~v in the venous tributaries. Prominent anterior .venous drainage resultS in the Orbital presgntatidn. 24
ORBITAL TRAUMA
447
Fig 15. Traumatic direct carotid cavernous fistula. (A) Axial CT bone windows demonstrate fractures of the superior orbital fissure, lateral sphenoid wall, and carotid canal (arrows). Note the bilateral comminuted temporal bone fractures. (B) Lateral internal carotid arter!ogram demonstrates a direct carotid cavernous fistula with anterior venous drainage into the superior (SOV) and inferior (IOV) ophthalmic veins a s well as posterior drainage into the inferior (IPS) and superior (SPS) petrosal sinuses.
REFERENCES
1. Lepore FE: Disorders of ocular motility following head trauma: Arch Neurol 52:924-926, 1995 2. zimmer-Galler IE, Bartley GB: Orbital emphysema: Case reports and a review of the literature. Mayo Clin Proc 69: I 15121, 1994 3. Ilankovan V, Hadley D, Moos K, el Attar A: A comparison of imaging techniques with surgical experience in orbital injuries. J Cranio-Max Fac Surg 19:348-352, 1991 4. Tonami H, Yamamoto I, Matsuda M, et al: Orbital fractures: Surface coil MR imaging. Radiology 179:789-794, 1991 5. Otto PM, Otto RA, Virapongse C, et al: Screening test for detection of metallic foreign bodies in the orbit before magnetic resonance imaging. Invest Radioi 27:308-311, 1992 6. Etherington RJ, Hourihan MD: Localization ofintraocular and intraorbital foreign bodies using computed tomography. Clin Radio140:610-614, 1989 7. Zinreich SJ, Miller NR, Aguayo JB, et al: Computed tomographic three dimensional localization and compositional evaluation of intraocular and orbital foreign bodies. Arch Ophthalmol 104:1477-1482, 1986 8. Wilson WB, Dreisbach JN, Lattin DE, Stears JC: Magnetic resonance imaging of non-metallic orbital foreign bodies. Am J Ophthal 105:612-617, 1988 9. Smith B, Regan WF: Blowout fracture of the orbit: Mechanism and correction of the internal orbital fracture. Am J Ophthalmo144:733-739, 1957 10. Mathog RH: Management of orbital blow-out fractures. Current issues in head and neck trauma. Otolaryngol Clin North Am 24:79-91, 1991 11. Converse JM, Smith B, Obear MF, Wood-Smith D: Orbital blowout fractures: A ten year survey. Plastic Recon Surg 39:20-36, 1967 12. de Man K, Wijngaarde R, Hes J, de Jong PT: Influence of age on the management of blow-out fractures of the orbital floor. Int J Oral Maxillofac Surg 20:330-336, 1991
13. Greenwald MJ, Boston D, Pensler JM, Radkowski MA: Orbital roof fractures in childhood. Ophthalmology 96:491-497, 1989 14. Koltai PJ, Amjad I, Meyer D, Feustel PJ: Orbital fractures in children. Arch Otolaryngol Head Neck Surg 121: 1375-1379, 1995 I5. Antonyshyn O, Gruss JS, Kassel EE: Blow-in fractures of the orbit. Plastic Recon Surg 84:10-20, 1989 I6. Chirico PA, Mirvis SE, Kelman SE, Karesh JW: Orbital "blow-in" fractures: Clinical and CT features. J Comput Assist Tomogr 13:1017-1022, 1989 17. Harris JH, Harris WH: Face, in Harris JH, Harris WH (eds): Radiology of Emergency Medicine, 2nd ed. Baltimore, MD, Williams and Wilkins, 1981 18. Heine RD, Catone GA, Bavitz JB, Grenadier MR: Naso-orbital-ethmoid injury: Report of a case and review of the literature. Oral Surg Oral Med Oral Pathol 69:542-549, 1990 19. Unger JM: Fractures of the nasolacrimal fossa and canal: A CT study of appearance, associated injuries, and significance in 25 patients. AJR 158:1321-! 324, 1992 20. Cook MW, Levin LA, Joseph MR Pinczower EF: Traumatic optic neuropathy: A meta-analysis. Arch Otolaryngol Head Neck Surg 122:389-392, 1996 2 I. Mark AS, Blake R Kolsky M: MRI evaluation of the third nerve. MRI Decisions March/Aplil:23-31, 1993 22. Remulla HD, Bilyk JR, Rubin PAD: Pseudo-entrapment of extraocular muscles in patients with orbital fractures. J CranioMax Trauma i:16-29, I995 23. Depper MH, Truwit CL, Dreisbach JN, Kelly WM: Isolated abducens nerve palsy: MR imaging findings. AJR 160:837-841, 1993 24. Goodwin JR, Johnson MH: Carotid injury secondary to blunt head trauma: Case report. J Trauma 37:119-122, 1994
HE ORBIT MAY be injured directly or indirectly, with both blunt and penetrating trauma occurring with equal frequency. Soft tissue swelling often obscures direct clinical evaluation of the globe, limits ocular motion, and may limit clinical assessment of vision. Plain film evaluation of the orbit may accurately depict the presence of bony injury, as well as the presence of radiopaque and radiolucent foreign bodies. However, the lack of soft tissue detail limits its utility for treatment planning. CT shows both soft tissue and bony injury, and more clearly defines the location and orientation of displaced bony fragments, foreign bodies and air. MRI may be complementary to CT scanning in certain patients, particularly with injuries involving the globe or optic nerve, but is contraindicated in the presence of a metallic foreign body. The presence of orbital emphysema or penetrating trauma, enophthalmos/exophthalmos, palpable bony step-off, visual loss or extra-ocular muscle deficit on physical examination indicates the need for cross-sectional imaging evaluation. 1,2
T
TECHNIQUE
In many emergency rooms, plain film evaluation of the orbit remains the standard initial imaging modality. Standard plain film examination of the orbit includes anteroposterior or Caldwell, lateral, and Water's views of the face. Although supplementary views may be obtained (eg, Rhese view of the optic foramen), subtle and complex fractures are best evaluated by CT scanning. The ability to obtain an adequate plain film examination of the orbit may be limited in the presence of concurrent trauma elsewhere, particularly cervical injuries. Standard CT examination should include both axial and direct coronal imaging at slice thicknesses of 3 mm or less, with images presented in both soft tissue and bone windows (preferably using bone algorithm reconstruction). Imaging may be obtained with either conventional axial or spiral/ helical modes. Helically acquired data may be retrospectively reconstructed in thinner sections (1
to 1.5 ram), allowing for improved coronal reconstructions when direct coronal imaging is not possible, or is limited by streak artifact from dental materials. Obfique sagittal reconstructions along the course of the optic nerve may also be useful in selected circumstances. Three-dimensional presentation of data sets can be performed, allowing interactive review and display, although the effort and time required to do so may be prohibitive in an acute setting. Contrast administration is not necessary. The use of MRI in acute trauma has not been studied prospectively in large series. Injuries to the orbit may be well demonstrated on MR1, and it is useful in selected cases, once metal foreign bodies have been excluded. 3,4 Standard evaluation of the orbit may be performed with a standard head coil or with a dedicated surface coil, and should include both axial and coronal Tl-weighted sequences (see the article by Belden, same issue). Oblique sagittal sequences may be useful for evaluation of the optic nerve injuries, while T2-weighted sequences and post-contrast infusion fat-suppressed images delineate globe injuries well (see the article by Kubal, same issue). Dynamic evaluation of extra-ocular muscle function may be obtained in patients with entrapment syndrome with or without diplopia. FOREIGN BODIES
Foreign bodies may be deposited into the orbital soft tissues as a consequence of penetrating injury, and must be localized prior to surgical debridement. X-rays in orthogonal planes may provide sufficient information, but CT shows smaller fragments and their relationship to the globe and optic nerve5,6 (Fig 1). Wood is generally appreciated From the Department of Radiology, University of Maryland Medical Systems, Baltimore, MD. Address reprint requests to Michael Rothman, MD, Anna Gudelsky Magnetic Resonance Imaging Facility, University of Maryland Medical Systems 22 S Greene St, Baltimore, MD 21201. Copyright © 1997 by W.B. Saunders Company 0887-2171/97/1806-000455. 00/0
Seminars in Ultrasound, CT, andMRI, Vo118, No 6 (December), 1997: pp 437-447
437
438
MICHAEL ROTHMAN
Fig 1. Metal foreign bodies sip shotgun injury and repair. (A) Lateral CT Scout film. Multiple metal projectiles overlie the face and orbits. Metal mesh fixes orbit floor (arrow). (B) Axial CT, bone window: 2 metal BBs in right orbit, mesh plate is elevated above orbit floor (arrow). C) Axial CT above level of (B), soft tissue window. Displacement of optic nerve by elevated mesh plate (arrow) (subsequently re-operated and repaired).
emergently as linear air density, whereas glass is usually hyperdense (Fig 2). Plastics vary in their composition and thus, in their CT appearance. 7 Metals are hyperdense, and may cause streak artifact. Plain films or CT may be used with confidence to exclude the presence of ocular metallic foreign bodies before MRI. MRI may also be used to localize non-metallic foreign bodies, s Retained foreign bodies may lead to infection and abscess formation. ISOLATED ORBITAL FRACTURES Blow-out Fractures
"Blow-out" fractures occur when direct blunt force is applied to the globe and orbit, with disruption of an orbital wall and resultant decompression of orbital contents. 9 The inferior or medial wall is
most often damaged, with the superior and lateral walls less commonly involved, l° By definition, the orbital rim is intact ("pure" blow-out fracture) il (Fig 3, 4). Herniation of orbital fat and periorbita into the adjacent maxillary or ethmoid sinuses may occur, and is easily observed on both CT and MRI. These injuries may be associated with displacement of the rectus muscles or their connective tissue attachments and limitation of range of motion of the globe (entrapment syndrome). 1° Children have an increased incidence of "trap-door" fractures and resultant limitation of range of motion as compared with adults) 2 Contusion and laceration of the extraocular muscles may also produce a restriction of motion. Fractures may allow communication of air into the orbit, often with air-fluid levels demonstrated within adjacent paranasal sinuses (Fig 5).
ORBITAL TRAUMA
439
tion of gaze more frequently than with blow-out fractures, and surgical intervention is necessary is all cases.15 As with blow-out fractures, involvement of the orbital rim separates pure and impure blow-in fractures. Superior fractures are associated with more severe cranial injuries, especially epidural hematomas and frontal lobe contusions ~6(Fig 6). COMPLEX ORBITAL FRACTURES
Complex fractures of the midface/orbit are welldefined by CT, including zygomaticomaxillary complex fracture (ZMC) or "tripod" fractures (the zygomatic arch, orbit, maxillary sinus, and zygomaticofrontal process), " N O E " (naso-orbitalethmoid), Le Fort type 2 and 3 fractures (involvement of the pterygoid plates, nasal cavity, and orbit walls), and skull base fractures extending through the optic canal, MRI may be helpful acutely in directly evaluating the intracanalicular portion of the optic nerve. CT and MRI may also be helpful in the evaluation of chronic sequelae of orbital injuries, such as entrapment syndromes (Fig 7), exophthalmos/increased orbital volume (Fig 6), enophthalmos/decreased orbital volume, visual disturbances/ diplopia, and post-surgical complications (Fig 1).
Zygomaticomaxillary Complex Fracture
Fig 2. Wood foreign body. (A) Axial CT. Linear air density (arrow heads) represents wooden FB. (B) Axial CT, delayed f011ow-up. Linear increased density (arrow heads) represents fluid accumulating in interstices of wooden FB. Surrounding soft tissue indicates hematoma and inflammatory reaction. Note additional FB (arrow) poorly observed on (A).
Extension of the fracture plane to involve the rim ("impure" blow-out fracture) generally indicates a more severe traumatic injury. 1t Involvement of the superior rim is particularly significant, and is associated with a greater likelihood of associated cranial injuries, especially in children. 13 As children age and the paranasal sinuses pneumatize, the incidence of orbital floor fractures increases. 14
Blow-in Fractures "Blow-in" fractures are a result of the application of blunt force near the orbit, with decompression and displacement of fracture fragments into the orbit. Patients present with proptosis and restric-
ZMC fractures are usually the result of direct trauma to the malar eminence, resulting in depression of the cheek, dental malocclusion, or trismus. Facial anesthesia due to trauma of the infraorbital nerve is common. The complex includes fractures of the zygomatic arch, orbit floor and rim, anterior, lateral and posterior walls of the maxillary sinus, and zygomaticofrontal process (Figs 8, 9). Nondisplaced fractures are termed "simple." "Complex" fractures are associated with more significant vascular or airway injuries due to the medially displaced and rotated fracture fragments. ~7 Although plain films may delineate the fracture lines well, CT is
Fig 3. Concurrent inferior and medial blow-out fractures. (A, B, C, D) Plain film, Caldwell view; coronal CT, bone and soft tissue windows; coronal Tl-weighted MRI. Left orbit floor and medial wall are disrupted, with dependent soft tissue density representing herniated orbital contents (*), bone fragment (arrow), and partial opacification of maxillary sinus. Medial rectus muscle (arrow head) is tented toward the opacified left ethmoid air cells and medial blow-out fracture. Soft tissue streaky density within intraconal space represents hematoma. (E,F) Axial CT and Tl-weighted MRI. Medial blow-out fracture and medial rectus tenting (arrow head) are better seen. Intraconal hematoma and left globe hemorrhage with choroidal detachment (large arrowhead) are also noted.
440
MICHAEL ROTHMAN
Fig 3 (on previous page).
ORBITAL TRAUMA
441
Fig 6. Superior blow-in fracture. Coronal T1-weighted MRI. Right superior orbit encephalocele (arrow), old, due to prior superior blow-in fracture.
Fig 4. Superior blow-out fracture. (A) Coronal CT, bone window. Comminuted fracture of the orbital roof (arrow). CT of the brain shows a subfrontal hematoma and cortical contusion.
preferred for its ability to accurately define the degree of displacement of the fracture fragments.
Naso-Orbital-Ethmoid Complex Fracture The NOE fracture occurs due to direct trauma to the midface and nasal bones. Concurrent complex bilateral facial trauma and multisystem injuries are commonly observed when the trauma is due to
high-speed motor vehicle accidents, but simple fractures are more frequent when the injury is due to a direct blow as from a fist.18 Fractures may include avulsion of the fossa, comminution of the fossa or canal, and linear fractures of the canaP 9 (Fig 10). Transection of the nasolacrimal apparatus may occur, but is infrequent. Telecanthus, or widening of the interorbital distance, may be observed acutely and is due to avulsion of the medial canthal ligament. Epiphora or lacrimal mucocele due to blockage of the duct, and rhinorrhea secondary to cerebrospinal fluid leak from a concurrent cribi-
Fig 5. Medial blow-out fracture. (A,B) Axial and coronal CT, bone window. Extensive intra- and extra-conal orbital air from lamina papyrcea disruption/ethmoid sinus outlines intraorbital structures.
442
MICHAEL ROTHMAN
Fig 8. Zygomaticomaxillary complex fracture (ZMC). (A) Plain film, Water's view. Left ZMC fracture, including zygomatic arch (a), orbit floor and rim (b), anterior, lateral (c) and posterior walls of the maxillary sinus, and zygomaticofrontal process (d).
form plate or frontal sinus fracture, may occur in delayed presentation. Le Fort Fractures
These midface fractures occur along lines of structural weakness, as defined by Le Fort in 1901. Three types are classically described (in order of increasing severity): (1) transverse fracture through the maxilla above the level of the hard palate including the pterygoid plates, resulting in dissociation of the maxilla from the midface; (2) pyramidal fracture crossing the nasal bridge and septum, medial orbital walls and floors, maxillary antra, and pterygoid plates, resulting in dissociation of the midface from the cranium; (3) transverse fracture through the nasal bridge, and orbits, then diverging through the zygomaticofrontal processes and arches, and the maxilla and pterygoid plates, resulting in craniofacial dissociation (Fig 11). Although originally described as bilaterally symmetrical, pure c
Fig 7. Medial blow-out fracture, chronic. (A, B, C) Axial and coronal CT soft tissue window, coronal CT bone window. Tented and clinically entrapped left medial rectus muscle (arrow head), with herniation of medial rectus muscle, fat, and periorbita into ethmoid air cells, Lack of sinus fluid, and clinical history, confirm chronicity. Note persistent intraorbital air on coronal CT, indicating continuing communication of sinus cavity and orbit.
ORBITAL TRAUMA
443
Fig 9. Zygomaticomaxillary complex fracture. (A, B, C, D) Axial, coronal anterior, coronal posterior and 3D CT, bone window. Right ZMC fracture, including zygomatic arch(a), orbit floor and rim (b), anterior, lateral and posterior walls of the maxillary sinus (c), and zygomaticofrontal process (d). This patient also has a right naso-orbital-ethmoid fracture (arrow).
fracture patterns are rare, and combinations of complex midface fractures are usually observed: the "facial smash" 17 (Figs 10, 12). Complications due to this severe facial trauma are extremely common. Soft tissue hematomas resulting in airway compromise must be excluded during the evaluation process. Immediate and delayed cerebrospinal fluid leaks occur more often with these injuries than with other orbitofacial fractures. Coexistent remote trauma is also frequent due to the high-velocity impact that produces these injuries) 7
TRAUMATIC CRANIAL NEUROPATHIES
Diplopia occurring in the setting of orbital trauma is common and may be due to either injury or restriction of the extraocular muscles or cranial nerves. Cranial nerve injury may occur at the brainstem, in the cisterns, at the skull base or cavernous sinus, or at the orbital apex. CT scanning in axial and coronal planes evaluates the extracranial and skull base segments effectively, but MRI, with high-resolution thin section sequences, best visualizes the intracranial extent of the cranial
444
MICHAEL ROTHMAN
Fig 10. Naso-orbital-ethmoid fracture/facial smash. (A, B) Axial CT inferior and superior levels. Comminuted, impacted bilateral facial fractures with displacement and rotation of nasolacrimal sac/lacrimal bone and duct (arrow). (C) Anteroposterior dacrocystogram transecting and obstructing the nasolacrimal duct (arrow).
nerves. Cranial nerves 2, 3, 4, 5, and 6 (optic, ophthalmic, trochlear, trigeminal, and abducens) may all be injured following trauma. Optic nerve injury may result from direct penetrating trauma, or may be due to compression or transection in association with fractures of the orbital apex/optic canal? ° Loss of visual acuity or visual field deficits are noted by the patient or discovered on physical examination. The presence of post-septal soft tissue density in and around the optic nerve sheath is indicative of perineural hematoma (Fig 13). Bony fragments may also displace or contuse the nerve (Fig 14). Isolated ophthalmic nerve (CN 111) palsy due to
trauma is less common than CN III palsy from other causes? ~Patients present with a combination of diplopia, ptosis, and pupillary dilation. The presence of neck pain, Homer's syndrome, or bruit on physical examination should prompt further evaluation of the vascular tree for the possibility of internal carotid dissection. Trochlear (CN IV) nerve palsy occurs secondary to trauma more often than from any other cause. CN IV innervates the superior oblique muscle, and its deficit results in unopposed action of the inferior oblique muscle. Identification of a trochlear deficit clinically is difficult as a palsy results in hypertropea, mimicking a blow-out fracture on physical examination. 2a
ORBITAL TRAUMA
445
Fig 11. Le Fort fracture. (A, B, C, D) Axial CT from inferior to superior, 3D reconstruction. Bilateral Le Fort fractures: right Le Fort I, II, Left Le Fort I, II, II1. Pterygoid plates fractures (large arrow head) define this complex.
Fig 12. Facial smash. (A, B) Axial CT bone and soft tissue windows. Bilateral facial smash-highly comminuted and impacted crush facial injury. Left globe is ruptured and filled with hemorrhage.
446
M CHAEL ROTHMAN
Trigeminal (CN VI) nerve palsy results in facial anesthesia and absent corneal reflex. It is commonly injured in fractures of the orbit floor or roof, especially if the rim is involved. Fractures through the orbital apex/fissures may also produce Clinical symptoms. ~7 Abducens palsy (CN V1) is the most frequently encountered cranial neuropathy and results in lat-
Fig 14. Optic canal fracture and optic nerve compression. (A, B) Axial and coronal CT, bone window, Complex skull base fracture-extending through right optic canal; with inferior displacement and clockwise rotation of the fracture fragment (arrow). Right sphenoid sinus Iocule is opacified, right pterygold plates are fractured (open arrows); right superior Orbit rim is fractured (arrowhead). ,
Fig 13. Penetrating trauma, (A, B, C) Axial and coronal CT, sagittal reconstruction along the course of the optic nerve. Perineural hematoma (h) along optic nerve following stab injury to inferiomedial orbit with a pencil.
eral rectus palsy and limitation of lateral gaze. The ner+e's long intracranial course is thought to be responsible for its increased susceptibility to traumatic injury.23 Acute or delayed onset of post-traumatic dipl0pia associated ~ith proptosi s and chemosis, sugge;ts a diagfiosis Of direct carotid cavernous fistula (CCF! (Fig. 15)'. Direct CCF results from a tear of the cavernous internal carotid artery that allows arterial blood [0 enter the cavernous sinus, reversing tl~e flo~v in the venous tributaries. Prominent anterior .venous drainage resultS in the Orbital presgntatidn. 24
ORBITAL TRAUMA
447
Fig 15. Traumatic direct carotid cavernous fistula. (A) Axial CT bone windows demonstrate fractures of the superior orbital fissure, lateral sphenoid wall, and carotid canal (arrows). Note the bilateral comminuted temporal bone fractures. (B) Lateral internal carotid arter!ogram demonstrates a direct carotid cavernous fistula with anterior venous drainage into the superior (SOV) and inferior (IOV) ophthalmic veins a s well as posterior drainage into the inferior (IPS) and superior (SPS) petrosal sinuses.
REFERENCES
1. Lepore FE: Disorders of ocular motility following head trauma: Arch Neurol 52:924-926, 1995 2. zimmer-Galler IE, Bartley GB: Orbital emphysema: Case reports and a review of the literature. Mayo Clin Proc 69: I 15121, 1994 3. Ilankovan V, Hadley D, Moos K, el Attar A: A comparison of imaging techniques with surgical experience in orbital injuries. J Cranio-Max Fac Surg 19:348-352, 1991 4. Tonami H, Yamamoto I, Matsuda M, et al: Orbital fractures: Surface coil MR imaging. Radiology 179:789-794, 1991 5. Otto PM, Otto RA, Virapongse C, et al: Screening test for detection of metallic foreign bodies in the orbit before magnetic resonance imaging. Invest Radioi 27:308-311, 1992 6. Etherington RJ, Hourihan MD: Localization ofintraocular and intraorbital foreign bodies using computed tomography. Clin Radio140:610-614, 1989 7. Zinreich SJ, Miller NR, Aguayo JB, et al: Computed tomographic three dimensional localization and compositional evaluation of intraocular and orbital foreign bodies. Arch Ophthalmol 104:1477-1482, 1986 8. Wilson WB, Dreisbach JN, Lattin DE, Stears JC: Magnetic resonance imaging of non-metallic orbital foreign bodies. Am J Ophthal 105:612-617, 1988 9. Smith B, Regan WF: Blowout fracture of the orbit: Mechanism and correction of the internal orbital fracture. Am J Ophthalmo144:733-739, 1957 10. Mathog RH: Management of orbital blow-out fractures. Current issues in head and neck trauma. Otolaryngol Clin North Am 24:79-91, 1991 11. Converse JM, Smith B, Obear MF, Wood-Smith D: Orbital blowout fractures: A ten year survey. Plastic Recon Surg 39:20-36, 1967 12. de Man K, Wijngaarde R, Hes J, de Jong PT: Influence of age on the management of blow-out fractures of the orbital floor. Int J Oral Maxillofac Surg 20:330-336, 1991
13. Greenwald MJ, Boston D, Pensler JM, Radkowski MA: Orbital roof fractures in childhood. Ophthalmology 96:491-497, 1989 14. Koltai PJ, Amjad I, Meyer D, Feustel PJ: Orbital fractures in children. Arch Otolaryngol Head Neck Surg 121: 1375-1379, 1995 I5. Antonyshyn O, Gruss JS, Kassel EE: Blow-in fractures of the orbit. Plastic Recon Surg 84:10-20, 1989 I6. Chirico PA, Mirvis SE, Kelman SE, Karesh JW: Orbital "blow-in" fractures: Clinical and CT features. J Comput Assist Tomogr 13:1017-1022, 1989 17. Harris JH, Harris WH: Face, in Harris JH, Harris WH (eds): Radiology of Emergency Medicine, 2nd ed. Baltimore, MD, Williams and Wilkins, 1981 18. Heine RD, Catone GA, Bavitz JB, Grenadier MR: Naso-orbital-ethmoid injury: Report of a case and review of the literature. Oral Surg Oral Med Oral Pathol 69:542-549, 1990 19. Unger JM: Fractures of the nasolacrimal fossa and canal: A CT study of appearance, associated injuries, and significance in 25 patients. AJR 158:1321-! 324, 1992 20. Cook MW, Levin LA, Joseph MR Pinczower EF: Traumatic optic neuropathy: A meta-analysis. Arch Otolaryngol Head Neck Surg 122:389-392, 1996 2 I. Mark AS, Blake R Kolsky M: MRI evaluation of the third nerve. MRI Decisions March/Aplil:23-31, 1993 22. Remulla HD, Bilyk JR, Rubin PAD: Pseudo-entrapment of extraocular muscles in patients with orbital fractures. J CranioMax Trauma i:16-29, I995 23. Depper MH, Truwit CL, Dreisbach JN, Kelly WM: Isolated abducens nerve palsy: MR imaging findings. AJR 160:837-841, 1993 24. Goodwin JR, Johnson MH: Carotid injury secondary to blunt head trauma: Case report. J Trauma 37:119-122, 1994