Pictorial review of extraconal and osseous orbital pathology - what can be found 'around' the orbits?

Transcription

1 Pictorial review of extraconal and osseous orbital pathology - what can be found 'around' the orbits? Poster No.: C-2011 Congress: ECR 2013 Type: Educational Exhibit Authors: M. Meissnitzer, T. Meissnitzer, K. Hergan, R. Forstner ; Salzburg/AT, Mariapfarr/AT Keywords: Education, MR, CT, Eyes, Neoplasia DOI: /ecr2013/C-2011 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 39

2 Learning objectives Fig. 1: Teaser To review imaging anatomy of the orbits. To focus on extraconal pathologies including osseous orbital lesions. To provide a pictorial review of extraconal and osseous orbital pathologies and put forward an algorithm for image interpretation. Images for this section: Page 2 of 39

3 Fig. 2: Bony orbital anatomy. Page 3 of 39

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5 Fig. 3: Hemangioma. Fig. 4: Complex fractures involving orbits. Page 5 of 39

6 Background We ask what pathologies can be found at the periphery of the orbits in imaging and how can we achieve accurate diagnosis. First step to correct diagnosis of these entities is profound knowledge of orbital anatomy in CT and MRI. Most helpful is the differentiation of four orbital compartments: ocular, conal, intra- and extraconal compartment. Location of a lesion to the orbits, followed by locating a lesion to its orbital compartment and clinical information will lead to the differential diagnosis. However, some lesions extend beyond these compartmental borders and effect more than one and up to all orbital compartments - again important to notice for the differntial diagnosis. Fig. 2: Bony orbital anatomy. The four orbital compartments: Page 6 of 39

7 - Ocular = ocular globe, deliniated by sclera - Orbital muscle and surrounding fascia form a cone-like intraorbital structure separating the intraconal from the extraconal compartment - Orbital musculature and surrounding fascia (Zinn's fascia) form the cone itsself referred to as conal compartment In our pictorial review we define the orbital periphery as any orbital structure outside the orbital cone. For didactic reasons and reasons of image analysis the orbital periphery can again be subdivided into three compartments: the extraconal intraorbital compartment (yellow), the periosteal or subperistoeal compartment and the osseous compartment (=bony orbits, coded in red). Anatomic structures that are part of orbital anatomy are extraconal fat, vessels (the most anterior segments of ophthalmic artery and vein), lymphatics, nerves (e.g. V1 und V2 of trigeminal nerve), lacrimal gland, perosteum and the bony orbital structures including adjacent sinuses. Fig. 5: Peripheral orbital anatomy. Page 7 of 39

8 Periorbital septum: The intraorbital space is bounded anteriorly by the periorbital septum. Its is important to discern the periorbital or orbital septum, in order to differentiate intraorbital from periorbital processes. Page 8 of 39

9 Fig. 6: Periorbital septum on axial T1W MR image. Page 9 of 39

10 Imaging of the orbital periphery heavily depends on CT or MRI and often both. Ultrasound plays a minor role and is generally performed by ophthalmologists. The osseous orbits are best visualized in CT, however MRI and CT are performed complementary due the excellent soft-tissue contrast and functional capabilities of MRI and the depiction of bony structures in CT. Images for this section: Fig. 5: Peripheral orbital anatomy. Page 10 of 39

11 Fig. 6: Periorbital septum on axial T1W MR image. Page 11 of 39

12 Imaging findings OR Procedure details Fig. 7: Imaging findings of different orbital pathologies in their respective peripheral orbital compartment. The following cases of our pictorial review show various pathologies affecting the extraconal space that we have recently seen in our day-to-day routine. We have chosen to present them point by point covering: Page 12 of 39

13 1) trauma 2) infection 3) tumor and tumor-like lesions In addition we will deal with pathologies originating from neighbouring structures that can affect the orbits. Fig. 8: Neighbouring pathologies possibly affecting the orbits. Trauma CT is the mainstay for evaluation of orbital trauma. Orbital fractures can be isolated or be part of more complex facial fractures. Bony fractures are evident as discontinuities of orbital osseous structures. Isolated orbital wall fractures Nasoorbitoethmoid (NOE) complex Blow-in, blow-out mechanism (fracture can also occur as part of a more complex fracture) fractures fracture of frontal sinus, ethmoid sinus, anterior cranial fossa, orbits, frontal bone, nasal bones Page 13 of 39

14 Zygomaticomaxillary complex fractures tripod or malar fracture: fracture of (ZMC) maxillary sinus, zygomatic arch, lateral orbital rim or orbitozygomatic suture Le Fort fractures only Le Fort II and II involve orbits Anterior skull base fracture intracranial orbital roof fracture, usually involves Fig. 9: Complex fractures involving the orbits. CT and MRI are both useful in evaluating for incarcerated intraorbital content such as fat or muscles. Special attention should be paid to optic nerve injuries which are beyond the scope of this article. A possible sequela of orbital trauma is carotid-cavernous fistula which can occur within weeks after trauma. Imaging findings include engorged and tortuous veins, intra- and periorbital edematous changes. Page 14 of 39

15 Case: A 53 year-old patient with blow- out fracture on the left after trauma. There are concomitant hemorrhagic changes and herniation of intraorbital fat into the maxillary sinus. Page 15 of 39

16 Fig. 10: Blow out fracture left eye. Case: A 17 year-old male after trauma of the right orbit. Air outlining the ossesous orbits in the extraconal space as an indirect sign of fracture of the lamina papyracea. Fig. 11: Fracture of lamina papyracea. Case: CT in a 43 presenting with bilateral orbital fractures. Left -sided orbital roof fracture and fracture along the infraorbital canal (coronal CT image). Orbital fracture on the right not displayed. The patient presented 6 weeks afterwards with carotid-cavernous fistula on the right side. MR images show engorged and tortuous right cavernous sinus and superior ophthalmic vein (arrows). Page 16 of 39

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18 Fig. 12: Carotid-cavernous fistula. Case: 20 year-old patient with severe head trauma due to motor vehicle accident presenting complex cranial and facial fractures involving the orbits on both sides. There is fracture of the anterior skull base (arrows indicating fracture line and intracranial air) and Le Fort fracture lines II (red line) and III (orange line) can be seen. Fig. 13: Complex fracture. Case: 22 year-old patient presenting with lateral orbital wall fracture (not shown) on the left as part of a more complex fracture. Fracture of maxillary sinus and zygomatic arch (arrows) constitute tripod or zygomatico-maxillary complex fracture. Page 18 of 39

19 Fig. 14: Tripod fracture left-sided. Infection Infectious processes of the orbits can manifest as abscess or cellulitis. It is important to diagnosis abscess formation aggressively. Any circumscribed intraorbital opacity in CT in patients with suspected intraorbital infection should be diagnosed as intraorbital abscess. Peripheral enhancement as required for abscess diagnosis in other areas is not required, hence the diagnosis of an intraorbital abscess can be made even from an unenhanced CT scan. Intraorbital cellulitis in CT is less circumscribed and a more diffuse intraorbital opacity compared to an abscess also without contrast enhancement. However, in children even delicate intraorbital opacities should be diagnosed as abscesses because the periorbital bony structures are a lot more fenestrated and disease spread occurs easily. Page 19 of 39

20 In cellulitis it is crucial to locate to process exactly with regard to the orbital septum, since periorbital cellulitis can be managed on an outpatient base and orbital cellulitis generally requires hospital admission. Complications of intraorbital infection include septic thrombophlebitis of inferior and superior ophthalmic vein. Case: 45 year-old patient presenting to the ER with a red hot eye. CT shows encapsulated lesion with peripheral enhancement in keeping with intraorbital abscess formation. Coronal reformations reveal that the lesion is originating from the nasolacrimal duct. Fig. 15: Subperiosteal abscess. Page 20 of 39

21 Case: 28 year-old female presenting with a red hot eye on the left. CT clearly shows opacities anterior to the periorbital septum (arrow), so in this patient there is no intraorbital pathology. The patient was successfully treated with antibiotics in an outpatient setting. Symptoms gradually decreased over a period of 10 days and eventually resolved entirely. Fig. 16: Periorbital cellulitis. Tumor and tumor-like lesions The list of orbital and periorbital tumors and tumor-like lesions is long and in most cases never complete. We provide cases of orbital periphery tumors that we have recently seen. The differential diagnosis is based on the orbital compartment that the lesion is originating from. Furthermore morphologic criteria on T1W, T2W, fat suppressed images and after contrast administration are most important. Recently, diffusion weighted imaging has gained importance. Low Signal intensity in T2W images is a typical finding for intraorbital lymphoma. Some tumors are very rare and the likelyhood to make this diagnosis is low. Page 21 of 39

22 Fig. 17: Tumor encounted in the orbital periphery. Case: 58 year-old female with diplopia and exopthalmus on the right, MRI revealed a 5 cm large mass lesion originating from the extraconal space with areas showing loss of signal on fat suppressed images. CT shows negative HU densities. The lesion is a lipoma well demonstrating that fat is the radiologist's friend. Page 22 of 39

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24 Fig. 18: Lipoma. Case: Orbital MRI in a 69 year-old patient with extraconal mass displaying low SI on T1W an intermediate SI on STIR images. The lesions shows nodular enhancement typical for hemangioma, which is one of the most frequent orbital masses. Page 24 of 39

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26 Fig. 19: Hemangioma. Case: 70 year-old male patient with medial orbital wall fracture mor than 20 years ago and now presenting with a 1,5 cm large extraconal intraorbital mass showing low SI on T1W and high SI on T2W lesion, there is no contrast enhancement. Diagnosis is orbital mucocele a common finding after remote trauma. Fig. 20: Mucocele. Case: 64 year-old female presenting with diplopia. MRI shows bilateral orbital mass lesions predominantly in the extraconal space (arrows). On the right the lesion extends into to intraconal space and displaces the optic nerve. Histologic diagnosis was lymphoma. Typical imaging findings included low SI on T2W images. Page 26 of 39

27 Fig. 21: Bilateral lymphoma. Case: 43 year-old male presenting with visual loss on the left. MRI shows a mass lesion at the tip of the orbital cone surrounding and compressing the optic nerve with avid contrast enhancement. Differential diagnosis included lymphoma, granulomatous disease or pseudotumor. Histologic analysis yielded diagnosis of lymphoma Page 27 of 39

28 Fig. 22: Lymphoma at tip of left orbit. Case: 20 year-old female presenting bony changes of maxillary, ethmoid and sphenoid bones pathognonomic for fibrous dysplasia. Page 28 of 39

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30 Fig. 23: Fibrous dysplasia Case: 70 year-old female presenting osteoplastic lesion of the right frontal bone, the bony orbit and the temporal bone. The lesion displays low SI on T2, there is thickening of the adjacent meninges. Findings suggest intraosseous meningioma which was confirmed histologically. Fig. 24: Intraosseous meningioma. Case: 57 year-old patient with osseous lesion of the frontal sinus and invasion of the right orbit. There is a second lesion in the sphenoid wing on the right - both lesions were thought to be metastasis but histologic diagnosis was multiple myeloma. Page 30 of 39

31 Fig. 25: Multiple myeloma. Images for this section: Page 31 of 39

32 Fig. 4: Complex fractures involving orbits. Page 32 of 39

33 Fig. 6: Periorbital septum on axial T1W MR image. Page 33 of 39

34 Fig. 7: Imaging findings of different orbital pathologies in their respective peripheral orbital compartment. Page 34 of 39

35 Fig. 10: Blow out fracture left eye. Page 35 of 39

36 Fig. 13: Complex fracture. Fig. 17: Tumor encounted in the orbital periphery. Page 36 of 39

37 Conclusion Take-Home Imaging Algorithm 1. Locate lesion to orbit. 2. Locate lesion to orbital compartment. 3. Incorporate clinical information (trauma, infection, tumor or tumor-like lesion), analyse imaging features in CT and MRI and provide differential diagnosis. KIS principle = keep it simple and practial. 4. For residents: Perform radiologic - pathologic correlations when histologic diagnosis is established. Images for this section: Page 37 of 39

38 Fig. 1: Teaser. Page 38 of 39

39 References Kubal W. Imaging of orbital trauma. RadioGraphics 2008; 28: LeBedis CA, Sakai O. Nontraumatic orbital conditions: diagnosis with CT and MR imaging in the emergent setting. Radiographics 2008; 28: Goh PS, Gi MT, Charlton A et al. Eur J Radiol 2008; 66: Aviv RI, Casselman J. Orbital Imaging: Part 1. Normal anatomy. Clin Radiol 2005; 60: Aviv RI, Miszkiel K. Orbital Imaging: Part 2. Intraorbital Pathology. Clin Radiol 2005; 60: Personal Information Page 39 of 39