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Show MRI Demonstrates Restricted Diffusion in Distal Optic Nerve in Atypical Optic Neuritis Oriel Spierer, MD, Liat Ben Sira, MD, Igal Leibovitch, MD, Anat Kesler, MD Abstract: A 4-year-old healthy girl with acute visual loss in the right eye had ophthalmoscopic evidence of a swollen optic disc combined with central retinal artery and vein occlusion in the affected eye. MRI showed that the intraorbital optic nerve on the affected side was thickened and enhancing. Diffusion-weighted imaging showed restricted diffusion in the distal intraorbital segment of the optic nerve, consistent with infarction attributed to compression or inflammation of the vessels serving the optic nerve and retina. Although such clinical phenomena have been described previously, this is the first patient to demonstrate restricted diffusion in an inflammatory optic neuropathy. The presence of restricted diffusion is helpful in excluding a neoplastic cause of a thickened optic nerve. Journal of Neuro-Ophthalmology 2010;30:31-33 doi: 10.1097/WNO.0b013e3181ce18eb 2010 by North American Neuro-Ophthalmology Society Among the many causes of optic nerve enlargement (1) is optic perineuritis (OPN), an inflammatory disorder involving the optic nerve sheaths. OPN has been defined as a form of idiopathic orbital inflammation (IOI) (2). MRI demonstrates enhancement around rather than within the optic nerve (3). The combination of IOI involving mainly the optic nerve and its sheath, together with occlusion of both central retinal artery and central retinal vein, has been described as a rare event with catastrophic visual consequences (4,5). There have been recent reports of acute optic nerve infarction demonstrated by diffusion-weighted imaging (DWI) (6-11), but DWI demonstration of restricted diffusion within the optic nerve has lagged behind DWI of other tracts in the brain because the intraorbital optic nerve is small and surrounded by bony structures that cause susceptibility artifacts on echo planar imaging, the sequence used to demonstrate restricted diffusion. We present a patient with an enlarged optic nerve with superimposed occlusion of the central retinal artery and vein caused by IOI. The presence of restricted diffusion, reported for the first time in this setting, allowed distinction from neoplastic infiltration. CASE REPORT A 4-year-old healthy girl was admitted with suspected blindness of the right eye of 24 hours duration. There was no light perception in the right eye, and a visual acuity of 20/20 in the left eye. Pupils were equal in size with a relative afferent pupillary defect in the right eye. Eye movements were normal with no pain on ocular movement and no proptosis. Ophthalmoscopy of the right eye disclosed a cherry red spot in the macula, scattered hemorrhages and exudates, narrowed arterioles, engorged veins, macular edema, and swelling of the optic disc (Fig. 1). Ophthal-moscopy of the left eye was normal. Neurologic and physical examination results were normal. Brain and orbit CT demonstrated a thickened right optic nerve as the only abnormality. MRI showed an enhancing, thickened right optic nerve and high T2 signal in the intraconal fat surrounding the nerve (Fig. 2AB). On DWI there was focal restricted diffusion of the distal intraorbital portion of the right optic nerve, confirmed on an apparent diffusion coefficient (ADC) map, and suggestive of infarction of the distal optic nerve (Fig. 2CD). Lumbar puncture yielded a normal opening pressure and cerebrospinal fluid formula. Treatment with high-dose methylprednisolone was immediately initiated for 3 days. In the following 2 weeks, the optic disc became pale with narrowed retinal blood vessels. There was no improvement in visual acuity over a 2-year follow-up period. Repeat MRI, performed 4 months later, showed reduced bulk and lack of restricted diffusion in the affected optic nerve (Fig. 3). Ophthalmology Department (OS, IL), Pediatric Radiology Unit (LBS), and Neuro-ophthalmology Unit (AK), Tel Aviv Sourasky Medical Center, Tel Aviv University, Tel Aviv, Israel. The first 2 authors contributed equally to this work. Address correspondence to Dr. Anat Kesler, MD, Tel Aviv Sourasky Medical Center, 6 Weizmann Street, Tel Aviv 64239, Israel; E-mail: kesler@netvision.net.il Spierer et al: J Neuro-Ophthalmol 2010; 30: 31-33 31 Original Contribution DISCUSSION In our patient, the thickened optic nerve and retinal vascular occlusion prompted consideration of optic nerve glioma or meningioma as alternative diagnoses to optic neuritis, OPN, and IOI. However, the imaging finding of restricted diffusion, which we attributed to compressive or vasculitic occlusion within the optic nerve, allowed us to dismiss consideration of a neoplasm and therefore we elected not to perform a biopsy. Instead we treated the patient with corticosteroids but with little hope of improving vision. The disappearance of restricted diffusion and partial reversal of optic thickness on a follow-up MRI confirmed that the process was inflammatory. Vascular occlusion of the retina and/or optic nerve in the setting of orbital inflammation has been previously described but without use of DWI. Winterkorn et al (4) reported an enlarged optic nerve and ipsilateral central retinal artery and vein occlusion in 2 patients. Both patients had clinical and imaging manifestations consistent with IOI involving mainly the optic nerve and its sheath. The authors postulated that distension of the optic nerve caused mechanical compression of the central retinal artery and vein, leading to occlusion. A more recent single case report FIG. 1. Ophthalmoscopy of the right eye at presentation shows a pale and swollen optic disc with splinter hemorrhages and exudates, macular edema, scattered retinal hemorrhages and exudates, narrowed arterioles, and engorged veins. FIG. 2. MRI performed at presentation. A. Postcontrast T1 axial MRI with fat saturation shows enhancement around the thickened optic nerve (arrow). B. T2 axial MRI with fat saturation shows a thick, hyperintense right optic nerve (arrow) and high signal in the surrounding intraconal fat. C. Diffusion-weighted imaging (DWI) shows focal high signal in the right optic nerve (arrow). D. Apparent diffusion coefficient map shows corresponding low signal (arrow), confirming that the high signal in C represents restricted diffusion. Original Contribution 32 Spierer et al: J Neuro-Ophthalmol 2010; 30: 31-33 (5) described similar phenomena. Because our patient did not have the typical clinical presentation and the classic imaging findings of IOI, the diagnosis was more likely OPN, although OPN may be a form of IOI (2). Six case reports have documented restricted diffusion in acute ischemic optic neuropathy (6-11) in perioperative hypotension (6), infection (8-10), ischemic optic neurop-athy (7), and ischemic optic neuropathy due to thrombo-cythemia (11). The first case report (6) involved a 61-year-old man who experienced severe bilateral posterior ischemic optic neuropathy after cardiac bypass surgery due to hypotension. Routine MRI sequences were normal, but DWI showed restricted diffusion within both intraorbital optic nerves. A later report (7) described restricted diffusion of the optic nerve in a patient with nonarteritic anterior and posterior ischemic optic neuropathy. Three additional reports (8-10) of restricted diffusion of the optic nerve have involved cavernous sinus thrombophlebitis (8), rhinocerebral mu-cormycosis, (9) and fungal sinusitis (10). A recent report (11) involved a patient with bilateral ischemic optic neuropathy due to thrombocythemia. Restricted diffusion was initially noted in acute ischemia. However, 2 recent studies (12,13) demonstrated this phenomenon in inflammatory and lymphoid lesions of the optic nerve. Restricted diffusion has not been reported in meningiomas and gliomas of the optic nerve and its sheath. REFERENCES 1. Rothfus WE, Curtin HD, Slamovits TL, et al. Optic nerve/ sheath enlargement. A differential approach based on high-resolution CT morphology. Radiology 1984;150:409-15. 2. Kennerdell JS, Dresner SC. The nonspecific orbital inflammatory syndromes. Surv Ophthalmol 1984;29:93-103. 3. Purvin V, Kawasaki A, Jacobson DM. Optic perineuritis: clinical and radiographic features. Arch Ophthalmol 2001; 119:1299-306. 4. Winterkorn JM, Odel JG, Behrens MM, et al. Large optic nerve with central retinal artery and vein occlusions from optic neuritis/perineuritis rather than tumor. J Neuroophthalmol 1994;14:157-9. 5. Foroozan R. Combined central retinal artery and vein occlusion from orbital inflammatory pseudotumour. Clin Exp Ophthalmol 2004;32:435-7. 6. Purvin V, Kuzma B. Intraorbital optic nerve signal hyperintensity on magnetic resonance imaging sequences in perioperative hypotensive ischemic optic neuropathy. J Neuroophthalmol 2005;25:202-4. 7. Al-Shafai LS, Mikulis DJ. Diffusion MR imaging in a case of acute ischemic optic neuropathy. Am J Neuroradiol 2006; 27:255-7. 8. Chen JS, Mukherjee P, Dillon WP, et al. Restricted diffusion in bilateral optic nerves and retinas as an indicator of venous ischemia caused by cavernous sinus thrombophlebitis. Am J Neuroradiol 2006;27:1815-26. 9. Mathur S, Karimi A, Mafee MF. Acute optic nerve infarction demonstrated by diffusion-weighted imaging in a case of rhinocerebral mucormycosis. Am J Neuroradiol 2007;28: 489-90. 10. Verma A, Jain KK, Mohan S, et al. Diffusion-weighted MR imaging in posterior ischemic optic neuropathy. Am J Neuroradiol 2007;28:1839-40. 11. Klein JP, Cohen AB, Kimberly WT, et al. Diffusion-weighted magnetic resonance imaging of bilateral simultaneous optic nerve infarctions. Arch Neurol 2009; 66:132-43. 12. Hatipoglu HG, Gurbuz MO, Yuksel E. Restricted diffusion in the optic nerve and retina demonstrated by MRI in rhino-orbital mucormycosis. J Neuroophthalmol 2009;29: 13-5. 13. Kapur R, Sepahdari AR, Mafee MF, et al. MR imaging of orbital inflammatory syndrome, orbital cellulitis, and orbital lymphoid lesions: the role of diffusion-weighted imaging. AJNR Am J Neuroradiol 2009;30:64-70. FIG. 3. MRI scans performed 4 months after presentation. A. T2 axial MRI with fat saturation shows reduced bulk in the affected right optic nerve. B. Diffusion-weighted imaging (DWI) shows a normal signal in the affected right optic nerve. C. Apparent diffusion coefficient map also shows a normal signal, confirming that there is no longer any restricted diffusion. Original Contribution Spierer et al: J Neuro-Ophthalmol 2010; 30: 31-33 33 |
