Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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April 11, 2024
Bilateral Optic Perineuritis
Background:
- Optic perineuritis is a rare inflammatory disorder of the optic nerve sheath (ONS), which can mimic but is distinct from acute demyelinating optic neuritis.
- Can be idiopathic or secondary to ANCA-vasculitis, syphilis, sarcoidosis, herpes zoster, or other autoimmune diseases and infections.
- Demographic of patients with OPN is typically older women.
Clinical Presentation:
- Idiopathic OPN
- Most cases present as unilateral, with ocular pain and pain with eye movement
- Visual symptoms such as blurring or spots can be seen, but may also present with normal visual acuity
- More likely to have sparing of central vision as compared with optic neuritis
- Other ocular features such as ptosis and exophthalmos can also be present
- Secondary OPN
- Presents similarly to idiopathic OPN; bilateral OPN more indicative of a systemic cause
Key Diagnostic Features:
- Circumferential perineural enhancement of the optic nerve ”sheath” on contrast-enhanced fat-saturated T1WI
- Sparing of the optic nerve (involvement of the ON sheath alone)
- May show subtle enhancement of the sclera and extraocular muscles
Differential Diagnosis:
- Optic neuritis
- Presents more often in younger patients, onset of vision loss more acute, central scotoma typically seen
- Imaging identifies swelling most easily seen in the retrobulbar intraorbital segment of the optic nerve
- May be associated with multiple sclerosis
- Optic nerve sheath meningioma
- May mimic OPN on MRI; CT can be helpful if calcifications are present in ONSM
- Neoplastic diseases that can affect the optic sheath (leukemia, lymphoma, Erdheim-Chester disease, metastasis)
- May also demonstrate nerve sheath enhancement and “tram-track” sign on axial imaging, but also associated with additional symptoms more specific to neoplasm
Treatment:
- High-dose corticosteroids are administered with a longer course and tapering of the dose. Recurrence is common and treatment should be re-initiated promptly during relapse, requiring close follow-up.
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