Clinical Pearls & Morning Reports
Published November 23, 2022
In a young woman, the differential diagnosis for diseases that affect the optic nerve starts with inflammatory disorders. Read the NEJM Case Records of the Massachusetts General Hospital here.
Q: What is a characteristic sign of optic nerve sheath meningioma on MRI?
A: Optic nerve sheath meningiomas arise from the meningeal tissue around the optic nerve fibers and typically compromise vision by compressing the optic nerve over time. Because optic nerve sheath meningiomas do not typically affect optic nerve tissue, MRI may show a characteristic “tram-track” sign, a pattern caused by simultaneous enhancement of tumor tissue and nonenhancement of the optic nerve.
Q: Are optociliary shunt vessels typical of optic nerve sheath meningiomas?
A: Optociliary shunt vessels form when drainage of the central retinal vein is occluded and blood flows through collaterals to peripapillary choroidal veins. Optociliary shunt vessels occur occasionally in the context of other conditions, but the classic association is with optic nerve sheath meningiomas.
A: A biopsy of the optic nerve sheath is rarely performed because in approximately 2% of patients, the procedure results in blindness due to vascular injury to the optic nerve. There are several approaches to performing a biopsy of the optic nerve sheath, but entry through the medial upper eyelid is the most common. This approach follows the shortest route to the nerve and does not require detachment of any extraocular muscles or removal of bone. In addition, the incision is placed in the eyelid crease, which has the most cosmetically acceptable outcome after healing is complete.
A: Optic nerve sheath meningiomas are typically managed with radiation therapy. Surgery is associated with a high risk of blindness in the affected eye. In most retrospective series, radiation therapy has resulted in durable tumor control in more than 90% of cases. Beyond tumor control and prevention of cosmetic changes, additional goals of treatment are vision retention and sometimes vision recovery, which are most likely to occur if treatment is initiated within weeks to months after the onset of symptoms. Patients with long-standing vision impairment do not typically have vision recovery.