Optic nerve sheath meningioma

  • Primary or secondary
  • Primary – arise from arachnoid sheath of optic nerve 
  • Secondary – spread from intracranial tumor from anterior clinoid process or sphenoid wing to involve orbit via optic canal or orbital fissure
  • Middle aged women
  • Bilateral lesions typical of neurofibromatosis type 2
  • Generalized circumferential or fusiform enlargement of optic nerve sheath complex, focal masses rarely
  • CT shows calcification in 20-50% cases
  • Tram-track sign: relative low signal of optic nerve in relation to enhancing tumor around the nerve. Not specific for meningiomas. DDs (pseudo tumor, optic neuritis, sarcoid, lymphoma, metastasis)
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Kanamalla, Uday S. “The optic nerve tram-track sign.” Radiology 227.3 (2003): 718-719.

Daniels, D. L., et al. “Magnetic resonance imaging of the optic nerves and chiasm.” Radiology 152.1 (1984): 79-83.