- 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
Imaging
- 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)
Read more
Kanamalla, Uday S. “The optic nerve tram-track sign.” Radiology 227.3 (2003): 718-719.