A, Swollen right optic nerve with tortuous arteries and dilated veins (left) and normal left optic nerve (right). B, Coronal (left) and axial (right) T1-weighted, gadoliniumenhanced MRI scans showing optic nerve sheath meningioma. Note tram tracks and enlargement of the optic nerve sheath. C, The meningioma is exposed through a craniotomy and superior orbitotomy. The intraoperative view shows the intracranial prechiasmal optic nerve. Note the cuff (arrow, dashes) of the meningioma wrapping around the optic nerve and extending out from the optic canal