Optic nerve sheath carcinomatosis masquerading as optic perineuritis: The first sign of gastric cancer relapse

Optic perineuritis (OPN) is a rare inflammatory disease involving the optic nerve sheath. Most cases are idiopathic, but associations with a variety of infectious and inflammatory conditions have been described. Patients with suspected OPN should also be investigated for neoplasms in the form of optic nerve sheath meningioma or meningeal carcinomatosis, given they share important clinical and radiological features. We present a case of suspected idiopathic bilateral OPN that was particularly challenging, eventually revealing a neoplastic etiology.