Which of the following is NOT known to cause disc edema?

• A. Melanocytoma
• B. Optic nerve sheath meningioma
• C. Optic nerve glioma
• D. Orbital cavernous hemangioma

Answer: (A)

Disc edema happens when the optic nerve head swells from impaired axoplasmic flow, often due to local tumor compression or venous congestion in the orbit or along the nerve. Optic nerve sheath meningioma and orbital cavernous hemangioma can both produce disc edema by compressing the optic nerve or disturbing venous drainage, leading to swelling at the disc. Optic nerve glioma can also cause edema when it disrupts nerve fibers and inflammation around the nerve. Melanocytoma of the optic disc, on the other hand, is a pigmented hamartoma that typically sits on the disc surface without causing edema; it often remains clinically quiet aside from its appearance. So, melanocytoma is not known to cause disc edema.