Primary reticulum cell sarcoma of the brain presenting as steroid-responsive optic neuropathy.

A 23-year-old woman presented with subacute monocular visual loss clinically resembling optic neuritis. CT scan revealed a cerebellar mass, biopsy of which led to the diagnosis of reticulum cell sarcoma (RCS). Corticosteroid therapy resulted in improvement of vision and a decrease in disc edema; this resolution was documented radiographically. While optic nerve involvement is sometimes seen in association with systemic lymphoproliferative disease, optic neuropathy as a manifestation of primary cerebral RCS is rare.