Sarcoidosis of the tentorium with cortical blindness

Sarcoidosis rarely involves the visual system posterior to the chiasm. A 55-year-old woman presented with fluctuating bilateral macular-sparing homonymous hemianopsia. The computed tomographic scan revealed an extensive contrast-enhancing density involving the tentorium, posterior falx, and adjacent medial occipital lobes and cerebellum. Spinal fluid studies revealed a mixed cellular response, and a biopsy of the meninges established the diagnosis of sarcoidosis. Ultimately, vision was lost, despite chronic steroid therapy. The presumed mechanism of visual loss is infiltration of the occipital lobes by meningeal granulomas, possibly with coexistent vascular occlusion.