Superficial siderosis of the central nervous system.

Two patients with superficial siderosis of the central nervous system are reported. Both developed progressive deafness over many years; one with associated anosmia and partial seizures; the other with progressive ataxia and diplopia. The cerebrospinal fluid was xanthochromic in one and the protein was raised in both. Magnetic resonance imaging revealed a hypodense rim around the eighth cranial nerve, cerebellum, brain stem and spinal cord. Despite extensive investigations the cause of the superficial siderosis in both patients remains undetermined.