Superficial siderosis of the central nervous system (SSCN) in a disease characterized by chronic deposition of hemosiderin in the leptomeninges, subpial tissue, spinal cord, and cranial nerves. Previously the diagnosis of SSCN could only be made at autopsy or during a neurosurgical procedure. Now, however, a diagnosis of SSCN can be made non-invasively by magnetic resonance imaging (MRI). We present the case of a 50-year-old male with SSCN accompanied by bilateral sensorineural hearing loss which gradually progressed to total deafness over a seven year period. This patient also had associated bilateral caloric weakness with episodes of severe recurrent headaches over the two preceding years. The deafness and gait disturbance, which were his chief complaints, were followed by other neurological manifestations including pyramidal tract signs, anosmia, and ageusia. High-field MRI on T-2 weighted images of the CNS showed diffuse marginal hypointensity of the cerebrum, brain stem, and cerebellum. Atrophy of the cerebellum and brain stem was also apparent. Low signal intensity along the proximal segment of the acoustic nerve and the facial nerve was noted from the cistern to the internal auditory canal. Neither bilateral transtympanic promontory nor round window electrical stimulation elicited any sound sensation. In this case it was thought that the acoustic nerve alone or both the acoustic nerve and the cochlea were affected by this disease. Consequently, cochlear implantation was not indicated. The source of bleeding into the subarachnoid space could not be detected despite thorough examination. This diagnosis will be made only by physicians who are aware of this rare entity and have knowledge of the characteristic clinical pathology.(ABSTRACT TRUNCATED AT 250 WORDS)