Superficial siderosis: a potentially important cause of genetic as well as non-genetic deafness.

Superficial siderosis is an important disease that is increasingly being recognized as a cause of sensorineural hearing loss. Hemosiderin, resulting from repeated episodes of subarachnoid bleeding, is deposited preferentially on the surface of the eighth nerve, cerebellum, and brain stem as a consequence of glial catabolism of ferritin within those structures. This deposition eventually results in destruction and demyelination within the central nervous system, leading to the cardinal clinical findings of superficial siderosis: hearing loss, ataxia, and myelopathy. This mechanism may contribute to the pathogenesis of several forms of genetic deafness, and should be considered as a diagnostic possibility in cases of late onset deafness even in the absence of an overt history of subarachnoid bleeding.