Superficial siderosis of the central nervous system: an underestimated cause of hearing loss.

Superficial siderosis of the central nervous system (CNS) is a rare disease resulting in the accumulation of haemosiderin in the meninges, the brain surface, the spinal cord and the cranial nerves. The pigment is deposited as a result of chronic bleeding in the subarachnoid space. This produces a clinical picture of deafness, ataxia, cranial nerve deficits and in the latest stages dementia. In some cases the source of bleeding can be identified, whilst in others it can not. Despite its rarity the disease should be considered in the differential diagnosis of sensorineural deafness, particularly as it is a progressive and in some cases curable disease which is easily diagnosed by magnetic resonance imaging (MRI). In this case report the haemosiderin was derived from an ependymoma of the fourth ventricle with extension into the cerebello-pontine angle. The first symptom was a worsening sensorineural hearing loss.