Superficial Siderosis of the Central Nervous System

Superficial siderosis of the central nervous system (CNS) is a rare disorder, which is the consequence of chronic subarachnoid haemorrhage. Brain MR scan (Fig. 1) shows a characteristic marginal low T₂-weighted signal of haemosiderin around the surface of the CNS, and has made antemortem diagnosis of this condition possible. Clinically, the cardinal features are progressive sensorineural deafness and cerebellar ataxia. Other features include myelopathy, polyradiculopathy, anosmia and dementia. The only effective way of treating the disorder is to identify the source of bleeding and remove it (Fearnley <i>et al</i>. 1995). <b>PATHOPHYSIOLOGY</b> Superficial siderosis of the CNS is a direct result of chronic subarachnoid haemorrhage with free iron in the CSF causing a chain of events leading to neuronal death, gliosis and haemosiderin deposition. It is the chronicity of the bleeding that is crucial to the development of superficial siderosis and the syndrome does not occur after a single bleed. It