Superficial siderosis

Superficial siderosis is a rare, disabling degenerative disorder of the brain and spinal cord. It develops when blood leaks into the subarachnoid space, the fluid-filled layer around the central nervous system, slowly and repeatedly over many years. The broken-down blood leaves an insoluble iron-bearing pigment called hemosiderin on the surface of the brain and the pia mater, and the iron released from that layer is toxic to the nerve tissue beneath it. Because the damage builds so gradually, the usual signs of progressive hearing loss in both ears, unsteady balance and gait (ataxia) and spinal cord weakness with pyramidal signs often appear decades after the original bleeding. In many patients no bleeding source is found, but dural tears, spinal surgery, tumors and head or nerve injuries can be the cause. Diagnosis rests on MRI, and treatment aims to find and close any bleeding source and to manage symptoms. It is commonly mistaken for multiple sclerosis or Parkinson's disease.