Superficial siderosis is deposition of hemosiderin in the subpial layers of the brain, spinal cord, and cranial nerves. The condition is most commonly associated with sensorineural hearing loss and cerebellar ataxia. Neurological dysfunction is usually progressive and irreversible.

Superficial siderosis is thought to be caused by chronic subarachnoid hemorrhage. The most common underlying causes of the hemorrhage include trauma to the head or spine, postsurgical effects from neurosurgical interventions, intracranial tumors, brachial plexus injuries, dural tears, cerebral amyloid angiopathy, and vascular malfunctions. The source of the bleeding is not identified in up to half of cases. Symptoms can start months to years after an episode of hemorrhage.

Superficial siderosis was previously thought to be rare; however, it is now estimated to occur in 1% of the elderly population. It usually occurs in adults but can occur in the pediatric population as well. Diagnosis is made using MRI or postmortem brain biopsy.

There is no effective treatment for this condition, and management is mainly symptomatic. Treatment of the underlying cause of subarachnoid bleeding may be helpful in preventing further deposition of hemosiderin.