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Superficial siderosis of the CNS is a chronic neurodegenerative disorder caused by progressive deposition of hemosiderin in the subpial layers of the brain, spinal cord, and cranial nerves due to chronic or recurrent bleeding into the subarachnoid space.

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Etiopathogenesis

Source of chronic bleeding:

• Dural defects (spinal dural tears, meningeal diverticula).
• CNS tumors (ependymoma, hemangioblastoma, meningioma).
• Vascular malformations (cavernomas, AVMs).
• Chronic subarachnoid hemorrhage (trauma, surgery).

Mechanism:

• Chronic/repeated hemorrhage → RBC breakdown → iron released → stored as hemosiderin in glial cells (Bergmann glia in cerebellum, subpial macrophages).
• Free iron catalyzes oxidative stress and neuronal injury, leading to progressive neurodegeneration.

Clinical Features

Classical triad: Slowly progressive, usually over years.

1. Sensorineural hearing loss (CN VIII involvement – most common).
2. Cerebellar ataxia (gait, limb).
3. Myelopathy (spastic paraparesis, pyramidal signs).

Other features:

• Anosmia, bladder dysfunction, dementia-like cognitive decline, cranial nerve palsies (especially I, V, VII).

Radiology