Beyond superficial siderosis

Superficial siderosis (SS) of the CNS results from hemosiderin deposition in the subpial layers of the brain and spinal cord.1,–,3 The hemosiderin deposition results from recurrent and persistent bleeding into the subarachnoid space and has a predilection for the cerebellum, spinal cord, and cranial nerves I, II, and VIII. Patients often present in adulthood with slowly progressive gait (less commonly appendicular) ataxia, and sensorineural hearing impairment. The presentation may mimic a degenerative cerebellar disorder. A remote history of injury or intradural surgery (frequently involving the posterior fossa) is common. Often decades elapse between the presumed inciting event and development of symptoms attributable to SS. MRI is the investigation of choice. The typical MRI finding is a characteristic, marginal, confluent T2 hypointensity on the surface of the brain and cord (figure 1, A–I).3 This is better appreciated on gradient-echo sequences. With widespread use of MRI, presymptomatic cases are being diagnosed and it is difficult to be certain about the true incidence of the disorder. In recent years SS has also been recognized as an MRI marker of cerebral amyloid angiopathy.4 Red blood cells or xanthochromia may be seen on CSF studies. Despite extensive investigations (brain and spine MRI, CT myelogram, magnetic resonance angiography, cerebrospinal angiography), the cause of bleeding is often not apparent. Figure 1 Neuroimaging findings in superficial siderosis (SS) (A–I) All images are from a 76-year-old woman with SS. T2-weighted axial (A–E, H, I) and sagittal (F, G) brain (A–E), cervical spine (F, H), and thoracic spine (G, I) MRIs show the characteristic confluent T2 hypointensity due to hemosiderin deposition along the cerebellar folia (A: arrows), around the medulla (A: dotted arrow), pons (B), midbrain (C), along the sylvian fissures (D), interhemispheric fissure (E), and along (F, G) and around (H, I) the cervical (F, H) and thoracic (G, …