Plain CT Scan: Subtle linear hypodensities along cerebellar folia (easy to miss).
MRI T1W Axial: Looks fairly normal, unless correlated with other sequences.
MRI T2W Axial: No apparent abnormality.
T2*GRE Axial: Linear areas of blooming along cerebellar folia.
SWI axial: Marked linear and nodular hypointense Susceptibility areas along cerebellar folia and basal cisterns.
Key Points of Superficial Siderosis:
- It is due to hemosiderin deposition in the subpial layers of the brain and spinal cord.
- The hemosiderin deposition is a consequence of recurrent and persistent bleeding into the subarachnoid space.
- The classic clinical presentation of SS includes adult-onset slowly progressive gait (less commonly appendicular) ataxia with cerebellar dysarthria and sensorineural hearing impairment. The bleeding source may be not be detected despite extensive neuroimaging
Imaging Hallmarks:
- Ferritin and Hemosiderin deposits appear hypointense on T2W, blooms on GRE and SWI.
- Located around the cerebellum, brainstem, interhemispheric fissure, cortical sulci, basal cisterns, along cranial nerves II, V, VII, and VIII & spinal cord.
- Cerebellar and Spinal cord atrophy may present.
What next:
- Screen entire spine with MRI.
- The surgical treatment of SS depends on early identification of the bleeding source.
- CT myelogram, dynamic CT myelogram, or digital substraction myelogram can identify a dural defect.
Reference: AJNR: Neuroimaging in Superficial Siderosis: An In-Depth Look