[Superficial siderosis, an underestimated entity]

To review the clinical and MRI aspects in a series of cases with superficial siderosis of the central nervous system.

We retrospectively reviewed the patients with imaging evidence of superficial siderosis, investigated in two radiological centers between January 2006 and January 2010. The patients with aneurysms or arterio-venous malformations were excluded from this study.

Cortical hemosiderin deposits were present in 25 (0.2%) of the 5904 MRIs with a T2-weighted gradient echo sequence. The classic association bilateral hypoacousia, ataxia and pyramidal signs were rarely found (two cases - 8%). Seven patients (28%) had a bilateral hearing impairment, seven (28%) a cerebellar syndrome and two (8%) a pyramidal syndrome. Sixteen patients (64%) had only supratentorial hemosiderin deposits. A cause of subarachnoid bleeding was identified in 76% of cases: amyloid angiopathy (40%), trauma (16%), cranio-spinal surgery (8%), cavernomas (8%) and brain tumors (4%).

Superficial siderosis seems to be more frequent than previously thought. The classic clinical triad is rare, although the asymptomatic cases are frequent. A source of subarachnoid bleeding is generally found. Amyloid angiopathy is a frequent etiology of superficial siderosis in elderly patients. In the absence of other causes of subarachnoid bleeding, superficial siderosis may become a magnetic resonance marker for amyloid angiopathy.