Superficial siderosis, an underestimated entity

Objective. - To review the clinical and MRI aspects in a series of cases with superficial siderosis of the central nervous system. Methods. - 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. Results. - 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%). Conclusion. - 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. (C) 2011 Elsevier Masson SAS. All rights reserved.