Superficial siderosis revealed by isolated cognitive impairment.

Superficial siderosis (SS) is a rare disorder due to chronic bleeding into the subarachnoid or intraventricular space. The most common clinical presentation is progressive ataxia and hearing loss. The authors report two patients who presented with dementia as the primary manifestation of SS. The cognitive impairment marked by cortical frontotemporoparietal dysfunction was consistent with the pattern of signal abnormalities seen on brain magnetic resonance imaging (MRI). Diagnosis of SS must be considered when T2*-weighted MRI shows typical signal hypointensity outlining the brain and spinal cord surfaces. Performing such MRI sequences appears to be of particular interest in the context of dementia etiological diagnosis.