Prevalence of cortical superficial siderosis in a memory clinic population

OBJECTIVE: To determine prevalence, topography, and severity of cortical superficial siderosis (SS), a recently recognized manifestation of cerebral amyloid angiopathy, and its possible association with Alzheimer disease (AD) in a memory clinic patient cohort. METHODS: We included 809 patients (56% men, aged 66 ± 10 years) from the Amsterdam Dementia Cohort between November 2010 and November 2012 scanned on a 3-tesla MRI system. We analyzed prevalence and topography of cortical SS according to demographic, clinical, and MRI data. Agreement for SS detection between 2 neuroradiologists was calculated by using Cohen κ. RESULTS: Agreement for detection of SS was excellent (unweighted κ of 0.81). In 17 patients (2.1%), cortical SS was found without a known cause. The prevalence of idiopathic SS differed according to diagnostic groups (p < 0.001): nearly 5% (95% confidence interval CI 2.8%-8.2%) in patients with AD (n = 168) vs 2% (95% CI 0.7%-6.0%) in patients with mild cognitive impairment (n = 143) and 2.5% (95% CI 0.7%-8.7%) in other types of dementia (n = 80). By contrast, SS was not found in patients with subjective complaints (n = 168) or in those with other disorders (n = 157). Presence of SS was associated with APOE ε4, microbleeds, and white matter hyperintensities (all p < 0.05) independent of diagnosis. CONCLUSION: The prevalence of cortical SS in a memory clinic setting is higher than reported in the general population but lower than reported in cerebral amyloid angiopathy. The relatively high prevalence of SS in AD suggests that SS is a relevant radiologic manifestation of amyloid pathology in AD. Presence of SS does not seem to predict severity of AD. Further longitudinal research is needed to investigate clinical relevance.