Cerebral subcortical small vessel disease and its relation to cognition in elderly subjects: a pathological study in the Oxford Project to Investigate Memory and Ageing (OPTIMA) cohort.

BACKGROUND: Subcortical small vessel disease (SVD) is known to contribute to vascular cognitive impairment and vascular dementia, but understanding about the extent of its influence is limited because there is a lack of consensus about how this pathology should be assessed.
METHODS: In this study we have made use of a simple, novel, image-matching scoring system to assess the extent of SVD in a group of 70 cases from the prospectively assessed Oxford Project to Investigate Memory and Ageing (OPTIMA) cohort. These cases were found at autopsy to have cerebrovascular disease and no other pathology except Braak stage 4 or less tau pathology, and insufficient amyloid plaque pathology to meet Consortium to Establish a Registry for Alzheimer's Disease (CERAD) criteria for the diagnosis of Alzheimer's disease. Pathology scores for SVD were correlated with cognitive scores [Mini-Mental State Examination (MMSE) and cognitive section of the Cambridge Examination for Mental Disorders in the Elderly (CAMDEX) (CAMCOG)] at the last clinical assessment before death.
RESULTS: The severity of SVD pathology was inversely related to cognitive score before death (P < 0.008 for MMSE and P < 0.024 for CAMCOG). Thirty-one per cent and 33% of cases were rated as demented by MMSE or CAMCOG respectively. The degree of dementia was generally mild. Age did not influence severity of SVD.
CONCLUSIONS: An image-based scoring system for SVD in a group of 70 elderly subjects enabled the severity of SVD pathology to be assessed with results that showed a significant correlation between SVD pathology severity and cognitive impairment.