Damage within a network of white matter regions underlies executive dysfunction in CADASIL

Objective: To identify the important sites of white matter disruption that underpin executive dysfunction in CADASIL ( cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), a genetic model of pure subcortical vascular disease. Methods: The anatomic pattern of correlation between tissue integrity and executive function was explored with diffusion tensor imaging ( DTI), which provides quantitative measures of tissue integrity. Eighteen nondemented patients with CADASIL underwent DTI and cognitive assessment. DTI was normalized to a standard template and correlations assessed at every voxel across the brain with Statistical Parametric Mapping with cluster- level correction for multiple comparisons. Results: For executive tasks, correlations were found in a number of discrete regions in the white matter of the frontal lobes. A distinct, nonoverlapping pattern of correlation was seen for verbal memory. Significant independent correlations remained in some regions after co- varying for age and IQ. Conclusions: Different cognitive functions correlate with structural integrity at different sites in the white and subcortical gray matter. The distribution of regions correlating specifically with executive function provides clues to the organization of the relevant cognitive networks and their important white matter projections. The cingulum bundle is one candidate tract that may carry anteroposterior connections important for executive processes.