Cognitive function correlates with frontal white matter apparent diffusion coefficients in patients with leukoaraiosis

Background and aims Diffusion weighted imaging (DWI) displays a high sensitivity to white matter changes, even in areas where no lesions are visible. Correlation with vascular risk factors and cognitive dysfunction seems to be feasible using this technique. We aimed to test relations between age, blood pressure and cognitive function,with lesion load and average Apparent Diffusion Coefficient (ADC) values in lesioned (LWM) and in normal appearing white matter (NAWM), in patients with age related white matter lesions (ARWML). Methods Subjects were 29 patients (mean age 72.6 +/- 5.2 years) with different severity of ARWML on MRI and no (or mild) disability assessed by the Instrumental Activities of Daily Living Scale. Imaging lesion load was quantified in bilateral frontal, temporal, parieto-occipital, basal ganglia and infratentorial regions, using a simple visual rating scale; ADC was measured bilaterally in Regions of Interest in parieto-occipital and frontal NAWM, and in frontal periventricular LWM. Neuropsychological examination consisted of Raven Colored Progressive Matrices, Rey's Complex Figure, Digit Canceling. Symbol digit Substitution, Inverse Digit Repetition and Verbal Fluency tests. Results Visual scales scores and ADC were significantly higher in frontal and parieto-occipital regions. Both were significantly correlated to age and blood pressure, in frontal (visual scale scores and ADC) and parieto-occipital regions (ADC). Attention skills were negatively correlated to ADC in LWM and NAWM in frontal regions and with frontal region visual scale scores. Conclusion Our findings suggest that severity of white matter ischemic changes is correlated with worse cognitive function, as well as advanced age and higher blood pressure.A higher vulnerability of frontal white matter to vascular disease seems to play an important role in executive dysfunction, mainly determined by impairment of attentional skills.DWI results suggest this could be true even for NAWM.