Focal white matter lesions (WMLs) can be attributed to small-vessel disease and are associated with variable degrees of demyelination, axonal loss and gliosisThe effect of WMLs on global cognitive performance in cross-sectional studies is relatively small, even for severe lesions, and amounts at most to 0.7 points out of a maximum of 30 on the Mini-Mental State Examination scaleIn longitudinal studies, the rate of cognitive deterioration attributable to WMLs is, on average, 12 times lower than that attributable to Alzheimer's diseaseOnly individuals with the more-severe degrees of WMLs have clinically relevant cognitive decline, and these patients might be candidates for drug therapy targeted to small-vessel cerebrovascular disease
Clinical neurologists are often presented a challenge by patients undergoing routine MRI who show spots and patches of various sizes in the hemispheric white matter that are hyperintense on T2-weighted scans and can be even better appreciated on fluid-attenuated inversion recovery (FLAIR) scans. These patients are often elderly and have hypertension, diabetes or both. When MRI is prescribed for cognitive impairment and the neuroradiologist attributes white matter lesions (WMLs) to focal chronic ischemia, the neurologist might be tempted to ascribe all or part of the cognitive impairment to cerebrovascular factors, prescribe a number of vasoactive drugs, and refrain from prescribing cholinesterase inhibitors.
