The effect of white matter low attenuation on cognitive performance in dementia of the Alzheimer type

The effect of leukoaraiosis or white matter low attenuation (WMLA) on cognitive function is not fully understood. We compared the neuropsychological performance of 37 Alzheimer's disease patients with WMLA on CT brain scans with a similar group of 31 Alzheimer's disease patients with no evidence of white matter lesions. Patients with WMLA performed significantly worse on tests of visuospatial function (Cube Analysis test, p = 0.004), and cognitive speed (Kenrick Digit Copying test, p = 0.05) compared to those with no visible white matter lesions. Patients with widespread WMLA performed generally worse in tests of cognitive function than those with frontal or a mixture of frontal and occipital WMLA. This was most significant in the areas of attention (forward digit span, p = 0.003), visual recognition (p = 0.004), and cognitive speed (p = 0.03). There is an association between impaired cognitive performance and the presence of WMLA in Alzheimer's disease patients, with WMLA probably contributing to the cognitive impairment. This is most evident in patients with widespread white matter lesions.