The relationship between white matter low attenuation on brain CT and vascular risk factors: a memory clinic study.

In order to discover the prevalence of white matter low attenuation (WMLA) in the brain and its relationship to vascular risk factors in our Memory Disorders Clinic patients we assessed brain CT scans of 202 patients referred to our clinic between January 1991 and December 1992. One hundred patients (49.5%) had WMLA, and the prevalence increased with increasing severity of cognitive impairment. It was 12% in patients with no evidence of dementia, 32% in those with isolated memory loss, and 59%) in patients with possible or probable dementia. There was a correlation between WMLA and systolic blood pressure, heart disease, peripheral vascular disease, focal neurological signs on examination and central atrophy on CT. No correlation was found between WMLA and low blood pressure, blood glucose or cholesterol level. Our findings indicate that WMLA probably plays an important role in cognitive impairment, and that thromboembolic rather than haemodynamic factors are probably more important in its pathogenesis.