Relationship between small cerebral white matter lesions and cognitive function in patients with Alzheimer's disease and amnestic mild cognitive impairment.

AIM The main purpose of the present study was to investigate the influence of small cerebral white matter lesions on cognitive functions, and its difference by clinical stage. METHODS A total of 160 patients with Alzheimer's disease and 40 older adults with amnestic mild cognitive impairment were enrolled in the present study. The Fazekas rating scale was used for the semi-quantitative measurement of white matter lesions. Participants whose scales were more than grade 2 were excluded. Associations between the degree of small white matter lesions and cognitive functions including memory, verbal fluency, working memory, processing speed, and executive function were examined. RESULTS We found that small white matter lesions influenced the performances of neuropsychological tests differently between Alzheimer's disease and amnestic mild cognitive impairment. Analysis of covariance showed significant effects of interaction on a test that assessed categorical verbal fluency. In the amnestic mild cognitive impairment group, small periventricular white matter hyperintensities were significantly associated with poor performances in categorical verbal fluency; whereas in the Alzheimer's disease group, such associations were not observed. Deep white matter hyperintensities did not influence any cognitive functions examined in both groups. CONCLUSIONS The results suggested the involvement of periventricular small white matter lesions on impairment in verbal fluency, and such influence might be different depending on an individual's clinical stage.