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Cognitive correlates of leukoaraiosis in the early stages of Alzheimer's disease.

To reveal cognitive correlates of leukoaraiosis (LA) in the early stages of Alzheimer's disease (AD) and to exclude confounding effects of aging, brain atrophy, education and dementive illness on cognition, we carefully selected a sample of 37 probable AD patients (NINCDS-ADRDA criteria, Hachinski ischemic score < 5) with similar indices of age, educational level, degree of brain atrophy and dementia severity (CDR 0.5, CDR 1 and MMSE score no lower than 20), and compared the results of neuropsychological testing of patients with and without LA. All patients underwent magnetic resonance imaging. LA was detected in 17 out of 37 cases. There were no significant differences between subjects with and without LA (Student's t-test, p>0.05) in tests that evaluate language, verbal intelligence and visuospatial functions, while the patients with LA showed poorer performance (p<0.05) in the tests evaluating verbal memory, attention/concentration and executive functions. The results obtained suggest that the patients with LA in the early stages of AD revealed dorsolateral prefrontal dysfunction syndrome due to disconnection of cortico-subcortical circuits. We found this syndrome to be more prenounced than it has been described in the non-demented elderly with LA. It may be that in patients suffering from degenerative illness, the brain has fewer compensatory reserves than in cases of "normal" aging, and it is more sensitive to ischemic damage caused by cerebral amyloid, arteriosclerotic or fibro-hyalinotic angiopathy. This typical neuropsychological syndrome is revealed only in the initial stage of AD in patients with LA. The follow-up progress of the atrophic-degenerative illness leads to overlapping of the specific neuropsychological syndrome by global cognitive impairment.