Cognitive reduction in presenile dementia related to regional abnormalities of the cerebral blood flow.

Fifty-five patients with presenile dementia were examined. There were 28 women and 27 men, and the mean age was 59 and 56 years respectively at the time of the study. A large series of psychometric tests was used, and with the aid of age-matched non-demented controls five significantly different cognitive reduction groups could be identified. In the demented patients the regional cerebral blood flow (rCBF) was determined with an eight-detector or 32-detector equipment. There was a rough proportionality between the cognitive reduction and a decrease of the cerebral blood flow (especially the flow in the grey matter). In addition, certain regional flow abnormalities correlated with specific cognitive functions in a manner resembling the cognitive defects found in focal brain lesions in the same region. Thus, patients who showed only memory disturbances demonstrated a focal flow reduction in the temporal region. More severely affected patients, with reduction of verbal abilities and signs of agnosia, showed very low flows in occipito-temporo-parietal parts of the hemisphere. The results offer a principal confirmation of the dynamic field theory concerning the functional organization of the cerebral cortex.