EEG and cognitive impairment in presenile dementia.

EEG and psychometric findings were studied in a group of 57 patients consisting of 19 cases of Alzheimer's disease, 7 cases of Pick's disease, 24 cases of cerebrovascular dementia (CVD) and a group of 7 cases with dementia of various other etiology. The diagnoses have so far been confirmed by autopsy in 23 out of 57 cases. EEG was evaluated by means of visual inspection. Psychometric studies enabled a classification into 5 psychometric defect groups according to the degree of dementia. An overall good correlation was found between the degree of dementia and EEG abnormality. A significant correlation between the test socre and the EEG was found only for the vocabulary test and paired associates test. However, on the reaction time test, color word test, and Koh's block design test, large patient groups were untestable, and a highly significant correlation was found between non-testability and severely abnormal EEG. The Alzheimer and the CVD groups differed distinctly, most of the Alzheimer cases showing a severe or moderate degree of EEG abnormality and dementia, whereas in the CVD cases, the dementia was less pronounced and the EEG often normal or only slightly abnormal. Four out of seven cases of Pick's disease had a normal EEG, which distinguished them from the Alzheimer cases which had a comparable psychometric defect.