Electrophysiological differences between subtypes of dementia.

The distinction between subtypes of dementia, in particular between 'cortical' and 'subcortical' dementias, is controversial. In order to study this we recorded the long latency auditory evoked potential in demented patients with clinically definite Huntington's disease, Parkinson's disease, and Alzheimer's disease. We compared the peak latencies of the components of this response both between these groups and with normal subjects, controlling for the effects of age. We found highly significant electrophysiological differences not only between the subcortical group (combined patients with Huntington's and Parkinson's disease) and the cortical group (patients with Alzheimer's disease), but also within the subcortical group itself. Using the pattern of electrophysiological response alone, we were able to classify correctly most of our patients using a logistic regression model. These results support the notion that there are distinguishable subtypes of dementia.