Positron emission tomographic study in Alzheimer's disease and Pick's disease.

Positron Emission Tomography has been used to compare patients with Alzheimer's disease and 3 patients with biopsy-proved Pick's disease to age-matched volunteers. In Alzheimer's disease, there was a trend to a decrease of the metabolism parallel to the severity of the affection. The hypometabolism was predominant in the temporo-parieto-occipital and the middle temporal regions. In 2 cases of Pick's disease with a classical "frontal syndrome", there was an important fronto-temporal hypometabolism, very suggestive of the diagnosis owing to both its location and intensity. A third patient presented with a slowly progressive dysphasia. A left perisylvian hypometabolism was observed before any evident anatomical abnormality. The clinical symptoms evolved to a dementia and the hypometabolism extended to both frontal lobes.