Subcortical dementia. Frontal cortex hypometabolism detected by positron tomography in patients with progressive supranuclear palsy.

The dementia associated with progressive supranuclear palsy (PSP) is considered to be subcortical because the cerebral cortex, unlike the subcortical structures, is usually free from major neuropathological lesions; the characteristic symptoms point to a dysfunction of the prefrontal lobe. The regional cerebral metabolic rate of glucose (rCMR Glu) was studied by positron emission tomography and 18F-fluoro-2-deoxyglucose18FDG in 6 patients presumed to have PSP and was compared with values found in 8 control subjects of similar age. The results obtained showed a highly significant rCMR Glu decrease in the prefrontal cortex of our patients. The loss of several subcortical afferents to prefrontal cortex may be responsible for the frontal cortical hypometabolism present in PSP.