Patterns of local cerebral glucose utilization were measured with positron emission, computed tomography using the 18F-fluorodeoxyglucose method in 13 patients with Huntington's disease (HD), 15 subjects at risk for HD, and 40 normal control subjects. These data were compared with computed tomographic measures of cerebral atrophy, with age, and with duration and severity of symptoms. The results indicate that in HD there is a characteristic decrease in glucose utilization in the caudate and putamen and that this local hypometabolism appears early and precedes bulk tissue loss. In contrast to patients with senile dementia, in these HD patients glucose utilization typically was normal throughout the rest of the brain, regardless of the severity of symptoms and despite apparent shrinkage of brain tissue. Our results suggest the possibility that the caudate may be hypometabolic in some asymptomatic subjects who are potential carriers of the autosomal dominant gene for HD.

[18F]Fluorodeoxyglucose scans were performed on 9 patients with Parkinson's disease and 14 normal subjects. Five patients were restudied after an interval of 3 to 4 years. We found no selective metabolic change in striatum, where dopamine deficit is known to be greatest, in affected patients; cerebral glucose metabolism was reduced uniformly throughout the parkinsonian brain (average 18% decrease). With increased severity of bradykinesia and the development of mild to moderate dementia, global brain metabolism in Parkinson's disease decreased further. In one moderately demented patient with Parkinson's disease, severe parietal cortex hypometabolism was found, similar to that seen in Alzheimer's disease. In contrast, mildly to moderately demented patients with Huntington's disease have marked caudate hypometabolism, but cerebral glucose metabolism is normal elsewhere. It appears that in addition to the well-known neurotransmitter loss in the nigrostriatal system, there is an abnormal metabolic process involving neurons throughout the parkinsonian brain.

Three cases of slowly progressive speech and language disturbance were studied at various points post onset (three, five and 15 years respectively). Language, neuropsychological and brain imaging (computer tomography and positron emission tomography) evaluations were completed on all three patients. The data suggest that the syndrome of "progressive aphasia": 1) does not involve a uniform symptom complex; 2) does not necessarily develop into a full blown dementia syndrome; 3) varies greatly in rate of progression from case to case; 4) is associated with normal brain structure (on computer tomography); and 5) is associated with abnormal left temporal lobe metabolism as measured by fluorodeoxyglucose (FDG) positron emission tomography (PET). One patient had histological findings consistent with Alzheimer's disease at necropsy.

Patterns of local cerebral glucose utilization were measured with positron emission tomography using the fluorine-18-labeled fluorodeoxyglucose (18FDG) method in 8 patients with Parkinson's disease, in 13 patients with Huntington's disease, in 15 subjects at risk for Huntington's disease, and in aged-matched normal control subjects. On the average, global cerebral metabolism in patients with Parkinson's disease was moderately reduced (20%), but the relative distribution of glucose utilization throughout the brain in these patients was normal. These results support the conclusion that alterations of the nigrostriatal pathway in Parkinson's disease have no major selective effect on the metabolism of particular cerebral regions. In Huntington's disease, however, there was a characteristic decrease in glucose utilization in the caudate nuclei and putamen, and this local hypometabolism appeared early and preceded bulk tissue loss. In patients with Huntington's disease, glucose utilization typically was normal throughout the rest of the brain, regardless of the severity of symptoms and despite the apparent shrinkage of brain tissue. The results also suggest the possibility that the caudate nuclei may be hypometabolic in some asymptomatic subjects who are potential carriers of the autosomal dominant gene for Huntington's disease.