The relationship of regional frontal hypometabolism to executive function: a resting fluorodeoxyglucose PET study of patients with epilepsy and healthy controls.

Executive dysfunction is common in patients with frontal lobe damage and may depend on the location of pathology within the frontal lobes. However, it is unclear how specific brain regions contribute to different aspects of executive functioning. Eighteen patients with frontal lobe epilepsy, 10 patients with juvenile myoclonic epilepsy, and 14 controls completed a series of tests that measure a broad range of executive functions. Resting fluorodeoxyglucose positron emission tomography scans were collected and regional cerebral rates of glucose uptake values were regressed on test scores. Results revealed that frontal lobe metabolic values were strong predictors of executive functioning in patients with epilepsy, but not in healthy controls. However, nonfrontal regions also contributed unique variance on several measures, suggesting that (1) a network of frontal and nonfrontal regions subserve many executive functions and (2) resting hypometabolism can be a useful predictor of executive dysfunction in patients with epilepsy.

The use of 2-deoxy-2-[18F]fluoro-D-glucose (FDG-PET) positron emission tomography in the routine diagnosis of epilepsy.

PURPOSE: Positron emission tomography with 2-deoxy fluoroglucose positron emission tomography (18-FDG-PET) is widely used in the pre-surgical evaluation of subjects with epilepsy, but little is known of its usefulness in a non-surgical population. PROCEDURES: We analyzed the sensitivity of PET as a diagnostic tool in a large unselected population of epilepsy subjects. Pre-surgical and non-surgical portions of this population were individually assessed as well. The relationship of PET abnormalities to other neurodiagnostic tests was examined. Statistical assessment relied primarily on contingency tables (chi-square tests), with ANOVA or non-parametric assessment used as necessary. RESULTS: While PET was more likely to identify areas of decreased metabolism in the surgical population than in the non-surgical populations, it nevertheless found a significant number of abnormalities in the total population and in the non-surgical group alone. Even in groups in which the clinical diagnosis was unknown, abnormalities were found 40% of the time. PET was useful as an exclusionary diagnostic tool for non-epileptic seizures (NES) and primary generalized epilepsies (PGE) with sensitivity, specificity, and accuracy > 90%. The PET was somewhat more sensitive than magnetic resonance imaging (MRI) in finding abnormalities in the total population, but was less sensitive than electroencephalography (EEG). CONCLUSION: PET may be a useful diagnostic tool in the general epilepsy population even when a definitive clinical diagnosis is not suggested by other modalities.