Abstracts

RATIONALE: Based on previous reports suggesting a relation between glucose consumption and glutamate cycling, the aim of this study was to investigate the relation between glucose metabolism and glutamate concentration in human brain, under normal and pathologic conditions. METHODS: Regional values of glucose metabolism measured with 2-deoxy-2[F-18]fluoro-D-glucose positron emission tomography (FDG PET), and single voxel proton magnetic resonance spectroscopy (1H MRS) measurements of the glutamate/glutamine/?-aminobutyric acid (Glx) tissue concentration were determined in 11 patients (5 girls and 6 boys, mean age 7.5 years) with medically intractable partial epilepsy. FDG PET and 1H MRS studies were performed in the interictal state in 7 patients and in the ictal/periictal state in 4 patients. Regions of interest were identified in epileptic cortex (determined by intracranial and/or scalp EEG) and in contralateral normal brain regions. RESULTS: Lower glucose metabolism and Glx concentration were found in the epileptic focus than in the contralateral normal cortex in all 7 patients examined in the interictal state, whereas higher glucose metabolism and higher Glx concentration were observed in the epileptic focus in the 4 patients who had ictal/periictal studies. Significant correlations were found between the values of cerebral glucose utilization and Glx concentration in epileptic brain regions (p=0.021), in nonepileptic brain regions (p=0.047) and in epileptic and nonepileptic regions combined (p=0.0009). CONCLUSIONS: These results demonstrate a significant relation between glucose metabolism and glutamate/glutamine concentration in normal and epileptic cerebral cortex, in both the interictal and ictal states. These data support the notion of coupling between glucose metabolism and glutamate cycling.