Widespread glucose hypometabolism in patients with hippocampal atrophy: Evaluation with 18F-fluorodeoxyglucose positron emission tomography

Positron emission tomography (PET) with 18 F-fluorodeoxyglucose was performed to measure the interictal local cerebral metabolic rate for glucose (ICMRGlc) in 18 patients observed to have hippocampal atrophy (HA) on magnetic resonance imaging (MRI). In all patients, the MRI showed unilateral atrophy of the hippocampus, and the side showing HA was ipsilateral to the EEG lateralization. PET scans were obtained in a semicoronal plane at an angle of −30 ° to the orbitomeatal line, approximately -60 ° to the long axis of the temporal lobe. The metabolic asymmetry was compared with the frequency of epileptic seizures, duration of illness, and intellectual deficit. The absolute values of ICMRGlc (mg/min/100g) in the hippocampus, extrahippocampal temporal lobe, and frontal lobe were significantly lower on the side ipsilateral to the epileptic focus than on the contralateral side. In patients with frequent seizures, there were greater asymmetry of the ICMRGlc in the extrahippocampal temporal lobe and less in the hippocampus, suggesting that the ipsilateral temporal lobe and contralateral hippocampus were affected by repeated seizures. In conclusion, in patients with presumed unilateral temporal lobe epilepsy and HA, PET studies demonstrated widespread glucose hypometabolism in extrahippocampal areas, and the semicoronal scan was useful in its evaluation.