Abstracts

¹⁸FDG PET is a useful tool to evaluate basal [italic]in vivo [/italic]brain metabolism, but has not been utilized extensively for the assessment of interictal functioning in temporal lobe epilepsy. Here, we aim to demonstrate the association of duration of epilepsy with cerebral glucose metabolism in temporal lobe epilepsy (TLE)., Patients from the Comprehensive Epilepsy Center (1999-2004) with pharmaco-resistant TLE defined by video/EEG monitoring that received 18FDG PET as part of their pre-surgical evaluation were included in the study. PET scan: A bolus injection of approximately 10 mCi [18F] FDG was administered 30 minutes prior to scan, using a Siemens ECAT EXACT 47 scanner. Summed images were then preprocessed for statistical analysis. Statistical Analysis: Data analysis was performed using MATLAB 7.1 and SPM 2 (Wellcome Department of Imaging Neuroscience, University College London, UK). Voxel-based data is reported at a voxel extent threshold of 50 voxels and with p[lt]0.001 (uncorrected) for both positive and negative correlation tests performed. Age at PET date was entered for all subjects as a possible confounder and controlled for within the design of the correlation model., The 50 subjects were divided into 2 groups, RTLE (n: 26) and LTLE (n: 24). The mean age at the time the PET scan was obtained was 37 [plusmn] 11 years for the LTLE and 37 [plusmn] 13 for the RTLE. The duration of epilepsy, age of onset, number of medications and educational achievement was not different between the groups. Visual analysis of PET scan showed ipsilateral hypometabolism only in epileptic temporal lobe in 30.8% of RTLE (8/26) and 20.8% of LTLE (5/24) group. Bitemporal hypometabolism was noted in 8.3% of LTLE and 11.5% of RTLE cases. Mesial temporal sclerosis (MTS) was present in 23.1% (6/26) of RTLE and 37.5% (9/24) of LTLE group. Quantitative analysis of FDG-PET images by SPM demonstrated a negative correlation controlled for the effects of age between duration of epilepsy and PET signal in the temporal lobe ipsilateral to the epileptogenic zone. A positive correlation was found between duration of epilepsy and metabolism in regions within the hemisphere contralateral to the epileptogenic zone, after controlling for the effects of age., Our results indicate that asymmetry of glcose metabolism in the temporal lobes of persons with TLE is associated with the duration of epilepsy. The relative increase in glucose metabolism contralateral to the epileptogenic temporal lobe may suggest the possibility of compensatory changes in the more normal hemisphere over time as was described in early stages of dementia with Down syndrome. Further studies are needed to clarify the clinical implication of this interictal PET abnormality in patients with TLE.,