Brain hypometabolism in patients with mesial-temporal sclerosis demonstrated by FDG-PET

The purpose of this study was to evaluate the extent of brain hypometabolism in patients with mesial-temporal sclerosis (MTS). Method: This retrospective study included 21 patients who had medically refractory complex partial seizures and were selected for surgical therapy after a comprehensive evaluation which included surface EEG recordings and neuroimaging studies (PET, SPECT and MRI). All patients were subjected to surgical intervention and had an histopathological confirmation of MTS. A semi-quantitative analysis of the PET images was performed using regions of interest in the following structures: frontal, parietal and occipital lobes, basal ganglia, thalami, cerebellum and three different regions in the temporal lobes, which included medial, inferior and lateral cortices. An asymmetry index (AI) was calculated, comparing the counts per pixel in the homologous structures in both brain hemispheres. The Al of the different structures were then correlated. Results: A significant correlation was demonstrated between the Al of the medial temporal cortices and the frontal lobe, parietal lobe, basal ganglia and thalami (r = 0.72, 0.62, 0.47 and 0.47 respectively with p < 0.05). Within the temporal lobe, highly significant correlations were demonstrated among the structures (as high as 0.86 between temporo-medial and temporo-inferior). Conclusion: These data indicated that hypometabolism extends beyond the epileptogenic focus in the temporal lobe in patients with complex partial seizure related to MTS. The metabolism in the medial portion of the temporal lobe is more correlated with the metabolism in the frontal Lobe than with those of the others brain structures outside the temporal lobe. The pathophysiological mechanisms of hypometabolism remain controversial.