TOPOGRAPHY OF INTERICTAL GLUCOSE HYPOMETABOLISM IN UNILATERAL MESIOTEMPORAL EPILEPSY

We mapped the regional cerebral glucose metabolism (rCMRGlu) in 20 pat ients suffering from medically refractory focal epilepsy of either lef t or right mesiotemporal origin (mTLE) during resting wakefulness. Aft er temporal lobectomy, histology demonstrated hippocampal sclerosis in 18 patients. Pixel-by-pixel comparisons with healthy control subjects showed significant (p < 0.001) depressions of the mean rCMRGlu ipsila teral to the epileptic focus in the mesiotemporal region, including th e hippocampus and the parahippocampal gyrus and middle temporal gyrus. Additional remote rCMRGlu depressions occurred bilaterally in the fro nto-orbital cortex and ipsilaterally in the posterior insula and the t halamus. Patients with left-sided mTLE had additional rCMRGlu depressi ons in the left inferior frontal gyrus (Broca's region) and superior t emporal gyrus at the parietotemporal junction, whereas corresponding r CMRGlu depressions were not present in patients with right mTLE, Neuro psychological testing showed impaired verbal fluency, verbal intellige nce, and verbal memory in the left mTLE patients. Correlations of the specific mean rCMRGlu depressions and the neuropsychological deficits suggest that impaired language functions in patients with left mTLE co uld result from functional changes beyond the temporal lobe.