PREFRONTAL ASYMMETRIC INTERICTAL GLUCOSE HYPOMETABOLISM AND COGNITIVEIMPAIRMENT IN PATIENTS WITH TEMPORAL-LOBE EPILEPSY

Depressions of regional cerebral metabolism beyond the epileptogenic z one have been demonstrated in patients with intractable temporal lobe epilepsy. However their clinical relevance, and the causes of prefront al metabolic asymmetries are less well understood. We investigated 96 temporal lobe epilepsy patients by FDG-PET and neuropsychological asse ssment who had a corresponding unilateral temporal hypometabolism, lef t hemisphere speech dominance, full scale IQ of >70 and no extratempor al lesion in MRIs. The regional glucose metabolism was determined in e ach patient in homologous regions including prefrontal cortex, and nor malized to whole brain metabolism. Regional differences of >10% were r egarded as asymmetrical. Prefrontal metabolic asymmetries were more fr equent in patients with left temporal lobe epilepsy (21 left, six righ t) and a history of secondarily generalized seizures. A multivariate a nalysis of variance revealed a main effect for prefrontal metabolic as ymmetry on neuropsychological 'frontal lobe measures', including verba l and performance intelligence measures. Prefrontal metabolic asymmetr y was not related to 'measures of episodic memory', presence of psychi atric symptoms or frontal interictal epileptiform discharges. We concl ude that prefrontal metabolic asymmetry is associated with cognitive i mpairment. Patients with temporal lobe epilepsy of the left speech dom inant hemisphere and a history of secondarily generalized seizures are at considerable risk of developing prefrontal metabolic asymmetry.