Correlation of severity of FDG-PET hypometabolism and interictal regional delta slowing in temporal lobe epilepsy

Purpose: We investigated the association of severity of hypometabolism detected by positron emission tomography (PET) with [F-18]fluorodeoxyglucose (FDG) and persistence of interictal EEG focal slowing in patients with refractory temporal lobe epilepsy. Methods: Eighty temporal lobes of 40 consecutive patients with intractable temporal lobe epilepsy (mean age, 43.5 years) were studied. All patients underwent video-EEG monitoring, magnetic resonance imaging (MRI), and FDG-PET. Patients with either normal MRI or with unilateral mesial temporal sclerosis, but no other structural abnormality, were included. Interictal EEG delta slowing was graded as none, infrequent (one episode or less/hour), intermediate (more than one episode/hour), or continuous. PET hypometabolism was graded as none, mild, moderate, or severe. Results: The severity of temporal lobe hypometabolism with PET was significantly correlated with the amount of delta activity in the interictal EEG, independent of MRI findings (Spearman r = 0.46; p < 0.0005). Conclusions: This observation suggests related underlying pathophysiologic mechanisms for metabolic and electrical dysfunction in temporal lobe epilepsy.