Hypoglycemic activation of focal abnormalities in the EEG of patients considered for temporal lobectomy.

EEGs were recorded in 22 patients with medically refractory complex partial epilepsy undergoing presurgical evaluation and 11 age-matched controls while subjected to moderate levels of hypoglycemia to determine if changes activated were predictive of underlying pathology. Five patients had fasting EEGs showing focal abnormalities not seen in the non-fasting state. With hypoglycemia, EEG tracings in normal individuals showed diffuse background slowing, whereas 7 of 22 patients developed focal temporal changes, including focal spike and focal slow wave activation. The development of focal changes correlated well with clinical data concerning underlying focal pathology; focal abnormalities were not evoked in patients with multifocal disease. Hypoglycemic activation of the EEG may be a useful technique for predicting the presence of pathology in patients considered for anterior temporal lobectomy.