Postoperative EEG and electrocorticography: relation to clinical outcome in patients with temporal lobe surgery

To evaluate the role of different EEG methods with respect to postoperative clinical follow-up, 32 non-lesionary epilepsy patients who had undergone temporal lobectomy were studied preoperatively and at 2-week, 3-month, and 1-year postoperative follow-up. Routine, sleep, and sphenoidal EEG recordings as well as intraoperative electrocorticography (ECoG) were made for all patients. At 1-year follow-up, the EEGs with sphenoidal electrodes and with sleep deprivation procedure provided important prognostic information; the appearance of seizures was associated with the presence of interictal epileptiform abnormalities in EEG. In the postresection ECoG, however, epileptiform abnormalities were not associated with clinical outcome or with postoperative epileptiform EEG at 1 year. Routine EEG reliably reflects clinical outcome after temporal lobectomy; with sphenoidal electrodes as well as with sleep deprivation procedure, the diagnostic yield can be further improved.