EEG predicts surgical outcome in lesional frontal lobe epilepsy

Background: Because of the relatively poor results of frontal lobe epilepsy (FLE) surgery, identification of prognostic factors for surgical outcome i s of great importance. Methods: To identify predictive factors for FLE surg ery, we analyzed the data of 61 patients (mean age at surgery 19.2) who had undergone presurgical evaluation and resective surgery in the frontal lobe . Postoperative follow-up ranged from 0.5 to 5 years (mean 1.78). Fifty-nin e patients had MRI-detectable lesions. Histopathologic examination showed d ysplasia (57.4%), tumor (16.4%), or other lesions (26.2%). Thirty postopera tively seizure-free patients were compared with 31 non-seizure-free patient s with respect to clinical history, seizure semiology, EEG and neuroimaging data, resected area, and postoperative data including histopathology. Resu lts: Three preoperative and two postoperative variables were related to poo r outcome: generalized epileptiform discharges, generalized slowing, use of intracranial electrodes, incomplete resection detected by MRI, and postope rative epileptiform discharges. The only preoperative factor associated wit h seizure-free outcome was the absence of generalized EEG signs. Multivaria te analysis showed that only the absence of generalized EEG signs predicts the outcome independently. Moreover, the occurrence of a somatosensory aura , secondarily generalized seizures, and negative MRI was identified as addi tional independent risk factors for poor surgical results. Conclusions: The absence of generalized EEG signs is the most predictive variable for a sei zure-free outcome in FLE surgery. Furthermore, nonlesional MRI, somatosenso ry aura, and secondarily generalized seizures are risk factors for poor sur gical results.