Seizure outcome after anterior temporal lobectomy and its predictors in patients with apparent temporal lobe epilepsy and normal MRI

Abstract

Purpose: Very little reliable information is available regarding the role of anterior temporal lobectomy (ATL), optimal presurgical evaluation strategy, post-ATL seizure outcome, and the factors that predict the outcome in patients with medically refractory temporal lobe epilepsy (TLE) and normal high-resolution magnetic resonance imaging (MRI). To be cost-effective, epilepsy surgery centers in developing countries will have to select candidates for epilepsy surgery by using the locally available technology and expertise. Methods: We reviewed the electroclinical and pathological characteristics and seizure outcome of 17 patients who underwent ATL for medically refractory TLE after being selected for ATL based on a noninvasive selection protocol without the aid of positron emission tomography (PET) or single-photon emission computed tomography (SPECT), despite a normal preoperative high-resolution MRI. Results: Seven (41%) patients achieved an excellent seizure outcome; five of them were totally seizure free. An additional five (29%) patients had >75% reduction in seizure frequency. The following pre-ATL factors predicted an excellent outcome: antecedent history of febrile seizures, strictly unilateral anterior temporal interictal epileptiform discharges (IEDs), and concordant type 1ictal EEG pattern. All the five patients with pathologically verified hippocampal formation neuronal loss were seizure free. The presence of posterior temporal, bilateral temporal, and generalized IEDs portended unfavorable post-ATL seizure outcome. Conclusions: A subgroup of patients destined to have an excellent post-ATL outcome can be selected from MRI-negative TLE patients by using history and scalp-recorded interictal and ictal EEG data. The attributes of these patients are antecedent history of febrile seizures, strictly unilateral anterior IEDs, and concordant type 1 ictal EEG pattern.