Lateralized postictal EEG delta predicts the side of seizure surgery in temporal lobe epilepsy

Purpose: The concordance of lateralized EEG postictal polymorphic delta act ivity (PPDA) to the side of seizure origin in temporal lobe epilepsy (TLE) has received limited study. Our objective was to study the lateralizing val ue of PPDA in patients with documented TLE. Methods: A cohort of consecutive adults with TLE, detailed presurgical eval uation before temporal lobectomy, and minimal follow-up of 2 years were inc luded. One author masked the ictal rhythm of presurgical EEGs and randomly presented 20 s of preictal and the postictal EEG to two electroencephalogra phers who were blind to all clinical data. They independently assigned PPDA to one of three categories: not present, bilateral, or lateralized (define d as newly appearing or an amplitude >50% of the preictal record). Results: Eighty seizures from 29 patients were studied. Fifteen patients ha d a left, and 14 had a right temporal lobectomy. Twenty-three patients were seizure free or substantially improved (defined as simple partial or noctu rnal seizures only). Lateralized PPDA was present in 64% of all EEGs and at least one record from 22 (76%) patients. Lateralized PPDA, when present, w as concordant with the side of surgery in 96% of the EEGs. Conclusions: Lateralized PPDA is highly predictive of the side of ultimate temporal lobectomy, and by inference the side of seizure origin.