Prognostic significance of postoperative spikes varied in different surgical procedures for mesial temporal sclerosis

Purpose We conducted this study to compare the occurrence and prognostic significance of early postoperative interictal epileptiform discharges (IEDs) on seizure outcomes between corticoamygdalohippocampectomy (CAH) and selective amygdalohippocampectomy (SAH). Methods We reviewed our database of patients who had epilepsy surgery with hippocampus atrophy or signal changes on brain MRIs and pathology of mesial temporal sclerosis. One hundred and seventy-seven CAH and 39 SAH patients were enrolled. Postoperative EEG within 30days, other preoperative variables and seizure outcome 2years after surgery were obtained for analysis. Engel's IA and IB were defined as seizure-free. Results There was no significant difference in the seizure-free rate between the two procedures (127 (71.8%) of CAH vs 30 (76.9%) of SAH, p =0.51). Postoperative IEDs were more frequently seen in the SAH group (64.1%) than in the CAH group (29.9%), p 0.001. The IEDs in the SAH group did not show correlation with the seizure outcome 2 years after surgery. In the CAH group, patients who had no postoperative IEDs showed a higher seizure-free rate compared to those with IEDs (78.2% vs 56.6%, p =0.003; OR 2.267, 95% CI 1.09-4.73, p =0.029 in multivariate logistic regression). Conclusions Early postoperative IEDs are more frequently seen in SAH than in CAH. Unlike in patients with CAH, the presence of IEDs after SAH was not a predictor of seizure recurrence. The type of surgery should be considered while utilizing postoperative IEDs for evaluating the prognosis.