Predictors of Postoperative Seizure Recurrence: A Longitudinal Study of Temporal and Extratemporal Resections

Abstract

Objective. We investigated the longitudinal outcome of resective epilepsy surgery to identify the predictors of seizure recurrence. Materials and Methods. We retrospectively analyzed patients who underwent resections for intractable epilepsy over a period of 7 years. Multiple variables were investigated as potential predictors of seizure recurrence. The time to first postoperative seizure was evaluated using survival analysis and univariate analysis at annual intervals. Results. Among 70 patients, 54 (77%) had temporal and 16 (23%) had extratemporal resections. At last follow-up (mean 48 months; range 24-87 months), the outcome was Engel class I in 84% (n = 59) of patients. Seizure recurrence followed two patterns: recurrence was "early" (within 2 years) in 82% of patients, of whom 83% continued to have seizures despite optimum medical therapy; recurrence was "late" (after 2 years) in 18%, of whom 25% continued to have seizures subsequently. Among the variables of interest, only resection site and ictal EEG remained as independent predictors of seizure recurrence over the long term (p < 0.05). Extratemporal resection and discordance between ictal EEG and resection area were associated with 4.2-fold and 5.6-fold higher risk of seizure recurrence, respectively. Conclusions. Extratemporal epilepsy and uncertainty in ictal EEG localization are independent predictors of unfavorable outcome. Seizure recurrence within two years of surgery indicates poor long-term outcome.

Figure 1

Kaplan-Meier survival analysis of class I seizure outcome: (a) shows the comparison between temporal resection (solid line) and extratemporal resection (dashed line); (b) shows the comparison between concordant ictal EEG (solid line) and discordant ictal EEG (dashed line) with respect to the resection site.