Seizure outcome and its predictors after frontal lobe epilepsy surgery

Frontal lobe epilepsy (FLE) surgery is the second most common focal resective surgery for drug-resistant epilepsy. Not many studies are available regarding the long-term surgical outcome of FLE. We studied the longitudinal outcome and predictors of seizure outcome following FLE surgery in a sizeable cohort of patients.

A total of 73 consecutive patients who underwent FLE surgery between January 1997 and May 2015 with a minimum follow-up of 1 year (range 1-16 years) were studied. Primary outcome was seizure freedom at last follow-up (Engel Class IA). "Seizure freedom" separately was defined as absence of seizures till last follow-up. Outcome predictors were subjected to multivariate analysis. Using Kaplan-Meier curve, we assessed the post-operative seizure freedom over time.

Twenty-five patients (34%) were seizure-free till last follow-up. The seizure freedom was 45%, 34%, 26%, 20% and 14% at the end of 1st, 2nd, 3rd, 4th and 5th post-operative year, respectively. Engel class I outcomes were 48%, 41%, 56%, 57% and 53% at end of 1st, 2nd, 3rd, 4th and 5th post-operative year, respectively. Predictors of seizure recurrence on multivariate analysis were older age at surgery (P = 0.032), longer duration of epilepsy (P = 0.031), presence of interictal epileptiform discharges in post-operative EEG on 7th day (P = 0.005), 3 months (P = 0.005) and 1 year (P = 0.0179). In subgroup analysis, duration of epilepsy of less than 2 years before surgery was a significant predictor for achieving seizure freedom (P = 0.029).

These results emphasize early surgery for better outcome in frontal lobe epilepsy. Post-operative EEG remained a good predictor for long-term outcome.