Surgical outcome and prognostic factors of frontal lobe epilepsy surgery

Frontal lobe epilepsy (FLE) surgery is the second most common surgery performed to treat pharmacoresistant epilepsy. Yet, little is known about long-term seizure outcome following frontal lobectomy. The aim of this study is to investigate the trends in longitudinal outcome and identify potential prognostic indicators in a cohort of FLE patients investigated using modern diagnostic techniques. We reviewed 70 patients who underwent a frontal lobectomy between 1995 and 2003 (mean follow-up 4.1 +/- 3 years). Data were analysed using survival analysis and multivariate regression with Cox proportional hazard models. A favourable outcome was defined as complete seizure-freedom, allowing for auras and seizures restricted to the first post-operative week. The estimated probability of complete seizure-freedom was 55.7% 95% confidence interval (CI) = 50-62 at 1 post-operative year, 45.1% (95% CI = 39-51) at 3 years, and 30.1% (95% CI = 21-39) at 5 years. Eighty per cent of seizure recurrences occurred within the first 6 post-operative months. Late remissions and relapses occurred, but were rare. After multivariate analysis, the following variables retained their significance as independent predictors of seizure recurrence: MRI-negative malformation of cortical development as disease aetiology risk ratio (RR) = 2.22, 95% CI = 1.40-3.47, any extrafrontal MRI abnormality (RR = 1.75, 95% CI = 1.12-2.69), generalized/non-localized ictal EEG patterns (RR = 1.83, 95% CI = 1.15-2.87), occurrence of acute post-operative seizures (RR = 2.17, 95% CI = 1.50-3.14) and incomplete surgical resection (RR = 2.56, 95% CI = 1.66-4.05) (log likelihood-ratio test P-value < 0.0001). More than half of patients in favourable prognostic categories were seizure-free at 3 years, and up to 40% were seizure-free at 5 years, compared to <15% in those with unfavourable outcome predictors. These data underscore the importance of appropriate selection of potential surgical candidates.