Epilepsy Surgery in the Frontal Lobe: Terra Incognita or New Frontier?

Abstract

Surgical Outcome and Prognostic Factors of Frontal Lobe Epilepsy Surgery. Jeha LE, Najm I, Bingaman W, Dinner D, Widdess-Walsh P, Luders H. Brain 2007;130(Pt 2):574–584. Epub 2007 Jan 5. 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.