Abstracts

Rationale: Since there has been controversy in determining which cases of frontal lobe epilepsy (FLE) should be approached with resective surgery, the aim of this study is to determine the favorable prognostic factors and long-term outcome. Methods: 71 patients diagnosed with FLE based on intracranial or scalp EEG monitoring by the Dartmouth Epilepsy Program were retrospectively reviewed. 58 patients with localizable FLE underwent resective surgery and have at least nine months of follow-up. Patient demographics, risk factors, seizure characteristics, diagnostic tests, imaging studies, and neuropsychological data were tabulated. Outcome measures (Engel, employment, seizure freedom during the last year of follow-up, and time to first recurrent seizure) were determined based upon yearly follow-up data. Results: Of the 58 resective patients, 20 (34%) had onset in the supplementary motor area (SMA) and medial frontal region, 15 (26%) in the frontal convexity, 13 (23%) in the orbitofrontal region, and 10 (17%) in the fronto-polar region. 52 (90%) underwent intracranial monitoring. 32 (55%) patients had lesions visible on MRI. The mean follow-up period was 82.9 months (>6.5 years). 57% of the resective patients had a class I outcome (either complete seizure freedom, only non-disabling simple partial seizures, freedom from disabling seizures during the last two years of follow-up, or only seizures induced by drug withdrawal) while 72% had a class II outcome (rare disabling seizures) or better. Orbitofrontal and SMA or medial frontal patients tended to do better than other locations (table 1, p=0.06). The mean time to the first seizure after surgery was 31 months. Only 13 patients (22%) never had another event (no auras or seizures with medication changes), corresponding to an Engel IA outcome. 7% of resective patients were seizure free for at least 1 year after initial postoperative seizure recurrence (a running-down effect) and 16% experienced initial seizure freedom for at least 1 year before seizure relapse, while 28% experienced alternating periods of seizure freedom and seizure relapse. 53% of the resective patients were seizure-free during the last year of follow-up. Of the 21 patients unemployed preoperatively, 32% were employed at last follow-up while 82% of the 35 patients employed preoperatively were employed at last follow-up. Postoperative employment correlated with Engel outcome (p=0.01). Age at surgery, risk factors, pathology, and the presence of lesions on preoperative MRI scans were not associated with long-term seizure outcome (p>0.05). Conclusions: Long-term outcome is favorable in FLE resective surgery. Though location of seizure focus is not significantly associated with outcome, the orbitofrontal and SMA or medial frontal syndromes tend to have better long-term outcomes. The lack of a significant association between the presence of a lesion on preoperative MRI scans and a better seizure outcome should be further investigated.