Long-term seizure outcome in frontal lobe epilepsy surgery

Abstract

Purpose: The purpose of this study was to report long-term seizure outcome in patients who underwent frontal lobe epilepsy (FLE) surgery.

Method: This retrospective study included 44 consecutive subjects who underwent resective surgery for intractable FLE at IRCCS NEUROMED (period 2001-2014), followed up for at least 2 years (mean: 8.7 years). All patients underwent noninvasive presurgical evaluation and/or invasive electroencephalography (EEG) monitoring when nonconcordant data were obtained or epileptogenic zone was hypothesized to be close to the eloquent cortex. Electroclinical, neuroimaging, surgical data, and histology were compared to seizure outcome.

Results: Mean epilepsy duration was 19 years; mean age at surgery was 31.6 years. Preoperative magnetic resonance imaging (MRI) showed a frontal lesion in 86.4 % of cases. Scalp video-electroencephalography (VEEG) monitoring detected a focal ictal onset in 90% of cases. Twenty-seven patients (61.4%) underwent invasive recordings. Resections involved dorsolateral (47.7%), medial (9%), orbital (13.6%), and rolandic (13.6%) region. Lobectomy within functional boundaries was performed in the remaining 7 cases (16%). Transient and permanent neurological deficits were observed in 2 and 3 cases, respectively. Histology revealed focal cortical dysplasia (45.5%), World Health Organization (WHO) I-II grade tumors (15.9%), gliosis (22.7%), vascular malformations (4.5%), Rasmussen encephalitis (6.8%), and normal tissue (4.5%). At last observation 68.1% of patients were in Engel's class I, 11.4% in class II, 9% in class III, and 11.4% in class IV. A favorable outcome was associated with focal ictal scalp EEG onset (p = 0.0357).

Conclusion: Surgery is a safe treatment option in drug-resistant FLE with a satisfying long-term outcome. These data highlight the importance of an appropriate selection of potential surgical candidates.

Keywords: Epilepsy surgery; Frontal lobe epilepsy; Presurgical evaluation; Seizure outcome; Subdural electrodes; Video-EEG monitoring.