gms | German Medical Science

Objective: Frontal lobe epilepsy (FLE) still remains challenging for surgery. Long-term seizure outcome ranges between 13-47% seizure free patients. The main difficulties are localization of the epileptic zone, protection of eloquent brain areas, and definition of resection borders in MRI negative patients. Presurgical application of magnetoencephalography (MEG), functional MRI and fiber tractography with definition of the presumed epileptic focus and eloquent brain areas using neuronavigation and intraoperative MRI (iopMRI) might lead to better seizure outcome.

Method: In this retrospective study, 43 patients (19 female, 24 male, mean age 35.8 ± 12.5 yrs) with FLE underwent presurgical evaluation at the Epilepsy Center, University Hospital Erlangen. Surgery was performed using 1.5T-iopMRI and neuronavigation in our Department of Neurosurgery between 2003 and 2013. Mean duration of epilepsy was 13.9 ± 13.1 years. Twenty-four patients received presurgical MEG (74-channel, two-sensor system Magnes II or whole head MEG system; 4-D Neuroimaging, San Diego, CA, USA). Surgery was performed according to the definition of the epileptogenic zone by MEG and invasive monitoring with the aid of neuronavigation and iopMR imaging. Additionally, in 15 patients functional MR imaging (motor and speech areas) and 17 patients DTI fiber tracking (for language and pyramidal tracts) were included in the surgical resection plan.

Results: Implementation of multimodal imaging led to complete removal of the MEG focus and the defined epileptogenic zone in 37 of 43 patients (86%). In six patients (14%), an intraoperative second look procedure according to intraoperative MRI findings of residual epileptogenic tissue was necessary to accomplish the planned extent of resection. Surgical complication rate was 4.6% (2/43) and transient neurological deficits occurred in 7% (3/43) of all patients. Complete seizure control (Engel Class IA) was achieved in 30/43 patients (69.9%, mean FU 41.3 months, from 13-124 months).

Conclusions: In our retrospective analysis, multimodal neuronavigation led to promising seizure control rates in patients with frontal lobe epilepsy. Even in cases where the epileptic lesion was located close to eloquent brain areas, a complete resection was achieved in 86% with acceptable surgical risks.

This study was supported by DFG grand No. STE 380-14/1 and 15/1.