gms | German Medical Science

Objective: Epilepsy surgery in patients with pharmacoresistant focal epilepsies is significantly more effective than pharmacotherapy in this group. Seizure freedom rates range from approx. 50-68% (Blümcke et al., 2017). In the presented retrospective study we evaluate the impact of resection of magnetoencephalography (MEG) localizations of interictal epileptic activity on postoperative seizure outcome in a large patient population.

Methods: MEG reports from all patients who underwent epilepsy surgery after MEG epileptic focus localization from 1990 to 2016 were evaluated retrospectively. Inclusion criteria were: Detection of interictal activity during the recording, classification as a robust result as stated in the report, availability of postoperative seizure outcome, information on the extent of resection in relation to the MEG findings (surgeon’s report or adequate intra- or postoperative MRI). MEG findings were classified in relation to the resection as being completely, partially or not resected at all.

Results: A total of 164 patients were included in the study. MEG localizations were resected completely in 68, partially in 65 and not at all in 32 patients. Mean follow-up was 4.0 years (3 months to 18 years), 81% of patients had a follow-up of at least one year. Median postoperative outcome was Engel 1 (1./3. quartile: Engel 1) in patients with complete MEG resection, Engel 2 (quartiles: Engel 1 and 3) with partial resection and Engel 2 (quartiles: Engel 1 and 3.75) with no resection. Correlation (Spearman) between resection and outcome was highly significant (r = -0.44, p<0.001).

Conclusion: Patients with complete resection of robust MEG localizations have significantly better outcome of epilepsy surgery and regularly become seizure free. Patients with partial or no resection may become seizure free after surgery but usually do not. MEG focus localization therefore provides significant clinical value for epilepsy surgery.