Abstracts

Rationale: Magnetoencephalography (MEG) and electroencephalography (EEG) source analysis have each been found to have unique strengths and weaknesses and may often be complementary.  However, it is not standard of practice to perform both for those patients who need further source localization as part of an epilepsy pre-surgical evaluation.  The purpose of this research is to contribute to a limited body of literature assessing the concordance versus discordance of patients’ interictal MEG and interictal EEG source analysis, and how that relates to postsurgical improvement of seizure frequency. Methods: A retrospective chart review was performed on forty-six patients who had undergone an epilepsy pre-surgical evaluation at the University of California, Los Angeles Seizure Disorder Center, and had undergone a MEG study at the University of California, San Francisco between September 2015-May 2017.  We excluded those patients who at the time of chart review had not undergone surgery, those who had not yet had follow up since surgery, and those who only had VNS programmed with initial settings.  The resultant sixteen patients had interictal EEG source analysis performed on the EEG data from their phase I epilepsy monitoring unit admission.  The researcher performing the EEG source analysis was blinded to the MEG results.  The data was analyzed using chi-squared and 2-sided Fisher’s exact tests with IBM SPSS software. Results: Sixteen patients (mean age 38.56, 62.5% female) were included in this study.  Surgery types included were resection (31.25%), responsive neurostimulation (RNS) (31.25%), vagus nerve stimulation (VNS) (25%), and laser ablation (12.5%).  The longest postoperative follow up period for each patient ranged from 3-28 months, with the largest group (37.5%) between 3-6 months.  Chi-squared analysis found that 100% of patients with concordant interictal MEG and interictal EEG source analysis had an improvement in postsurgical seizure frequency, and 60% of patients with discordant interictal MEG and interictal EEG source analysis did not have an improvement in postsurgical seizure frequency.  The data demonstrate that there is a statistically significant (p=0.034) relationship between the concordance of interictal MEG and interictal EEG source analysis as it relates to postsurgical seizure outcomes. Conclusions: Our data suggest that concordance versus discordance of interictal MEG and interictal EEG source analysis may help predict postsurgical seizure outcomes.  The study is limited by small sample size, various types of surgical procedures included, and the majority of patients had a short postoperative follow up duration.  Future studies may also want to include ictal EEG source analysis in their investigation as well.  The results of this study may help to guide presurgical epilepsy decision-making for patient cases that need further source localization. Funding: None