Abstracts

Rationale: In people with drug resistant focal epilepsy magnetoencephalography (MEG) is an important noninvasive diagnostic tool in the pre-surgical evaluation. Although the single equivalent current dipole is the most reliable and clinically useful magnetic source imaging technique, advanced source analysis may provide additional information regarding the epileptogenic zone. Methods: Fifteen-minute resting-state MEG were retrospectively analyzed with CSI Coherence is a measure of oscillating neuronal activity and their synchronicity across the cortex, which defines the neuronal network connectivity. Patients were split into 3 groups: 1) Right temporal lobe epilepsy (TLE) Engel class I outcome (N= 11) vs controls (N= 8), 2) Left temporal lobe Engel class I (N= 6) vs controls (N= 6), 3) Left temporal lobe Engel class I (N=6) vs class IV (N= 7). A t-test was conducted to assess group difference in average coherence values for each pair of brain regions (N= 1,431). A P value was produced for each region pair. The false discovery rate (FDR) was used to adjust for multiple testing. Only Large effect coherence network difference that were significant were included in the analysis. The networks for each comparison group were stratified according to laterality (Right intrahemispheric, Left intrahemispheric or interhemispheric networks), as well as focal network. Results: There were differences in areas of coherence between right and left TLE that did not necessarily indicate coherence in those regions compared to controls. These results are different than what one would expect, specifically the temporal lobe connectivity was higher in controls. When comparing L TLE Class I to class IV, class IV had more widespread and interhemispheric areas of high coherence (Fig.1). Conclusions: Significant differences in coherence were not observed in patients with right or left TLE compared to controls. However, there were distinctly different focal networks in left TLE class I patients compared to left TLE class IV patients. Although the comparison of right and left TLE patients to controls was not expected, the differences between left TLE epilepsy class I and class IV outcomes may provide a measure to pre-operatively predict post-operative outcome. Funding: No funding received