Abstracts

Rationale: We aimed at evaluating feasibility and accuracy of automated interictal EEG Source Imaging (ESI) based on presurgical high-density (HD) EEG and comparing different electrode setups.

Methods: Thirty consecutive patients with drug-resistant focal epilepsy and >3 hours of 257-channel EEG recording were retrospectively included. Four electrode setups were compared: 257 (the complete HD EEG set), 204 (excluding neck and facial electrodes), 40 (low density with facial electrodes), and 25 (IFCN standard) channels. For each patient and each EEG setup, up to 4 clusters of spikes were automatically detected and localized. For ESI, the patient’s individual structural MRI was segmented into 6 tissues (white matter, gray matter, CSF, skull, scalp and air) to generate the head model. In the gray matter, dipoles with 4mm spacing were distributed and sLORETA was used as the inverse solution. The source with maximum energy at the averaged spike’s half-rising phase was compared to resected zone. Based on the known surgical outcome related to 12-month postsurgical follow-up (surgical outcome: 18 with ILAE 1+2 and 12 with ILAE 3-5), the performance of ESI to localize the SOZ at sublobar level was quantified by calculating the sensitivity, specificity and accuracy.

Results: By reviewing all detected clusters, 38% were identified as epileptic genuine spikes. Twenty-one patients with the 25-, 204-, and 257-channel setup and 24 patients with the 40-channel setup had at least one genuine spike cluster. By considering the automated ESI analysis for 25-, 40-, 204- and 257-channel setup reached a sensitivity of 67%(n=12), 71%(n=14), 59%(n=12) and 75%(n=12), specificity of 68%(n=9), 60%(n=10), 50%(n=10), and 67%(n=9) and finally accuracy of 67%(n=21), 67%(n=24), 55%(n=22) and 71%(n=21), respectively. Differences between the different EEG montages were statistically not remarkable (p >0.05).

Conclusions: Automated interictal ESI analysis using HD EEG is feasible with a good accuracy. The accuracy of automated ESI with HD-EEG is not superior to ESI with the standard clinical EEG setup with 25 electrodes.

Funding: Please list any funding that was received in support of this abstract.: This study was funded by the German Research Foundation [grant DFG 422589384 to B. J. Vorderwülbecke], the Swiss National Science Foundation [grants SNSF 163398 and Sinergia 180365 to M. Seeck], the Swiss National Science Foundation [grants CRSII5 180365 and CRSII5 170873 to P. van Mierlo], and the Swiss National Science Foundation [grants SNSF 169198, 192749, and CRSII5 170873 to S. Vulliémoz]. The funders were not involved in the study design, in the collection, analysis and interpretation of data, in the writing of the report, or in the decision to submit the article for publication.