Study of broadband frequency analysis in stereo-electroencephalography for intractable epilepsy

Abstract

Objective To investigate the characteristics of preictal and ictal stereo-electroencephalography (SEEG) in intractable epilepsy using multifrequency quantity analysis and to provide neuro-electrophysiological evidence for accurate identification of epileptogenic zone. Methods We retrospectively analyzed the data of 95 intractable epilepsy patients, who underwent preoperative evaluation involving stereo-electroencephalography(SEEG) and subsequent epileptogenic zonectomy between January 2015 and March 2016 at Beijing Tiantan Hospital, Capital Medical University. Preictal and ictal SEEG data of 16 patients, with the sampling rate over 2, 000 Hz, were analyzed using multifrequency quantity method and that patients were followed up for 10.0 ± 2.7 months. Results The ictal onset rhythm in those 16 patients covered the frequency bands of 0.2-4.0 Hz and 8-500 Hz. Notably, the quantitative analysis showed that the infraslow activity (0.2-1.0 Hz), fast activity(12-30 Hz) and high-frequency oscillations (80-500 Hz) were more correlated with the seizure onset zone rather than non-seizure onset zone(P<0.001). Conclusions The infraslow activity (0.2-1.0 Hz) and high-frequency oscillations (80-500 Hz) in the seizure onset zone seem to demonstrate pronounced increase in preictal period. Broadband frequency analysis of ictal electroencephalography (EEG) could facilitate accurate localization of epileptogenic zone by identifying subtle changes that might be difficult to recognize in conventional analysis. Key words: Epilepsy; Electroencephalography; Stereoelectroencephalography; High-frequency oscillations