Ictal High-Frequency Oscillation for Lateralizing Patients With Suspected Bitemporal Epilepsy Using Wavelet Transform
Tao Han1,2,3, Zhexue Xu1,2,3, Jialin Du1,2,3
1Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China.
Frontiers in Neuroinformatics
|July 19, 2019
Summary
Objective verification using wavelet transform and Granger causality aids in lateralizing the seizure onset zone in bilateral temporal lobe epilepsy (TLE). This combination of methods improves accuracy for temporal lobectomy, benefiting patients with refractory seizures.
Area of Science:
- Neurology
- Neuroscience
- Biomedical Engineering
Background:
- Identifying the epileptogenic focus in bilateral temporal lobe epilepsy (TLE) is challenging with conventional electroencephalography (EEG) and electrocorticography (ECoG).
- High-frequency oscillations (HFOs) show promise as biomarkers for lateralizing the seizure onset zone (SOZ) in TLE.
- Objective verification methods are needed to enhance the accuracy of HFO detection for surgical planning.
Purpose of the Study:
- To prospectively evaluate the utility of wavelet transform (WT) and Granger causality (GC) analyses for objective lateralization of the SOZ in patients with refractory TLE.
- To investigate the characteristics of pre- and ictal HFOs and their propagation patterns using WT and GC.
Main Methods:
- Prospective study of 10 patients with refractory TLE undergoing ECoG with wide-band frequency amplifiers (2,048 Hz).
- Analysis of pre- and ictal HFOs using wavelet transform (WT) to identify frequency bands and bandpass boundaries.
- Application of Granger causality (GC) analysis to assess the directionality and degree of HFO propagation between the SOZ and adjacent regions.
Main Results:
- Ictal HFOs were predominantly observed between 80–115 Hz (average 92.59 ± 10.23 Hz), with a distinct boundary between pre-ictal and ictal HFOs.
- GC analysis revealed that in five patients, the highest GC degree was within the SOZ itself, while in the other five, it was in the SOZ and adjacent regions.
- GC analysis confirmed WT findings and suggested HFOs initiate locally and propagate to adjacent brain areas.
Conclusions:
- The combination of WT and GC analyses provides objective and accurate lateralization of the SOZ in patients with suspected bitemporal epilepsy.
- HFOs, analyzed by WT and GC, serve as reliable biomarkers for guiding surgical decisions in TLE.
- These objective methods enhance diagnostic accuracy, potentially improving outcomes for temporal lobectomy.
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