Abstract Details

Title Comparison of EEG Signal Characteristics Between Subdural and Depth Intracranial EEG Electrodes

Topic Epilepsy/Clinical Neurophysiology (EEG)

Presentation(s) P3 - Poster Session 3 (11:45 AM-12:45 PM)

Poster/Presentation
Number 9-009

Objective This study compares the EEG signal characteristics of subdural electrodes (SDE) and stereo-depth EEG (sEEG) electrodes placed within close proximity in patients undergoing monitoring for drug-resistant epilepsy (DRE).

Background DRE affects roughly one-third of epilepsy patients. Both SDE and sEEG electrodes are commonly used in invasive monitoring, yet limited research directly compares their signal profiles.

Design/Methods From 2012 to 2018, we evaluated intracranial EEG (icEEG) data from patients at a surgical epilepsy center. We identified electrode pairs (SDE and sEEG) within 5 mm of each other, with 24 contacts (12 pairs) meeting our criteria for signal-to-noise ratio and data completeness. Power spectral densities were analyzed using Welch's method, and coherence across standard frequency bands was calculated using fast-Fourier transform.

Results We observed a median distance of 3.7 mm between the electrode contact pairs. Time-aware analysis highlighted the coherence's strength primarily in the high- gamma (HG) band, where the median (r) was 0.889. Additionally, the median power ratios between the SDE and sEEG signal was 1.99. This ratio decreased from high- gamma to infra-low frequencies, with medians of 2.07 and 0.97, respectively. The power spectral densities (PSDs) for the sEEG and SDE electrodes demonstrated a strong correlation, with a median correlation coefficient (r) of 0.99 and an interquartile range (IQR) from 0.915 to 0.996.

Conclusions

We found a frequency-dependent relationship between SDE and sEEG signals, with the strongest coherence in the HG band. Variations are likely due to differences in electrode design and placement. These findings have implications for surgical epilepsy care and Brain-Computer Interface (BCI) design.

Keywords: Subdural EEG, stereo EEG, intracranial EEG, spectral analysis, signal characteristics high-frequency oscillations (HFOs).

Authors/Disclosures
Cigdem Isitan-Alkawadri, MD (University of Pittsburgh Medical Center) PRESENTER	Dr. Isitan-Alkawadri has nothing to disclose.
Ayse G. Kocoglu kinal, MD	Dr. Kocoglu kinal has nothing to disclose.
Qi Yan (Yale University)	No disclosure on file
Anto Bagic, MD, PhD (UPMC/Univesrity of Pittsburgh)	Dr. Bagic has nothing to disclose.
Dennis Spencer (Yale University)	No disclosure on file
Rafeed Alkawadri	No disclosure on file

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