Human Recorded Signal Properties of Endovascular EEG Compared to Conventional Scalp EEG.

OBJECTIVE: Endovascular EEG (eEEG) has emerged as a brain monitoring technique that offers a balance between signal fidelity and invasiveness. Endovascular electrodes match subdural recordings in bandwidth and signal-to-noise ratio in animal studies, however, their signal properties remain sparsely quantified in humans. This study evaluated eEEG signals from five human participants undergoing intracarotid amobarbital injection (Wada test), while simultaneous scalp and endovascular EEG were recorded. METHODS: All signals were preprocessed with artifact rejection and independent component analysis (ICA). Power spectral density (PSD), imaginary coherence (ImagC), phase-locking value (PLV), and amplitude envelope correlation (AmpC) were computed to quantify signal quality and functional connectivity. RESULTS: The eEEG signals exhibited approximately ×3.7 higher power than concurrent scalp EEG, and nearest endovascular-scalp electrode pairs showed consistently higher coupling across all participants (mean difference 4.9 percentage points, range 1.8-7.6% across individuals), with effects most pronounced at distances $< $30 mm. CONCLUSION: These findings support the feasibility of eEEG for neuromonitoring and demonstrate its potential for simple brain-computer interface (BCI) applications. SIGNIFICANCE: This work provides quantitative measures of the signal power and correlation with scalp EEG, obtained directly in humans for a microcatheter-deliverable wire electrode, establishing human operating bounds for endovascular EEG as a minimally invasive neural interface.