NeuroDepth: an ultra long whole brain reachable multi-channel probe for real-time precise functional localization of deep human brain tumor margins.

Precise intraoperative delineation of deep glioma margins remains challenging, as existing imaging modalities are limited by brain shift, poor penetration depth, or low spatial resolution, thus compromising surgical accuracy. Electrophysiological differences between tumor and normal tissues offer potential biomarkers, but lack high-resolution in vivo validation. We developed NeuroDepth, a tungsten-based multi-channel microelectrode array. With an implantation depth of up to 9 cm and 8 recording sites, the probe provides whole-brain accessibility. Its 15 µm diameter recording sites enable single-cell spatial resolution, while a 30 kHz sampling rate ensures high temporal fidelity for real-time signal acquisition. In this study, NeuroDepth was applied intraoperatively for the first time to monitor deep human glioma tissue. Spatial electrophysiological heterogeneity and longitudinal path-dependent variations revealed electrophysiological markers distinguishing tumor versus normal tissues. Compared with normal cortical surface recordings, glioma regions exhibited elevated neuronal firing rates, altered spike morphologies, and enhanced local field potential synchrony. Neuronal avalanche analysis revealed aberrant criticality within glioma tissue, suggesting unique dynamic network properties useful for boundary detection. A longitudinal recording along the cortex-white matter-tumor trajectory identified a characteristic "rebound" in neuronal activity upon entering the tumor, providing a clear demarcation signature. NeuroDepth demonstrates a new paradigm for intraoperative guidance, leveraging real-time electrophysiological detection to map deep tumor margins at a quantifiable single-cell resolution. It emerges as a promising tool to enhance resection accuracy while protecting functional brain areas.