Constructing 2D maps of human spinal cord activity and isolating the functional midline with high-density microelectrode arrays

Abstract

Intraoperative neuromonitoring (IONM) is a widely used practice in spine surgery for early detection and minimization of neurological injury. IONM is most commonly conducted by indirectly recording motor and somatosensory evoked potentials from either muscles or the scalp, which requires large-amplitude electrical stimulation and provides limited spatiotemporal information. IONM may inform of inadvertent events during neurosurgery after they occur, but it does not guide safe surgical procedures when the anatomy of the diseased spinal cord is distorted. To overcome these limitations and to increase our understanding of human spinal cord neurophysiology, we applied a microelectrode array with hundreds of channels to the exposed spinal cord during surgery and resolved spatiotemporal dynamics with high definition. We used this method to construct two-dimensional maps of responsive channels and define with submillimeter precision the electrophysiological midline of the spinal cord. The high sensitivity of our microelectrode array allowed us to record both epidural and subdural responses at stimulation currents that are well below those used clinically and to resolve postoperative evoked potentials when IONM could not. Together, these advances highlight the potential of our microelectrode arrays to capture previously unexplored spinal cord neural activity and its spatiotemporal dynamics at high resolution, offering better electrophysiological markers that can transform IONM.

Electrochemical and electrophysiological considerations for clinical high channel count neural interfaces

“… 31 , 32 To mitigate this tradeoff, new fabrication and interconnection strategies evolved to achieve thousands 33 – 35 to tens of thousands 36 of electrode channels in a variety of species, including humans. 37 …”

Advances and Perspectives on Organic Materials for Neuroelectronic Interface Devices★

“…图 1 (a)神经系统接口器件的基本物理特性示意图 [8][9][10][11][12][13][14] . (b)面向神经电子接口的有机材料功能需求示意图 Figure 1 (a) Schematic diagram of basic physics properties of interface devices in nervous system.…”

The Use of Intraoperative Neuromonitoring for Cervical Spine Surgery: Indications, Challenges, and Advances

“…The first electrodes used for IONM were direct needle leads in the 1960s. Since then, there have been new electrodes available: paddle and percutaneous leads in the 1980s, tined leads in the 1990s, multi-column electrodes, or "lead arrays" in the 2000s, and most recently, high-density electrode arrays [9]. The use of high-density electrode arrays improves signal processing by decreasing the distance between grouped electrodes, allowing for more electrodes to be implemented in a confined space, and increasing the ability to better detect neurophysiologic signals [10].…”