Intraoperative microseizure detection using a high-density micro-electrocorticography electrode array

Abstract

One-third of epilepsy patients suffer from medication-resistant seizures. While surgery to remove epileptogenic tissue helps some patients, 30-70% of patients continue to experience seizures following resection. Surgical outcomes may be improved with more accurate localization of epileptogenic tissue. We have previously developed novel thin-film, subdural electrode arrays with hundreds of microelectrodes over a 100-1,000 mm2 area to enable high-resolution mapping of neural activity. Here we used these high-density arrays to study microscale properties of human epileptiform activity. We performed intraoperative micro-electrocorticographic recordings within epileptic cortex (the site of seizure onset and early spread) in nine patients with epilepsy. In two of these patients, we obtained recordings from cortical areas distal to the epileptic cortex. Additionally, we recorded from two non-epileptic patients with movement disorders undergoing deep brain stimulator implantation as non-epileptic tissue controls. A board-certified epileptologist identified microseizures, which resembled electrographic seizures normally observed with clinical macroelectrodes. Epileptic cortex exhibited a significantly higher microseizure rate (2.01 events/min) than non-epileptic cortex (0.01 events/min; permutation test, P=0.0068). Using spatial averaging to simulate recordings from larger electrode contacts, we found that the number of detected microseizures decreased rapidly with increasing contact diameter and decreasing contact density. In cases in which microseizures were spatially distributed across multiple channels, the approximate onset region was identified. Our results suggest that micro-electrocorticographic electrode arrays with a high density of contacts and large coverage are essential for capturing microseizures in epilepsy patients and may be beneficial for localizing epileptogenic tissue to plan surgery or target brain stimulation.

High-resolution neural recordings improve the accuracy of speech decoding

“…Our high-density μECoG arrays recorded neural signals in SMC that produced significantly higher fidelity HG-ESNR as compared to standard intracranial methods (ECoG/SEEG). This result is in keeping with previous work that sampled microscale epileptic activity using high-density μECoG arrays, which revealed a striking heterogeneity in the spatio-temporal dynamics of interictal events 47,48 . Importantly, microseizures were observed occurring on just two electrodes spaced 750 μm apart, and were not visible on neighboring electrodes.…”

“…2D ) at <2mm spacing, which both extends previous work with coarser spatial sampling and demonstrates the informative nature of signals at the millimeter scale 26,27 . This result is also in keeping with previous work that sampled microscale epileptic activity using high-density μECoG arrays which revealed a striking heterogeneity in the spatio-temporal dynamics of interictal events 48,49 . Importantly, in that work, microseizures were most often observed occurring on just one to two electrodes spaced 750 μm apart and were not visible on neighboring electrodes.…”

“…This result is in keeping with previous work that sampled microscale epileptic activity using high-density µECoG arrays, which revealed a striking heterogeneity in the spatiotemporal dynamics of interictal events 45,46 . Importantly, microseizures were observed occurring on just two electrodes spaced 750 µm apart, and were not visible on neighboring electrodes.…”

Multiplexed Surface Electrode Arrays Based on Metal Oxide Thin‐Film Electronics for High‐Resolution Cortical Mapping

“…[10][11][12][13] These micro-ECoG (μECoG) arrays with micro-scale spatial resolution (<1 mm) have become an enabling technology for neuroscience research, providing access to localized information not available with standard methods. [12][13][14][15][16][17][18] For instance, μECoG arrays have revealed the possibility of capturing action potentials from the surface of the human cortex with nonpenetrating electrodes, [12] as well as other novel cortical signals not locked to rhythmic brain activity. [14] Furthermore, their highresolution and broad-area coverage allows for the exploration of neural processing and functional interactions across local and broadly distributed networks during different stages of neural computation.…”

“…In the context of drug-resistant epilepsy, high-channel count arrays could significantly improve the delineation of functional and pathological tissue boundaries for surgical recession by offering more refined biomarkers, such as microscale seizures and high-frequency oscillations, not detectable with clinical ECoG grids. [15][16][17] Additionally, these arrays hold the potential to significantly enhance the performance of future brain-computer interface systems. For example, advanced μECoG arrays have been instrumental in the development of high-performance speech neuroprostheses, as their broad cortical coverage and high spatial density have proven essential in improving speech decoding from articulatory vocaltract representations distributed throughout the sensorimotor cortex.…”