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

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.

Effective Use of Ketamine-Dexmedetomidine Following Propofol-Induced Hyperlactatemia: A Case Report.

There are limited options for intravenous anesthetics and a lack of available information on the use of ketamine infusion during intracranial surgeries. We present a patient case report of hyperlactatemia during a craniotomy with neuromonitoring while on a propofol infusion with arterial lactate rising from 2.1 mmol/L to a peak of 5.0 mmol/L before reducing to 3.9 mmol/L after the transition to a mixed ketamine and dexmedetomidine infusion in order to maintain neuromonitoring quality and an appropriate depth of anesthesia. No complications were caused by the use of ketamine during this extended neurosurgery case.

Novel Use of Stimulating Fence-Post Technique for Functional Mapping of Subcortical White Matter During Tumor Resection: A Technical Case Series.

BACKGROUND: Maximal safe resection remains a key principle in infiltrating glioma management. Stimulation mapping is a key adjunct for minimizing functional morbidity while "fence-post" procedures use catheters or dye to mark the tumor border at the start of the procedure prior to brain shift. OBJECTIVE: To report a novel technique using stereotactically placed electrodes to guide tumor resection near critical descending subcortical fibers. METHODS: Navigated electrodes were placed prior to tumor resection along the deep margin bordering presumed eloquent tracts. Stimulation was administered through these depth electrodes for subcortical motor and language mapping. RESULTS: Twelve patients were included in this preliminary technical report. Seven patients (7/12, 58%) were in asleep cases, while the other 5 cases (5/12, 42%) were performed awake. Mapping of motor fibers was performed in 8 cases, and language mapping was done in 1 case. In 3 cases, both motor and language mapping were performed using the same depth electrode spanning corticospinal tract and the arcuate fasciculus. CONCLUSION: Stereotactic depth electrode placement coupled with stimulation mapping of white matter tracts can be used concomitantly to demarcate the border between deep tumor margins and eloquent brain, thus helping to maximize extent of resection while minimizing functional morbidity.

Intraoperative neuromonitoring for one-level lumbar discectomies is low yield and cost-ineffective.

BACKGROUND: Intraoperative neuromonitoring is a common, well-established modality used in spine surgery to prevent intraoperative neural injury. Neuromonitoring use in lumbar discectomy, however, is based on surgeon preference, without evidence-based data. The purpose of this research was to determine intraoperative utility and overall cost effectiveness of neuromonitoring for lumbar discectomy. METHODS: We retrospectively reviewed adult patients who underwent a lumbar discectomy, with at least 1 month of follow-up at a single tertiary care center. Patient age, sex, body mass index (BMI), lumbar level operated, and operative time and cost were collected. Neuromonitoring and operative reports were reviewed for any electromyography (EMG) abnormalities noted intraoperatively, pre- and post-operative motor exam and post-operative pain relief were collected. RESULTS: Ninety-one (47 with and 44 without neuromonitoring) lumbar discectomy cases were reviewed. There was no significant difference between mean age, sex, and BMI between the two groups. There was a significant (p = 0.006) increase in operating room time (174 min; with vs. 144 min; without neuromonitoring). Neuromonitoring was associated with a significant (p = 0.006) overall operative cost ($21,949; with vs. $18,064; without). Of the 47 cases with neuromonitoring; one had abnormal intraoperative EMG activity, which returned to normal by case conclusion. No patient in either group demonstrated new post-operative motor weakness. There was no difference in the number of patients who endorsed post-operative pain relief between the two groups. CONCLUSIONS: Neuromonitoring for lumbar discectomy confers greater operative time and cost, without any difference in neurological outcome.