OBJECTIVE:Spinal cord sensory networks strongly interact with descending motor circuits. We targeted this interaction by pairing motor cortex stimulation with coordinated cervical spinal cord stimulation. Using separate non-invasive and epidural experiments, we tested the hypothesis that the strongest muscle response would occur when paired brain and spinal cord stimuli simultaneously converge within the spinal cord. METHODS:For non-invasive experiments, we measured motor evoked potentials in response to transcranial magnetic stimulation (TMS) and transcutaneous spinal cord stimulation (TSCS). We compared this noninvasive approach to intraoperative paired stimulation experiments using dorsal epidural electrodes in individuals undergoing surgery for cervical myelopathy. RESULTS:In 16 individuals with chronic spinal cord injury (SCI) and 15 uninjured individuals, suprathreshold TMS augmented target muscle responses (11.0%) when subthreshold TSCS stimuli converged synchronously in the spinal cord. Facilitation correlated with TSCS intensity. Facilitation did not correlate with SCI level or severity, indicating spared circuits were sufficient for this effect. Noninvasive pairing produced less facilitation compared to intraoperative (epidural) pairing. CONCLUSIONS:Sensorimotor interactions in the cervical spinal cord can be targeted with paired stimulation in individuals with and without SCI. SIGNIFICANCE:Properly timed paired stimulation may enhance synaptic responsiveness after SCI.

PURPOSE:We aim to develop a robust method to improve the estimation accuracy of motor-evoked potential (MEP) recruitment curves (RCs), including motor threshold, in small-sample settings which typically involve fewer than 40 stimuli. METHODS:We present a hierarchical Bayesian (HB) method to model MEP size as a rectified-logistic function of stimulation intensity. This method is designed to account for small samples, handle outliers without discarding data, quantify estimation uncertainty, and simulate synthetic data that closely matches real observations, useful for optimizing experimental design. We validate its performance on transcranial magnetic stimulation (TMS), epidural spinal cord stimulation (SCS), and synthetic TMS datasets, and provide an open-source library for Python, called hbMEP, for diverse applications. RESULTS:The rectified-logistic outperformed sigmoidal functions in predictive accuracy on TMS and SCS datasets, as demonstrated through cross-validation. A mixture extension of the HB model improved robustness to outliers by further increasing its predictive accuracy. The HB model reduced threshold estimation error by up to 70% on sparse synthetic TMS data compared to non-hierarchical models. Bayesian estimation with the HB model reduced the required number of participants by at least 23% to detect a shift in threshold with 80% power, compared to frequentist testing. Empirical results on human SCS data further validated its applicability to real data. CONCLUSION:By improving accuracy on sparse data, our method minimizes the number of stimuli needed to probe each individual's neuromuscular parameters across multiple muscles simultaneously, thereby reducing session duration and the risk of inadvertent neuromodulation. Our approach provides a more statistically powerful and conclusive framework for inferring changes in threshold, and therefore corticospinal excitability. The hbMEP library streamlines and unifies the analysis of RCs across stimulation modalities and experimental paradigms.

Degenerative spondylolisthesis (DS) is a common cause of lumbar stenosis and potentially dynamic instability that frequently causes radiculopathy. While paraspinal muscle degeneration is thought to contribute to spondylolisthesis severity, this relationship has yet to be fully characterized. A retrospective analysis was performed of all neurosurgical patients admitted to the Columbia Neurosurgery Spinal Division for treatment of L4-5 DS between January 2018 and March 2024. Preoperative lumbopelvic parameters and slip percentage (SP) were calculated from standing radiographs; paraspinal muscle volume (PMV) and fatty infiltration (FI) were derived from MRI images using 3D Slicer (Earth, TX). Correlation and multiple linear regression analyses were used to assess the relationship between SP and PMV, FI, and spinopelvic parameters. 221 patients (69M/152F) with average SP of 24.18±0.09% were included. Except for intervertebral angle (IVA) and pelvic tilt (PT), other parameters showed no difference between patients with Meyerding Grade I versus II spondylolisthesis. However, PMV was lower and FI higher in the Grade II than Grade I group (p<0.01). There was a positive correlation between SP and metrics of fat replacement (e.g. multifidus FI [r=0.336, p<0.001]) and a negative correlation between SP and metrics of PMV (e.g. total MV [r=-0.270]). A stepwise multivariate regression method was used to develop a model that included MFI, IVA, and LL; while statistically significant, this model only accounted for 16.6% of variance in SP. In this single center retrospective study, greater degree of spondylolisthesis was modestly associated with lower PMV and increased FI, suggesting that paraspinal muscle degeneration may be one of several important factors in the development of spondylolisthesis.

INTRODUCTION: Neurofibromatosis type 2 (NF2) patients develop spinal neoplasms. Determining indications for spine surgery remains challenging, as localization of spine related symptoms can be confounded by intracranial or peripheral neuropathology. Additionally, patient selection must be balanced with pre-existing comorbidities NF2 incurs with the goal to maintain or improve quality of life. METHODS: Seventy-nine patients were enrolled retrospectively based upon NF2 diagnosis and radiographic presence of spine tumors from three tertiary academic centers. Demographic data, clinical findings, treatment course, and spine tumor pathology were collected for all patients. RESULTS: Forty-eight percent of patients received spine surgery (38/79, 48.1%). Patients undergoing spine surgery had lower age of symptom onset (15.4 vs. 25.6, p = 0.015), increased cervical (4.2 vs 2.4, p = 0.005) and overall spine tumor burden (10.3 vs 6.2, p < 0.001) and presence of neck (9 vs 1, p = 0.006) and radicular pain (8 vs 1, p = 0.012). Over a quarter of our patients received BEV (25/79, 31.6%), with majority experiencing symptom onset before age 20 (17/19, 89.5%). Schwannoma was the most common BEV-treated pathology. Only one patient experienced worsening of tumor burden at one year while on BEV, and five patients required spine surgery after receiving BEV. CONCLUSIONS: NF2 patients who require spine surgery typically present at younger ages with large cervical spine tumor burden and associated symptomology. It is crucial that surgery-associated demographics and symptomology are identified. BEV was utilized in patients with aggressive, early-onset spine disease. Further, BEV halted spine disease progression in all patients except one, with minimal additional spine surgery required. Its ability to slow aggressive, NF2-associated spine tumors should be considered for clinical trial.

Volitional movement requires descending input from motor cortex and sensory feedback through the spinal cord. We previously developed a paired brain and spinal electrical stimulation approach in rats that relies on convergence of the descending motor and spinal sensory stimuli in the cervical cord. This approach strengthened sensorimotor circuits and improved volitional movement through associative plasticity. In humans it is not known whether dorsal epidural SCS targeted at the sensorimotor interface or anterior epidural SCS targeted within the motor system is effective at facilitating brain evoked responses. In 59 individuals undergoing elective cervical spine decompression surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord with epidural electrodes while muscle responses were recorded in arm and leg muscles. Spinal electrodes were placed either posteriorly or anteriorly, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and spinal sensory (posterior) but not spinal motor (anterior) stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred only when descending motor and spinal afferent stimuli were timed to converge in the spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, paired stimulation effects were present regardless of the severity of myelopathy as measured by clinical signs or spinal cord imaging. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation.

Although epidural stimulation of the lumbar spinal cord has emerged as a powerful modality for recovery of movement, how it should be targeted to the cervical spinal cord to activate arm and hand muscles is not well understood, particularly in humans. We sought to map muscle responses to posterior epidural cervical spinal cord stimulation in humans. We hypothesized that lateral stimulation over the dorsal root entry zone would be most effective and responses would be strongest in the muscles innervated by the stimulated segment. Twenty-six people undergoing clinically indicated cervical spine surgery consented to mapping of motor responses. During surgery, stimulation was performed in midline and lateral positions at multiple exposed segments; six arm and three leg muscles were recorded on each side of the body. Across all segments and muscles tested, lateral stimulation produced stronger muscle responses than midline despite similar latency and shape of responses. Muscles innervated at a cervical segment had the largest responses from stimulation at that segment, but responses were also observed in muscles innervated at other cervical segments and in leg muscles. The cervical responses were clustered in rostral (C4-C6) and caudal (C7-T1) cervical segments. Strong responses to lateral stimulation are likely due to the proximity of stimulation to afferent axons. Small changes in response sizes to stimulation of adjacent cervical segments argue for local circuit integration, and distant muscle responses suggest activation of long propriospinal connections. This map can help guide cervical stimulation to improve arm and hand function. NEW & NOTEWORTHY A map of muscle responses to cervical epidural stimulation during clinically indicated surgery revealed strongest activation when stimulating laterally compared to midline and revealed differences to be weaker than expected across different segments. In contrast, waveform shapes and latencies were most similar when stimulating midline and laterally, indicating activation of overlapping circuitry. Thus, a map of the cervical spinal cord reveals organization and may help guide stimulation to activate arm and hand muscles strongly and selectively.

Learning of skilled movement requires coincident activation of motor and sensory connections. In rats we have developed a spinal cord associative plasticity protocol which relies on synchronized stimulation of the brain and cervical spinal cord. Immediate facilitation of cortical motor evoked potentials occurs when spine and brain stimulation are timed to converge in the spinal cord. Repeated application of these synchronized pulses for 5-30 minutes induces lasting changes in spinal excitability and produces improvements in dexterity in rats [1-2]. We hypothesized that appropriately timed epidural stimulation targeting the dorsal root entry zones of the human cervical spinal cord would facilitate cortical motor evoked responses in people.

Brain metastases (BM) of pancreatic origin are extremely rare. We review the literature around BM of pancreatic origin and describe a 38-year-old woman who developed BM 10 months after pancreaticoduodenectomy for treatment of pancreatic adenocarcinoma. She underwent resection and fractionated stereotactic radiotherapy followed by re-resection and Gamma Knife radiosurgery (GKRS) when the lesion recurred. She then developed two new BM, and was treated with GKRS. The patient is alive without progression 38 months after her most recent GKRS.

BACKGROUND CONTEXT: Computer-based surgical simulations are intended to serve as a safe and cost-effective training platform that provides the user with a detailed depiction of the surgical anatomy, realistic force feedback, and an accurate tissue response. Although this technology has been utilized in various surgical subspecialties, its potential for spine surgery has not been adequately explored.