New frontiers in intraoperative neurophysiologic monitoring: a narrative review.

Background and Objective: Neurological insults during surgery arise from anatomic and/or physiologic perturbations. Intraoperative neurophysiologic monitoring (IONM) fills a critical role of ensuring that any neurological insults during certain surgical procedures are caught in real-time to prevent patient harm. IONM provides immediate feedback to the surgeon and anesthesiologist about the need for an intervention to prevent a neurologic deficit postoperatively. As important as it seems to have IONM available to any patient having surgery where a neurological injury is possible, the truth is that IONM is unavailable to large swaths of people around the world. This review is intended to bring attention to all of the ways IONM is critically important for a variety of surgeries and highlight the barriers preventing most patients around the world from benefiting from the technology. Expansion of IONM to benefit patients from all over the world is the new frontier. Methods: We searched all English language original papers and reviews using Embase and MEDLINE/PubMed databases published from 1995 to 2022. Different combinations of the following search terms were used: intraoperative neuromonitoring, neurosurgery, low-income countries, cost, safety, and efficacy. Key Content and Findings: We describe common IONM modalities used during surgery as well as explore barriers to implementation of IONM in resource-limited regions. Additionally, we describe ongoing efforts to establish IONM capabilities in new locations around the world. Conclusions: In this paper, we performed a review of the literature on IONM with an emphasis on the basic understanding of clinical applications and the barriers for expansion into resource-limited settings. Finally, we provide our interpretation of "new frontiers" in IONM quite literally facilitating access to the tools and education so a hospital in Sub-Saharan Africa can incorporate IONM for their high-risk surgeries.

Toxicology Screening Testing in Patients Undergoing Spine Surgery: A Prospective Observational Pilot Study.

BACKGROUND: Chronic opioid use and polypharmacy are commonly seen in chronic pain patients presenting for spine procedures. Substance abuse and misuse have also been reported in this patient population. Negative perioperative effects have been found in patients exposed to chronic opioid, alcohol, and recreational substances. Toxicology screening testing (TST) in the perioperative period provides useful information for adequate preoperative optimization and perioperative planning. METHODS: We designed a pilot study to understand this population's preoperative habits including accuracy of self-report and TST-detected prescribed and unprescribed medications and recreational substances. We compared the results of the TST to the self-reported medications using Spearman correlations. RESULTS: Inconsistencies between TST and self-report were found in 88% of patients. Spearman correlation was 0.509 between polypharmacy and intraoperative propofol use, suggesting that propofol requirement increased as the number of substances used increased. CONCLUSIONS: TST in patients presenting for spine surgery is a useful tool to detect substances taken by patients because self-report is often inaccurate. Discrepancies decrease the opportunity for preoperative optimization and adequate perioperative preparation.

Toward a mouse neuroethology in the laboratory environment.

In this report we demonstrate that differences in cage type brought unexpected effects on aggressive behavior and neuroanatomical features of the mouse olfactory bulb. A careful characterization of two cage types, including a comparison of the auditory and temperature environments, coupled with a demonstration that naris occlusion abolishes the neuroanatomical changes, lead us to conclude that a likely important factor mediating the phenotypic changes we find is the olfactory environment of the two cages. We infer that seemingly innocuous changes in cage environment can affect sensory input relevant to mice and elicit profound effects on neural output. Study of the neural mechanisms underlying animal behavior in the laboratory environment should be broadened to include neuroethological approaches to examine how the laboratory environment (beyond animal well-being and enrichment) influences neural systems and behavior.

Sensory-dependent asymmetry for a urine-responsive olfactory bulb glomerulus.

An unusual property of the olfactory system is that sensory input at the level of the first synapse in the olfactory bulb takes place at two mirror-image glomerular maps that appear identical across the axis of symmetry. It is puzzling how two identical odor maps would contribute to sensory function. The functional units in these maps are the glomeruli, ovoid neuropil structures formed by axons from olfactory sensory neurons expressing the same olfactory receptor. Here we find that the genetically identified P2 glomeruli are asymmetric across the axis of symmetry in terms of responsiveness to urine volatiles and neuroanatomical structure. Furthermore, P2 asymmetry is modified by sensory deprivation and abolished by decreased BDNF levels. Thus, while mirror odor maps show symmetry at the macroscopic level in maps encompassing the entire surface of the olfactory bulb, they display asymmetry at the level of the single glomerulus.

Emerging views on the distinct but related roles of the main and accessory olfactory systems in responsiveness to chemosensory signals in mice.

In rodents, the nasal cavity contains two separate chemosensory epithelia, the main olfactory epithelium, located in the posterior dorsal aspect of the nasal cavity, and the vomeronasal/accessory olfactory epithelium, located in a capsule in the anterior aspect of the ventral floor of the nasal cavity. Both the main and accessory olfactory systems play a role in detection of biologically relevant odors. The accessory olfactory system has been implicated in response to pheromones, while the main olfactory system is thought to be a general molecular analyzer capable of detecting subtle differences in molecular structure of volatile odorants. However, the role of the two systems in detection of biologically relevant chemical signals appears to be partially overlapping. Thus, while it is clear that the accessory olfactory system is responsive to putative pheromones, the main olfactory system can also respond to some pheromones. Conversely, while the main olfactory system can mediate recognition of differences in genetic makeup by smell, the vomeronasal organ (VNO) also appears to participate in recognition of chemosensory differences between genetically distinct individuals. The most salient feature of our review of the literature is that there are no general rules that allow classification of the accessory olfactory system as a pheromone detector and the main olfactory system as a detector of general odorants. Instead, each behavior must be considered within a specific behavioral context to determine the role of these two chemosensory systems. In each case, one system or the other (or both) participates in a specific behavioral or hormonal response.

Transforming growth factor beta contributes to lung leak in rats given interleukin-1 intratracheally.

Interleukin-1 (IL-1) is increased in lung lavages obtained from patients with acute lung injury (ALI) and administering recombinant human IL-1alpha (rhIL-1alpha) (50 ng) intratracheally causes an acute, neutrophil-dependent, oxidative lung leak in rats that closely resembles human ALI. In the present work, the authors tested the hypothesis that transforming growth factor beta (TGFbeta) contributes to the lung inflammation and injury that develops in rats given IL-1 intratracheally. They found that intravenous administration of a monoclonal antibody to TGFbeta (1.D.11.16, 0.5 mg/kg) attenuated lung injury responses, specifically lung leak index, lung lavage protein concentrations, and blood oxygenation abnormalities, that are observed 5 hours after intratracheal instillation of IL-1 in rats, but did not decrease indices of lung inflammation, specifically myeloperoxidase (MPO) activity in lung tissue, neutrophil counts in lung lavage, and cytokine-induced neutrophil chemoattractant (CINC) levels in lung lavage, in rats given IL-1 intratracheally. The results suggest that TGFbeta contributes to lung leak, but not lung inflammation, following intratracheal administration of IL-1 in rats.