Intraoperative Monitoring of the External Urethral Sphincter Reflex: A Novel Adjunct to Bulbocavernosus Reflex Neuromonitoring for Protecting the Sacral Neural Pathways Responsible for Urination, Defecation and Sexual Function.

PURPOSE: Intraoperative bulbocavernosus reflex neuromonitoring has been utilized to protect bowel, bladder, and sexual function, providing a continuous functional assessment of the somatic sacral nervous system during surgeries where it is at risk. Bulbocavernosus reflex data may also provide additional functional insight, including an evaluation for spinal shock, distinguishing upper versus lower motor neuron injury (conus vs. cauda syndromes) and prognosis for postoperative bowel and bladder function. Continuous intraoperative bulbocavernosus reflex monitoring has been utilized to provide the surgeon with an ongoing functional assessment of the anatomical elements involved in the S2-S4 mediated reflex arc including the conus, cauda equina and pudendal nerves. Intraoperative bulbocavernosus reflex monitoring typically includes the electrical activation of the dorsal nerves of the genitals to initiate the afferent component of the reflex, followed by recording the resulting muscle response using needle electromyography recordings from the external anal sphincter. METHODS: Herein we describe a complementary and novel technique that includes recording electromyography responses from the external urethral sphincter to monitor the external urethral sphincter reflex. Specialized foley catheters embedded with recording electrodes have recently become commercially available that provide the ability to perform intraoperative external urethral sphincter muscle recordings. RESULTS: We describe technical details and the potential utility of incorporating external urethral sphincter reflex recordings into existing sacral neuromonitoring paradigms to provide redundant yet complementary data streams. CONCLUSIONS: We present two illustrative neurosurgical oncology cases to demonstrate the utility of the external urethral sphincter reflex technique in the setting of the necessary surgical sacrifice of sacral nerve roots.

Analyzing the value of IONM as a complex intervention: The gap between published evidence and clinical practice.

OBJECTIVE: Intraoperative neurophysiological monitoring (IONM) was investigated as a complex intervention (CI) as defined by the United Kingdom Medical Research Council (MRC) in published studies to identify challenges and solutions in estimating IONM's effects on postoperative outcomes. METHODS: A scoping review to April 2022 of the influence of setting on what was implemented as IONM and how it influenced postoperative outcomes was performed for studies that compared IONM to no IONM cohorts. IONM complexity was assessed with the iCAT_SR tool. Causal graphs were used to represent this complexity. RESULTS: IONM implementation depended on the surgical procedure, institution and/or surgeon. "How" IONM influenced neurologic outcomes was attributed to surgeon or institutional experience with the surgical procedure, surgeon or institutional experience with IONM, co-interventions in addition to IONM, models of IONM service delivery and individual characteristics of the IONM provider. Indirect effects of IONM mediated by extent of tumor resection, surgical approach, changes in operative procedure, shorter operative time, and duration of aneurysm clipping were also described. There were no quantitative estimates of the relative contribution of these indirect effects to total IONM effects on outcomes. CONCLUSIONS: IONM is a complex intervention whose evaluation is more challenging than that of a simple intervention. Its implementation and largely indirect effects depend on specific settings that are usefully represented in causal graphs. SIGNIFICANCE: IONM evaluation as a complex intervention aided by causal graphs and multivariable analysis could provide a valuable framework for future study design and assessments of IONM effectiveness in different settings.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

EOY summary 2018.

Clinical monitoring and technology are at the heart of anesthesiology, and new technological developments will help to define how anesthesiology will evolve as a profession. Anesthesia related research published in the JCMC in 2018 mainly pertained to ICU sedation with inhaled agents, anesthesia workstation technology, and monitoring of different aspects of depth of anesthesia.

Foundations for evidence-based intraoperative neurophysiological monitoring.

In this review, we recommend means to enhance the evidence-base for intraoperative neurophysiological monitoring (IONM). We address two preliminary issues: (1) whether IONM should be evaluated as a diagnostic test or an intervention, and (2) the state of the evidence for IONM (as presented in systematic reviews, for example). Three reasons may be suggested to evaluate at least some IONM applications as interventions (or as part of an "interventional cascade"). First, practical barriers limit our ability to measure IONM diagnostic accuracy. Second, IONM results are designed to be correlated with interventions during surgery. Third, IONM should improve patient outcomes when IONM-directed intervention alters the course of surgery. Observational evidence for IONM is growing yet more is required to understand the conditions under which IONM, in its variety of settings, can benefit patients. A multi-center observational cohort study would represent an important initial compromise between the pragmatic difficulties with conducting controlled trials in IONM and the Evidence-Based Medicine (EBM) view that large scale randomized trials are required. Such a cohort study would improve the evidence base and (if justified) provide the rationale for controlled trials.

Pelvic autonomic neuromonitoring: present reality, future prospects.

Currently, the means to assess the autonomic nervous system primarily depend on end organ functional measurement: intravesical pressure, skin resistance, and penile strain gauge tension, for example. None of these measures has been generally accepted in the operating room. Nevertheless, the segmental and peripheral pelvic autonomic nerve supply is placed at risk during both pelvic and lower spine surgery. In this difficult era of suboptimal post-prostatectomy outcomes, the urological literature does reveal the salutary development of safer dissection techniques about the peri-prostatic and cavernous plexus. Means of reliably specific nerve identification remain elusive. The need for actual nerve monitoring (not just identification) has only recently been proposed. Data from the animal lab reinforce an appreciation of the intimate and elegant interconnectedness of autonomic and somatic structures, particularly at the segmental level. Also, the biochemistry of erectile tissue engorgement (in both sexes) is very well understood (the electrophysiology increasingly so). Understanding these principles should permit parallel investigation and implementation of neurophysiological techniques which both identify and monitor pelvic autonomic function. The predicates for these proposed new approaches in the operating room are discussed in this review.

Intraoperative recording of the bulbocavernosus reflex.

: The bulbocavernosus reflex (BCR) is mediated by the sacral somatic afferent/efferent periphery as well as the sacral cord. Unfortunately, the reflex has suffered from a partly deserved reputation as difficult to implement. However, recent stratagems have improved the test's reliability. Multipulse stimulation (enhanced by double trains as required) and exacting recording technique can yield positive and remarkably reproducible results in patients of all ages and either sex. In this review, we document a 94% baseline BCR acquisition rate among 100 consecutive cases in one institution. Acceptance and routine use of the BCR is needed to help assure optimal post-operative low sacral function in intradural and extradural surgeries at the level of conus medullaris, cauda equina, sacral plexus, and the pudendal nerve. Case studies within this review illustrate the power of the BCR to predict patient outcome or, much more importantly, reverse incipient patient injury in real time.

Intraoperative neuromonitoring alerts that reverse with intervention: treatment paradox and what to do about it.

Intervention-mediated recovery from adversely changed evoked potential recordings may provide evidence for improved outcomes during neurophysiological intraoperative monitoring. However, these reversible signal changes (RSCs) are ambiguous because the patient's neurologic status cannot be known either at signal decline or after intervention. This article describes methods to reduce this ambiguity. Randomized control trials are not always possible or ethical. Recent thought on grading evidence has acknowledged that guidelines first described by Sir Austin Bradford Hill may support evidence for causation. Causality guidelines identified RSCs most likely to be truly positive in three reported studies. Diagnostic statistics were revised accordingly. A range of revised positive predictive values and likelihood ratios was calculated in the three studies, using causality guidelines. The revised data were similar to those reported for other diagnostic tests used in medicine. The RSCs may be assessed using causality guidelines for more accurate reporting of diagnostic statistics while preserving information related to surgical intervention and recovery that is lost with end of surgery diagnostics or when RSCs are ignored. A method is described for including RSCs in diagnostic statistics. This approach will more readily permit assessment of the value of neurophysiological intraoperative monitoring in prediction and prevention of neurologic deficits.

Practice guidelines for the supervising professional: intraoperative neurophysiological monitoring.

The American Society of Neurophysiological Monitoring (ASNM) was founded in 1988 as the American Society of Evoked Potential Monitoring. From the beginning, the Society has been made up of physicians, doctoral degree holders, technologists, and all those interested in furthering the profession. The Society changed its name to the ASNM and held its first Annual Meeting in 1990. It remains the largest worldwide organization dedicated solely to the scientifically based advancement of intraoperative neurophysiology. The primary goal of the ASNM is to assure the quality of patient care during monitored procedures along the neuraxis. This goal is accomplished through programs in education, advocacy of basic and clinical research, and publication of guidelines. The ASNM is committed to the development of medically sound and clinically relevant guidelines for intraoperative neurophysiology. Guidelines are formulated based on exhaustive literature review, recruitment of expert opinion, and broad consensus among ASNM membership. Input is likewise sought from sister societies and related constituencies. Adherence to a literature-based, formalized process characterizes the construction of all ASNM guidelines. The guidelines covering the Professional Practice of intraoperative monitoring were established by a committee of nearly 30 total participants and ultimately endorsed by the Board of Directors of ASNM on January 24th 2013. That document follows.

Spinal cord injury from electrocautery: observations in a porcine model using electromyography and motor evoked potentials.

We have previously investigated electromyographic (EMG) and transcranial motor evoked potential (MEP) abnormalities after mechanical spinal cord injury. We now report thermally generated porcine spinal cord injury, characterized by spinal cord generated hindlimb EMG injury activity and spinal cord motor conduction block (MEP loss). Electrocautery (EC) was delivered to thoracic level dural root sleeves within 6-8 mm of the spinal cord (n = 6). Temperature recordings were made near the spinal cord. EMG and MEP were recorded by multiple gluteobiceps intramuscular electrodes before, during, and after EC. Duration of EC was titrated to an end-point of spinal motor conduction block (MEP loss). In 5/6 roots, ipsilateral EMG injury activity was induced by EC. In 4/5 roots, EMG injury activity was identified before MEP loss. In all roots, a minimum of 20 s EC and a temperature maximum of at least 57 °C at the dural root sleeve were required to induce MEP loss. Unexpectedly, conduction block was preceded by an enhanced MEP in 4/6 trials. EMG injury activity, preceding MEP loss, can be seen during near spinal cord EC. Depolarization and facilitation of lumbar motor neurons by thermally excited descending spinal tracts likely explains both hindlimb EMG and an enhanced MEP signal (seen before conduction block) respectively. A thermal mechanism may play a role in some unexplained MEP losses during intraoperative monitoring. EMG recordings might help to detect abnormal discharges and forewarn the monitorist during both mechanical and thermal injury to the spinal cord.

Neurophysiologic monitoring of the spinal accessory nerve, hypoglossal nerve, and the spinomedullary region.

This review of hypoglossal nerve, spinal accessory nerve, and spinomedullary region intraoperative monitoring details pertinent central and extramedullary anatomy, an updated understanding of proper free-run EMG recording methods and recent developments in stimulation technique and instrumentation. Mapping and monitoring the floor of the fourth ventricle, especially the vagal/hypoglossal trigone region, are emphasized. Although cranial nerve transcranial electrical motor evoked potential recordings can afford appreciation of corticobulbar/corticospinal tract function and secure a more dependable measure of proximate extramedullary somatoefferents, the sometimes difficult implementation and the, as yet, unresolved alert criteria of these recordings demand critical appraisal. Nearby and intimately associated cardiochronotropic and barocontrol neural networks are described; their better understanding is recommended as an important adjunct to "routine" neural monitoring. Finally, an Illustrative case is presented to highlight the many strengths and weaknesses of "state of the art" lower cranial nerve/spinomedullary region monitoring.

Electromyography in the detection of mechanically induced spinal motor tract injury: observations in diverse porcine models.

OBJECT: Porcine spinal cords were mechanically injured at the thoracic level while recording muscle-derived electrically stimulated transcranial motor evoked potentials (TcMEPs) and electromyography (EMG) readings from the same electrode derivations. The authors postulated that midthoracic spinal cord injury caused by diverse methods can trigger hindlimb EMG activity. Early detection of hindlimb EMG activity may permit avoidance of motor conduction block (TcMEP loss). METHODS: Twelve pigs underwent midthoracic spinal cord exposure. Spinal cord sectioning was performed to define dorsal column versus lateral spinal cord contribution to muscle-derived electrically stimulated spinal cord motor evoked potentials (SC MEPs) and TcMEPs (in 2 pigs). A bipolar needle stimulator was placed within intramedullary sites to 1) acquire electrically stimulated motor evoked potentials in the hindlimbs, and 2) induce mechanically stimulated hindlimb EMG activity at sites responsive to electrical stimulation (in 2 pigs). Transcranial MEPs and EMG recordings were observed during spinal cord distraction (in 3 pigs), slow and rapid extradural spinal cord compression with a metal caliper (in 3 pigs), and rapid extradural spinal cord compression with a spring-loaded clip (in 2 pigs). RESULTS: Lateral cord (but not dorsal column) sectioning abolished both SC MEPs and TcMEPs. Intramedullary electrical and mechanical stimulation within the lateral (but not dorsal) cord elicited ipsilateral hindlimb MEPs and EMG activity ("EMG injury discharge"), respectively. Distraction inconsistently produced EMG injury discharges concomitant with TcMEP loss. Rapid extradural spinal cord compression with a metal caliper or spring-loaded clip consistently induced EMG injury discharges (in 4 of 4 pigs); slow compression did not elicit EMG activity. Brief extradural spring-loaded clip compressions (1-2 seconds) elicited EMG injury discharges without TcMEP loss; 14-second clip compression effected EMG injury discharges and TcMEP loss, which recovered after clip removal. CONCLUSIONS: Electromyographic activity (referred to as "EMG injury discharges" in the present study) can be elicited both by intramedullary manipulation and rapidly applied transaxial spinal cord compression. Preliminary observations suggest that these EMG injury discharges precede and may anticipate TcMEP loss. Presumably, rapid deformation of spinal motor tracts (which appear to lie within the lateral porcine spinal cord) generates descending volleys which can bring to firing threshold lumbar motor neurons (and recording of EMG injury discharges). Intraoperative neuromonitoring of high-risk spinal surgeries at the spinal cord level may benefit from the addition of EMG recording to tests of spinal cord motor conduction such as TcMEP. Further clinical trials are required to examine EMG efficacy in this context.

Electromyography detects mechanically-induced suprasegmental spinal motor tract injury: review of decompression at spinal cord level.

OBJECTIVE: Herein, we report use of electromyography (EMG) to anticipate corticospinal conduction block, as defined by muscle-derived transcranial electrical motor evoked potential (TCE MEP) loss, during extradural spinal cord decompression. METHODS: One hundred and eighty-four patients underwent cervical (173) or thoracic (11) decompression. The same derivations were recorded for EMG and TCE MEP neuromonitoring. When highly repetitive, complex, and prolonged EMG discharges were identified in myotomes below the operated level (severe suprasegmentally-generated EMG discharges=severe SEDs), a report of possible spinal cord impact was made and a TCE MEP obtained. TCE MEP loss (with or without antecedent SEDs) was defined as >90% amplitude reduction compared to baseline recordings. RESULTS: Severe SEDs, seen in 15 cases, anticipated TCE MEP loss in 7/15. In 13/15 severe SED cases, manipulations near dura were the proximate cause. Interventions after TCE MEP loss included changed instrumentation, re-positioning, increased blood pressure, wake-up test, and surgical pause. CONCLUSIONS: SEDs can be identified during extradural spinal cord decompression. Severe SED occurrence is associated with a approximately 50% risk of subsequent corticospinal conduction block. SIGNIFICANCE: Although SED occurrence does not provide specific information for lesions of the fast neurons of the corticospinal tract, SED surveillance during decompression at spinal cord level can supplement TCE MEP recording.

Surface electrodes are not sufficient to detect neurotonic discharges: observations in a porcine model and clinical review of deltoid electromyographic monitoring using multiple electrodes.

OBJECTIVE: In order to define the preferred electromyographic monitoring method during spine surgery, (1) a porcine model of neurotonic generation after lumbar root compression was developed and (2) intraoperative use of deltoid muscle intramuscular needle, subdermal needle, and surface electrodes was retrospectively reviewed. METHODS: In pigs, an array of intramuscular needle, subdermal needle, and surface electrode derivations was differentially amplified at identical gain and filter settings. Nerve root compression generated neurotonic discharges whose amplitudes were compared at each derivation. Clinically, 25 deltoid muscles in 13 patients were simultaneously monitored (during cervical spine surgery at the C4-C5 level) with surface, subdermal needle, and intramuscular needle electrode pairs, differentially amplified at identical gain and filter settings. Non-repeating neurotonic discharges were assigned, by amplitude and morphology, to best derivation (intramuscular, subdermal, surface or combination); coincident amplitudes were measured at the maximum deflection among the three derivations. Actual voltage detected between clinical methods was analyzed with Friedman's test and any detection versus none by general estimating equations(GEE) using SAS. The advantage of two needles over one in detection of any voltage was assessed using McNemar's test. RESULTS: Compressed porcine lumbar roots generated neurotonics which were identifiable at intramuscular sites only. Clinically, 31 neurotonics were identified: 20/31 at intramuscular, 5/31 at subdermal, and 6/31 equally well at intramuscular and subdermal derivations. Intramuscular detected neurotonics better than subdermal derivations (z = 2.9, P < .004). No voltage was recorded at the surface in 16/31 neurotonics. For detection of any voltage, intramuscular was better than subdermal (z = -1.5, P = .04) or surface electrodes (z = -2.7, P < .001). CONCLUSIONS: Electromyographic moni- toring of spine surgery should not be done by surface electrodes. Because sensitive neurotonic detection requires near field recording, intramuscular electrodes are preferred. Monitoring of a myotome at particularly increased risk may suggest multiple intramuscular electrodes.

The initial use of free-running electromyography to detect early motor tract injury during resection of intramedullary spinal cord lesions.

OBJECTIVE: The resection of intramedullary spinal cord lesions (ISCLs) can be complicated by neurological deficits. Neuromonitoring has been used to reduce intraoperative risk. We have used somatosensory evoked potentials (SEPs) and muscle-derived transcranial electrical motor evoked potentials (myogenic TCE-MEPs) to monitor ISCL removal. We report our retrospective experience with the addition of free-running electromyography (EMG). METHODS: Thirteen patients underwent 14 monitored ISCL excisions. Anesthesia was maintained with minimal inhalant to reduce motoneuron suppression and enhance the myogenic TCE-MEPs. Free-running EMG was examined in the four limbs for evidence of abnormal bursts, prolonged tonic discharge, or sudden electrical silence. Warning of an electromyographic abnormality or myogenic TCE-MEP loss prompted interventions, including blood pressure elevation, a pause in surgery, a wake-up test, or termination of surgery. Pre- and postoperative neurological examinations determined the incidence of new deficits. RESULTS: The combined use of free-running EMG and myogenic TCE-MEPs detected all eight patients with a new motor deficit after surgery; there was one false-positive report. In three of the eight true-positive cases, an electromyographic abnormality immediately anticipated loss of the myogenic TCE-MEPs. Two patients with abnormal EMGs but unchanged myogenic TCE-MEPs experienced mild postoperative worsening of motor deficits; myogenic TCE-MEPs alone would have generated false-negative reports in these cases. CONCLUSION: During resection of ISCLs, free-running EMG can supplement motor tract monitoring by TCE-MEPs. Segmental and suprasegmental elicitation of neurotonic discharges can be observed in four-limb EMG. Abnormal electromyographic bursts, tonic discharge, or abrupt electromyographic silence may anticipate myogenic TCE-MEP loss and predict a postoperative motor deficit.