Practice guidelines for the supervising professional: intraoperative neurophysiological monitoring.

The American Society of Neurophysiological Monitoring (ASNM) was founded in 1989 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 procedures monitoring the nervous system. This goal is accomplished primarily through programs in education, advocacy of basic and clinical research, and publication of guidelines, among other endeavors. The ASNM is committed to the development of medically sound and clinically relevant guidelines for the performance of 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 neurophysiological monitoring were initially published January 24th, 2013, and subsequently that document has undergone review and revision to accommodate broad inter- and intra-societal feedback. This current version of the ASNM Professional Practice Guideline was fully approved for publication according to ASNM bylaws on February 22nd, 2018, and thus overwrites and supersedes the initial guideline.

Temporary Reversal of Blood Flow During Transcarotid Artery Revascularization Does Not Change Brain Electrical Activity in Lead-In Cases of the ROADSTER 1 Multicenter Trial.

PURPOSE: To evaluate any intraoperative electroencephalographic (EEG) changes accompanying reversed flow with the ENROUTE Transcarotid Neuroprotection System during transcarotid artery revascularization (TCAR). METHODS: A post hoc analysis was performed of the first 81 consecutive lead-in patients (mean age 72.8±8 years; 61 men) enrolled in the ROADSTER 1 trial at 5 participating institutions. All patients had high-grade carotid artery stenosis [53 (59.3%) left sided; 12 (14.8%) contralateral occlusions] and high-risk criteria for carotid endarterectomy. A third had symptoms of either stroke (13, 16.0%) or transient ischemic attack (14, 17.3%). This subset of early patients underwent EEG monitoring to detect any cerebral changes during reversed flow as an added safety measure mandated by the ROADSTER 1 trial protocol. RESULTS: Mean flow reversal time was 12.9±8.2 minutes. The goal mean arterial pressure during reversed flow was 100 mm Hg, but 7 (8.6%) patients suffered hypotension. One (1.2%) patient had slight EEG changes secondary to blood pressure fluctuation; these resolved with blood pressure elevation. No other EEG changes were noted. One (1.2%) patient had a postoperative stroke and another (1.2%) had postoperative myocardial infarction (MI), leading to 2.5% 30-day stroke/death/MI rate. CONCLUSION: Temporary reversal of blood flow during TCAR is a safe maneuver and does not cause cerebral ischemia in the vast majority of patients, including those with contralateral carotid occlusion. Carotid stenting performed with reversed blood flow mitigates cerebral embolization and periprocedural stroke without concern for brain ischemia.

Proposal: different types of alteration and loss of consciousness in epilepsy.

There are at least five types of alterations of consciousness that occur during epileptic seizures: auras with illusions or hallucinations, dyscognitive seizures, epileptic delirium, dialeptic seizures, and epileptic coma. Each of these types of alterations of consciousness has a specific semiology and a distinct pathophysiologic mechanism. In this proposal we emphasize the need to clearly define each of these alterations/loss of consciousness and to apply this terminology in semiologic descriptions and classifications of epileptic seizures. The proposal is a consensus opinion of experienced epileptologists, and it is hoped that it will lead to systematic studies that will allow a scientific characterization of the different types of alterations/loss of consciousness described in this article.

Deep Brain Stimulation of Heschl Gyrus: Implantation Technique, Intraoperative Localization, and Effects of Stimulation.

BACKGROUND: Tinnitus is a source of considerable morbidity, and neuromodulation has been shown to be a potential treatment option. However, the location of the primary auditory cortex within Heschl gyrus in the temporal operculum presents challenges for targeting and electrode implantation. OBJECTIVE: To determine whether anatomic targeting with intraoperative verification using evoked potentials can be used to implant electrodes directly into the Heschl gyrus (HG). METHODS: Nine patients undergoing stereo-electroencephalogram evaluation for epilepsy were enrolled. HG was directly targeted on volumetric magnetic resonance imaging, and framed stereotaxy was used to implant an electrode parallel to the axis of the gyrus by using an oblique anterolateral-posteromedial trajectory. Intraoperative evoked potentials from auditory stimuli were recorded from multiple electrode contacts. Postoperatively, stimulation of each electrode was performed and participants were asked to describe the percept. Audiometric analysis was performed for 2 participants during subthreshold stimulation. RESULTS: Sounds presented to the contralateral and ipsilateral ears produced evoked potentials in HG electrodes in all participants intraoperatively. Stimulation produced a reproducible sensation of sound in all participants with perceived volume proportional to amplitude. Four participants reported distinct sounds when different electrodes were stimulated, with more medial contacts producing tones perceived as higher in pitch. Stimulation was not associated with adverse audiometric effects. There were no complications of electrode implantation. CONCLUSION: Direct anatomic targeting with physiological verification can be used to implant electrodes directly into primary auditory cortex. If deep brain stimulation proves effective for intractable tinnitus, this technique may be useful to assist with electrode implantation. ABBREVIATIONS: DBS, deep brain stimulatorEEG, electroencephalographyHG, Heschl gyrus.

Below the belt: sensory mapping and monitoring in the sacral-pudendal region.

Originally described in 1982, scalp somatosensory evoked potential responses can be recorded after stimulation of multiple different pudendal nerve- and sacral root-supplied structures. The resulting P40 response is usually the highest amplitude at Cz. Responses are generally easy to resolve and therefore should be of equivalent ease to follow for neurophysiologic intraoperative monitoring versus lower limb peripheral nerve somatosensory evoked potentials (e.g., tibial or fibular [peroneal] nerves), but sizeable reports of pudendal somatosensory evoked potential monitoring are few. Direct orthodromic sensory nerve action potential recording from the cauda equina in response to single such sacral stimuli has been reported of utility for preserving roots that participate in urinary control during dorsal rhizotomy procedures for spasticity. Technical application of both techniques is quite straightforward. As in most areas of neurophysiologic intraoperative monitoring, there are no well-constructed historical control series informing use of these techniques and, certainly, no clinical trials. Given the socially devastating consequences of urinary and anal continence disturbances and a fairly high rate of functional postoperative disturbances when sacral roots are manipulated, this field begs more active clinical investigation.

The possibility of clinical trials in neurophysiologic intraoperative monitoring: a review.

There is substantial controversy regarding the current evidence basis of practice for neurophysiologic intraoperative monitoring (NIOM). The randomized controlled trial is clearly the highest level of evidence of efficacy for intervention in health care. The low rate of new neurologic deficits in many types of surgeries for which NIOM is considered means that statistical power would require tremendous trial size; however, there are some surgeries with higher rates of new neurologic deficit for which this effect is not the case. For some surgeries, NIOM has clearly become the standard of care, and there would be no equipoise in randomization to NIOM versus no NIOM at all. For this situation, careful study design to permit comparison of different NIOM approaches or anesthesiological regimens might permit the achievement of equipoise. In oncological contexts, NIOM is often used to delimit the extent of resection to avoid motor new neurologic deficits, but this approach may lower complete resection rates; in this setting, a randomization to restrictive versus permissive NIOM parameters limiting resection could test the long-term advantages of motor versus oncological outcomes. Clearly, randomized controlled trial demonstration of NIOM efficacy for the prevention of new neurologic deficits would be difficult to accomplish. However, with careful choice of surgical population and randomization design, prospective trials would in fact not be impossible.

Simultaneous direct cortical motor evoked potential monitoring and subcortical mapping for motor pathway preservation during brain tumor surgery: is it useful?

ABSTRACT OF REVIEWED ARTICLE: The warning-sign hierarchy between quantitative subcortical motor mapping and continuous motor evoked potential monitoring during resection of supratentorial brain tumors: clinical article.Seidel K, Beck J, Steiglitz L, Schucht P, Raabe A.J Neurosurg 2013; 118:287-296. OBJECTIVE: Mapping and monitoring are believed to provide an early warning sign to determine when to stop tumor removal to avoid mechanical damage to the corticospinal tract (CST). The objective of this study was to systematically compare subcortical monopolar stimulation thresholds (1-20 mA) with direct cortical stimulation (DCS)-motor evoked potential (MEP) monitoring signal abnormalities and to correlate both with new postoperative motor deficits. The authors sought to define a mapping threshold and DCS-MEP monitoring signal changes indicating a minimal safe distance from the CST. METHODS: A consecutive cohort of 100 patients underwent tumor surgery adjacent to the CST while simultaneous subcortical motor mapping and DCS-MEP monitoring were used. Evaluation was performed regarding the lowest subcortical mapping threshold (monopolar stimulation, train of 5 stimuli, interstimulus interval 4.0 milliseconds, pulse duration 500 microseconds) and signal changes in DCS-MEPs (same parameters, 4 contact strip electrode). Motor function was assessed 1 day after the surgery, at discharge, and at 3 months postoperatively. RESULTS: The lowest individual motor thresholds (MTs) were as follows (MT in mA, number of patients): >20 mA, n = 12; 11 to 20 mA, n = 13; 6 to 10 mA, n = 20; 4 to 5 mA, n = 30; and 1 to 3 mA, n = 25. Direct cortical stimulation showed stable signals in 70 patients, unspecific changes in 18, irreversible alterations in 8, and irreversible loss in 4 patients. At 3 months, 5 patients had a postoperative new or worsened motor deficit (lowest mapping MT 20 mA, 13 mA, 6 mA, 3 mA, and 1 mA). In all 5 patients, DCS-MEP monitoring alterations were documented (2 sudden irreversible threshold increases and 3 sudden irreversible MEP losses). Of these 5 patients, 2 had vascular ischemic lesions (MT 20 mA, 13 mA) and 3 had mechanical CST damage (MT: 1 mA, 3 mA, and 6 mA; in the latter 2 cases, the resection continued after mapping and severe DCS-MEP alterations occurred thereafter). In 80% of patients with a mapping MT of 1 to 3 mA and in 75% of patients with a mapping MT of 1 mA, DCS-MEPs were stable or showed unspecific reversible changes, and none had a permanent motor worsening at 3 months. In contrast, 25% of patients with irreversible DCS-MEP changes and 75% of patients with irreversible DCS-MEP loss had permanent motor deficits. CONCLUSIONS: Mapping should primarily guide tumor resection adjacent to the CST. Direct cortical stimulation-motor evoked potential is a useful predictor of deficits, but its value as a warning sign is limited because signal alterations were reversible in only approximately 60% of the present cases and irreversibility is a post hoc definition. The true safe mapping MT is lower than previously thought. The authors postulate a mapping MT of 1 mA or less where irreversible DCS-MEP changes and motor deficits regularly occur. Therefore, they recommend stopping tumor resection at an MT of 2 mA at the latest. The limited spatial and temporal coverage of contemporary mapping may increase error and may contribute to false, higher MTs.

Continuous and routine EEG in intensive care: utilization and outcomes, United States 2005-2009.

OBJECTIVES: To evaluate the effect of intensive care unit continuous EEG (cEEG) monitoring on inpatient mortality, hospital charges, and length of stay. METHODS: A retrospective cross-sectional study was conducted using the Nationwide Inpatient Sample, a dataset representing 20% of inpatient discharges in nonfederal US hospitals. Adult discharge records reporting mechanical ventilation and EEG (routine EEG or cEEG) were included. cEEG was compared with routine EEG alone in association with the primary outcome of in-hospital mortality and secondary outcomes of total hospital charges and length of stay. Demographics, hospital characteristics, and medical comorbidity were used for multivariate adjustments of the primary and secondary outcomes. RESULTS: A total of 40,945 patient discharges in the weighted sample met inclusion criteria, of which 5,949 had reported cEEG. Mechanically ventilated patients receiving cEEG were younger than routine EEG patients (56 vs 61 years; p < 0.001). There was no difference in the 2 groups in income or medical comorbidities. cEEG was significantly associated with lower in-hospital mortality in both univariate (odds ratio = 0.54, 95% confidence interval 0.45-0.64; p < 0.001) and multivariate (odds ratio = 0.63, 95% confidence interval 0.51-0.76; p < 0.001) analyses. There was no significant difference in costs or length of stay for patients who received cEEG relative to those receiving only routine EEG. Sensitivity analysis showed that adjusting for diagnosis-related groups (DRGs) for any neurologic diagnoses, DRGs for neurologic procedures, and specific DRGs for epilepsy/convulsions did not substantially alter the association of cEEG with reduced inpatient mortality. CONCLUSIONS: cEEG is favorably associated with inpatient survival in mechanically ventilated patients, without adding significant charges to the hospital stay.

The American Academy of Neurology's top five choosing wisely recommendations.

OBJECTIVE: To discuss the American Academy of Neurology (AAN)'s Top Five Recommendations in the Choosing Wisely campaign promoting high-value neurologic medicine and physician-patient communication. The AAN published its Top Five Recommendations in February 2013 in collaboration with the American Board of Internal Medicine Foundation and Consumer Reports. METHODS: A Choosing Wisely Working Group of 10 AAN members was formed to oversee the process and craft the evidence-based recommendations. AAN members were solicited for recommendations, the recommendations were sent out for external review, and the Working Group members (article authors) used a modified Delphi process to select their Top Five Recommendations. RESULTS AND RECOMMENDATIONS: The Working Group submitted 5 neurologic recommendations to the AAN Practice Committee and Board of Directors; all 5 were approved by both entities in September 2012. Recommendation 1: Don't perform EEGs for headaches. Recommendation 2: Don't perform imaging of the carotid arteries for simple syncope without other neurologic symptoms. Recommendation 3: Don't use opioids or butalbital for treatment of migraine, except as a last resort. Recommendation 4: Don't prescribe interferon-ß or glatiramer acetate to patients with disability from progressive, nonrelapsing forms of multiple sclerosis. Recommendation 5: Don't recommend carotid endarterectomy for asymptomatic carotid stenosis unless the complication rate is low (<3%).

Intraoperative neurophysiologic monitoring: are we really that bad?

STUDY DESIGN: Retrospective review of a prospectively collected, multicenter database. OBJECTIVE: To assess the rates of new neurologic deficit (NND) associated with spine surgery. SUMMARY OF BACKGROUND DATA: New neurologic deficit is a potential complication of spine surgery but previously reported rates are often limited by small sample size and single-surgeon experiences. METHODS: The Scoliosis Research Society morbidity and mortality database was queried for spinal surgery cases complicated by NND from 2004 to 2007, including nerve root deficit, cauda equina deficit, and spinal cord deficit. Use of neuromonitoring was assessed. Recovery was stratified as complete, partial, or none. Rates of NND were stratified based on diagnosis, age (pediatric, <21 years; adult, ≥21 years), and surgical parameters. RESULTS: Of the 108,419 cases reported, NND was documented for 1,064 (1.0%), including 662 nerve root deficits, 74 cauda equina deficits, and 293 spinal cord deficits (deficit not specified for 35 cases). Rates of NND were calculated on the basis of diagnosis. Revision cases had a 41% higher rate of NND (1.25%) compared with primary cases (0.89%; P < 0.001). Pediatric cases had a 59% higher rate of NND (1.32%) compared with adult cases (0.83%; P < 0.001). The rate of NND for cases with implants was more than twice that for cases without implants (1.15% vs. 0.52%; P < 0.001). Neuromonitoring was used for 65% of cases, and for cases with new nerve root deficit, cauda equina deficit, and spinal cord deficit, changes in neuromonitoring were reported in 11%, 8%, and 40%, respectively. The respective percentages of no recovery, partial, and complete recovery for nerve root deficit were 4.7%, 46.8%, and 47.1%, respectively; for cauda equina deficit, they were 9.6%, 45.2%, and 45.2%, respectively; and for spinal cord deficit, the percentages were 10.6%, 43%, and 45.7%, respectively. CONCLUSION: Our data demonstrate that even among skilled spinal deformity surgeons, NNDs are inherent potential complications of spine surgery. These data provide general benchmark rates for NND with spine surgery as a basis for patient counseling and for ongoing efforts to improve safety of care.