Intraoperative Neurophysiologic Monitoring - CAM 70158

Description
Intraoperative neurophysiologic monitoring describes a variety of procedures used to monitor the integrity of neural pathways during high-risk neurosurgical, orthopedic, and vascular surgeries. It involves the detection of electrical signals produced by the nervous system in response to sensory or electrical stimuli to provide information about the functional integrity of neuronal structures. This evidence review does not address established neurophysiologic monitoring (i.e., somatosensory-evoked potentials, motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyography of cranial nerves, electroencephalography, electrocorticography), during spinal, intracranial, or vascular procedures.

Additional Information
2017 Clinical Input
Clinical input obtained in 2017 supports that the following indication provides a clinically meaningful improvement in net health outcome and is consistent with generally accepted medical practice:

Use of intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve for individuals undergoing cervical spine surgery with:
- prior anterior cervical surgery, particularly revision anterior cervical discectomy and fusion, revision surgery through a scarred surgical field, reoperation for pseudarthrosis, or revision for failed fusion;
- multilevel anterior cervical discectomy and fusion; and
- preexisting recurrent laryngeal nerve pathology, when there is residual function of the recurrent laryngeal nerve.

Thus, the above indication may be considered medically necessary considering the suggestive evidence and clinical input support.

2014 Clinical Input
Clinical input obtained in 2014 and professional society guidelines have supported the use of intraoperative neurophysiologic monitoring during spinal, intracranial, or vascular procedures. There was general agreement that intraoperative neurophysiologic monitoring of visual-evoked potentials and motor-evoked potentials using transcranial magnetic stimulation is investigational. It should be noted there is controversy about the utility of intraoperative neurophysiologic monitoring in some surgical procedures. Most of the published literature is from Europe, and, while many articles have reported the sensitivity and specificity of motor-evoked potentials for predicting postsurgical neurologic deficits, few have reported intraoperative interventions undertaken in response to information from monitoring.

Background
INTRAOPERATIVE NEUROPHYSIOLOGIC MONITORING
The principal goal of intraoperative neurophysiologic monitoring (IONM) is identification of nervous system impairment on the assumption that prompt intervention will prevent permanent deficits. Correctable factors at surgery include circulatory disturbance, excess compression from retraction, bony structures, hematomas, or mechanical stretching. The technology is continuously evolving with refinements in equipment and analytic techniques, including recording, with several patients monitored under the supervision of a physician who is outside the operating room.

The different methodologies of monitoring are described next.

Sensory-Evoked Potentials
Sensory-evoked potential (SEP) describes the responses of the sensory pathways to sensory or electrical stimuli. Intraoperative monitoring of SEPs is used to assess the functional integrity of central nervous system (CNS) pathways during surgeries that put the spinal cord or brain at risk for significant ischemia or traumatic injury. The basic principles of SEP monitoring involve identification of a neurologic region at risk, selection and stimulation of a nerve that carries a signal through the at-risk region, and recording and interpretation of the signal at certain standardized points along the pathway. Monitoring of SEPs is commonly used during the following procedures: carotid endarterectomy, brain surgery involving vasculature, surgery with distraction compression or ischemia of the spinal cord and brainstem, and acoustic neuroma surgery. SEPs can be further broken down into the following categories by type of simulation used.

Somatosensory-Evoked Potentials
Somatosensory-evoked potentials (SSEPs) are cortical responses elicited by peripheral nerve stimulations. Peripheral nerves, such as the median, ulnar, or tibial nerves, are typically stimulated, but, in some situations, the spinal cord may be stimulated directly. Recording is done either cortically or at the level of the spinal cord above the surgical procedure. Intraoperative monitoring of SSEPs is most commonly used during orthopedic or neurologic surgery to prompt intervention to reduce surgically induced morbidity and/or to monitor the level of anesthesia. One of the most common indications for SSEP monitoring is in patients undergoing corrective surgery for scoliosis. In this setting, SSEP monitors the status of the posterior column pathways and thus does not reflect ischemia in the anterior (motor) pathways. Several different techniques are commonly used, including stimulation of a relevant peripheral nerve with monitoring from the scalp, from interspinous ligament needle electrodes, or from catheter electrodes in the epidural space.

Brainstem Auditory-Evoked Potentials
Brainstem auditory-evoked potentials (BAEPs) are generated in response to auditory clicks and can define the functional status of the auditory nerve. Surgical resection of a cerebellopontine angle tumor, such as an acoustic neuroma, places the auditory nerves at risk, and BAEPs have been extensively used to monitor auditory function during these procedures.

Visual-Evoked Potentials
Visual-evoked potentials (VEPs) with light flashes are used to track visual signals from the retina to the occipital cortex. VEP monitoring has been used for surgery on lesions near the optic chiasm. However, VEPs are very difficult to interpret due to their sensitivity to anesthesia, temperature and blood pressure.

Motor-Evoked Potentials
Motor-evoked potentials (MEPs) are recorded from muscles following direct or transcranial electrical stimulation of motor cortex or by pulsed magnetic stimulation provided by a coil placed over the head. Peripheral motor responses (muscle activity) are recorded by electrodes placed on the skin at prescribed points along the motor pathways. MEPs, especially when induced by magnetic stimulation, can be affected by anesthesia. The Digitimer electrical cortical stimulator received U.S. Food and Drug Administration (FDA) premarket approval in 2002. Devices for transcranial magnetic stimulation have not been approved by FDA for this use.

Multimodal IONM, in which more than 1 technique is used, most commonly with SSEPs and MEPs, has also been described.

Electromyogram Monitoring and Nerve Conduction Velocity Measurements
Electromyography (EMG) monitoring and nerve conduction velocity measurements can be performed in the operating room and may be used to assess the status of the cranial or peripheral nerves (e.g., to identify the extent of nerve damage before nerve grafting or during resection of tumors). For procedures with a risk of vocal cord paralysis due to damage to the recurrent laryngeal nerve (i.e., during carotid artery, thyroid, parathyroid, goiter, or anterior cervical spine procedures), monitoring of the vocal cords or vocal cord muscles has been performed. These techniques may also be used during procedures proximal to the nerve roots and peripheral nerves to assess the presence of excessive traction or other impairment. Surgery in the region of cranial nerves can be monitored by electrically stimulating the proximal (brain) end of the nerve and recording via EMG activity in the facial or neck muscles. Thus, monitoring is done in the direction opposite that of SEPs, but the purpose is similar: to verify that the neural pathway is intact.

Electroencephalogram Monitoring
Spontaneous electroencephalography (EEG) monitoring can also be used during surgery and can be subdivided as follows:

EEG monitoring has been widely used to monitor cerebral ischemia secondary to carotid cross-clamping during a carotid endarterectomy. EEG monitoring may identify those patients who would benefit from the use of a vascular shunt during the procedure to restore adequate cerebral perfusion. Conversely, shunts, which have an associated risk of iatrogenic complications, may be avoided in those patients with a normal EEG. Carotid endarterectomy may be done with the patient under local anesthesia so that monitoring of cortical function can be directly assessed.
Electrocorticography (ECoG) is the recording of the EEG directly from a surgically exposed cerebral cortex. ECoG is typically used to define the sensory cortex and map the critical limits of a surgical resection. ECoG recordings have been most frequently used to identify epileptogenic regions for resection. In these applications, ECoG does not constitute monitoring, per se.

Intraoperative neurophysiologic monitoring, including SSEPs and MEPs using transcranial electrical stimulation, BAEPs, EMG of cranial nerves, EEG, and ECoG, has broad acceptance, particularly for spine surgery and open abdominal aorta aneurysm repairs. These indications have long been considered standard of care, as evidenced by numerous society guidelines, including those from the American Academy of Neurology, American Clinical Neurophysiology Society, American Association of Neurological Surgeons, Congress of Neurologic Surgeons, and American Association of Neuromuscular & Electrodiagnostic Medicine.^{1,2,3,4,5,6,7} Therefore, this evidence review focuses on monitoring of the recurrent laryngeal nerve during neck and esophageal surgeries and monitoring of peripheral nerves.

Related Policies
20190 Navigated Transcranial Magnetic Stimulation

Policy
Intraoperative neurophysiologic monitoring, which includes somatosensory-evoked potentials, motorevoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyography (EMG) of cranial nerves, electroencephalography, and electrocorticography, may be considered MEDICALLY NECESSARY during spinal, intracranial, or vascular procedures.

Intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve may be considered MEDICALLY NECESSARY in patients undergoing:

high-risk thyroid or parathyroid surgery, including:
- total thyroidectomy
- repeat thyroid or parathyroid surgery
- surgery for cancer
- thyrotoxicosis
- retrosternal or giant goiter
- thyroiditis
anterior cervical spine surgery associated with any of the following increased risk situations:
- prior anterior cervical surgery, particularly revision anterior cervical discectomy and fusion, revision surgery through a scarred surgical field, reoperation for pseudarthrosis or revision for failed fusion
- multilevel anterior cervical discectomy and fusion
- pre-existing recurrent laryngeal nerve pathology, when there is residual function of the recurrent laryngeal nerve.

Intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve during anterior cervical spine surgery not meeting the criteria above or during esophageal surgeries is considered investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY.

NOTE: Laryngeal nerve and facial nerve monitoring are not separately allowable if the provider rendering the service is part of the operating room team (including but not limited to surgeon, surgical assistant, scrub and circulating nurses and anesthesia).

Intraoperative monitoring of visual-evoked potentials is considered investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY.

Due to the lack of monitors approved by the U.S. Food and Drug Administration, intraoperative monitoring of motor-evoked potentials using transcranial magnetic stimulation is considered investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY.

Intraoperative EMG and nerve conduction velocity monitoring during surgery on the peripheral nerves is considered NOT MEDICALLY NECESSARY.

Note: These policy statements refer only to use of these techniques as part of intraoperative monitoring. Other clinical applications of these techniques, such as visual-evoked potentials and EMG, are not considered in this policy.

Train of Four (TOF) monitoring is considered an integral component of other services being rendered and is not available for separate reimbursement.

Policy Guidelines
Intraoperative neurophysiologic monitoring including somatosensory-evoked potentials and motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyography of cranial nerves, electroencephalography, and electrocorticography has broad acceptance, particularly for spine surgery and open abdominal aorta aneurysm repairs. Therefore, this evidence review focuses on monitoring of the recurrent laryngeal nerve during neck surgeries and monitoring of peripheral nerves.

Constant communication between surgeon, neurophysiologist, and anesthetist are required for safe and effective intraoperative neurophysiologic monitoring.

CODING
Please see the Codes table for details.

Benefit Application
BlueCard^®/National Account Issues
Intraoperative monitoring is considered reimbursable as a separate service only when a licensed health care practitioner, other than the operating surgeon, interprets the monitoring. The monitoring is performed by a healthcare practitioner or technician who is in attendance in the operating room throughout the procedure.

Implementation of a local policy on this technology may also involve discussions about credentialing of those providing the intraoperative monitoring services, as well as on-site versus remote real-time review and interpretation.

Coding for intraoperative monitoring uses time-based codes; they are not based on the number (single vs. multiple) of modalities used.

Rationale
Early literature focused on intraoperative monitoring of cranial and spinal nerves. This evidence review focuses on more recently investigated techniques, including monitoring of the recurrent laryngeal nerve and peripheral nerves.

Evidence reviews assess the clinical evidence to determine whether the use of technology improves the net health outcome. Broadly defined, health outcomes are length of life, quality of life, and ability to function, including benefits and harms. Every clinical condition has specific outcomes that are important to patients and managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of technology, 2 domains are examined: the relevance, and quality and credibility. To be relevant, studies must represent 1 or more intended clinical use of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial (RCT) is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. Randomized controlled trials are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

Promotion of greater diversity and inclusion in clinical research of historically marginalized groups (e.g., People of Color [African-American, Asian, Black, Latino and Native American]; LGBTQIA (lesbian, gay, bisexual, transgender, queer, intersex, asexual); women; and people with disabilities [physical and invisible]) allows policy populations to be more reflective of and findings more applicable to our diverse members. While we also strive to use inclusive language related to these groups in our policies, use of gender-specific nouns (e.g., women, men, sisters, etc.) will continue when reflective of language used in publications describing study populations.

Recurrent Laryngeal Nerve Monitoring During Thyroid or Parathyroid Surgery
Clinical Context and Therapy Purpose
The purpose of intraoperative neurophysiologic monitoring is to provide a treatment option that is an alternative to or an improvement on existing therapies, such as surgery without neurophysiologic monitoring, in patients who are undergoing thyroid or parathyroid surgery and are at high risk of injury to the recurrent laryngeal nerve.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals who are undergoing thyroid or parathyroid surgery and at high risk of injury to the recurrent laryngeal nerve.

Interventions
The therapy being considered is intraoperative neurophysiologic monitoring.

Intraoperative neurophysiologic monitoring describes a variety of procedures used to monitor the integrity of neural pathways during high-risk neurosurgical, orthopedic, and vascular surgeries. It involves the detection of electrical signals produced by the nervous system in response to sensory or electrical stimuli to provide information about the functional integrity of neuronal structures.

Comparators
Comparators of interest include surgery without neurophysiologic monitoring.

Outcomes
The general outcomes of interest are morbid events, functional outcomes, and quality of life.

The existing literature evaluating intraoperative neurophysiologic monitoring as a treatment for patients who are undergoing thyroid or parathyroid surgery and at high risk of injury to the recurrent laryngeal nerve has varying lengths of follow-up. While studies described below all reported at least 1 outcome of interest, longer follow-up was necessary to fully observe outcomes.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Systematic Reviews
Henry et al. (2017) reported on a systematic review of meta-analyses published up to February 2017 that compared intraoperative neurophysiologic monitoring with direct recurrent laryngeal nerve visualization by assessing rates of vocal fold palsy.⁷ Reviewers included 8 meta-analyses of RCTs or observational studies (prospective or retrospective) and selected the best evidence based on the Jadad algorithm. The 8 meta-analyses differed significantly in the literature search methodology, databases included, the inclusion of quality assessment, and most did not include a study quality assessment. Pisanu et al. (2014) was found to be the highest-quality meta-analysis;⁸ it showed no statistically significant reductions in recurrent laryngeal nerve injury between procedures using intraoperative neurophysiologic monitoring versus direct recurrent laryngeal nerve visualization. However, reviewers also noted that recent developments in intraoperative neurophysiologic monitoring technology such as continuous vagal intraoperative neurophysiologic monitoring and staged thyroidectomy might provide additional benefits, which were out of the scope of their systematic review and need to be further assessed in prospective multicenter trials.

Sun et al. (2017) reported on a meta-analysis of recurrent laryngeal nerve injury during thyroid surgery with or without intraoperative neurophysiologic monitoring.⁹ Included were 2 prospective cohort studies and 7 retrospective cohort studies. Results are summarized in Tables 1 and 2. Intraoperative neurophysiologic monitoring was associated with a reduction in overall and permanent recurrent laryngeal nerve palsy in thyroid reoperations. Limitations included small sample sizes and study heterogeneity.

Pardal-Refoyo and Ochoa-Sangrador (2016) reported on a systematic review of recurrent laryngeal nerve injury during total thyroidectomy with or without intraoperative neurophysiologic monitoring.10, Included were 1 large (N = 1,000) and 1 small (N = 23) RCT and 52 case series that estimated the risk to the recurrent laryngeal nerve. Twenty-nine studies used recurrent laryngeal nerve monitoring and 25 did not. Results are summarized in Tables 1 and 2. The observed differences in the subgroup analysis were imprecise because the number of observed instances of paralysis was very low.

Table 1. Characteristics of Systematic Reviews

Study	Dates	Trials	Participants	N (Range)	Design	Duration
Pardal-Refoyo and Ochoa-Sangrador (2016)¹⁰	1987 – 2013	2 RCTs 52 case series	Studies reporting incidence of RLN paralysis after single-stage total thyroidectomy through open cervicotomy	30,922 (23 to 2546 patients)	RCTs Case series	NR
Sun et al. (2017)⁹	Up to Aug 2016	9	Studies reporting incidence of RLN complications after thyroid surgery	2436 nerves at risk (1109 with IONM, 1327 without IONM)	Prospective and retrospective cohort studies	NR
Henry et al. (2017)⁷	Up to Feb 2017	8 meta-analyses	Meta-analyses of RCTs and non-RCTs comparing IONM with direct visualization for RLNs during thyroidectomy	8 meta-analyses (6 to 23 patients)	Meta-analyses	NR

IONM: intraoperative neurophysiologic monitoring; NR: not reported; RCT: randomized controlled trial; RLN: recurrent laryngeal nerve.

Table 2. Results of Systematic Reviews

Study	Risk of Bilateral RLN Paralysis	Transient RLN Palsy	Permanent RLN Palsy
Pardal-Refoyo and Ochoa-Sangrador (2016)¹⁰
ARR (95% CI)	2.75% (NR)^a	NR	NR
NNT (95% CI)	364 (NR)^a	NR	NR
I² (p)	8% (NR)^a	NR	NR
	Overall RLN Palsy
Sun et al. (2017)⁹
With IONM	4.69%	3.98%^b	1.26%^b
Without IONM	9.27%	6.63%^b	2.78%^b
RR (95% CI)	0.434 (0.206 to 0.916)	0.607 (0.270 to 1.366)	0.426 (0.196 to 0.925)
NNT (95% CI)	NR	NR^b	NR^b
I² (p)	70.2% (.029)	67.4%^b (.227)	13.7%^b(.031)

ARR: absolute risk reduction; CI: confidence interval; IONM: intraoperative neurophysiologic monitoring NNT: number needed to treat; NR: not reported; RLN: recurrent laryngeal nerve; RR: relative risk.
a Sample size of 11947 patients.
b Sample of 7 studies.

Randomized Controlled Trials
Barczynski et al. (2009) reported results of the largest RCT evaluating recurrent laryngeal nerve monitoring as summarized in Tables 3 and 4.¹¹ Recurrent laryngeal nerve monitoring was performed with electrodes on the vocal muscles through the cricothyroid ligament, which may not be the method currently used in the United States in high-risk patients, defined as those undergoing surgery for cancer, thyrotoxicosis, retrosternal or giant goiter, or thyroiditis. The prevalence of transient recurrent laryngeal nerve paresis was 2.9% lower in patients who had recurrent laryngeal nerve monitoring (p = .011) compared with those who received visual identification only. In low-risk patients, there was no significant difference in recurrent laryngeal nerve injury rates between monitoring and no monitoring. Notably, high-risk patients with prior thyroid or parathyroid surgery were excluded from this trial. A benefit of recurrent laryngeal nerve monitoring was also shown in patients undergoing high-risk total thyroidectomy.¹²

Table 3. Summary of Key Randomized Controlled Trial Characteristics

Study	Countries	Sites	Dates	Participants	Active	Comparator
Barczynski et al. (2009)¹¹	Poland	1	2006 – 2007	Patients undergoing bilateral neck surgery	500	50

Table 4. Summary of Key Randomized Controlled Trial Results

Study	RLN Injury	RLN Paresis	Permanent RLN Palsy
Barczynski et al. (2009)¹¹
RLN visualization alone, n/N	8/500	NR	NR
RLN visualization plus monitoring, n/N	NR	NR	NR
ARR (95% CI) (p)	2.3% (NR) (.007)	1.9% (NR) (.011)	0.4% (NR) (NS)

ARR: absolute risk reduction; CI: confidence interval; NNT: number needed to treat; NR: not reported; NS: not significant; RLN: recurrent laryngeal nerve.

Section Summary: Recurrent Laryngeal Nerve Monitoring During Thyroid or Parathyroid Surgery
The evidence on the use of intraoperative neurophysiologic monitoring in reducing recurrent laryngeal nerve injury includes a large RCT and systematic reviews assessing thyroid and parathyroid surgery. The strongest evidence derives from an RCT of 1,000 patients undergoing thyroid surgery. This RCT found a minimal effect of intraoperative neurophysiologic monitoring overall but a significant reduction in recurrent laryngeal nerve injury in patients at high-risk for injury. High-risk in this trial was defined as surgery for cancer, thyrotoxicosis, retrosternal or giant goiter, or thyroiditis. The high-risk category may also include patients with prior thyroid or parathyroid surgery or total thyroidectomy.

Recurrent Laryngeal Nerve Monitoring During Cervical Spine Surgery
Clinical Context and Therapy Purpose
The purpose of intraoperative neurophysiologic monitoring is to provide a treatment option that is an alternative to or an improvement on existing therapies, such as surgery without neurophysiologic monitoring, in patients who are undergoing anterior cervical spine surgery and are at high risk of injury to the recurrent laryngeal nerve.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals who are undergoing anterior cervical spine surgery and at high risk of injury to the recurrent laryngeal nerve.

Interventions
The therapy being considered is intraoperative neurophysiologic monitoring.

Comparators
Comparators of interest include surgery without neurophysiologic monitoring.

Outcomes
The general outcomes of interest are morbid events, functional outcomes, and quality of life.

The existing literature evaluating intraoperative neurophysiologic monitoring as a treatment for patients who are undergoing anterior cervical spine surgery and at high risk of injury to the recurrent laryngeal nerve has varying lengths of follow-up. While studies described below all reported at least 1 outcome of interest, longer follow-up was necessary to fully observe outcomes.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Systematic Reviews
Ajiboye et al. (2017) reported on the results of a systematic review that included 10 studies (N = 26,357).¹³ All studies were of low methodologic quality but had a low risk of bias. Only studies that compared the risk of nerve injury using intraoperative neurophysiologic monitoring with no intraoperative neurophysiologic monitoring were included. Based on data from these 2 studies, there was no statistically significant difference in the risk of neurologic injury with or without intraoperative neurophysiologic monitoring (odds ratio [OR], 0.726; 95% confidence interval [CI], 0.287 to 1.833; p = .498) (Tables 5 and 6).

Erwood et al. (2016) reported on the results of a meta-analysis that summarized the relative rate of recurrent laryngeal nerve injury following revision anterior cervical discectomy and fusion.¹⁴ The meta-analysis did not report recurrent laryngeal nerve injury rate with intraoperative neurophysiologic monitoring versus without intraoperative neurophysiologic monitoring. Based on pooled data from 3 prospective cohort studies and 5 retrospective series (N = 238), reviewers reported an overall recurrent laryngeal nerve injury rate of 14.1% (95% CI, 9.8% to 19.1%) (Tables 5 and 6).

Daniel et al. (2018) published a literature review and meta-analysis evaluating intraoperative neurophysiologic monitoring during spinal operative surgical procedures.¹⁵ Six retrospective studies, published between 2006 and 2016, with a total of 335,458 patients (range, 74 to 231,067) were included. Pooled OR for neurological events with and without intraoperative neurophysiologic monitoring was 0.72 (95% CI, 0.71 to 1.79; p = .4584), and sensitivity analysis, which included only 2 studies, had a pooled OR of 0.199 (95% CI, 0.038 to 1.035; p = .055). The review was limited by the lack of prospective studies, by only 3 of the included studies being considered to have high methodological quality assessment, and by many heterogeneous spinal procedures with different rates of neurological events and wide CIs being included.

Table 5. Characteristics of Systematic Reviews

Study	Dates	Trials	Participants	N (Range)	Design	Duration
Ajiboye et al. (2017)¹³	NR	10	Studies reporting IONM use for ACSS	26,357 (16 to 22,768)	9 retrospective, 1 prospective	NR
Erwood et al. (2016)¹⁴	1998 – 2015	8	Studies reporting reoperative ACSS for RLN	238 (13 to 63)	5 prospective, 3 retrospective	2 wk to 24 mo
Daniel et al. (2018)¹⁵	2006 – 2016	6	Studies reporting IONM use for spinal surgical procedures	335,458 (74 to 231,067)	2 cohort, 4 retrospective	NR

ACSS: anterior cervical spine surgery; IONM: intraoperative neurophysiologic monitoring; NR: not reported; RLN: recurrent laryngeal nerve.

Table 6. Results of Systematic Reviews

Study	Risk of Neurologic Injury
Ajiboye et al. (2017)¹³
OR^a,b (95% CI)	0.726 (0.287 to 1.833)
I² (p)	0% (.44)
Erwood et al. (2016)¹⁴
Estimate^c(95% CI)	0.14 (0.10 to 0.19)
I² (p)	10.7% (NR)
Daniel et al. (2018)¹⁵
OR^a (95% CI)	0.72 (0.71 to 1.79)
I² (p)	NR (.4584)

CI: confidence interval; NR: not reported; OR: odds ratio.
a Risk of neurologic injury after spine surgery with or without intraoperative neurophysiologic monitoring.
b Included 2 studies.
c Overall rate of recurrent laryngeal nerve injury.

Section Summary: Recurrent Laryngeal Nerve Monitoring During Cervical Spine Surgery
The evidence on the use of intraoperative neurophysiologic monitoring in reducing recurrent laryngeal nerve injury during cervical spinal surgery includes 3 systematic reviews. Two of the 3 analyses compared the risk of nerve injury using intraoperative neurophysiologic monitoring with no intraoperative neurophysiologic monitoring and found no statistically significant difference.

Recurrent Laryngeal Nerve Monitoring During Esophageal Surgery
Clinical Context and Therapy Purpose
The purpose of intraoperative neurophysiologic monitoring is to provide a treatment option that is an alternative to or an improvement on existing therapies, such as surgery without neurophysiologic monitoring, in individuals who are undergoing esophageal surgery.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals who are undergoing esophageal surgery.

Interventions
The therapy being considered is intraoperative neurophysiologic monitoring.

Comparators
Comparators of interest include surgery without neurophysiologic monitoring.

Outcomes
The general outcomes of interest are morbid events, functional outcomes, and quality of life.

The existing literature evaluating intraoperative neurophysiologic monitoring as a treatment for patients who are undergoing esophageal surgery has varying lengths of follow-up. While studies described below all reported at least 1 outcome of interest, longer follow-up was necessary to fully observe outcomes.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Systematic Review
Chen et al. (2023) conducted a systematic review on the efficacy of intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve during esophagectomy (Tables 7 and 8).¹⁶ Ten studies that compared intraoperative neurophysiologic monitoring to no monitoring during esophagectomy with mediastinal lymph node dissection were included. Table 9 summarizes the results of the analysis. Intraoperative neurophysiologic monitoring significantly reduced the incidence of recurrent laryngeal nerve palsy (OR, 0.32; 95% CI, 0.19 to 0.54; p < .0001; I2 = 42%) and increased the number of mediastinal lymph nodes dissected (weighted mean difference, 4.26; 95% CI, 1.63 to 6.89; p = .002; I2 = 49%). However, there were no significant differences in total operation time or hospital length of stay. Limitations include a significant publication bias (p = .02), lack of randomization in all but 1 study, use of historical control groups in some studies, and small sample sizes.

Table 7. Comparison of Trials/Studies Included in Systematic Review

Study	Chen et al. (2023)¹⁶
Komatsu et al. (2022)¹⁷	⚫
Huang et al. (2022)¹⁸	⚫
Zhao et al. (2022)¹⁹	⚫
Yuda et al. (2022)²⁰	⚫
Takeda et al. (2020)²¹	⚫
Fujimoto et al. (2021)²²	⚫
Kobayashi et al. (2018)²³	⚫
Zhu et al. (2018)²⁴	⚫
Hikage et al. (2017)²⁵	⚫
Zhong et al. (2014)²⁶	⚫

Table 8. Systematic Review Characteristics

Study	Dates	Trials	Participants	N (Range)	Design	Duration
Chen et al. (2023)¹⁶	2014 – 2022	10	Patients with esophageal malignancy undergoing esophagectomy with mediastinal lymph node dissection	949 (16 – 142)	1 RCT, 9 nonrandomized studies	NR

NR: not reported; RCT: randomized controlled trial.

Table 9. Systematic Review Results

Study	Recurrent laryngeal nerve palsy	Number of mediastinal lymph nodes dissected	Total operation time	Length of hospital stay
Chen et al. (2023)¹⁶
949	949	340	452	568
Odds ratio (95% CI)	0.32 (0.19 to 0.54)	4.26^a (1.63 to 6.89)	-12.33^a (-33.94 to 9.28)	-2.07^a (-6.61 to 2.46)
I² (p)	42% (< .0001)	49% (.002)	59% (0.26)	56% (.37)

CI: confidence interval.
a Weighted mean difference.

Section Summary: Recurrent Laryngeal Nerve Monitoring During Esophageal Surgery
One systematic review of 10 studies (mostly nonrandomized) on esophageal surgery was identified. Intraoperative neurophysiologic monitoring reduced recurrent laryngeal nerve injury in the combined analysis, but well-designed studies are needed to confirm these results.

Monitoring Peripheral Nerves
Clinical Context and Therapy Purpose
The purpose of intraoperative neurophysiologic monitoring is to provide a treatment option that is an alternative to or an improvement on existing therapies, such as surgery without neurophysiologic monitoring, in individuals who are undergoing surgery proximal to a peripheral nerve.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals who are undergoing surgery proximal to a peripheral nerve.

Interventions
The therapy being considered is intraoperative neurophysiologic monitoring.

intraoperative neurophysiologic monitoring describes a variety of procedures used to monitor the integrity of neural pathways during high-risk neurosurgical, orthopedic, and vascular surgeries. It involves the detection of electrical signals produced by the nervous system in response to sensory or electrical stimuli to provide information about the functional integrity of neuronal structures.

Comparators
Comparators of interest include surgery without neurophysiologic monitoring.

Outcomes
The general outcomes of interest are morbid events, functional outcomes, and quality of life.

The existing literature evaluating intraoperative neurophysiologic monitoring as a treatment for patients who are undergoing surgery proximal to a peripheral nerve has varying lengths of follow up. While studies described below all reported at least 1 outcome of interest, longer follow-up was necessary to fully observe outcomes.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Case-Control Study
Kneist et al. (2013) assessed monitoring peripheral nerves during surgery in a case-control study of 30 patients.²⁷ In patients undergoing total mesorectal excision, impaired anorectal function was observed in 1 (7%) of 15 patients who had intraoperative neurophysiologic monitoring compared with 6 (40%) of 15 without monitoring. Kneist et al. (2013) also reported on erectile function following low anterior rectal resection in a pilot study with 17 patients.²⁸ In this study, the combined intraoperative measurement of the bladder and internal anal sphincter innervation was a strong predictor of postoperative erectile function, with a sensitivity of 90%, specificity of 86%, positive predictive value of 90%, and negative predictive value of 86%. The possibility of intervention during surgery was not addressed.

Case Series
Clarkson et al. (2011) described the use of intraoperative nerve recording for suspected brachial plexus root avulsion.²⁹ Included in this retrospective review were 25 consecutive patients who underwent intraoperative nerve recording during surgery for unilateral brachial plexus injury. Of 55 roots thought to be avulsed preoperatively, 14 (25%) were found to be intact using intraoperative nerve recording. Eleven of them were then used for reconstruction, of which 9 (82%) had a positive functional outcome.

Electrophysiologic monitoring has also been reported to guide selective rhizotomy for glossopharyngeal neuralgia in a series of 8 patients.³⁰

Use of intraoperative neurophysiologic monitoring of peripheral nerves has also been reported in patients undergoing orthopedic procedures, including tibial/fibular osteotomies, hip arthroscopy for femoroacetabular impingement, and shoulder arthroplasty.^31,32,33

Section Summary: Monitoring Peripheral Nerves
Surgical guidance with peripheral intraoperative neurophysiologic monitoring has been reported in case series and 1 case-control study. Other case series have reported on the predictive ability of monitoring of peripheral nerves. No prospective comparative studies identified have assessed whether outcomes are improved with neurophysiologic monitoring.

Spinal Instrumentation Requiring Screws or Distraction
Clinical Context and Therapy Purpose
The purpose of intraoperative neurophysiologic monitoring is to provide a treatment option that is an alternative to or an improvement on existing therapies, such as surgery without neurophysiologic monitoring, in individuals who are undergoing spinal instrumentation requiring screws or distraction.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals who are undergoing spinal instrumentation requiring screws or distraction.

Interventions
The therapy being considered is intraoperative neurophysiologic monitoring.

Comparators
Comparators of interest include surgery without neurophysiologic monitoring.

Outcomes
The general outcomes of interest are morbid events, functional outcomes, and quality of life.

The existing literature evaluating intraoperative neurophysiologic monitoring as a treatment for patients who are undergoing spinal instrumentation requiring screws or distraction has varying lengths of follow up. While studies described below all reported at least 1 outcome of interest, longer follow-up was necessary to fully observe outcomes.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Systematic Reviews
Reddy et al. (2022) conducted a systematic review and meta-analysis of 13 studies that used intraoperative triggered electromyographic monitoring to detect early malposition of screws during instrumentation of the lumbar spine.³⁴ The electromyographic alarm trigger varied from 5 mA to 11 mA among studies. Among the 2,236 patients in the analysis, postoperative neurologic deficit occurred in 3.04%. The proportion of patients who developed postoperative neurologic deficit but did not reach the alarm threshold during surgery was 13.28%. Sensitivity and specificity of intraoperative triggered electromyographic monitoring were 49% and 88%, respectively.

Thirumala et al. (2017) conducted a systematic review of the diagnostic accuracy of intraoperative transcranial motor evoked potentials to detect neurologic deficit during idiopathic scoliosis correction surgery.³⁵ Twelve studies were included (none randomized) that represented 2102 patients with idiopathic scoliosis. The alarm criteria for significant change in motor evoked potentials ranged among studies from 50% to 80% decrease in amplitude. Neurologic deficits occurred in 1.38% of patients. Among the 95 patients with a motor evoked potential change that indicated a new neurologic deficit, 38 (40%) had reversible deficits and 33 (34.7%) had irreversible deficits. Sensitivity and specificity of intraoperative monitoring were 91% and 96%, respectively (I2 = 89%).

Table 10. Comparison of Trials/Studies Included in Systematic Reviews

Study	Reddy et al. (2022)³⁴	Thirumala et al. (2017)³⁵
Alemo et al. (2010)³⁶	⚫
Bindal et al. (2007)³⁷	⚫
Bose et al. (2002)³⁸	⚫
Clements et al. (1996)³⁹	⚫
Darden et al. (1996)⁴⁰	⚫
Luo et al. (2012)⁴¹	⚫
Maguire et al. (1995)⁴²	⚫
Papadopoulos et al. (2005)⁴³	⚫
Sutter et al. (2007)⁴⁴	⚫
Welch et al. (1997)⁴⁵	⚫
Wood et al. (2010)⁴⁶	⚫
Wood et al. (2014)⁴⁷	⚫
Melachuri et al. (2021)⁴⁸	⚫
Accadbled et al. (2006)⁴⁹		⚫
Eggspuehler et al. (2007)⁵⁰		⚫
El-Hawary et al. (2006)⁵¹		⚫
Feng et al. (2012)⁵²		⚫
Kundnani et al. (2010)⁵³		⚫
Lo et al. (2008)⁵⁴		⚫
Luk et al. (2001)⁵⁵		⚫
MacDonald et al. (2007)⁵⁶		⚫
Noonan et al. (2002)⁵⁷		⚫
Pastorelli et al. (2011)⁵⁸		⚫
Pereon et al. (1998)⁵⁹		⚫
Schwartz et al. (2007)⁶⁰		⚫

Table 11. Systematic Review Characteristics

Study	Dates	Trials	Participants	N (Range)	Design	Duration
Reddy et al. (2022)³⁴	1995 – 2020	13	Adults (≥ 18 years) undergoing elective lumbar spine surgery with screws not due to trauma or tumor	2,236 (16 to 1,179)	Prospective and retrospective cohorts	Ranged from immediately postoperative to 6 months
Thirumala et al. (2017)³⁵	1998 – 2012	12	Patients undergoing idiopathic scoliosis correction surgery	2915 (25 – 1,121)	Prospective and retrospective cohorts	Ranged from immediately postoperative to 3 months

Table 12. Systematic Review Results

Study	Postoperative neurologic deficits	Sensitivity	Specificity	Odds ratio of stimulation predicting postoperative neurologic deficit
Reddy et al. (2022)³⁴
2236	2236	2236	2236	2236
Pooled effect (95% CI)	3.04%	0.49 (0.36 to 0.63)	0.88 (0.80 to 0.93)	2.32 (1.37 to 3.26)
Thirumala et al. (2017)³⁵
2102	2102	2102	2102	2102
Pooled effect (95% CI)	1.38%	0.91 (0.34 to 1.00)	0.95 (0.92 to 0.98)	250.42 (10.87 to 5766.62)

CI: confidence interval.

Observational Studies
Numerous cohort studies have evaluated the effect of intraoperative neurophysiologic monitoring during spinal procedures requiring instrumentation. Some of these studies reported measures of accuracy. For example, Murphy et al. (2022) conducted a retrospective evaluation of 169 patients who underwent spinal surgery with intraoperative neurophysiologic monitoring.⁶¹ Signal changes occurred in 45 patients (26.6%). Of the 21 patients whose signals did not improve before the end of the procedure, none developed postoperative neurologic deficits. The rate of false positives was 38% and false negatives was 1.8%.

Tsirikos et al. (2020) studied a cohort of 1,155 patients who underwent spinal deformity surgery using somatosensory evoked potentials and transcranial electrical motor evoked potentials.⁶² No patients had postoperative neurologic deficits and there were no false negative events. Rates of true positive events, transient true positive events, and transient false positive events were 0.17%, 0.69%, and 0.69%, respectively. Sensitivity of the multimodal intraoperative monitoring technique was 100%, specificity was 99.3%, positive predictive value was 55.6%, and negative predictive value was 100%.

Sutter et al. (2007) conducted a prospective study of 1,017 patients who underwent multimodal intraoperative monitoring during spinal surgery.⁴⁴ Monitoring techniques included sensory spinal evoked potentials, cortical evoked potentials, electromyographic monitoring, and motor evoked potentials. True negative cases occurred in 935 (91.9%) patients, false negative cases occurred in 8 (0.79%) patients, true positive cases occurred in 66 (6.5%) patients, and false positive cases occurred in 8 (0.79%) patients. Specificity and sensitivity of multimodal intraoperative monitoring were 99% and 89%, respectively.

Section Summary: Spinal Instrumentation Requiring Screws or Distraction
Two systematic reviews and numerous observational studies have concluded that intraoperative neurophysiologic monitoring has high sensitivity and specificity in detecting neurologic deficits. Various surgical settings that require spinal instrumentation have been studied, including lumbar surgery and scoliosis correction surgery.

The purpose of the following information is to provide reference material. Inclusion does not imply endorsement or alignment with the evidence review conclusions.

Clinical Input From Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process, through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.

2017 Input
Clinical input was sought to help determine whether the use of intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve for individuals undergoing cervical spine surgery would provide a clinically meaningful improvement in net health outcome and whether the use is consistent with generally accepted medical practice. In response to requests, clinical input was received from 5 specialty society-level responses while this policy was under review in 2017.

For individuals undergoing cervical spine surgery who receive intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve, clinical input supports this use provides a clinically meaningful improvement in net health outcome and indicates this use is consistent with generally accepted medical practice in a subgroup of appropriately selected patients. The following patient selection criteria are based on clinical expert opinion and information from clinical study populations:

prior anterior cervical surgery, particularly revision anterior cervical discectomy and fusion, revision surgery through a scarred surgical field, reoperation for pseudarthrosis, or revision for failed fusion;
multilevel anterior cervical discectomy and fusion; and
preexisting recurrent laryngeal nerve pathology, when there is residual function of the recurrent laryngeal nerve.

2014 Input
In response to requests, input was received from 5 physician specialty societies (7 responses) and 2 academic medical centers while this policy was under review in 2014. Input agreed that intraoperative neurophysiologic monitoring with somatosensory-evoked potentials, motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyography of cranial nerves, electroencephalography, or electrocorticography might be medically necessary during spinal, intracranial, or vascular procedures. There was general agreement that intraoperative neurophysiologic monitoring of visual-evoked potentials and motor-evoked potentials using transcranial magnetic stimulation is investigational. Input was mixed on whether intraoperative neurophysiologic monitoring of peripheral nerves would be considered medically necessary. Some reviewers recommended monitoring some peripheral nerves during spinal surgery (eg, nerve roots, percutaneous screw placement, lateral transpsoas approach to the lumbar spine). Other reviewers suggested using intraoperative neurophysiologic monitoring during resection of peripheral nerve tumors or surgery around the brachial plexus or facial/cranial nerves.

Practice Guidelines and Position Statements
Guidelines or position statements will be considered for inclusion in Supplemental Information if they were issued by, or jointly by, a U.S. professional society, an international society with U.S. representation, or National Institute for Health and Care Excellence (NICE). Priority will be given to guidelines that are informed by a systematic review, include strength of evidence ratings, and include a description of management of conflict of interest.

American Academy of Neurology
In 1990 (updated in 2012), the American Academy of Neurology (AAN) published an assessment of intraoperative neurophysiologic monitoring, with an evidence-based guideline update by the AAN and the American Clinical Neurophysiology Society (ACNS)in 2012 (guideline last reaffirmed on October 17, 2020).^1,2 The 1990 assessment indicated that monitoring requires a team approach with a well-trained physician-neurophysiologist to provide or supervise monitoring. Electroencephalogram (EEG) monitoring is used during carotid endarterectomy or for other similar situations in which cerebral blood flow is at high risk. Electrocorticography from surgically exposed cortex can help to define the optimal limits of surgical resection or identify regions of greatest impairment, while sensory cortex somatosensory-evoked potentials can help to localize the central fissure and motor cortex. Auditory-evoked potentials, along with cranial nerve monitoring can be used during posterior fossa neurosurgical procedures. Spinal cord somatosensory-evoked potentials are frequently used to monitor the spinal cord during orthopedic or neurosurgical procedures around the spinal cord, or cross-clamping of the thoracic aorta. Electromyographic monitoring during procedures near the roots and peripheral nerves can be used to warn of excessive traction or other impairment of motor nerves. At the time of the 1990 assessment, motor-evoked potentials were considered investigational by many neurophysiologists. The 2012 update, which was endorsed by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM), concluded that the available evidence supported intraoperative neurophysiologic monitoring using somatosensory-evoked potentials or motor-evoked potentials when conducted under the supervision of a clinical neurophysiologist experienced with intraoperative neurophysiologic monitoring. Evidence was insufficient to evaluate intraoperative neurophysiologic monitoring when conducted by technicians alone or by an automated device.

In 2012, the AAN published a model policy on principles of coding for intraoperative neurophysiologic monitoring and testing (last amended July 31, 2018).⁶³ The background section of this document provides the following information on the value of intraoperative neurophysiologic monitoring in averting neural injuries during surgery:

"Value of EEG Monitoring in Carotid Surgery. Carotid occlusion, incident to carotid endarterectomies, poses a high-risk for cerebral hemispheric injury. Electroencephalogram (EEG) monitoring is capable of detecting cerebral ischemia, a serious prelude to injury. Studies of continuous monitoring established the ability of electroencephalogram EEG to correctly predict risks of postoperative deficits after a deliberate, but necessary, carotid occlusion as part of the surgical procedure. The surgeon can respond to adverse EEG events by raising blood pressure, implanting a shunt, adjusting a poorly functioning shunt, or performing other interventions.
Multicenter Data in Spinal Surgeries. An extensive multicenter study conducted in 1995 demonstrated that [intraoperative neurophysiologic monitoring] using [sensory-evoked potentials] reduced the risk of paraplegia by 60% in spinal surgeries. The incidence of false negative cases, wherein an operative complication occurred without having been detected by the monitoring procedure, was small: 0.06%.
Technology Assessment of Monitoring in Spinal Surgeries. A technology assessment by the McGill University Health Center...reviewed 11 studies and concluded that spinal [intraoperative neurophysiologic monitoring] is capable of substantially reducing injury in surgeries that pose a risk to spinal cord integrity. It recommended combined sensory-evoked potentials/motor-evoked potential monitoring, under the presence or constant availability of a monitoring physician, for all cases of spinal surgery for which there is a risk of spinal cord injury.
Value of Combined Motor and Sensory Monitoring. Numerous studies of post-surgical paraparesis and quadriparesis have shown that both sensory-evoked potentials and motor-evoked potential monitoring had predicted adverse outcomes in a timely fashion. The timing of the predictions allowed the surgeons the opportunity to intervene and prevent adverse outcomes. The 2 different techniques (sensory-evoked potentials and motor-evoked potential) monitor different spinal cord tracts. Sometimes, one of the techniques cannot be used for practical purposes, for anesthetic reasons, or because of preoperative absence of signals in those pathways. Thus, the decision about which of these techniques to use needs to be tailored to the individual patient’s circumstances.
Protecting the Spinal Cord from Ischemia during Aortic Procedures. Studies have shown that [intraoperative neurophysiologic monitoring] accurately predicts risks for spinal cord ischemia associated with clamping the aorta or ligating segmental spinal arteries. [Intraoperative neurophysiologic monitoring] can assess whether the spinal cord is tolerating the degree of relative ischemia in these procedures. The surgeon can then respond by raising blood pressure, implanting a shunt, re-implanting segmental vessels, draining spinal fluid, or through other interventions...
Value of EMG [electromyogram] monitoring. Selective posterior rhizotomy in cerebral palsy significantly reduces spasticity, increases range of motion, and improves functional skills. Electromyography during this procedure can assist in selecting specific dorsal roots to transect. Electromyogram (EMG) can also be used in peripheral nerve procedures that pose a risk of injuries to nerves...
Value of Spinal Monitoring using somatosensory-evoked potentials and motor-evoked potentials. According to a recent review of spinal monitoring using somatosensory-evoked potential and motor-evoked potentials by the Therapeutics and Technology Assessment Subcommittee of AAN and ACNS, [intraoperative neurophysiologic monitoring] is established as effective to predict an increased risk of the adverse outcomes of paraparesis, paraplegia, and quadriplegia in spinal surgery (4 Class I and 7 Class II studies). Surgeons and other members of the operating team should be alerted to the increased risk of severe adverse neurologic outcomes in patients with important [intraoperative neurophysiologic monitoring] changes (Level A)."

The AAN model policy also offered guidance on personnel and monitoring standards for intraoperative neurophysiologic monitoring and somatosensory-evoked potential.

American Association of Neurological Surgeons and Congress of Neurological Surgeons
In 2018, the American Association of Neurological Surgeons (AANS) and Congress of Neurological Surgeons updated their position statement on intraoperative neurophysiologic monitoring during routine spinal surgery.⁶⁴ They stated that intraoperative neurophysiologic monitoring, especially motor evoked potential, “is a reliable diagnostic tool for assessment of spinal cord integrity during surgery” (Level 1 evidence). Intraoperative motor evoked potentials may also “predict recovery in traumatic cervical spinal cord injury.” However, AANS and Congress of Neurological Surgeons found no evidence that such monitoring provides a therapeutic benefit. The statement also recommends that intraoperative neurophysiologic monitoring should be used when the operating surgeon believes it is warranted for diagnostic value, such as with “deformity correction, spinal instability, spinal cord compression, intradural spinal cord lesions, and when in proximity to peripheral nerves or roots.” In addition, they recommend spontaneous and evoked electromyography “for minimally invasive lateral retroperitoneal transpsoas approaches to the lumbar spine" and during screw insertion.

In 2014, the same organizations published guidance on electrophysiological monitoring for lumbar fusion procedures.⁶⁵ The authors concluded that there was a lack of high quality studies and that routine intraoperative monitoring during lumbar fusion could not be recommended. Evidence regarding the efficacy of intraoperative monitoring to recover nerve function or affect the outcome of surgery.

American Association of Neuromuscular and Electrodiagnostic Medicine
In 2023 , the AANEM updated their position statement on electrodiagnostic medicine.⁵ The recommendations indicated that intraoperative sensory-evoked potentials have demonstrated usefulness for monitoring of spinal cord, brainstem, and brain sensory tracts. The AANEM stated that intraoperative somatosensory-evoked potential monitoring is indicated for select spine surgeries in which there is a risk of additional nerve root or spinal cord injury. Indications for somatosensory-evoked potential monitoring may include, but are not limited to, complex, extensive, or lengthy procedures, and when mandated by hospital policy. However, intraoperative somatosensory-evoked potential monitoring may not be indicated for routine lumbar or cervical root decompression.

American Clinical Neurophysiology Society
In 2009, the ACNS recommended standards for intraoperative neurophysiologic monitoring.4, Guideline 11A included the following statement:⁶⁶

“The monitoring team should be under the direct supervision of a physician with training and experience in neurophysiologic intraoperative monitoring. The monitoring physician should be licensed in the state and privileged to interpret neurophysiologic testing in the hospital in which the surgery is being performed. He/she is responsible for real-time interpretation of neurophysiologic intraoperative monitoring data. The monitoring physician should be present in the operating room or have access to intraoperative neurophysiologic monitoring data in real-time from a remote location and be in communication with the staff in the operating room. There are many methods of remote monitoring, however any method used must conform to local and national protected health information guidelines. The specifics of this availability (i.e., types of surgeries) should be decided by the hospital credentialing committee. In order to devote the needed attention, it is recommended that the monitoring physician interpret no more than three cases concurrently.”

American Head and Neck Society
In 2022, the American Head and Neck Society Endocrine Surgery Section and the International Neural Monitoring Study Group published a clinical review of intraoperative nerve monitoring during pediatric thyroid surgery.⁶⁷ The review stated that intraoperative neurophysiologic monitoring can be considered in all pediatric thyroid surgeries. Procedures for which monitoring may be most beneficial include: total thyroidectomy, hemithyroidectomy in which the contralateral vocal cord is paralyzed, and reoperative surgeries.

American Society of Neurophysiological Monitoring
In 2018, the American Society of Neurophysiological Monitoring (ASNM) published practice guidelines for the supervising professional on intraoperative neurophysiologic monitoring.15, The ASNM (2013) position statement on intraoperative motor-evoked potential monitoring indicated that motor-evoked potentials are an established practice option for cortical and subcortical mapping and monitoring during surgeries risking motor injury in the brain, brainstem, spinal cord, or facial nerve.⁶⁸

Scoliosis Research Society
In 2020, the Scoliosis Research Society published an information statement on neurophysiologic monitoring during spinal deformity surgery.⁶⁹ The society concluded that neurophysiologic monitoring can allow for early detection of complications and possibly prevent postoperative neurologic injury, and is considered optimal care when the spinal cord is at risk, which warrants a strong recommendation unless there are contraindications. The standard method of intraoperative monitoring should include transcranial motor evoked potentials and somatosensory evoked potentials with or without electromyographic monitoring.

National Institute for Health and Care Excellence
In 2008, a guidance from NICE on intraoperative neurophysiologic monitoring during thyroid surgery found no major safety concerns.⁷⁰ Regarding efficacy, intraoperative neurophysiologic monitoring was indicated as helpful “in performing more complex operations such as reoperative surgery and operations on large thyroid glands.”

U.S. Preventive Services Task Force Recommendations
Not applicable

Ongoing and Unpublished Clinical Trials
Some currently unpublished trials that might influence this review are listed in Table 13.

Table 13. Summary of Key Trials

NCT No.	Trial Name	Planned Enrollment	Completion Date
Ongoing
NCT05710016	Evaluation Of Intra-Operative Neuro-Monitoring Alarm During Complex Spine Surgery	20	Dec 2023
NCT01630785	Retrospective Data Analysis of Neurophysiological Data for Intraoperative or Epilepsy Monitoring	5000	Dec 2025

NCT: national clinical trial.

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Papadopoulos EC, Girardi FP, Sama A, et al. Accuracy of single-time, multilevel registration in image-guided spinal surgery. Spine J. 2005; 5(3): 263-7; discussion 268. PMID 15863081
Sutter MA, Eggspuehler A, Grob D, et al. Multimodal intraoperative monitoring (MIOM) during 409 lumbosacral surgical procedures in 409 patients. Eur Spine J. Nov 2007; 16 Suppl 2(Suppl 2): S221-8. PMID 17912559
Welch WC, Rose RD, Balzer JR, et al. Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study. J Neurosurg. Sep 1997; 87(3): 397-402. PMID 9285605
Wood MJ, Mannion RJ. Improving accuracy and reducing radiation exposure in minimally invasive lumbar interbody fusion. J Neurosurg Spine. May 2010; 12(5): 533-9. PMID 20433301
Wood MJ, McMillen J. The surgical learning curve and accuracy of minimally invasive lumbar pedicle screw placement using CT based computer-assisted navigation plus continuous electromyography monitoring - a retrospective review of 627 screws in 150 patients. Int J Spine Surg. 2014; 8. PMID 25694919
Melachuri SR, Melachuri MK, Anetakis K, et al. Diagnostic Accuracy of Thresholds Less Than or Equal to 8 mA in Pedicle Screw Testing During Lumbar Spine Procedures to Predict New Postoperative Lower Extremity Neurological Deficits. Spine (Phila Pa 1976). Jan 15 2021; 46(2): E139-E145. PMID 33347093
Accadbled F, Henry P, de Gauzy JS, et al. Spinal cord monitoring in scoliosis surgery using an epidural electrode. Results of a prospective, consecutive series of 191 cases. Spine (Phila Pa 1976). Oct 15 2006; 31(22): 2614-23. PMID 17047554
Eggspuehler A, Sutter MA, Grob D, et al. Multimodal intraoperative monitoring during surgery of spinal deformities in 217 patients. Eur Spine J. Nov 2007; 16 Suppl 2(Suppl 2): S188-96. PMID 17632737
El-Hawary R, Sucato DJ, Sparagana S, et al. Spinal cord monitoring in patients with spinal deformity and neural axis abnormalities: a comparison with adolescent idiopathic scoliosis patients. Spine (Phila Pa 1976). Sep 01 2006; 31(19): E698-706. PMID 16946643
Feng B, Qiu G, Shen J, et al. Impact of multimodal intraoperative monitoring during surgery for spine deformity and potential risk factors for neurological monitoring changes. J Spinal Disord Tech. Jun 2012; 25(4): E108-14. PMID 22367467
Kundnani VK, Zhu L, Tak H, et al. Multimodal intraoperative neuromonitoring in corrective surgery for adolescent idiopathic scoliosis: Evaluation of 354 consecutive cases. Indian J Orthop. Jan 2010; 44(1): 64-72. PMID 20165679
Lo YL, Dan YF, Teo A, et al. The value of bilateral ipsilateral and contralateral motor evoked potential monitoring in scoliosis surgery. Eur Spine J. Sep 2008; 17 Suppl 2(Suppl 2): S236-8. PMID 17874145
Luk KD, Hu Y, Wong YW, et al. Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery. Spine (Phila Pa 1976). Aug 15 2001; 26(16): 1772-7. PMID 11493849
Macdonald DB, Al Zayed Z, Al Saddigi A. Four-limb muscle motor evoked potential and optimized somatosensory evoked potential monitoring with decussation assessment: results in 206 thoracolumbar spine surgeries. Eur Spine J. Nov 2007; 16 Suppl 2(Suppl 2): S171-87. PMID 17638028
Noonan KJ, Walker T, Feinberg JR, et al. Factors related to false- versus true-positive neuromonitoring changes in adolescent idiopathic scoliosis surgery. Spine (Phila Pa 1976). Apr 15 2002; 27(8): 825-30. PMID 11935104
Pastorelli F, Di Silvestre M, Plasmati R, et al. The prevention of neural complications in the surgical treatment of scoliosis: the role of the neurophysiological intraoperative monitoring. Eur Spine J. May 2011; 20 Suppl 1(Suppl 1): S105-14. PMID 21416379
Péréon Y, Bernard JM, Fayet G, et al. Usefulness of neurogenic motor evoked potentials for spinal cord monitoring: findings in 112 consecutive patients undergoing surgery for spinal deformity. Electroencephalogr Clin Neurophysiol. Jan 1998; 108(1): 17-23. PMID 9474058
Schwartz DM, Auerbach JD, Dormans JP, et al. Neurophysiological detection of impending spinal cord injury during scoliosis surgery. J Bone Joint Surg Am. Nov 2007; 89(11): 2440-9. PMID 17974887
Murphy B, Murphy E, Irwin J, et al. Review of the Role of Intraoperative Neurophysiological Monitoring in Spinal Surgery With a Focus on the True and False Positives and a Clinical Correlation. Int J Spine Surg. Jun 2022; 16(3): 548-553. PMID 35772981
Tsirikos AI, Duckworth AD, Henderson LE, et al. Multimodal Intraoperative Spinal Cord Monitoring during Spinal Deformity Surgery: Efficacy, Diagnostic Characteristics, and Algorithm Development. Med Princ Pract. 2020; 29(1): 6-17. PMID 31158841
American Academy of Neurology. Model Coverage Policy: Principles of Coding for Intraoperative Neurophysiologic Monitoring (IOM) and Testing. 2012; https://www.aan.com/siteassets/home-page/tools-and- resources/practicing-neurologist--administrators/billing-and-coding/model-coverage- policies/16iommodelpolicy_tr.pdf. Accessed March 1, 2023.
American Association of Neurological Surgeons (AANS)/Congress of Neurological Surgeons (CNS). Joint Section on Disorders of the Spine and Peripheral Nerves updated position statement: intraoperative electrophysiological monitoring. January 2018. https://www.spinesection.org/statement-detail/intraoperative-electrophysiological-monitoring. Accessed March 1, 2023.
Sharan A, Groff MW, Dailey AT, et al. Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 15: electrophysiological monitoring and lumbar fusion. J Neurosurg Spine. Jul 2014; 21(1): 102-5. PMID 24980592
American Clinical Neurophysiology Society. Guideline 11A: Recommended Standards for Neurophysiologic Intraoperative Monitoring Principles. 2009; https://www.acns.org/pdf/guidelines/Guideline-11A.pdf. Accessed March 3, 2023.
Diercks GR, Rastatter JC, Kazahaya K, et al. Pediatric intraoperative nerve monitoring during thyroid surgery: A review from the American Head and Neck Society Endocrine Surgery Section and the International Neural Monitoring Study Group. Head Neck. Jun 2022; 44(6): 1468-1480. PMID 35261110
Macdonald DB, Skinner S, Shils J, et al. Intraoperative motor evoked potential monitoring - a position statement by the American Society of Neurophysiological Monitoring. Clin Neurophysiol. Dec 2013; 124(12): 2291-316. PMID 24055297
Halsey MF, Myung KS, Ghag A, et al. Neurophysiological monitoring of spinal cord function during spinal deformity surgery: 2020 SRS neuromonitoring information statement. Spine Deform. Aug 2020; 8(4): 591-596. PMID 32451978
National Institute for Health and Care Excellence (NICE). Intraoperative nerve monitoring during thyroid surgery [IPG255]. 2008; https://www.nice.org.uk/guidance/ipg255/chapter/1-guidance. Accessed March 6, 2023.
Centers for Medicare & Medicaid Services. National Coverage Determination (NCD) for Electroencephalographic Monitoring During Surgical Procedures Involving the Cerebral Vasculature (160.8). 2006; https://www.cms.gov/medicare-coverage-database/details/ncd-details.aspx?NCDId = 77&ncdver = 2&CoverageSelection = National&KeyWord = monitoring&KeyWordLookUp = Title&KeyWordLookUp = Title&KeyWordLookUp = Title&KeyWordSearchType = And&KeyWordSearchType = And&KeyWordSearchType = And&bc = gAAAACAAAAAA&. Accessed March 6, 2023.
Centers for Medicare & Medicaid Services. Billing Medicare for Remote Intraoperative Neurophysiology Monitoring in CY 2013. Updated September 2020; https://www.cms.gov/medicare/medicare-fee-for-service-payment/physicianfeesched/downloads/faq-remote-ionm.pdf. Accessed March 6, 2023.

Coding Section

Codes	Number	Description
CPT	95829	Electrocardiogram at surgery (separate procedure)
	95865	Needle electromyography; larynx
	95867-95868	Needle electromyography of cranial nerve supplied muscle(s) code range
	95907-95913	Nerve conduction study code range
	95940	Continuous intraoperative neurophysiology monitoring in the operating room, one on one monitoring requiring personal attendance, each 15 minutes (List separately in addition to code for primary procedure)
	95941	Continuous intraoperative neurophysiology monitoring, from outside the operating room (remote or nearby) or for monitoring of more than one case while in the operating room, per hour (List separately in addition to code for primary procedure)
	95925-95927; 95938	Somatosensory-evoked potential study code range
	95928-95929; 95939	Central motor evoked potential study (transcranial motor stimulation) code range
	95930	Visual evoked potential (VEP) checkerboard or flash testing, central nervous system except glaucoma, with interpretation and report
	95955	Electroencephalogram (EEG) during non-intracranial surgery (e.g., carotid surgery)
HCPCS	G0453	Continuous intraoperative neurophysiology monitoring, from outside the operating room (remote or nearby), per patient, (attention directed exclusively to one patient) each 15 minutes (list in addition to primary procedure)
ICD-10-CM	C41.2	Malignant neoplasm of vertebral column
	C71.0-C71.9	Malignant neoplasm of brain; code range
	C72.0	Malignant neoplasm of spinal cord
	C73	Malignant neoplasm of thyroid gland
	C75.0	Malignant neoplasm of parathyroid gland
	C79.31-C79.32	Secondary malignant neoplasm of brain and cerebral meninges; code range
	D33.0-D33.9	Benign neoplasm of brain and other parts of central nervous system; code range
	D34	Benign neoplasm of thyroid gland
	D35.1	Benign neoplasm of parathyroid gland
	D43.0-D43.9	Neoplasm of uncertain behavior of brain and central nervous system; code range
	D44.0	Neoplasm of uncertain behavior of thyroid gland
	D44.2	Neoplasm of uncertain behavior of parathyroid gland
	D49.6	Neoplasm of unspecified behavior of brain
	E04.0-E04.9	Other nontoxic goiter code range
	E05.00-E05.91	Thyrotoxicosis code range
	E06.0-E06.9	Thyroiditis code range
	E21.0-E21.5	Hyperparathyroidism code range (E21.0 is primary hyperparathyroidism)
	I71.00-I71.9	Aortic aneurysm and dissection; code range (Deleted I71.3 I71.4, I71.5, I71.6, Added I71.30-I71.33, I71.40-I17.43, I71.50-I71.53, I71.60-I71.63 eff 10/01/2022)
	M50.00-M50.93	Cervical disc disorders; code range
	M48.00-M48.08	Spinal stenosis; code range
	M40.00-M40.57	Kyphosis and lordosis; code range
	M41.00-M41.9	Scoliosis; code range
	I65.01-I65.9	Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction; code range
ICD-10-PCS	4A0002Z	Measurement of Central Nervous Conductivity, Open Approach
	4A0004Z	Measurement of Central Nervous Electrical Activity, Open Approach
	4A000BZ	Measurement of Central Nervous Pressure, Open Approach
	4A00X2Z	Measurement of Central Nervous Conductivity, External Approach
	4A00X4Z	Measurement of Central Nervous Electrical Activity, External Approach
	4A01029	Measurement of Peripheral Nervous Conductivity, Sensory, Open Approach
	4A0102B	Measurement of Peripheral Nervous Conductivity, Motor, Open Approach
	4A01329	Measurement of Peripheral Nervous Conductivity, Sensory, Percutaneous Approach
	4A0132B	Measurement of Peripheral Nervous Conductivity, Motor, Percutaneous Approach
	4A01X29	Measurement of Peripheral Nervous Conductivity, Sensory, External Approach
	4A01X2B	Measurement of Peripheral Nervous Conductivity, Motor, External Approach
	4A1002Z	Monitoring of Central Nervous Conductivity, Open Approach
	4A1004Z	Monitoring of Central Nervous Electrical Activity, Open Approach
	4A100BZ	Monitoring of Central Nervous Pressure, Open Approach
	4A10X2Z	Monitoring of Central Nervous Conductivity, External Approach
	4A10X4Z	Monitoring of Central Nervous Electrical Activity, External Approach
	4A11029	Monitoring of Peripheral Nervous Conductivity, Sensory, Open Approach
	4A1102B	Monitoring of Peripheral Nervous Conductivity, Motor, Open Approach
	4A11329	Monitoring of Peripheral Nervous Conductivity, Sensory, Percutaneous Approach
	4A1132B	Monitoring of Peripheral Nervous Conductivity, Motor, Percutaneous Approach
	4A11X29	Monitoring of Peripheral Nervous Conductivity, Sensory, External Approach
	4A11X2B	Monitoring of Peripheral Nervous Conductivity, Motor, External Approach
	4B00XVZ	Measurement of Central Nervous Stimulator, External Approach
	4B01XVZ	Measurement of Peripheral Nervous Stimulator, External Approach
	4B0FXVZ	Measurement of Musculoskeletal Stimulator, External Approach
	F01Z77Z	Facial Nerve Function Assessment using Electrophysiologic Equipment
	F01Z87Z	Neurophysiologic Intraoperative Assessment using Electrophysiologic Equipment
	F01Z8JZ	Neurophysiologic Intraoperative Assessment using Somatosensory Equipment
	F01Z9JZ	Somatosensory Evoked Potentials Assessment using Somatosensory Equipment
Type of service	Surgery
Place of service	Inpatient

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies and accredited national guidelines.

History From 2013 Forward

01/05/2024	Annual review, no change to policy intent. Updating rationale and references.
01/12/2023	Annual review, no change to policy intent. Updating coding, rationale and references. Removing appendixes as they are no longer relevant
01/03/2022	Annual review, no change to policy intent. Updating description, rationale and references.
01/05/2021	Annual review, no change to policy intent. Updating rationale, references, guidelines and coding.
07/08/2020	Interim review to add policy statement regarding train of four (TOF). No other changes.
01/21/2020	Annual review, no change to policy intent. Updating rationale, references and description.
05/21/2019	Corrected last review date. No other changes made.
01/30/2019	Annual review, updating rationale and references.
11/14/2018	Interim review updating note section to include facial nerve monitoring and adding specificity to the providers included in the note. No other changes made.
09/11/2018	Interim review, updating coding. No other changes made.
02/15/2018	Annual review, adding policy verbiage regarding the medical necessity of laryngeal nerve monitoring. Also updating title, background, description, guidelines, rationale and references.
01/04/2017	Annual review, no change to policy intent.
01/13/2016	Annual review, no change to policy intent. Updating background, description, rationale and references.
01/29/2015	Annual review, no change to policy intent. Added coding & related policy. Updated guidelines, rationale and references.
01/14/2014	Annual review. Updated rationale and references. Added benefit applications. No change to policy intent.

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Intraoperative Neurophysiologic Monitoring - CAM 70158