Intraoperative Neurophysiologic Monitoring

POLICY NUMBER

A.7.01.58

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.

Intraoperative Neurophysiologic Monitoring

The principal goal of intraoperative neurophysiologic monitoring is the 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 below.

Sensory-Evoked Potentials

Sensory-evoked potentials describe the responses of the sensory pathways to sensory or electrical stimuli. Intraoperative monitoring of sensory-evoked potentials is used to assess the functional integrity of central nervous system pathways during surgeries that put the spinal cord or brain at risk for significant ischemia or traumatic injury. The basic principles of sensory-evoked potential 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 interpreting the signal at certain standardized points along the pathway. Monitoring of sensory-evoked potentials 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. Sensory-evoked potentials can be further categorized by the type of simulation used, as follows.

Somatosensory-Evoked Potentials

Somatosensory-evoked potentials 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. The recording is done either cortically or at the level of the spinal cord above the surgical procedure. Intraoperative monitoring of somatosensory-evoked potentials 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 somatosensory-evoked potential monitoring is in patients undergoing corrective surgery for scoliosis. In this setting, somatosensory-evoked potential 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 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 brainstem auditory-evoked potentials have been extensively used to monitor auditory function during these procedures.

Visual-Evoked Potentials

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

Motor-Evoked Potentials

Motor-evoked potentials are recorded from muscles following direct or transcranial electrical stimulation of motor cortex or pulsed magnetic stimulation provided using 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. Motor-evoked potentials, especially when induced by magnetic stimulation, can be affected by anesthesia. The Digitimer electrical cortical stimulator received the U.S. Food and Drug Administration (FDA) premarket approval in 2002. Devices for transcranial magnetic stimulation have not been approved by the FDA for this use.

Multimodal intraoperative neurophysiologic monitoring, in which more than one technique is used, most commonly with somatosensory-evoked potentials and motor-evoked potentials, has also been described.

Electromyogram Monitoring and Nerve Conduction Velocity Measurements

Electromyogram (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 (eg, 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 (ie, 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 electromyogram activity in the facial or neck muscles. Thus, monitoring is done in the direction opposite that of sensory-evoked potentials, but the purpose is similar, to verify that the neural pathway is intact.

Electroencephalogram Monitoring

Spontaneous electroencephalogram (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 activity. 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 activity 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, electrocorticography does not constitute monitoring, per se.

Intraoperative neurophysiologic monitoring, including somatosensory-evoked potentials and motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyogram (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 the 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. Therefore, this policy focuses on monitoring of the recurrent laryngeal nerve during neck and esophageal surgeries and monitoring of peripheral nerves.

A number of electroencephalography and electromyography monitors have been cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process. FDA product code: GWQ.

Intraoperative neurophysiologic monitoring of motor-evoked potentials using transcranial magnetic stimulation does not have FDA approval.

Related policies -

• Navigated Transcranial Magnetic Stimulation

POLICY

Intraoperative neurophysiologic monitoring, which includes somatosensory-evoked potentials, motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, electromyography 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 individuals 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

  • preexisting 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.

Intraoperative monitoring of visual-evoked potentials is considered investigational.

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.

Intraoperative electromyography and nerve conduction velocity monitoring during surgery on the peripheral nerves is considered investigational.

Intraoperative monitoring typically is done in the operating room (OR) by a technician, with a physician as a remote backup. In some ORs’ there is a central physician monitoring room, where a physician may simultaneously monitor several cases.

Intraoperative monitoring is considered reimbursable as a separate service only when a licensed physician, other than the operating surgeon, performs the monitoring while in attendance in the operating room throughout the procedure.

POLICY EXCEPTIONS

Federal Employee Program (FEP) Members Only: Effective 03/10/11, intraoperative monitoring is considered reimbursable as a separate service only when a licensed healthcare 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.

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Constant communication among the surgeon, neurophysiologist, and anesthetist is required for safe and effective intraoperative neurophysiologic monitoring.

Medically Necessary is defined as those services, treatments, procedures, equipment, drugs, devices, items or supplies furnished by a covered Provider that are required to identify or treat a Member's illness, injury or Mental Health Disorders, and which Company determines are covered under this Benefit Plan based on the criteria as follows in A through D:

A.  consistent with the symptoms or diagnosis and treatment of the Member's condition, illness, or injury; and

B.  appropriate with regard to standards of good medical practice; and

C.  not solely for the convenience of the Member, his or her Provider; and

D.  the most appropriate supply or level of care which can safely be provided to Member. When applied to the care of an Inpatient, it further means that services for the Member's medical symptoms or conditions require that the services cannot be safely provided to the Member as an Outpatient.

For the definition of medical necessity, “standards of good medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. BCBSMS makes no payment for services, treatments, procedures, equipment, drugs, devices, items or supplies which are not documented to be Medically Necessary. The fact that a Physician or other Provider has prescribed, ordered, recommended, or approved a service or supply does not in itself, make it Medically Necessary.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

8/2002: Approved by Medical Policy Advisory Committee (MPAC).

3/2004: Code Reference section completed.

2/6/2007: Policy reviewed, no changes.

9/20/2007: Code Reference section updated. ICD-9 2007 revisions added to policy, ICD9 Procedure code 00.94 added for 10/01/2007 revisions.

10/02/2009: Coding Section updated to include coding rule information specific to CPT-4 code 95920. CPT-4 codes 95961 and 95962 removed from Covered Codes Table. ICD-9 Procedure code 04.19 removed from Covered Codes Table. ICD-9 Diagnosis codes 433.10, 433.11, 737.30- 737.34, 737.39, 737.43, and 754.2 removed from Covered Codes Table. Added verbiage, "* Some covered procedure codes have multiple descriptions. Coverage will only be made for covered codes when used for services outlined within the policy statement section." to the Covered Codes Section.

06/21/2011: Policy statement revised to state that motor-evoked potentials using transcranial electrical stimulation may be considered medically necessary, and motor-evoked potential using transcranial magnetic stimulation is investigational. The Policy Exceptions section was updated to add the following verbiage: "Federal Employee Program (FEP) Members Only: Effective 03/10/11, intraoperative monitoring is considered reimbursable as a separate service only when a licensed healthcare 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."

12/21/2012: Added the following new 2013 CPT codes to the Code Reference section: 95940, 95941, and G0453.

08/01/2014: Policy reviewed; description updated regarding motor-evoked potentials. Removed deleted CPT code 95920 from the Code Reference section.

08/27/2015: Code Reference section updated for ICD-10. Removed deleted CPT code 95920 and ICD-9 procedure code 89.19 from the Code Reference section.

09/29/2015: Policy reviewed; policy statements unchanged. Policy Guidelines section updated to add medically necessary and investigative definitions.

05/31/2016: Policy number A.7.01.58 added.

09/29/2017: Code Reference section updated to add new ICD-10 procedure codes 4A1074G, 4A1084G, 4A1174G, and 4A1184G. Effective 10/01/2017.

12/13/2017: Policy title changed from "Intra-operative Neurophysiologic Monitoring (sensory-evoked potentials, motor-evoked potentials, EEG monitoring)" to "Intraoperative Neurophysiologic Monitoring." Policy description updated regarding monitoring of the recurrent laryngeal nerve and devices. First medically necessary statement updated to change "intraoperative monitoring" to "intraoperative neurophysiologic monitoring." Added policy statement that intraoperative neurophysiologic monitoring of the recurrent laryngeal nerve may be considered medically necessary in patients undergoing high-risk thyroid or parathyroid surgery and anterior cervical spine surgery. Added statement that 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.

05/03/2018: Policy reviewed; no changes.

05/13/2019: Policy description updated regarding indications for intraoperative neurophysiologic monitoring. Policy statements unchanged.

05/20/2020: Policy description and guidelines updated. Policy statements unchanged.

12/22/2020: Code Reference section updated regarding deleted CPT code.

07/16/2021: Policy description updated. Policy statements unchanged. Policy Guidelines updated to change "Nervous/Mental Conditions" to "Mental Health Disorders" and "Medically Necessary" to "medical necessity."

06/01/2022: Policy reviewed. Policy statement regarding intraoperative electromyography and nerve conduction velocity monitoring updated to change "not medically necessary" to "investigational." Policy intent unchanged. Code Reference section updated to remove deleted CPT code 92585 from the code description for CPT code 95940. "Not Medically Necessary" codes table changed to "Investigational."

05/15/2023: Policy description updated. Policy statement updated to change "patients" to "individuals."

05/21/2024: Policy reviewed; no changes.

05/14/2025: Policy reviewed; no changes.

SOURCE(S)

Blue Cross Blue Shield Association policy # 7.01.58

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.

Covered Codes

Investigational Codes

CPT copyright American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.