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Intra-operative neurophysiologic monitoring (IONM) describes a variety of procedures that have been 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.
The principal goal of intra-operative monitoring is the identification of nervous system impairment in the hope that prompt intervention will prevent permanent deficits. Correctable factors at surgery include circulatory disturbance, excess compression from retraction, bony structures, or 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 potential (SEP) describes the responses of the sensory pathways to sensory or electrical stimuli. Intra-operative monitoring of sensory-evoked potentials is used to assess the functional integrity of Central Nervous System (CNS) pathways during operations 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 interpretation of 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 broken down into the following categories according to the type of simulation used:
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 yet received approval from 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
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 peripheral nerves, eg, to identify the extent of nerve damage before nerve grafting or during resection of tumors. In addition, these techniques may be used during procedures around the nerve roots and around 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 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.
Spontaneous electroencephalogram (EEG) monitoring can also be recorded during surgery and can be subdivided as follows:
Related policies -
POLICYIntraoperative monitoring, which includes somatosensory-evoked potentials, motor-evoked potentials using transcranial electrical stimulation, brainstem auditory-evoked potentials, EMG of cranial nerves, EEG, and electrocorticography (ECoG), may be considered medically necessary during spinal, intracranial, or vascular procedures.
Intra-operative monitoring of visual-evoked potentials is considered investigational.
Due to the lack of FDA approval, intraoperative monitoring of motor-evoked potentials using transcranial magnetic stimulation is considered investigational.
Intraoperative EMG and nerve conduction velocity monitoring during surgery on the peripheral nerves is considered not medically necessary.
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 EXCEPTIONSFederal 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.
Investigative service is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized by certifying boards and/or approving or licensing agencies or published peer review criteria as standard, effective medical practice for the treatment of the condition being treated and as such therefore is not considered medically necessary.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
POLICY HISTORY8/2002: 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.
Blue Cross Blue Shield Association policy # 7.01.58
CODE REFERENCEThis 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.
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)
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)