CMS Nerve Conduction Studies and Electromyography Form

Summary Of Evidence

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Analysis of Evidence

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This contractor expects healthcare professionals who perform electrodiagnostic testing will be appropriately trained and/or credentialed, either by a formal residency/fellowship program, certification by a nationally recognized organization, or by an accredited post-graduate training course covering anatomy, neurophysiology and forms of electrodiagnostics including both nerve conduction studies (NCS) and electromyography (EMG), acceptable to this contractor, in order to provide the proper testing and assessment of the patient's condition, and appropriate safety measures.

The electrodiagnostic evaluation is an extension of the neurologic portion of the physical examination. Both require a detailed knowledge of a patient and his/her disease. Training in the performance of electrodiagnostic procedures in isolation of knowledge about clinical diagnostic and management aspects of neuromuscular diseases, may not be adequate for proper performance of an electrodiagnostic evaluation and correct interpretation of electrodiagnostic test results. Without awareness of the patterns of abnormality expected in different diseases and knowledge that the results of NCS and EMG may be similar in different diseases, diagnosis solely by EMG-NCS findings may be both inadequate and ultimately be detrimental to the patient.

Guidelines about proper qualifications for qualified health care professionals performing electrodiagnostic evaluations have been developed and published by American Association of Neuromuscular and Electrodiagnostic Medicine and other medical organizations, including the American Medical Association, the American Academy of Neurology, the American Academy of Physical Medicine and Rehabilitation, American Neurological Association, the American Board of Physical Therapy Specialties in Clinical Electrophysiology, and the Department of Veterans Affairs.

Both EMGs and NCSs are usually required for a clinical diagnosis of peripheral nervous system disorders. Performance of one type of testing does not eliminate the need for the other. The intensity and extent of testing with EMG and NCS are matters of clinical judgment developed after the initial pre-test evaluation, and later modified during the testing procedure.

Decisions to continue, modify, or conclude a testing rely on knowledge of anatomy, physiology and neuromuscular diseases. Ongoing real-time assessment of data is required during the clinical diagnostic evaluation, and especially during EMG examination.

Nerve conduction studies are used to measure action potentials resulting from peripheral nerve stimulation which are recordable over the nerve or from an innervated muscle. With this technique, responses are measured between two sites of stimulation, or between a stimulus and a recording site.

Nerve conduction studies are of two general types: sensory and motor. Either surface or needle electrodes can be used to stimulate the nerve or record the response. Axonal damage or dysfunction generally results in loss of nerve or muscle potential response amplitude, whereas demyelination leads to prolongation of conduction time and slowing of conduction velocity.

Obtaining and interpreting NCS results requires extensive interaction between the performing qualified health care professional and the patient and is most effective when both obtaining raw data and interpretation are performed concurrently on a real-time basis.

Results of the NCS reflect on the integrity and function of:

(I) the myelin sheath (Schwann cell derived insulation covering an axon), and
(II) the axon (an extension of neuronal cell body) of a nerve.

Interruption of axon and dysfunction of myelin will both affect NCS results.

It is often also valuable to test conduction status in proximal segments of peripheral nerves. This assessment can be accomplished by H-reflex, F-wave, and blink reflex testing. These proximal segments include the first several centimeters of a compound nerve emerging from the spinal cord or brainstem. H-reflex, F-waves, and Blink reflex testing accomplish this task better than distal NCS.

Electromyography (EMG) is the study and recording of intrinsic electrical properties of skeletal muscles. This is carried out with a needle electrode. Generally, the needles are of two types: monopolar or concentric. Electromyography is undertaken together with NCS. Unlike NCS, however, EMG testing relies on both auditory and visual feedback to the electromyographer. This testing is also invasive in that it requires needle electrode insertion and adjustment at multiple sites, and at times anatomically critical sites. As in NCS, during EMG studies, the electromyographer depends on ongoing real-time interpretation based knowledge of clinical diagnoses being evaluated to decide whether to continue, modify, or conclude a test. This process requires knowledge of anatomy, physiology, and neuromuscular diseases.

EMG results reflect not only on the integrity of the functioning connection between a nerve and its innervated muscle, but also on the integrity of a muscle itself. The axon innervating a muscle is primarily responsible for the muscle’s volitional contraction, survival, and trophic functions. Thus, interruption of the axon will alter the EMG. A few prime examples of conditions in which EMG is potentially helpful are disc disease producing spinal nerve dysfunction, advanced nerve compression in peripheral lesions, Amyotrophic Lateral Sclerosis (ALS), polyneuropathy, etc. After an acute neurogenic lesion, EMG changes may not appear for several days to weeks in the innervated muscles. Primary muscle disease such as polymyositis will also alter a normal EMG pattern. Myotonic disorders may show a pattern of spontaneous repetitive discharges on needle exploration.

In summary, axonal and muscle involvement are most sensitively detected by EMGs, and myelin and axonal involvement are best detected by NCSs.

Physical Therapists Performing EMGs

Please refer to associated article Billing and Coding: Nerve Conduction Studies and Electromyography for further guidance.

1. Nerve Conduction Studies
   The dichotomy into axonal and demyelinating neuropathies provides a practical means of correlating electrical abnormalities with major pathophysiologic changes in the nerve. Electrical studies can be of help in localization of an abnormality, and in distinguishing one variety of neuropathy from another: for example, diffuse vs. multifocal; axonal vs. demyelinating. Such distinction has diagnostic value. Specific classification of nerve injuries into neuropraxia and axonotmesis can be made based on conduction studies and EMG. Such classification has a bearing on prognosis and treatment.
   1. Focal neuropathies or compressive lesions such as carpal tunnel syndrome, ulnar neuropathies, or root lesions, for localization.
   2. Traumatic nerve lesions, for diagnosis and prognosis.
   3. Diagnosis or confirmation of suspected generalized neuropathies, such as diabetic, uremic, metabolic, or immune.
   4. Repetitive nerve stimulation in diagnosis of neuromuscular junction disorders such as myasthenia gravis, myasthenic syndrome.
   5. There may be other instances, not detailed here, where NCS may be of use. Not all possible or potential indications are addressed here.

   The broad diagnostic scope of NCS is recognizable by the foregoing description. There may be instances where questions about an indication, or need for a study, will arise. The clinical history and examination, carried out before the study, must always describe and document clearly and comprehensibly the need for the planned test. A "rule-out" diagnosis is typically not acceptable. The Contractor is cognizant of the fact that patients are not always referred with a definite diagnosis in mind. Often, pain, paresthesia, or weakness in an extremity is the reason for an NCS or EMG. These common symptoms result not only from axonal and myelin dysfunction but also from systemic, non-neurological illnesses. EMG and NCS may help in making this distinction. Therefore, symptom-based diagnoses such as "pain in limb" weakness, disturbance in skin sensation, or "paresthesia" are acceptable provided the clinical assessment unequivocally supports the need for a study. To cite but one example of many, an EMG or NCS is irrelevant as a first order diagnostic test for limb pain resulting from immediate antecedent trauma or acute bone injury.

   Both EMGs and NCSs are required for a clinical diagnosis of peripheral nervous system disorders. EMG results reflect on the integrity of the functioning connection between a nerve and its innervated muscle and on the integrity of a muscle itself. Performance of one does not eliminate the need for the other. The intensity and extent of testing with EMG and NCS are matters of clinical judgment developed after the initial pre-test evaluation, and later modified during the testing procedure.

   Decisions to continue, modify, or conclude a test also rely on a knowledge base of anatomy, physiology, and neuromuscular diseases. There is a requirement for ongoing real-time clinical diagnostic evaluation, especially during EMG examination. Also, EMG examination is invasive. Needle placement in the exact muscle of interest is essential. It requires needle exploration near vital structures as the pleura, femoral neurovascular bundle, peritoneum, intraspinal spaces, carotid artery, orbit, and brachial plexus. Risk of infection from AIDS, Hepatitis B-E, Creutzfeldt-Jakob encephalopathy, and hemorrhage from anticoagulation can be managed by proper techniques.

   The electrodiagnostic evaluation is an extension of the neurologic portion of the physical examination. Both require a detailed knowledge of a patient and his/her disease. Training in the performance of electrodiagnostic procedures, in isolation without awareness and ability to diagnose and manage neuromuscular diseases, is not always adequate for electrodiagnostic consultation. Recognition and experience in the management of disparate diseases that produce common electrodiagnostic findings may be necessary. For example, EMG-NCS findings may overlap in the following pairs of disorders: inflammatory myopathies and ALS, ALS and multi-level radiculopathies, myotonia of channelopathies (periodic paralyses) and myotonic dystrophies, focal neuropathies such as Carpal Tunnel Syndrome, and proximal plexopathies. Other instances where knowledge of disease behavior is crucial are Chronic Inflammatory Demyelinating Neuropathy and Multifocal Motor Neuropathy. These entities display electrodiagnostic features that resemble generalized polyneuropathies. Neuromuscular transmission disorders require separation based on clinical presentation and electrical features. Treatment will depend on differentiating among them. Without awareness of the disease spectrum, diagnosis solely by EMG-NCS findings may be either wrong or detrimental to the patient.

   The following definitions are from the American Association of Neuromuscular & Electrodiagnostic Medicine Recommended Policy for Electrodiagnostic Medicine:

   The stimulation of nerves is similar across all NCSs; the characteristics of motor, sensory, and mixed NCSs are different and are discussed separately below. In each case, an appropriate nerve is stimulated, and recording is made either from the appropriate nerves or from muscle supplied by the motor nerve.

   1. Motor. Motor NCSs are performed by applying electrical stimulation at various points along the course of a motor nerve while recording the electrical response from an appropriate muscle. Response parameters include amplitude, latency, configuration, and motor conduction velocity.
   2. Sensory. Sensory NCSs are performed by applying electrical stimulation near a nerve and recording the response from a distant site along the nerve. Response parameters include amplitude, latency, and configuration.
   3. Mixed NCSs are performed by applying electrical stimulation near a nerve containing both motor and sensory fibers (a mixed nerve) and recording from a different location along that nerve that also contains both motor and sensory nerve fibers. Response parameters include amplitude, latency, configuration, and motor conduction velocity.
   4. Motor and/or sensory nerve conduction studies performed using automated devices (for example devices such as NC-stat® System) cannot support testing of other locations and other nerves as needed depending on the concurrent results of testing.

   When the beneficiary has a high pre-test or a prior probability for having the diagnosis of Carpal Tunnel Syndrome, the NC-stat® System (alone) will be allowed, one service per arm, using the correct procedural code for Motor and/or Sensory Nerve Conduction studies. The diagnosis codes for Carpal tunnel syndrome, right upper limb, left upper limb, or bilateral upper limbs should be used. All other diagnosis codes will be denied as not medically necessary.

   Nerve conduction studies performed independent of needle EMG may only provide a portion of the information needed to diagnose muscle, nerve root, and most nerve disorders. When the NCS is used on its' own without integrating needle EMG findings, or when an individual relies solely on a review of NCS data, the results can be misleading, and important diagnoses may be missed.

   In most instances, both NCS and usually EMG are necessary to perform diagnostic testing. While a provider may choose to perform just an NCS, when performed alone it is usually considered not medically necessary. The only exception to this is a situation when a provider may consider it appropriate to perform an NCS without doing an EMG for the diagnosis of carpal tunnel syndrome with a high pre-test probability.

2. Electromyography
   Neurogenic disorders can be distinguishable from myopathic disorders by a carefully performed EMG. For example, both polymyositis and ALS produce manifest weakness. The former carries a very different prognosis and treatment than the latter. An EMG is very valuable in making this distinction. Similarly, classification of nerve trauma into axonal vs. demyelinating categories, with corresponding differences in prognoses, are possible with EMG. Below is a list of common disorders where an EMG, in tandem with properly conducted NCS, will be helpful in diagnosis:
   
   
   1. Nerve compression syndromes, including carpal tunnel syndrome and other focal compressions.
   2. Radiculopathy - cervical, lumbosacral.
   3. Mono/polyneuropathy - metabolic, degenerative, hereditary.
   4. Myopathy - including poly-and dermatomyositis, myotonic and congenital myopathies.
   5. Plexopathy - idiopathic, trauma, infiltration.
   6. Neuromuscular junction disorders - myasthenia gravis. Single fiber EMG is of special value here.
   7. At times, immediately prior to botulinum toxin injection, for localization.
   8. At times, immediately prior to injection of phenol or other substances for nerve blocking or chemodenervation.

There may be other instances, not detailed here, where EMG may be of use.

Use of EMG with Botulinum Toxin Injection
Electromyography may be used to optimize the anatomic location of botulinum toxin injection. It is expected there will be one study performed per anatomic location of injection, if needed.

Limitations:

Nerve Conduction Studies
Nerve conduction studies can be reimbursed only once per nerve, or named branch of a nerve, regardless of the number of sites tested or the number of methods used on that nerve. For instance, testing the ulnar nerve at wrist, forearm, below elbow, above elbow, axilla, and supraclavicular regions will all be considered as a single nerve. Motor and sensory nerve testing are considered separate tests. Nerve conduction test when performed with preconfigured electrodes customized to a specific anatomic site is payable only once per limb studied and cannot be used in conjunction with any other nerve conduction codes. 

Routine testing for polyneuropathy of diabetes or end stage renal disease (ESRD) is not considered medically necessary and is not covered. Testing for the sole purpose of monitoring disease intensity or treatment efficacy in these two conditions is also not covered.

Psychophysical measurements (current, vibration, thermal perceptions), even though they may involve delivery of a stimulus, are considered to be part of the physical exam and may not be billed as a separate service.

Current Perception Threshold/Sensory Nerve Conduction Threshold Test (sNCT) – is not covered by Medicare. Please review CMS Publication 100-3, Medicare National Coverage Determinations Manual, Chapter 1, Section 160.23 Sensory Nerve Conduction Threshold Tests (sNCT) and associated article Billing and Coding: Nerve Conduction Studies and Electromyography for further guidance.

Examination using portable hand-held devices, or devices which are incapable of real-time waveform display and analysis, and incapable of both NCS and EMG testing, will be included in the E/M service. They will not be paid separately. Examples include the Axon II or delta fiber analysis testing and/or machines with other names.

Nerve conduction studies must provide a number of response parameters in a real-time fashion to facilitate provider interpretation. Those parameters include amplitude, latency, configuration and conduction velocity. Medicare does not accept diagnostic studies that do not provide this information or those that provide delayed interpretation as substitutes for NCS. Raw measurement data obtained and transmitted trans-telephonically or over the Internet, therefore, does not qualify for the payment of the electrodiagnostic service codes included in this LCD.

Medicare does not expect to receive claims for nerve conduction testing accomplished with discriminatory devices that use fixed anatomic templates and computer-generated reports used as an adjunct to physical examination routinely on all patients.

Electromyography
It is expected that providers will use the correct procedural code for sampling muscles other than the paraspinals associated with the extremities, which have been tested. Medicare would not expect to see this code billed when the paraspinal muscles corresponding to an extremity are tested and when the extremity EMG code is also billed. The necessity and reasonableness of the following uses of EMG studies have not been established:

• exclusive testing of intrinsic foot muscles in the diagnosis of proximal lesions
• definitive diagnostic conclusions based on paraspinal EMG in regions bearing scar of past surgeries (e.g., previous laminectomies)
• pattern-setting limited limb muscle examinations, without paraspinal muscle testing for a diagnosis of radiculopathy
• EMG testing shortly after trauma, before EMG abnormalities would have reasonably had time to develop
• surface and macro EMG’s
• multiple uses of EMG in the same patient at the same location of the same limb for the purpose of optimizing botulinum toxin injections.

For outpatient settings other than Comprehensive Outpatient Rehabilitation Facility (CORF)s, references to "physicians" throughout this policy include non-physicians, such as nurse practitioners, clinical nurse specialists, and physician assistants. Such non-physician practitioners, with certain exceptions, may certify, order, and establish the plan of care as authorized by State law. (See Sections 1861[s][2] and 1862[a][14] of Title XVIII of the Social Security Act; 42 CFR, Sections 410.74, 410.75, 410.76 and 419.22; 58 FR 18543, April 7, 2000.) Each practitioner must provide only those services within the scope of practice for each state.