History/Background and/or General Information
Electrodiagnostic testing builds on the neurologic portion of the physical examination. Both require a detailed knowledge of the 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 is not 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 nerve conduction studies (NCS) and electromyography (EMG) may be similar in different diseases, diagnosis solely by EMG-NCS findings is inadequate and potentially detrimental to the patient.
Both EMG and NCS 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.
NCS 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.
NCS 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 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 also often 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.
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 one of two types: monopolar or concentric. EMG is undertaken together with NCS. Unlike NCS, however, EMG testing relies on both auditory and visual feedback to the electromyographer. This testing is invasive in that it requires needle electrode insertion and adjustment at multiple sites which are at times, anatomically critical. As in NCS, during EMG studies, the electromyographer depends on ongoing real-time interpretation 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 the integrity of the functioning connection between a nerve and its innervated muscle but also the integrity of the 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), and polyneuropathy. 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 EMG and myelin and axonal involvement are best detected by NCS.
Covered Indications
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 on the basis of conduction studies and electromyography. Such classification has a bearing on prognosis and treatment.
- Focal neuropathies or compressive lesions such as carpal tunnel syndrome, ulnar neuropathies or root lesions, for localization.
- Traumatic nerve lesions, for diagnosis and prognosis.
- Diagnosis or confirmation of suspected generalized neuropathies, such as diabetic, uremic, metabolic or immune.
- Repetitive nerve stimulation in diagnosis of neuromuscular junction disorders such as myasthenia gravis, myasthenic syndrome.
- 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, and instead it is required that the medical record establishes the necessity of the testing by making clear how the test results will alter management of the specific patient. 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 NCV 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 also on the integrity of a muscle itself. Performance of one may 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 actually 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 often inadequate 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 as Carpal Tunnel Syndrome and proximal plexopathies. Other instances where knowledge of disease behavior is crucial are Chronic Inflammatory Demyelinating Neuropathy (CIDP) 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 wrong, detrimental to the patient or both.
The following definitions are from the American Association of Neuromuscular & Electrodiagnostic Medicine Recommended Policy for Electrodiagnostic Medicine (page 2)
https://www.aanem.org/getmedia/3275d71c-81dc-4b23-96a7-03173ecf8446/Recommended_Policy_EDX_Medicine_062810.pdf
"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.
a. 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.
b. 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.
c. 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."
Nerve conduction studies performed using preconfigured electrode array(s) (i.e., 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 priori probability for having the diagnosis of Carpal Tunnel Syndrome, the automated devices (for example NC-stat® System) (alone) will be allowed, one service per arm. All other diagnoses will be denied as not medically necessary. Please refer to the article Billing and Coding: Nerve Conduction Studies and Electromyography (A57123).
Nerve conduction studies performed independent of needle electromyography (EMG) may only provide a portion of the information needed to diagnose muscle, nerve root, and most nerve disorders. When the nerve conduction study (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 a NCS, when performed alone it is usually considered to be a screening exam. The only exception to this is a situation when a provider may consider it appropriate to perform a NCS without doing an EMG for the diagnosis of carpal tunnel syndrome with a high pre-test probability.
Electromyography
Neurogenic disorders can be distinguishable from myopathic disorders by a carefully performed EMG. For example, both polymyositis and ALS (Amyotrophic Lateral Sclerosis) produce manifest weakness. The former carries a very different prognosis and treatment than the latter. An EMG is 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:
- Nerve compression syndromes, including carpal tunnel syndrome and other focal compressions.
- Radiculopathy - cervical, lumbosacral.
- Mono/polyneuropathy - metabolic, degenerative, hereditary.
- Myopathy - including poly-and dermatomyositis, myotonic and congenital myopathies.
- Plexopathy - idiopathic, trauma, infiltration.
- Neuromuscular junction disorders - myasthenia gravis. Single fiber EMG is of special value here.
- When clinically necessary, immediately prior to botulinum toxin injection, for localization.
- When clinically necessary, 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
EMG 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, and that the record will evidence the necessity for use of EMG.
Limitations:
The number of tests performed should be the minimum needed to establish an accurate diagnosis.
Categorically, there are general standards accepted for repeat electrodiagnostic testing in certain categories of diseases. Not more than two electrodiagnostic evaluations per 12-month period are generally accepted for carpal tunnel syndrome, radiculopathy, mononeuropathy, polyneuropathy, myopathy, and neuromuscular junction disease.
Not more than three electrodiagnostic evaluations in a 12-month period are generally accepted for motor neuropathy and plexopathy. Therefore, repeat electrodiagnostic testing should not be needed in a 12-month period in the majority of all cases. The medical record establishes medical necessity of any service or procedure and should be available to verify the need for repeat testing on any patient.
Nerve Conduction Studies
Screening testing for polyneuropathy of diabetes or end stage renal disease (ESRD) 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. Please refer to CMS IOM Publication 100-03, Medicare National Coverage Determinations (NCD) Manual, Chapter 1, Part 2, Section 160.23 Sensory Nerve Conduction Threshold Tests (sNCTs).
Examination using portable hand-held devices or devices which are incapable of real-time wave-form display and analysis and incapable of both NCS and EMG testing will be included in the E/M (evaluation and management) service. They will not be paid separately. Examples include: The Axon II or delta fiber analysis testing and/or similarly limited machines with other names.
NCS 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. Diagnostic studies are not accepted 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 payment of the electrodiagnostic services included in this LCD.
It is not expected 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 and these must not be submitted using the electrodiagnostic services in this LCD.
Electromyography
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 EMGs
- 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 LCD 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.
As published in the CMS IOM Publication 100-08, Medicare Program Integrity Manual, Chapter 13, Section 13.5.4, an item or service may be covered by a contractor LCD if it is reasonable and necessary under the Social Security Act Section 1862 (a)(1)(A). Contractors shall determine and describe the circumstances under which the item or service is considered reasonable and necessary.
Provider Qualifications
The Centers for Medicare & Medicaid Services (CMS) Online Manual System, Publication 100-08, Medicare Program Integrity Manual, Chapter 13, Section 13.5.4 outlines that “reasonable and necessary” services are “ordered and furnished by qualified personnel.” Services will be considered medically reasonable and necessary only if performed by appropriately trained providers. It is expected that healthcare professionals who perform electrodiagnostic (ED) 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 NCS and EMG) acceptable to this Contractor in order to provide the proper testing and assessment of the patient's condition and appropriate safety measures. It would be highly unlikely that this training and/or credentialing is possessed by providers other than Neurologists, or Physical Medicine & Rehabilitation physicians.
Guidelines for proper qualifications of health care professionals performing electrodiagnostic evaluations have been developed and published by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) and other medical organizations, including the AMA, the American Academy of Neurology, the American Academy of Physical Medicine and Rehabilitation, American Neurological Association, the American Board of Physical Therapy Specialties (ABPTS) in Clinical Electrophysiology, and the Department of Veterans Affairs.
Physical Therapists Performing EMGs
Program Memorandum Transmittal B-01-28/Change Request 850 sets forth revised levels of physician supervision required for diagnostic tests payable under the Medicare Physician Fee Schedule. Effective July 1, 2001, certain codes were assigned new supervision levels. This implementation date would make it possible for physical therapists to acquire the certification required to perform these services without supervision. A physical therapist who is presently certified by the American Board of Physical Therapy Specialties can perform procedures assigned the new supervision levels without supervision.
Physical therapists who do not possess the ABPTS (American Board of Physical Therapy Specialties) certification by July 1, 2001, may continue to furnish those tests that require the certification if they have been furnishing such diagnostic tests prior to May 1, 2001.
