This A/B MAC expects that all healthcare professionals involved in the
performance of electrodiagnostic (ED) testing, including technicians, will be
appropriately trained and/or credentialed, either by a formal
residency/fellowship program (physicians), certification by a nationally
recognized organization, or by an accredited post-graduate training course
covering anatomy, neurophysiology and forms of EDs, such as nerve conduction
studies (NCS) and electromyography (EMG) that are 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 and rehabilitation physicians.  
  
This A/B MAC also expects that the laboratories in which these studies are
performed meet basic safety and quality standards regarding such issues as
electrical safety and electrical equipment maintenance, needle handling, blood
spill management, etc. Such standards have been established by the American
Association of Neuromuscular and Electrodiagnostic Medicine (AANEM).  
  
The ED evaluation is an extension of the neurologic portion of the history and
physical examination. Both require a detailed knowledge of a patient and
his/her disease. Training in the performance of ED procedures in isolation of
knowledge about clinical diagnostic and management aspects of neuromuscular
diseases may not be adequate for proper performance of an ED evaluation and
correct interpretation of ED 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 ED evaluations have been developed and published by AANEM and other
medical organizations, including the American Medical Association (AMA), the
American Academy of Neurology (AAN), the American Academy of Physical Medicine
and Rehabilitation (AAPMR), American Neurological Association (ANA), the
American Board of Physical Therapy Specialties (ABPTS) in Clinical
Electrophysiology, and the Department of Veterans Affairs (VA).  
  
Both EMGs and NCSs are usually required for a clinical diagnosis of peripheral
nervous system disorders. Performance of 1 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. This A/B MAC
expects that EMGs will be conducted in conjunction with nerve conduction
velocity (NCV) in all testing instances. The only exception would be in
situations where a contraindication to performing an EMG exists. In such
cases, the circumstances for the contraindication should be clearly documented
in the medical record.  
  
It is expected that only an appropriate and sufficient number of ED studies
will be performed to arrive at an appropriate diagnosis. The AANEM has
published a "Model Policy for Needle EMG and NCS" outlining recommendations
pertaining to a reasonable maximum number of studies, per diagnostic
indication, necessary for a practitioner to arrive at a diagnosis in 90% of
patients with that final diagnosis. It is recommended that the ED provider
utilize this table as a guideline when performing testing.  
  
Decisions to continue, modify or conclude an EMG/NCS test 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. As such, the provider performing the testing and/or
interpretation should be present on the site and immediately available during
the 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 2 sites of stimulation, or
between a stimulus and a recording site.  
  
NCS are of 2 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 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.  
  
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 2 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 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 the clinical diagnosis 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.

**A. 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 1 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
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 the 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 a 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 1 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 1 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 such as the pleura, femoral neurovascular bundle, peritoneum,
intraspinal spaces, carotid artery, orbit and brachial plexus. Risk of
infection from acquired immune deficiency syndrome (AIDS), Hepatitis B-E,
Creutzfeldt-Jakob encephalopathy, and hemorrhage from anticoagulation can be
managed by proper techniques.  
  
The ED 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 ED procedures, in isolation
without awareness and ability to diagnose and manage neuromuscular diseases,
is not always adequate for ED consultation. Recognition and experience in the
management of disparate diseases that produce common ED 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 polyneuropathy (CIDP) and multifocal
motor neuropathy. These entities display ED 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 AANEM 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.

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 and sensory
conduction velocity.

c. Mixed -

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 both sensory and motor conduction velocity.

NCS 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 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.  
  
 **B. 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 a
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**  
EMG may be used to optimize the anatomic location of botulinum toxin
injection. It is expected there will be 1 study performed per anatomic
location of injection, if needed.  
  
**Limitations:**  
  
 **Screening testing for polyneuropathy of diabetes or endstage renal disease
(ESRD)** is NOT covered. Testing for the sole purpose of monitoring disease
intensity or treatment efficacy in these 2 conditions is also not covered.  
  
 **Current Perception Threshold/Sensory Nerve Conduction Threshold Test
(sNCT)** - is not covered by Medicare.  
  
 **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 scars 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), 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 and 42 CFR, Sections 410.74, 410.75, 410.76 and 419.22.)
Each practitioner must provide only those services within the scope of
practice for each state.