Medical Policy

Policy Num:      02.001.026 
Policy Name:    Electromyography and Nerve Conduction Studies 
Policy ID:          [02.001.026]  [Ac / B / M+ / P-]  [2.01.95]

Last Review:     September 09, 2024
Next Review:     July 20, 2025
               

Related Policies:
02.001.015 Paraspinal Surface Electromyography to Evaluate and Monitor Back Pain

Electromyography and Nerve Conduction Studies

SUMMARY

Description

Electromyography (EMG) and nerve conduction studies (NCS), also collectively known as an electrodiagnostic assessment, evaluate the electrical functioning of muscles and peripheral nerves. These tests are diagnostic aids for the evaluation of myopathy and peripheral neuropathy by identifying, localizing, and characterizing electrical abnormalities in the skeletal muscles and peripheral nerves.

Summary of Evidence

For individuals with suspected peripheral neuropathy or myopathy who receive electrodiagnostic assessment including EMG and NCS, the evidence includes small observational studies on a few diagnoses, such as carpal tunnel syndrome, radiculopathy, and myopathy. Relevant outcomes are test accuracy, symptoms, functional outcomes, and quality of life. Because electrodiagnostic assessment is considered the criterion standard for evaluating the electrical function of peripheral nerves and muscles, there is no true alternative reference standard against which the sensitivity and specificity of particular EMG/NCS abnormalities for particular clinical disorders can be calculated. Different studies have used different reference standards, such as EMG/NCS measures of healthy individuals or clinical examination results. In general, these tests are considered more specific than sensitive, and normal results do not rule out the disease. The limited evidence has shown a wide range of sensitivities, which are often less than 50%. The specificity is expected to be considerably higher but the data are insufficient to provide precise estimates of either sensitivity or specificity. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

Additional Information

For individuals with suspected peripheral neuropathy or myopathy who receive electrodiagnostic assessment including EMG and NCS, guidelines from specialty societies indicate this use is consistent with generally accepted medical practice.

Objective

The objective of this evidence review is to evaluate whether electromyography and nerve conduction study improves the net health outcome in patients suspected peripheral neuropathy and/or myopathy.

Policy

Electrodiagnostic assessment, consisting of electromyography, nerve conduction study, and related measures, may be considered medically necessary as an adjunct to history, physical exam, and imaging studieswhen the following criteria are met:

• Signs and symptoms of peripheral neuropathy and/or myopathy are present; and
• Definitive diagnosis cannot be made by physical exam and imaging studies alone; and
• Work-up for one or more of the following categories of disease is indicated (see Policy Guidelines section):
  • Compressive neuropathies
  • Nerve root compression
  • Traumatic nerve injuries
  • Generalized and focal neuropathies/myopathies
  • Plexopathies
  • Motor neuron diseases
  • Neuromuscular junction disorders.

A repeat electrodiagnostic assessment may be considered medically necessary when at least one of the following criteria has been met:

• Development of new symptoms or signs suggesting a second diagnosis in a patient who has received an initial diagnosis; or
• Interim progression of disease following an initial test that was inconclusive, such that a repeat test is likely to elicit additional findings; or
• Unexpected change(s) in the course of disease or response to treatment, suggesting that the initial diagnosis may be incorrect and that reexamination is indicated.

Electrodiagnostic assessment, consisting of electromyography, nerve conduction study, and related measures, is considered investigational when the above criteria are not met, including but not limited to, the following situations:

• Screening of asymptomatic individuals
• Serial assessments to evaluate progression of disease in a patient with a previously diagnosed neuropathy or myopathy
• Evaluation of treatment response in a patient with previously diagnosed neuropathy or myopathy
• Evaluation of disease severity in a patient with previously diagnosed neuropathy or myopathy.

Policy Guidelines

The following list gives specific diagnoses, according to categories of testing listed in the policy statement, for which electromyography (EMG) and nerve conduction study (NCS) generally provide useful information in confirming or excluding the diagnosis, above that provided by clinical examination and imaging alone. The list includes the most common diagnoses for testing but is not exhaustive. There may also be less common disorders for which EMG/NCS provide useful diagnostic information.

• Compressive neuropathies
  • Carpal tunnel syndrome
  • Ulnar nerve entrapment
  • Thoracic outlet syndrome
  • Tarsal tunnel syndrome
  • Other peripheral nerve entrapments
• Nerve root compression (when physical exam and magnetic resonance imaging are inconclusive):
  • Cervical nerve root compression
  • Thoracic nerve root compression
  • Lumbosacral nerve root compression
• Traumatic nerve injuries
• Generalized and focal polyneuropathies:
  • Diabetic neuropathy
  • Uremic neuropathy
  • Alcohol-related neuropathy
  • Hereditary neuropathies:
    • Charcot-Marie-Tooth
    • Other hereditary neuropathies
  • Demyelinating polyneuropathies:
    • Guillain-Barré syndrome (acute)
    • Chronic idiopathic demyelinating polyneuropathy
• Generalized myopathies:
  • Polymyositis
  • Dermatomyositis
  • Muscular dystrophies
• Plexopathies:
  • Cervical plexopathy
  • Brachial plexopathy
  • Lumbosacral plexopathy
• Motor neuron diseases:
  • Amyotrophic lateral sclerosis
  • Progressive muscular atrophy
  • Progressive bulbar palsy
  • Pseudobulbar palsy
  • Primary lateral sclerosis
• Neuromuscular junction disorders:
  • Myasthenia gravis
  • Myasthenic syndrome
  • Lambert-Eaton syndrome.

The following recommendations on the number of repeat services are reproduced from the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) position statement (2023 ). These estimates do not represent absolute maximums for all individuals; they are defined by AANEM as being sufficient to make a diagnosis in at least 90% of individuals with that particular diagnosis. Therefore, there may be a small percentage of cases that require a greater number of tests than specified in Table PG1.

Table PG1. Recommended Maximum Number of Electrodiagnostic Studies for Specific Diagnoses

Adapted from American Association of Electrodiagnostic Medicine (2023 )
EMG: electromyography; NCS: nerve conduction study; RNS: repetitive nerve stimulation.

The AANEM position statement (2023 ) also included minimum standards for a lab performing electrodiagnostic evaluation:

• The tests should be medically indicated.

• The tests should be performed using equipment that provides an assessment of all parameters of the recorded signals. Equipment designed for screening purposes is not acceptable.

• The number of tests performed should be the minimum needed to establish an accurate diagnosis.

• The NCS should be performed by a physician or by a trained individual under the direct supervision of a physician.

• A trained physician must perform the needle EMG exam.

• One physician should perform and supervise all components of the electrodiagnostic testing and all testing should occur on the same date of service.

• The NCS and needle EMG exam results should be integrated into a unifying report and diagnostic impression.

Coding

See the Codes table for details.

Benefit Application

BlueCard/National Account Issues

State or federal mandates (eg, Federal Employee Program) may dictate that certain U.S. Food and Drug Administration-approved devices, drugs, or biologics may not be considered investigational, and thus these devices may be assessed only by their medical necessity.

Benefits are determined by the group contract, member benefit booklet, and/or individual subscriber certificate in effect at the time services were rendered. Benefit products or negotiated coverages may have all or some of the services discussed in this medical policy excluded from their coverage.

Background

Electrodiagnostic ASSESSMENT

Electromyography (EMG) and nerve conduction study (NCS) are used as adjuncts to clinical evaluation of myopathy and peripheral neuropathy.^1,These tests intend to evaluate the integrity and electrical function of muscles and peripheral nerves. They are performed when there is clinical suspicion for a myopathic or neuropathic process and when clinical examination and standard laboratory testing cannot make a definitive diagnosis.

Test results do not generally provide a specific diagnosis. Rather, they provide additional information that assists physicians in characterizing a clinical syndrome. EMG/NCS may be useful when there is no clear etiology when symptoms are severe or rapidly progressing, or when symptoms are atypical (eg, asymmetrical, acute onset, or appearing to be autonomic).

According to the American Association of Neuromuscular & Electrodiagnostic Medicine (2023 ) , electrodiagnostic assessment has the following goals^2,:

1."Identify normal and abnormal nerve, muscle, motor or sensory neuron, and NMJ [neuromuscular junction] functioning.

2.Localize region(s) of abnormal function.

3.Define the type of abnormal function.

4.Determine the distribution of abnormalities.

5.Determine the severity of abnormalities.

6.Estimate the date of a specific nerve injury.

7.Estimate the duration of the disease.

8.Determine the progression of abnormalities or recovery from abnormal function.

9.Aid in diagnosis and prognosis of the disease.

10.Aid in selecting treatment options.

11.Aid in following response to treatment by providing objective evidence of change in NM [neuromuscular] function.

12.Localize correct locations for injections of intramuscular agents…."

Components of the electrodiagnostic exam may include needle EMG, NCS, repetitive nerve stimulation study, somatosensory evoked potentials, and blink reflexes.

Electromyography

Needle Electromyography

An EMG needle electrode is inserted into selected muscles, chosen by the examining physician depending on the differential diagnosis and other information available during the exam.^2, The response of the muscle to electrical stimulation is recorded. Three components are evaluated: observation at rest, action potential with minimal voluntary contraction, and action potential with maximum contraction.^3,

Single Fiber Electromyography

In single-fiber EMG, a needle electrode records the response of a single muscle fiber. This test can evaluate "jitter," which is defined as the variability in the time between activation of the nerve and generation of the muscle action potential. Single fiber EMG can also measure fiber density, which is defined as the mean number of muscle fibers for 1 motor unit. .^2,

Nerve Conduction Studies

In NCS, both motor and sensory nerve conduction are assessed. For motor conduction, electrical stimuli are delivered along various points on the nerve, and the electrical response is recorded from the appropriate muscle. For sensory conduction, electrical stimuli are delivered to 1 point on the nerve, and the response is recorded at a distal point on the nerve. Parameters recorded include velocity, amplitude, latency, and configuration.^2,

Late Wave Responses

Late waves are a complement to the basic NCS and evaluate the functioning of the proximal segment of peripheral nerves, such as the nerve root and the anterior horn cells. There are 2 types of late responses: the H-reflex and the F wave.

The H-reflex is elicited by stimulating the posterior tibial nerve and measuring the response in the gastrocnemius muscle. It is analogous to the ankle reflex and can be prolonged by radiculopathy at S1 or by peripheral neuropathy.^3,

The F wave is assessed by supramaximal stimulation of the distal nerve and can help estimate the conduction velocity in the proximal portion of the nerve.^3, This will provide information on the presence of proximal nerve abnormalities, such as radiculopathy or plexopathy.

Repetitive Nerve Stimulation

Repetitive nerve stimulation studies evaluate the integrity and function of the neuromuscular junction. The test involves stimulating a nerve repetitively at variable rates and recording the response of the corresponding muscle(s).^3, Disorders of the neuromuscular junction will show a diminished muscular response to repetitive stimulation.

Somatosensory Evoked Potentials

Somatosensory evoked potentials evaluate nerve conduction in various sensory fibers of both the peripheral and central nervous system and test the integrity and function of these nerve pathways.^2, They are typically used to assess nerve conduction in the spinal cord and other central pathways that cannot be assessed by standard NCS.

Blink Reflexes

The blink reflexes, which are analogs of the corneal reflex, are evaluated by stimulating the orbicularis oculi muscle at the lower eyelid. They are used to localize lesions in the fifth or seventh cranial nerves.^2,

Differential Diagnosis

The specific components of an individual test are not standardized. Rather, a differential diagnosis is developed by the treating physician, and/or the clinician performing the test, and the specific components of the exam are determined by the disorders being considered in the differential. Also, the differential diagnosis may be modified during the exam to reflect initial findings, and this may also influence the specific components included in the final analysis.^2,

Regulatory Status

EMG/NCS measure nerve and muscle function and may be indicated when evaluating limb pain, weakness related to possible spinal nerve compression, or other neurologic injury or disorder. A number of electromyographic devices have received marketing clearance by the U.S. Food and Drug Administration (FDA). Several devices are listed in Table 1.

Table 1. Electromyographic Devices Approved by FDA

FDA: U.S. Food and Drug Administration.

Rationale

This evidence review was created in August 2014 with a search of the PubMed database. The most recent literature update was performed through April 26, 2024.

Evidence reviews assess whether a medical test is clinically useful. A useful test provides information to make a clinical management decision that improves the net health outcome. That is, the balance of benefits and harms is better when the test is used to manage the condition than when another test or no test is used to manage the condition.

The first step in assessing a medical test is to formulate the clinical context and purpose of the test. The test must be technically reliable, clinically valid, and clinically useful for that purpose. Evidence reviews assess the evidence on whether a test is clinically valid and clinically useful. Technical reliability is outside the scope of these reviews, and credible information on technical reliability is available from other sources.

Promotion of greater diversity and inclusion in clinical research of historically marginalized groups (e.g., People of Color [African-American, Asian, Black, Latino and Native American]; LGBTQIA (Lesbian, Gay, Bisexual, Transgender, Queer, Intersex, Asexual); Women; and People with Disabilities [Physical and Invisible]) allows policy populations to be more reflective of and findings more applicable to our diverse members. While we also strive to use inclusive language related to these groups in our policies, use of gender-specific nouns (e.g., women, men, sisters, etc.) will continue when reflective of language used in publications describing study populations.

Population Reference No. 1

Suspected Peripheral Neuropathy or Myopathy

Clinical Context and Test Purpose

The purpose of electrodiagnostic testing in patients who have suspected peripheral neuropathy or myopathy is to aid in the diagnosis of disease and to guide treatment.

The following PICO was used to select literature to inform this review.

Populations

The relevant population of interest is individuals who have suspected peripheral neuropathy or myopathy. The population falls into the broad categories of compressive neuropathies, nerve root compression, traumatic nerve injuries, generalized and focal neuropathies and myopathies, plexopathy, motor neuron disease, and neuromuscular junction disorders.

Interventions

The relevant intervention of interest is electrodiagnostic assessment, consisting of electromyography (EMG), nerve conduction studies (NCS), and related measures, to evaluate the integrity and electrical function of muscles and peripheral nerves.

Comparators

The relevant comparators of interest are standard clinical diagnostic tools and practices currently being used to inform decisions on the diagnosis of suspected peripheral neuropathy or myopathy: history, physical exam, laboratory studies, and imaging studies when appropriate.

Outcomes

The clinical utility would be supported by a reduction in pain or other symptoms and improvement in functional measures and quality of life measures specific to the condition. Alternatively, evidence of clinical utility may be derived from a chain of evidence linking improvement in diagnostic accuracy with improvements in treatment guided by a correct diagnosis.

Beneficial outcomes include aiding in the diagnosis of disease and guiding treatment that results in a reduction in symptoms such as pain, numbness, or tingling, and improvements in functional outcomes of muscle strength and quality of life measures.

If patients are diagnosed with peripheral neuropathies or myopathies based on inaccurate EMG or NCS results, unnecessary treatment may be initiated when watchful waiting may be the more appropriate management approach.

Study Selection Criteria

Methodologically credible studies were selected using the following principles:

• To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for randomized controlled trials;

• In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.

• To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
•  Studies with duplicative or overlapping populations were excluded.

Clinically Valid

A test must detect the presence or absence of a condition, the risk of developing a condition in the future, or treatment response (beneficial or adverse).

In general, EMG and NCS are considered the criterion standards for establishing abnormalities of the electrical system of nerves and muscles, and hence there is a lack of a true reference standard.

Below are examples of representative literature on clinical validity.

Carpal Tunnel Syndrome

Systematic Reviews

A 2016 clinical practice guideline on the management of carpal tunnel syndrome (CTS) was published by the American Academy of Orthopaedic Surgeons (AAOS), which included a systematic review of the literature as part of its guideline development process.^4,The guideline found moderate evidence (evidence from 2 or more moderate quality studies) to support that "diagnostic questionnaires and/or electrodiagnosis studies could be used to aid the diagnosis of carpal tunnel syndrome." Furthermore, AAOS noted that the evaluation of electrodiagnostic tests requires a reference standard against which the performance of the diagnostic test can be compared, but there is currently no consensus supporting a single diagnostic tool as a reference standard for CTS.

Observational Studies

Two studies identified calculated the sensitivity and specificity of EMG and NCS.^5,6, One study used Carpal Tunnel Syndrome-6 (CTS-6) test results as a comparator  ^5,  and the other used mean values of normal controls as comparators.^6,

Fowler et al (2014) evaluated the diagnostic accuracy of electrodiagnostic testing and ultrasound for diagnosing CTS, using validated clinical diagnostic criteria as the reference standard ( Table 2).^5, The reference standard was a validated clinical diagnostic tool (CTS-6 score). The electrodiagnostic exam was considered positive when there was a distal motor latency of 4.2 ms or more or a distal sensory latency of 3.2 ms or more. Sensitivity, specificity, positive predictive value, and negative predictive values were calculated ( Table 3). This study was limited by the imperfect nature of the reference standard (CTS-6 is not a true criterion standard for diagnosis) and suboptimal sensitivity.

Chang et al (2006) examined the sensitivity and specificity of various motor and sensory NCS parameters in 280 consecutive patients (360 hands) with suspected CTS and 150 normal controls (see Table 2).^6, In the 360 hands with suspected CTS, 328 (91%) had at least 1 electrodiagnostic abnormality and 9% had normal exams. For individual NCS measures, the sensitivity ranged from 73% to 87% and the specificity ranged from 97% to 99% (see Table 3). Among the 150 controls, NCS readings were mostly within the normal range, with a few sensory and motor findings falling in the abnormal range.

Table 2. Summary of Nonrandomized Study Characteristics for Carpal Tunnel Syndrome

CTS: carpal tunnel syndrome; CTS-6: Carpal Tunnel Syndrome-6; D1: thumb; D2: index finger; D4: ring finger; DL: distal latency; EMG: electromyography; M-R: median-radial sensory latency difference; M-U: median-ulnar sensory latency difference; NCS: nerve conduction studies; NR: not reported; W-P MCV: wrist-palm motor conduction velocity; W-P SCT: wrist-palm sensory conduction time; W-P SCV: wrist-palm sensory conduction velocity.

Table 3. Summary of Nonrandomized Study Results for Carpal Tunnel Syndrome

CI: confidence interval; D1: thumb; D2: index finger; D4: ring finger; DL: distal latency; EMG: electromyography; M-R: median-radial sensory latency difference; M-U: median-ulnar sensory latency difference; NPV: negative predictive value; NR: not reported; PPV: positive predictive value; SDL: sensory distal latency; US: ultrasound; W-P MCV: wrist-palm motor conduction velocity; W-P SCT: wrist-palm sensory conduction time; W-P SCV: wrist-palm sensory conduction velocity.a Compared with Carpal Tunnel Syndrome-6 test resultsb Compared with mean values of normal controls ± 2.5 standard deviations.

Two studies calculated correlations between EMG and NCS with other measures rather than calculating sensitivity and sensitivity.^7,8, Homan et al (1999) evaluated the association among clinical symptoms, physical exam, and electrodiagnostic studies in 824 individuals with suspected work-related CTS from 6 job facilities.^7, A total of 449 individuals had at least 1 positive finding on any exam. Of these, only 3% had positive findings on all 3 domains (symptoms, physical exam, NCS). Overall, there was poor agreement across the 3 measures (κ range, 0-0.18). Tulipan et al (2017) retrospectively studied 50 patients presenting for CTS treatment.^8, Patients completed the Disabilities of the Arm, Shoulder, and Hand questionnaire and the 12-Item Short-Form Health Survey. There were no significant correlations between Disabilities of the Arm, Shoulder, and Hand questionnaire and the 12-Item Short-Form Health Survey scores with median motor or sensory latency measures.

Lumbar Radiculopathy

The North American Spine Society published evidence-based guidelines on the diagnosis and treatment of lumbar radiculopathy in 2012.^9, These guidelines were based on a systematic review of the literature identifying studies of diagnostic techniques. Five studies on the diagnostic accuracy of electrophysiologic tests were discussed; 2 case-control studies and 3 case series. Sensitivities for various EMG and NCS parameters ranged from 17% to 65%. In the 2 studies that included a normal control group, specificity for EMG abnormalities was 100% and 87%, respectively.

After the North American Spine Society publication, Mondelli et al (2013) evaluated EMG findings in patients with lumbosacral radiculopathy and herniated disc. The diagnosis of radiculopathy due to herniated disc was based on a combination of clinical symptoms and magnetic resonance imaging results.^10, A total of 108 consecutive patients with monoradiculopathy at L4, L5, or S1 were enrolled from 4 electrodiagnostic laboratories. At least 1 EMG abnormality was recorded in 42% of patients, with the most common being a delay in the F wave minimum latency. EMG abnormalities could be predicted on multivariate regression by the presence of clinical symptoms, including muscle weakness, abnormal reflexes, and the presence of paresthesias.

Peroneal Neuropathy

The Association of Neuromuscular & Electrodiagnostic Medicine (AANEM; 2005) published an evidence review in support of practice parameters on the utility of electrodiagnostic testing for patients with suspected peroneal neuropathy.^11, Reviewers performed a systematic review of the literature through July 2003 on the utility of EMG/NCS. Eleven studies met inclusion criteria, 4 of which were prospective. Eight studies described the use of motor NCS, 8 described the use of sensory NCS, and 5 described the use of needle EMG. Strength of evidence assessments considered the studies to be class III or IV level of evidence. The strongest study design (n=4 studies) used a cohort of patients with clinically diagnosed peroneal neuropathy and reported the sensitivity of EMG/NCS. Sensitivity rates for EMG/NCS varied widely by the type of measure, and the specific area tested, ranging from 19% to 91%. Specificity was not reported. Reviewers concluded that certain NCS parameters were useful for diagnosing peroneal neuropathy and proposed a specific testing strategy to maximize sensitivity. EMG was not found to be useful for confirming the diagnosis of peroneal neuropathy but was helpful in excluding alternative diagnoses.

Pediatric Myopathy

Evidence was identified comparing the accuracy of EMG and NCS with muscle biopsy in children with a suspected myopathy. The intent of this line of research is to evaluate whether a diagnosis can be made with certainty using clinical exam plus EMG or NCS, thereby avoiding muscle biopsy.

Rabie et al (2007) compared the diagnostic accuracy of EMG with muscle biopsy in children who had neuropathies or myopathies.^12, The authors retrospectively identified 27 children between the ages of 6 days to 16 years who had EMG studies, a muscle biopsy, and a final diagnosis assigned by the treating physician(s). Final diagnoses were congenital myopathy (5 patients), nonspecific myopathy (6 patients), congenital myasthenic syndrome (3 patients), juvenile myasthenia gravis (1 patient), arthrogryposis multiplex congenital (2 patients), hereditary motor and sensory neuropathy (1 patient), bilateral peroneal neuropathies (1 patient), and normal (8 patients). In general, the sensitivity of EMG for detecting abnormalities implied by the final diagnosis was low. For example, the sensitivity of EMG for detecting myopathic motor unit potentials in any myopathy was 47% (7/15), and the sensitivity for congenital myopathies was 40% (2/5). The sensitivity was especially low for patients younger than 2 years of age compared with older children, but this comparison was limited by small numbers of patients in each group.

Ghosh and Sorenson (2014) performed a retrospective chart review of 227 patients who received EMG studies between 2009 and 2013.^13, Seventy-two (32%) patients also received muscle biopsy, and these 72 patients constituted the study group. The criterion standard was myopathy confirmed by muscle biopsy or by genetic testing. The overall sensitivity of EMG was 91%, with the most commonly missed diagnosis being metabolic myopathy. The overall specificity was 67%, which is lower than most other reports of specificity, raises concern whether the sensitivity of muscle biopsy is lower than expected, thus resulting in EMG results that are true-positives being classified as false-positives.

Clinically Useful

A test is clinically useful if the use of the results informs management decisions that improve the net health outcome of care. The net health outcome can be improved if patients receive correct therapy, or more effective therapy, or avoid unnecessary therapy, or avoid unnecessary testing.

To determine the clinical utility of EMG and NCS, studies need to evaluate the use of EMG and NCS testing to guide treatment decisions and then report health outcomes following the treatments. No studies of this type were identified.

Direct Evidence

Direct evidence of clinical utility is provided by studies that have compared health outcomes for patients managed with and without the test. Because these are intervention studies, the preferred evidence would be from randomized controlled trials.

Chain of Evidence

Indirect evidence on clinical utility rests on clinical validity. If the evidence is insufficient to demonstrate test performance, no inferences can be made about clinical utility.

The lack of high-quality evidence on the clinical utility of EMG and NCS is reflected by the lack of evidence-based guidelines. Most existing guidelines rely on expert consensus. This section reviews guidelines from 3 organizations, focusing on the methods of the development process, and the rigor of evidence review. The 3 organizations are AANEM, AAOS (CTS only), and the American Academy of Neurology (AAN). The Practice Guidelines and Position Statements discussion in the Supplemental Information section summarizes the recommendations of the guidelines.

The AANEM (2023) made recommendations on electrodiagnostic medicine based on the consensus of 43 experts in the field of electrodiagnostic medicine.^2, The AANEM provided no information on the selection process for these individuals but noted that they were neurologists or physiatrists representing diverse practice types and locations.

The AAOS (2016) published practice guidelines on the diagnosis and treatment of CTS.^4, The authors included both practicing physicians, as clinical experts, and methodologists who were free of potential conflicts of interest. The guideline was developed by creating structured PICO questions, which directed the systematic literature search. Upon completion of the systematic reviews, the physician experts and methodologists evaluated and integrated all material to develop the final recommendations, which were based only on the best available evidence for any given outcome.

The AAN (2004) published a position statement on electrodiagnostic assessment.^14, According to AAN, "A position statement is a concise explanation of AAN's position on a certain issue that includes background information and the rationale behind the Academy's position. The position statement, generally not exceeding 1000 words, is in-depth and must reference all supporting evidence." The AAN document on EMG did not provide a literature review or references to accompany recommendations.

Section Summary: Suspected Peripheral Neuropathy or Myopathy

EMG/NCS testing is generally considered to be specific but not sensitive. However, the evidence on the diagnostic accuracy of EMG and NCS is poor, in part because of the lack of a true reference standard. In the scattered evidence identified, sensitivity was often less than 50%, and specificity was most commonly in the range of 80% to 100%. Because of the small quantity and poor quality of the evidence, precise estimates of sensitivity and specificity for specific disorders cannot be made. No studies were identified that evaluated clinical utility. Existing guidelines from prominent major specialty societies in electrodiagnostic medicine consist primarily of expert consensus. For guidelines based on an evidence review, such as the AAOS guidelines, the evidence was not sufficient to make evidence-based recommendations. All 3 societies have included general recommendations on the utility of electrodiagnostic testing as an adjunct to clinical diagnosis for myopathic and neuropathic disorders. Guidelines supporting these recommendations do not offer detailed indications for patient testing by diagnosis.

Summary of Evidence

For individuals with suspected peripheral neuropathy or myopathy who receive electrodiagnostic assessment including EMG and NCS, the evidence includes small observational studies on a few diagnoses, such as CTS, radiculopathy, and myopathy. Relevant outcomes are test accuracy, symptoms, functional outcomes, and quality of life. Because electrodiagnostic assessment is considered the criterion standard for evaluating the electrical function of peripheral nerves and muscles, there is no true alternative reference standard against which the sensitivity and specificity of particular EMG/NCS abnormalities for particular clinical disorders can be calculated. Different studies have used different reference standards, such as EMG/NCS measures of healthy individuals or clinical examination results. In general, these tests are considered more specific than sensitive, and normal results do not rule out the disease. The limited evidence has shown a wide range of sensitivities, which are often less than 50%. The specificity is expected to be considerably higher but the data are insufficient to provide precise estimates of either sensitivity or specificity. The evidence is insufficient to determine that the technology results in an improvement in the health net outcome.

Supplemental Information

The purpose of the following information is to provide reference material. Inclusion does not imply endorsement or alignment with the evidence review conclusions.

PRACTICE GUIDELINES AND POSITION STATEMENTS

Guidelines or position statements will be considered for inclusion in ‘Supplemental Information' if they were issued by, or jointly by, a US professional society, an international society with US representation, or National Institute for Health and Care Excellence (NICE). Priority will be given to guidelines that are informed by a systematic review, include strength of evidence ratings, and include a description of management of conflict of interest.

American Association of Neuromuscular & Electrodiagnostic Medicine

The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) has published several position statements on the recommended coverage policy for electromyography (EMG) and nerve conduction study (NCS).

The first iteration of the recommended policy for electrodiagnostic medicine was initially published in 1997. Since then, there have been several updates, most recently in 2023.^2, This specific position statement provides detailed information on appropriate coding and billing (see Policy Guidelines). They also regularly update their model policy for EMG and NCS (most recently updated in 2022), which outlines AANEM's key positions and recommendations.^15, Needle EMG and NCS testing is recommended for the following indications:

1. "Focal neuropathies, entrapment neuropathies, or compressive lesions/syndromes such as carpal tunnel syndrome, ulnar neuropathies, or root lesions, for localization.

2. Traumatic nerve lesions, for diagnosis and prognosis.

3. Generalized neuropathies, such as metabolic (ie diabetic, uremic, etc), toxic, hereditary, or immune-mediated.

4. This document also listed situations where electrodiagnostic assessment is considered investigational.

5. Neuromuscular junction disorders such as myasthenia gravis, myasthenic syndrome, or botulism.

6. Symptom-based presentations such as ‘pain in limb', weakness, cramping/twitching, disturbance of skin sensation or ‘paresthesia' when appropriate pre-test evaluations are inconclusive and the clinical assessment unequivocally supports the need for the study.

7. Radiculopathy-cervical, thoracic, lumbosacral.

8. Plexopathy - including idiopathic, traumatic, inflammatory or infiltrative, radiation-induced.

9. Myopathy - including inflammatory myopathies like polymyositis and dermatomyositis, myotonic disorders, and congenital myopathies.

10. Precise muscle location for injections such as botulinum toxin, phenol, etc.  

• In 2005, the AANEM published practice parameters on the utility of EMG/NCS for the diagnosis of peroneal neuropathy.^11, This evidence-based review focused on whether EMG/NCS are useful in diagnosing peroneal neuropathy and/or in determining prognosis. Table 4 lists recommendations AANEM deemed "possibly useful, to make or confirm" a diagnosis. This guideline was most recently reaffirmed in October 2020. 

Table 4. Guidelines on Diagnosis of Peroneal Neuropathy

AT: anterior tibialis; COE: class of evidence; EDB: extensor digitorum brevis; EDX: electrodiagnostic; EMG: electromyography; LOR: level of recommendation; NCS: nerve conduction study.

A 2003 consensus statement on diagnosing multifocal motor neuropathy from AANEM^16, has stated: "Multifocal motor neuropathy is a diagnosis that is based on recognition of a characteristic pattern of clinical symptoms, clinical signs, and electrodiagnostic findings. The fundamental electrodiagnostic finding is partial conduction block of motor axons."

In 2018, the AANEM published a policy statement on the use of EMG for distal symmetric polyneuropathy.^17, The statement described 5 situations in which EMG would be beneficial for patients with distal symmetric polyneuropathy: "1) determining primary and alternative diagnoses; 2) determining severity, duration, and prognosis of disease; 3) evaluating risk of associated problems; 4) determining the effect of medications; and 5) evaluating the effect of toxic exposures."

In 2020, the AANEM issued a consensus statement on the utility and practice of electrodiagnostic (EDX) testing in the pediatric population.^18, The following conclusions were made:

• "…certain categories of inherited diseases such as muscular dystrophy and SMA [spinal muscular atrophy] do not routinely require EMG as part of the diagnostic evaluation. However, in atypical cases EDX testing can provide critical assistance with narrowing of the differential diagnosis."

• "…techniques and practice for this important diagnostic test modality will continue to evolve in the future."

• "EDX testing in children will continue to complement other diagnostic test modalities such as serum tests, muscle biopsy, imaging, and genetic testing."

American Academy of Orthopaedic Surgeons

In 2016, the American Academy of Orthopaedic Surgeons (AAOS)published updated guidelines on the management of carpal tunnel syndrome.^4, Table 5 lists relevant recommendations to this policy.

Table 5. Guidelines on Diagnosis of Carpal Tunnel Syndrome

aEvidence from 2 or more "Low" strength studies with consistent findings or evidence from a single study for recommending for or against the intervention or diagnostic test or the evidence is insufficient or conflicting and does not allow a recommendation for or against the intervention.bEvidence from 2 or more "moderate" quality studies with consistent findings, or evidence from a single "high" quality study for recommending for or against the intervention.

American Academy of Neurology

In 2004, the American Academy of Neurology (AAN) approved a position statement, endorsed by the AANEM and the American Academy of Physical Medicine & Rehabilitation, on diagnostic electromyography that included the following^14,:

• "Clinical needle electromyography (EMG) is an invasive medical procedure during which the physician inserts an electrode into a patient's muscles to diagnose the cause of muscle weakness. Needle EMG allows physicians to distinguish a wide range of conditions, from carpal tunnel syndrome to ALS (Lou Gehrig disease).

• Needle EMG is also an integral component of the neurological examination that cannot be separated from the physician's evaluation of the patient. The test is dynamic and depends upon the visual, tactile, and audio observations of the examiner. There is no way for physicians to independently verify the accuracy of reports performed by non-physicians.

• Misdiagnosis can mean delayed or inappropriate treatment (including surgery) and diminished quality of life. Because needle EMG is strictly diagnostic, the procedure clearly and exclusively falls within the practice of medicine."

North American Spine Society

In 2012, the North American Spine Society published guidelines on the diagnosis and treatment of lumbar disc herniation.^9, This document made the following statement about the use of EMG/NCS for diagnosis of lumbar disc herniation:

"Electromyography, nerve conduction studies and F-waves are suggested to have limited utility in the diagnosis of lumbar disc herniation with radiculopathy. H-reflexes can be helpful in the diagnosis of an S1 radiculopathy, though are not specific to the diagnosis of lumbar disc herniation. (Grade of Recommendation: B)"

U.S. Preventive Services Task Force Recommendations

Not applicable.

Medicare National Coverage

Sensory nerve conduction threshold tests are distinct from "assessment of nerve conduction velocity, amplitude and latency" and from "short-latency somatosensory evoked potentials."

In 2004, the Centers for Medicare & Medicaid affirmed its 2002 noncoverage policy, concluding: "that the use of any type of sNCT [sensory nerve conduction threshold test] device (e.g., ‘current output' type device used to perform current perception threshold [CPT], pain perception threshold [PPT], or pain tolerance threshold [PTT] testing or ‘voltage input' type device used for voltage-nerve conduction threshold (v-NCT) testing) to diagnose sensory neuropathies or radiculopathies in Medicare beneficiaries is not reasonable and necessary." "^19,

Ongoing and Unpublished Clinical Trials

A search of ClinicalTrials.gov in   April 2024   did not identify any ongoing or unpublished trials that would likely influence this review.

References

1. Gooch CL, Weimer LH. The electrodiagnosis of neuropathy: basic principles and common pitfalls. Neurol Clin. Feb 2007; 25(1): 1-28. PMID 17324718
2. American Association of Neuromuscular & Electrodiagnostic Medicine. Recommended policy for electrodiagnostic medicine. 2023. https://www.aanem.org/clinical-practice-resources/position-statements/position-statement/recommended-policy-for-electrodiagnostic-medicine. Accessed April 26, 2024.
3. Lee DH, Claussen GC, Oh S. Clinical nerve conduction and needle electromyography studies. J Am Acad Orthop Surg. 2004; 12(4): 276-87. PMID 15473679
4. American Academy of Orthopaedic Surgeons. Management of Carpal Tunnel Syndrome Evidence-Based Clinical Practice Guideline. February 29, 2016; https://www.aaos.org/globalassets/quality-and-practice-resources/carpal-tunnel/cts_cpg_4-25-19.pdf. Accessed April 26, 2024.
5. Fowler JR, Munsch M, Tosti R, et al. Comparison of ultrasound and electrodiagnostic testing for diagnosis of carpal tunnel syndrome: study using a validated clinical tool as the reference standard. J Bone Joint Surg Am. Sep 03 2014; 96(17): e148. PMID 25187592
6. Chang MH, Liu LH, Lee YC, et al. Comparison of sensitivity of transcarpal median motor conduction velocity and conventional conduction techniques in electrodiagnosis of carpal tunnel syndrome. Clin Neurophysiol. May 2006; 117(5): 984-91. PMID 16551510
7. Homan MM, Franzblau A, Werner RA, et al. Agreement between symptom surveys, physical examination procedures and electrodiagnostic findings for the carpal tunnel syndrome. Scand J Work Environ Health. Apr 1999; 25(2): 115-24. PMID 10360466
8. Tulipan JE, Lutsky KF, Maltenfort MG, et al. Patient-Reported Disability Measures Do Not Correlate with Electrodiagnostic Severity in Carpal Tunnel Syndrome. Plast Reconstr Surg Glob Open. Aug 2017; 5(8): e1440. PMID 28894661
9. North American Spine Society (NASS) Evidence-Based Clinical Guidelines Committee. Evidence-Based Clinical Guidelines for Multidisciplinary Spine Care. 2012; https://www.spine.org/Documents/ResearchClinicalCare/Guidelines/LumbarDiscHerniation.pdf. Accessed April 26, 2024.
10. Mondelli M, Aretini A, Arrigucci U, et al. Clinical findings and electrodiagnostic testing in 108 consecutive cases of lumbosacral radiculopathy due to herniated disc. Neurophysiol Clin. Oct 2013; 43(4): 205-15. PMID 24094906
11. Marciniak C, Armon C, Wilson J, et al. Practice parameter: utility of electrodiagnostic techniques in evaluating patients with suspected peroneal neuropathy: an evidence-based review. Muscle Nerve. Apr 2005; 31(4): 520-7. PMID 15768387
12. Rabie M, Jossiphov J, Nevo Y. Electromyography (EMG) accuracy compared to muscle biopsy in childhood. J Child Neurol. Jul 2007; 22(7): 803-8. PMID 17715269
13. Ghosh PS, Sorenson EJ. Diagnostic yield of electromyography in children with myopathic disorders. Pediatr Neurol. Aug 2014; 51(2): 215-9. PMID 24950662
14. American Academy of Neurology (AAN). Position Statement: diagnostic electromyography in the practice of medicine. 2004; https://www.aan.com/advocacy/diagnostic-electromyography-position-statement. Accessed April 26, 2024.
15. American Association of Neuromuscular & Electrodiagnostic Medicine. Model Policy for Needle Electromyography and Nerve Conduction Studies. 2022; https://www.aanem.org/clinical-practice-resources/position-statements/position-statement/model-policy-for-nerve-conduction-studies-and-needle-electromyography. Accessed April 25, 2024.
16. Olney RK, Lewis RA, Putnam TD, et al. Consensus criteria for the diagnosis of multifocal motor neuropathy. Muscle Nerve. Jan 2003; 27(1): 117-21. PMID 12508306
17. AANEM policy statement on electrodiagnosis for distal symmetric polyneuropathy. Muscle Nerve. Feb 2018; 57(2): 337-339. PMID 29178499
18. Kang PB, McMillan HJ, Kuntz NL, et al. Utility and practice of electrodiagnostic testing in the pediatric population: An AANEM consensus statement. Muscle Nerve. Feb 2020; 61(2): 143-155. PMID 31724199
19. Centers for Medicare & Medicaid Services. National Coverage Determination (NCD) for Sensory Nerve Conduction Threshold Tests (sNCTs) (160.23). 2004; https://www.cms.gov/medicare-coverage-database/details/ncd-details.aspx?NCDId=270&ncdver=2&CoverageSelection=National&KeyWord=Sensory+Nerve+Conduction+Threshold+Tests. Accessed April 26, 2024.

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