Nerve Conduction Studies and Electromyography

This LCD supplements but does not replace, modify or supersede existing Medicare applicable National Coverage Determinations (NCDs) or payment policy rules and regulations for nerve conduction studies and electromyography. Federal statute and subsequent Medicare regulations regarding provision and payment for medical services are lengthy. They are not repeated in this LCD. Neither Medicare payment policy rules nor this LCD replace, modify or supersede applicable state statutes regarding medical practice or other health practice professions acts, definitions and/or scopes of practice. All providers who report services for Medicare payment must fully understand and follow all existing laws, regulations and rules for Medicare payment for nerve conduction studies and electromyography and must properly submit only valid claims for them. Please review and understand them and apply the medical necessity provisions in the policy within the context of the manual rules. Relevant CMS manual instructions and policies may be found in the following Internet-Only Manuals (IOMs) published on the CMS Web site:

IOM Citations:

• CMS IOM Publication 100-02, Medicare Benefit Policy Manual,
• Chapter 15, Section 80 Requirements for Diagnostic X-Ray, Diagnostic Laboratory, and Other Diagnostic Tests
• CMS IOM Publication 100-03, Medicare National Coverage Determinations (NCD) Manual,
• Chapter 1, Part 2, Section 160.23 Sensory Nerve Conduction Threshold Tests (sNCTs)
• CMS IOM Publication 100-08, Medicare Program Integrity Manual,
• Chapter 13, Section 13.5.4 Reasonable and Necessary Provision in an LCD

Social Security Act (Title XVIII) Standard References:

• Title XVIII of the Social Security Act, Section 1833(e) states that no payment shall be made to any provider for any claim that lacks the necessary information to process the claim.
• Title XVIII of the Social Security Act, Section 1862(a)(1)(A) states that no Medicare payment may be made for items or services which are not reasonable and necessary for the diagnosis or treatment of illness or injury.
• Title XVIII of the Social Security Act, Section 1862(a)(7). This section excludes routine physical examinations.

Code of Federal Regulations (CFR) References:

• CFR, Title 42, Volume 2, Chapter IV, Part 410.32(d)(3) Diagnostic x-ray tests, diagnostic laboratory tests, and other diagnostic tests: Conditions.

Compliance with the provisions in this LCD may be monitored and addressed through post payment data analysis and subsequent medical review audits.

History/Background and/or General Information

Electrodiagnostic (EDX) studies are an extension of a clinical assessment for evaluation of an assortment of focal and generalized neuromuscular disorders of the peripheral nervous system and the central nervous system. Assessment of these disorders generally includes a focused neuromuscular history and physical examination, the development of a differential diagnosis and EDX studies. The EDX studies are founded on the history and physical and suspected diagnosis and are followed by an assessment of muscles and nerves using nerve conduction studies (NCSs) and needle electromyography (NEMG), and the determination of a final diagnosis. The NCSs are performed and interpreted with the NEMG on site and in real time.^1-2 NCSs may be conducted without NEMG in some situations, such as entrapment neuropathies, but this should be the exception rather than the normal practice pattern. When NCSs are conducted without NEMG, beneficial data that may be important in determining an accurate diagnosis are commonly missing. The results of the NEMG studies can frequently provide an alternative etiology or coexisting disorder in the case of a suspected disorder.^1,3

EDX studies provide beneficial information regarding location, chronicity, severity, and pathophysiology to help determine a diagnosis and monitor a disease process in response to therapy.¹

Covered Indications

1. NCSs and NEMG are considered medically reasonable and necessary when they are performed and interpreted at the same time, on site, and in real time for any of the following circumstances:

1. 1. Plexopathy - including idiopathic, traumatic, inflammatory or infiltrative, radiation-induced,¹ brachial plexopathies (e.g., neuralgic amyotrophy, thoracic outlet syndrome), and lumbosacral plexopathies (e.g., diabetic, non-diabetic lumbosacral radiculoplexus neuropathy)⁴
   2. Focal neuropathies (e.g., entrapment neuropathies or compressive lesions/syndromes such as carpal tunnel syndrome,^5-8 ulnar neuropathy,^9-10 tarsal tunnel syndrome,¹¹ femoral neuropathy, saphenous neuropathy, lateral femoral cutaneous neuropathy, peroneal (fibular) neuropathy, tibial neuropathies, sciatic neuropathy)^1,12-18
   3. Generalized neuropathies such as metabolic (e.g., diabetic, uremic), toxic, hereditary or immune-mediated^1,19-20
   4. Motor neuron disease (e.g., amyotrophic lateral sclerosis [ALS] or Lou Gehrig’s disease)^1,21-22
   5. Myopathy - including inflammatory myopathies such as polymyositis and dermatomyositis, congenital myopathies,²³ congenital and hereditary dystrophic and nondystrophic myopathies, including myotonic muscular dystrophy, acquired myopathies (drug induced myopathy associated with statins, thyroid related), metabolic myopathies (e.g., McArdle disease)^1,24
   6. Myotonic disorders (e.g., drug induced myotonia)²⁵
   7. Neuromuscular junction disorders (e.g., myasthenia gravis, Lambert-Eaton myasthenic syndrome, botulism)^1,26-27
   8. Polyneuropathies^1,28-30
   9. Radiculopathy - cervical,³¹ thoracic or lumbosacral^1,32-33
   10. Spinal cord disorders³¹ (i.e., myelopathy)
   11. 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 study¹
   12. Traumatic nerve lesions, for diagnosis and prognosis¹

2. Neuromuscular Junction (NMJ) Testing is considered medically reasonable and necessary for any of the following conditions:
   
   
   1. Botulinum toxicity^1,3
   2. Motor neuron disease (e.g., ALS or Lou Gehrig’s disease)¹
   3. Myopathy^1,34
   4. Myasthenia gravis^27,34-35
   5. Myasthenic syndrome (e.g., Lambert-Eaton myasthenic syndrome)^1,3

3. NCSs when performed without NEMG are considered medically reasonable and necessary for the following situations:

1. 1. Individuals treated with anticoagulants^35-36 such as warfarin (Coumadin), rivaroxaban (Xarelto), dabigatran (Pradaxa), apixaban (Eliquis), edoxaban (Lixiana), clopidogrel (Plavix), ticagrelor (Brilinta), ticlopidine (Ticlid), prasugrel (Effient), varapaxar (Zontivity), dipyridamole, cilostazol (Pletal)
   2. Individuals with significant lymphedema in the affected extremity³⁶
   3. Individuals being evaluated for carpal tunnel syndrome or tarsal tunnel syndrome^3,11
      

4. NEMG when performed without NCSs is considered medically reasonable and necessary for the following situations:

1. 1. Guidance for botulinum toxin treatment injections when it is difficult to isolate affected muscles^1,37
   2. Laryngeal neuropathy³⁸
   3. Constipation³⁹
   4. Fecal incontinence³⁹
   5. Lower urinary tract symptoms^40-42
   6. Patients with risk factors for urinary retention^40-44

5. Single Fiber Electromyography (SFEMG) is considered medically reasonable and necessary for the following condition:

• 1. Ocular myasthenia⁴⁵ 
     
  2. Myasthenia gravis^27,34-35
  3. Myasthenic syndrome (e.g., Lambert-Eaton myasthenic syndrome)²⁷

Limitations

The following are considered not medically reasonable and necessary:

1. EDX studies where the interpretation is delayed and not completed at the time the study is performed^2,8,46 The NCS must be performed and interpreted with the NEMG on site and in real time^1-2
2. EDX studies (NCS and NEMG) not performed in accordance with the CMS regulations defined for supervision for diagnostic tests (Refer to the CMS IOM Pub 100-02, Medicare Benefit Policy Manual, Chapter 15, Section 80 Requirements for Diagnostic X-Ray, Diagnostic Laboratory, and Other Diagnostic Tests)
3. Non-invasive EDX studies using portable hand-held devices or automated point of care nerve conduction monitoring systems, which are incapable of real-time waveform display and analysis^3,47-53
4. Testing for polyneuropathy of diabetes in patients without clinical deficits or for the sole purpose of monitoring disease intensity or treatment efficacy³
5. Quantitative Sensory Testing (QST) (e.g., hot-cold, touch, vibration)^54-58
6. NCSs accomplished with discriminatory devices that use fixed anatomic templates and computer-generated reports used as an adjunct to physical examination routinely on all patients¹
7. Physiologic recording of movement disorder symptoms, including bradykinesia, dyskinesia, and tremor using wearable devices with accelerometers or gyroscopes⁵⁹
8. NCSs or EMG for muscle pain without the presence of other abnormalities on examination or in laboratory testing⁶⁰
9. NEMG for the following situations:
   • Definitive diagnosis based on paraspinal NEMG in areas with scar from past surgeries (e.g., previous laminectomies)³
   • Surface electromyography (SEMG)^3,61-63
   • Macroelectromyography (macro-EMG)³
   • NEMG for isolated neck or back pain after a motor vehicle accident⁶⁰

10. Studies performed beyond the reasonable maximum number of studies recommended in the American Medical Association (AMA) Current Procedural Terminology (CPT^®) Codebook, Appendix J, Electrodiagnostic Medicine Listing of Sensory, Motor, and Mixed Nerves. These recommendations are supported by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM).¹ Additional studies may be considered upon redetermination.

Please refer to the CMS IOM Publication 100-03, Medicare National Coverage Determinations (NCD) Manual, Chapter 1, Part 2, Section 160.23 Sensory Nerve Conduction Threshold Tests (sNCTs) for additional limitations.

Repeat EDX assessment may be needed in certain circumstances. The frequency for repeating EDX studies in a given patient by a given EDX provider for a given diagnosis per year can be reasonably limited. The following number of studies per 12-month period per diagnosis per provider are suitable: 1) Two studies for carpal tunnel-unilateral, carpal tunnel-bilateral, radiculopathy, mononeuropathy, polyneuropathy, myopathy, and NMJ disorders. 2) Three studies for motor neuron disease and plexopathy. These limits should not apply if the patient requires assessment by more than one EDX provider (i.e., a second opinion or an expert opinion at a tertiary care center) in a given year or if the patient requires evaluation for a second diagnosis in a given year.¹

Repeat EDX studies are rare and should not be necessary in a 12-month period in 80% of all cases.¹ Additional studies may be considered upon redetermination. In such circumstances, the rationale for the repeat study should be included in the medical record. Comparison with the previous study findings should be documented.

Provider Qualifications

Services will be considered medically reasonable and necessary when all aspects of care are within the scope of practice of the provider’s professional licensure, when performed according to the supervision requirements per state scope of practice laws, and when all procedures are performed by appropriately trained providers in the appropriate setting.

Notice: Services performed for any given diagnosis must meet all of the indications and limitations stated in this LCD, the general requirements for medical necessity as stated in CMS payment policy manuals, any and all existing CMS national coverage determinations, and all Medicare payment rules.

A literature search was conducted using the following key words: electrodiagnostic study; electrophysiologic study; electromyography; nerve conduction study (NCS); sensory nerve conduction study; nerve conduction velocity; quantitative sensory testing. The literature search was filtered to locate articles within 5-10 years, full-text articles, clinical trials, and systematic reviews. In general, improved health outcomes of interest include patient quality of life and function.

Guidelines and consensus statements from the AANEM have been incorporated throughout the summary of evidence. These guidelines and consensus statements offer evidence-based recommendations for the evaluation and treatment of muscle and nerve disorders in the practice of EDX medicine. These recommendations have been developed in cooperation with physicians who specialize in neuromuscular and EDX medicine.⁶⁴

EDX Studies

EDX studies are an extension of a clinical assessment for evaluation of an assortment of focal and generalized neuromuscular disorders of the peripheral nervous system and the central nervous system. EDX studies provide beneficial information regarding location, chronicity, severity, and pathophysiology to help determine a diagnosis and monitor a disease process in response to therapy.¹

An EDX assessment generally includes a focused neuromuscular history and physical examination, the development of a differential diagnosis and EDX testing that is founded on the history and physical and suspected diagnosis followed by an assessment of muscles and nerves using NCSs and NEMG, and the determination of a final diagnosis. According to the standard of care in clinical practice guidelines, these components cannot be predetermined or standardized.^1,46

EDX studies include the following: NEMG, SEMG, NCSs, late responses (i.e., H-reflex studies, F-wave studies), NMJ studies, somatosensory evoked potentials (SEPs), QST and autonomic nervous system function testing.¹  It is expected that EDX studies are performed and interpreted on site and in real time. In accordance with the AMA CPT^® Codebook, "Waveforms must be reviewed on site in real time...." The NEMG may provide an alternative etiology or coexisting disorder in the situation of a suspected disorder. The AANEM indicates that performing both studies together is vitally important when assessing patients with suspected radiculopathy, plexopathy, and motor nerve or motor neuron disease.^8,46 NCSs may be conducted without NEMG in some situations, such as entrapment neuropathies, but this should be the exception rather than the normal practice pattern.³

NCS

Evidence-based literature indicates that NCSs with or without late responses can be efficient for diagnosing and evaluating the following conditions: peripheral nerve entrapment^13-16; generalized neuropathies^19-20; polyneuropathies^28-29; neuromuscular junction disorders^26-27; myopathies including polymyositis, dermatomyositis, and congenital myopathies²³; motor neuron disease^21-22; spine disorders and radiculopathy³¹; and guidance for botulinum toxin injections when it is difficult to isolate affected muscles.³⁷

AANEM

The AANEM¹ indicates that a typical NCS should include: 1) Development of a differential diagnosis based upon an appropriate history and physical examination; 2) NCS (recording and studying of the electrical responses from peripheral nerves or the muscles); 3) Completion of indicated NEMG studies to evaluate the differential diagnosis and to complement the NCS.

On Site in Real Time: The AANEM⁸ indicates that when performing NCSs the waveform must be reviewed on site and in real time, with reports prepared onsite by the examiner, consistent with the AMA CPT^® Codebook descriptions. The AANEM defines the use of the term onsite as that where the history and physical examination, performance of NCS and NEMG, analysis of electrodiagnostic data and determination of diagnosis occur in the same location, usually an electrodiagnostic laboratory. Similarly, real time is defined as that which allows for information from the history and physical to be integrated with the performance of testing, allowing for the testing of both NCS and NEMG to be tailored/modified to the individual situation as needed before leaving the lab.²

NCSs: NCSs, also referred to as nerve conduction velocity (NCV) studies, are performed to assess the integrity and diagnose diseases of the peripheral nervous system. NCSs assess action potentials following peripheral nerve stimulation which include the speed (conduction velocity and/or latency), size (amplitude), and shape of the response. Pathological findings include conduction slowing, conduction block, or reduced response. Results of the NCS reflect on the integrity and function of the myelin sheath and the axon of a nerve. Interruption of axon and dysfunction of myelin will both affect NCS results.^1,3

While the stimulation of nerves is similar across all NCSs, the attributes of motor, sensory, and mixed NCSs are different; a) Motor NCSs are conducted by applying electrical stimulation at different 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 NCSs are performed by applying electrical stimulation near a nerve and recording the response from a distant site along the nerve. Response parameters comprise amplitude, latency, and configuration. c) Mixed NCSs are achieved 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 motor and sensory nerve fibers. Response parameters comprise amplitude, latency, configuration, and motor conduction velocity.^1,3

NEMG: Allows for interpretation of the muscle’s electrical qualities at rest and during activation. This interpretation includes analysis of the recruitment pattern and morphology and characteristic sound of motor unit potentials and spontaneous electrical activity. NEMG studies are interpreted in real time, as they are being performed. NEMG is performed to exclude, diagnose, describe, and follow diseases of the peripheral nervous system. NEMG involves the recording and study of electrical activity of skeletal muscle using a needle electrode.^1,3

H-reflex/F-wave Study: Late response (H-reflex and F-wave study) testing is a type of NCS usually performed on nerves more proximal to the spine. The H-reflex involves conduction from the periphery to and from the spinal cord. The H-reflex study involves the assessment of the gastrocnemius/soleus muscle complex in the calf and is usually performed bilaterally due to the need to assess symmetrical results in determining abnormalities. The F-wave study is a late response similar to the H-reflex. F-wave studies are used to assess the proximal segments of the motor nerve function and are performed in combination with the examination of motor nerves. Both studies are helpful in diagnosing conditions of radiculopathies, plexopathies, polyneuropathies (particularly with multifocal conduction block, Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy), and proximal mononeuropathies.¹ Late response studies are complementary to NCS and are performed during the same evaluation.

Conditions Recommended for Electrodiagnostic Testing: 1) Focal neuropathies, entrapment neuropathies, or compressive lesions/syndromes such as carpal tunnel syndrome, ulnar neuropathies,¹² or root lesions, for localization; 2) Traumatic nerve lesions, for diagnosis and prognosis; 3) Generalized neuropathies, such as metabolic (i.e., diabetic, uremic, etc.), toxic, hereditary or immune-mediated; 4) Neuromuscular junction disorders such as myasthenia gravis, myasthenic syndrome or botulism; 5) 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; 6) Radiculopathy-cervical, thoracic, lumbosacral; 7) Plexopathy - including idiopathic, traumatic, inflammatory or infiltrative, radiation-induced; 8) Myopathy-including inflammatory myopathies like polymyositis and dermatomyositis, myotonic disorders, and congenital myopathies; and 9) Precise muscle location for injection of intramuscular agents (e.g., botulinum toxin, phenol or other substances for nerve blocking or chemodenervation).^1,3

NEMG Performed in the Setting of Lymphedema: Based on the literature, the AANEM's position is that there are no contraindications to NEMG in patients with lymphedema. However, the AANEM believes that reasonable caution should be taken in performing needle examinations in lymphedematous regions to avoid complications. Clinical judgment should be used in deciding whether the risk of complication is greater than the value of the information to be obtained from the NEMG.³⁶

NEMG Performed in Patients with Disorders of Hemostasis: Based on the literature, the AANEM’s position is that the use of NEMG in patients with and without increased bleeding risk is safe. However, the AANEM believes that reasonable caution should be taken in performing NEMG and each case should be considered individually with regard to the potential benefits of the study relative to the risks of intramuscular hemorrhage or other bleeding.³⁶

Generally, for NEMG or SFEMG examination in patients with platelets < 50,000 or international normalized ratio (INR) > 1.5, caution should be exerted by using the smallest caliber needle and using extra pressure/time for hemostasis. Per available literature, judicious caution should be used if assessment of cranial nerves and paraspinal muscles would be further undertaken. In addition, muscles that can possibly lead to remote risk of compartment syndrome like tibialis posterior, flexor pollicis longus, should be averted in these specific patients that exceed the above-mentioned criteria.³⁶

Carpal Tunnel Syndrome (CTS)

CTS, the most common entrapment neuropathy of the upper extremity, is generally diagnosed by history and physical assessment, and EDX studies (NCS and sometimes NEMG) are utilized as objective measures to confirm existence of a median mononeuropathy. The NCSs verify CTS by identifying impaired median nerve conduction across the carpal tunnel. The NEMG evaluates pathologic changes in the muscles innervated by the median nerve.^5-6 Evidence-based clinical practice guidelines recommend EDX studies to confirm a clinical diagnosis of CTS.⁷

Ulnar Neuropathy

Dy and Mackinnon⁹ performed a systematic review and meta-analyses of the literature regarding evaluation and management of ulnar neuropathy. Compression of the ulnar nerve at the elbow joint is frequently referred to as cubital tunnel syndrome.¹⁰ Evidence-based literature indicates a thorough clinical history and physical examination and prudent assessment of EDX studies are useful to help confirm the diagnosis, localize the site and quantify the grade of compression and in establishing the prognosis of recovery with nonoperative and operative management in patients with ulnar neuropathy.^9-10 In long-standing or severe compression of the ulnar nerve, NCSs show a reduction in amplitude that reflects an overall decline in the number of functioning nerve fibers. NEMG demonstrates abnormal activity during the insertional phase (indicating muscle denervation), fibrillations during resting phase (a sine qua non for motor axon loss), and the manifestation of motor unit action potentials during the recruitment phase (signifying attempted reinnervation by either collateral sprouting or axonal reinnervation).⁹

Tarsal Tunnel Syndrome (TTS)

Patel et al¹¹ provides an AANEM practice topic regarding an evidence-based practice parameter that addresses the effectiveness of EDX testing in the diagnosis of TTS (tibial neuropathy at the ankle). The AANEM indicates that NCSs can be beneficial to substantiate the diagnosis of tibial neuropathy at the ankle. But the efficacy for NEMG in the evaluation of TTS is uncertain.

Entrapment Neuropathies of the Lower Extremity

Craig¹⁷ provides a review of the literature concerning the use of EDX studies for entrapment neuropathies of the lower extremity (e.g., femoral neuropathy, saphenous neuropathy, obturator neuropathy, lateral femoral cutaneous neuropathy, peroneal (fibular) neuropathy, tibial neuropathies, sciatic neuropathy, gluteal neuropathies). Evidence-based literature indicates that the preliminary approach to suspected neurologic injury encompasses a judicious physical examination to describe the distribution of motor and sensory loss. Electromyography is utilized to verify and localize the neurologic injury, evaluate the severity of the injury to facilitate prognostication, help in developing a management plan, and exclude confounding or coexisting neurologic injury.¹⁷

For femoral neuropathy, NCSs of the femoral nerve can be performed by stimulating the femoral nerve at the inguinal ligament and recording over the quadriceps. A comparison can be made with the clinically normal opposite side. Attaining a compound action potential of at least 50% for the opposite side indicates a good prognosis for recovery within a year. The NEMG study should include the quadriceps and the iliopsoas. Anomalies in the iliopsoas indicate the nerve lesion is within the pelvis.¹⁷

In situations of suspected saphenous nerve injury causing saphenous neuropathy, a NCS may be conducted although these are technically challenging, and responses can be slight; results should be contrasted with the unaffected side. Outcomes of a NEMG should be normal and are helpful to rule out femoral neuropathy, L4 radiculopathy, or a lumbar plexopathy.¹⁷

Currently, there is no NCS offered to evaluate the obturator nerve. However, NEMG is beneficial in verifying suspected obturator neuropathy with abnormalities in the adductor muscles. If assessing the adductor magnus, it is vital to appreciate that the sciatic nerve also contributes to its motor innervation. Evaluation of femoral-innervated muscles and paraspinal muscles should be conducted to rule out plexus injury or radiculopathy.¹⁷

Lateral femoral cutaneous neuropathy may be verified by conducting a NCS and contrasting results with the opposite side although attaining a response is technically challenging. Ultrasound may be used to detect nerve location and enhances the capability to record sensory nerve action potentials. NEMG is beneficial to rule-out other disorders, such as L2 radiculopathy, high lumbar plexopathy or femoral neuropathy.¹⁷

In situations of suspected peroneal (fibular) neuropathy, a NCS can be beneficial in locating a peroneal lesion. Peroneal motor conduction to the extensor digitorum brevis (EDB) muscles should be conducted, stimulating the nerve at three sites: the anterior ankle, fibular head, and popliteal fossa.¹⁸ A NEMG should assess the tibialis anterior, peroneus longus, and biceps femoris to evaluate the severity of the injury and help guide prognosis.¹⁸ It is essential to realize the EDB muscles can be denervated because of local trauma or with distal neuropathy.¹⁷ In addition, in one-third of people, an accessory peroneal nerve that arises from the superficial peroneal nerve can contribute to the EDB. This variation may be detected when the amplitude acquired when stimulating above the fibular head is greater than when stimulating below the fibular head and is confirmed by acquiring a response stimulating behind the lateral malleolus. Peroneal motor conduction may also be acquired from the anterior tibialis. Contrasting with the opposite side is useful in calculating the degree of axon loss. Decrease of the superficial peroneal sensory response signifies a lesion distal to the dorsal root ganglia. Tibial motor, F-response, and sural nerve studies are beneficial in ruling out a peripheral neuropathy or a more widespread lesion, such as a plexopathy or sciatic injury. NEMG assists to further locate the lesion, exclude other causes of foot drop, and evaluate the severity of the axon loss.¹⁷

When a tibial neuropathy is suspected, EDX testing of suspected tibial lesions should involve sural sensory responses, which will be variably affected in proximal tibial lesions. Demonstrable asymmetry with respect to comparing sural sensory responses between the two limbs can be helpful with borderline normal responses. A decrease in tibial motor responses to the abductor hallucis will be observed. When TTS (a common variant of tibial neuropathy) is suspected, medial and lateral plantar responses should be conducted. These can be challenging to acquire, particularly with thick calluses or preexisting peripheral neuropathy. Contrasting with the contralateral limb should be completed before drawing any conclusions from low or absent responses. NEMG will show denervation in the medial gastrocnemius or posterior tibialis in proximal tibial lesions. Mid leg lesions may spare muscles that affect the long toe flexors and foot intrinsics only. In cases of severe TTS, physical exam may reveal atrophy of the first dorsal interosseous and adductor hallucis muscles resultant to pathology of the lateral and medial plantar branches respectively. Abnormalities of these muscles are also observed in early peripheral neuropathies so contrasting with the opposite side is recommended. Differential diagnosis of tibial neuropathy involves S1 radiculopathy, sciatic neuropathy, and lumbar plexopathy. Therefore, careful physical examination of hamstring muscles innervated by the tibial branch of the sciatic nerve as well as nontibial innervated S1 muscles should be performed.¹⁷

A NCS in sciatic neuropathy will yield decreased amplitudes of the superficial peroneal sensory and sural sensory responses. Also, both tibial and peroneal motor responses will be low, without evidence of a focal conduction block at the knee. The NEMG assessment is especially effective in localizing the lesion. Evidence of denervation will be observed in both the peroneal and tibial divisions and in more proximal hamstring muscles. The short head of the biceps femoris is particularly beneficial in circumstances in which the peroneal division is preferentially injured, as it is the only muscle innervated by the peroneal division while still part of the sciatic nerve proper. Assessment of other gluteal muscles and paraspinal muscles should be executed to rule out a more proximal plexus injury or L5-S1 radiculopathy.¹⁷

Currently, there is no NCS offered to evaluate the gluteal nerves. However, obtaining electrodiagnostic abnormalities in NEMG testing of the gluteal muscles can be beneficial in identifying gluteal neuropathies.¹⁷

Distal Symmetric Polyneuropathy (DSP)

Dupuis et al³⁰ performed a retrospective chart review for 105 patients referred to an electromyography laboratory for neuropathy, polyneuropathy or lower extremity sensory changes with clinical histories of lower extremity numbness, tingling, or pain, and no mention of unilateral or asymmetric symptoms. The goal of the study was to evaluate the symmetry between the right and the left lower extremity NCS in a cohort of patients with symptoms of DSP.

Of the 105 patient charts reviewed, 53 patients had bilateral sural sensory, peroneal motor and tibial motor studies performed. Patient diagnoses included neuropathy (76), normal or indeterminate (19), mononeuropathy (4) and radiculopathy (6).

Existing consensus criteria for the diagnosis of DSP are an abnormality (> 99th or < 1st percentile) of any element of nerve conduction in two separate nerves, one of which must be the sural nerve.

Considerable agreement was noted between abnormalities in individual nerve parameters of the left and right lower extremities for all 105 patients, particularly in the sural nerve. There was also considerable agreement regarding whether the left and right lower extremities met the electrodiagnostic criteria for DSP (k = 0.77) for the 53 patients with bilateral sural, peroneal, and tibial studies. The authors concluded that this study has shown that patients with symmetric neuropathy symptoms have a high degree of agreement in NCS parameters between sides; therefore, bilateral lower extremity NCS may have limited benefit in the assessment of suspected DSP.³⁰

Cervical Radiculopathy (CR)

Pawar et al³¹ performed a cross-sectional study to assess the diagnostic value of different motor and sensory nerve conduction study parameters in 100 patients aged 40 years and above clinically diagnosed with CR. Typical modalities to diagnose CR include clinical examination, radiological imaging and electrophysiologic assessment. Usually imaging with a computed tomography (CT) myelogram or magnetic resonance imaging (MRI) scan can detect a structural lesion entrapping the nerve roots; however, radiculopathy and polyradiculopathy can occur without a radiologically detectable structural lesion. Frequently, the patient’s history and physical assessment are insufficient to differentiate CR from other neurologic sources of neck and arm pain. In these situations, EDX studies are generally performed.

Exclusion criteria included patients with diabetes mellitus, clinical or electrophysiological confirmation of polyneuropathy, duration of symptoms less than three weeks or spinal surgery within the past 15 years. An MRI was performed on study participants. The study concluded that among motor nerve conduction parameters compound muscle action potential is more sensitive as compared to distal motor latency and conduction velocity and sensory nerve conduction parameters are less sensitive in diagnosing CR. The study showed that NCSs are a useful supportive diagnostic tool for suspected CR.³¹

Brachial Plexopathies and Lumbosacral Plexopathies

Rubin⁴ performed a review of the literature regarding the brachial and lumbosacral plexus, including the clinical characteristics, EDX approaches, and appraisal and treatment of brachial and lumbosacral plexopathies. EDX testing using a combination of NCS and NEMG is an important and vital element of the assessment of brachial plexopathies (e.g., neuralgic amyotrophy, thoracic outlet syndrome). EDX studies assist to: a) verify localization to the brachial plexus while eliminating (or recognizing) radiculopathies or mononeuropathies; b) detect the segment(s) of the plexus implicated; c) describe the pathophysiology of nerve injury (e.g., axonal or demyelinating); d) establish the degree of axon loss; and e) evaluate for evidence of reinnervation or recovery of the nerves. Generally, EDX studies do not establish the etiology of the plexopathy, but on occasion certain findings may point towards a potential cause. In assessing a brachial plexopathy, both NCS and NEMG give these types of information.

The objectives of conducting EDX studies in lumbosacral plexopathies (e.g., diabetic and non-diabetic lumbosacral radiculoplexus neuropathy) are similar to those for brachial plexopathies and involve assisting to localize the disorder to the lumbosacral plexus, rule-out more common lumbosacral radiculopathies, and characterize the pathophysiology and severity of nerve injury. Although there are fewer NCSs that can be conducted to assess the lumbosacral plexus contrasted to the brachial plexus, the same EDX concepts apply; abnormal sensory NCS and the absence of NEMG findings in the lumbosacral paraspinals are supportive of a plexopathy.⁴

Lumbosacral Radiculopathy

Cho et al³² provides an evidence-based practice guideline developed from a systematic review of the literature performed by the Lumbosacral Radiculopathy Task Force as charged by the AANEM to assess the efficacy of EDX studies in the diagnosis of lumbosacral radiculopathies. Evidence-based literature indicates that the diagnosis of lumbosacral radiculopathy is founded on clinical history and physical examination, imaging studies, and EDX studies. EDX studies are particularly beneficial in situations with negative imaging results or atypical clinical appearances while in circumstances with abnormal imaging results, EDX testing functions in a complementary diagnostic role.

Conclusions of the study indicate: 1) In cases with suspected lumbosacral radiculopathy, the following EDX studies may assist in developing the clinical diagnosis: a) peripheral limb NEMG. b) paraspinal mapping (PM) with NEMG in lumbar radiculopathy. c) H-reflex in S1 radiculopathy. 2) Evidence-based literature implies a low sensitivity of peroneal and posterior tibial F-waves. 3) There is insufficient evidence to draw clear conclusions for the efficacy of the following EDX studies: a) dermatomal/segmental SEP of the L5 or S1 dermatomes. b) PM with NEMG in sacral radiculopathy. c) motor evoked potential (MEP) with root stimulation in formulating an independent diagnosis of lumbosacral radiculopathy.³²

Lumbar Central Spinal Stenosis (LCSS)

Chang and Park³³ performed a retrospective chart review to examine the results of NCSs and NEMG in 32 patients (average age 66.9 + 7.4 years) with moderate and severe LCSS and contrast findings of EDX tests in 15 patients (average age 65.2 + 8.0 years) without LCSS (control group). The results showed that patients with moderate or severe LCSS exhibited substantially lower distal amplitudes of the compound motor action potential of both peroneal and tibial nerves in comparison with the control group. The NEMG results showed that positive sharp waves and fibrillation potentials were exclusively discerned in patients with severe LCSS group (28.6%). The authors concluded that the results of this study may be beneficial to diagnose radiculopathy as a result of LCSS and to distinguish it from other peripheral nerve pathologies.³³

Vocal Cord Paralysis

Munin et al³⁸ performed a systematic review of the literature using the American Academy of Neurology (AAN) criteria for rating of diagnostic accuracy. This study was conducted to develop a consensus statement for using laryngeal electromyography for the diagnosis and treatment of vocal cord paralysis.

Recurrent laryngeal neuropathy (RLN) is a peripheral nerve lesion resulting in vocal fold paralysis. Laryngeal electromyography (LEMG) is used to assess neuromuscular function following laryngeal nerve injury to assist in decision making about diagnosis, prognosis, and subsequent rehabilitative procedures. The severity of nerve injury (e.g., conduction block, axonal loss, or a combination of both) will affect the patient’s recovery from RLN.

The results of the study show that LEMG is important in the clinical management of a patient with vocal fold paralysis as the LEMG modified clinical management about 48% of the time by changing the initial diagnosis from RLN. Cricoarytenoid fixation and superior laryngeal neuropathy were the most frequent diagnoses discerned when the pretest impression was RLN.³⁸

NMJ Disorders

Neuromuscular junction testing, also known as repetitive nerve stimulation, is an electrodiagnostic test that is used to diagnose NMJ disorders such as myasthenia gravis and Lambert-Eaton myasthenic syndrome.^27,34-35 The test involves recording muscle responses to a series of nerve stimuli and may be used in association with NCSs of the same nerves. At least one motor and one sensory nerve conduction study should be performed in a clinically involved limb, preferably in the distribution of a nerve studied with repetitive stimulation or SFEMG. At least one distal and one proximal muscle should be studied by a NEMG examination to exclude a neuropathy or myopathy that can be associated with abnormal repetitive stimulation studies or SFEMG. At least one of the muscles should be clinically involved and both muscles should be in clinically involved limbs.¹ Evidence-based guidelines recommend NMJ or SFEMG to confirm a clinical diagnosis of myasthenia gravis or Lambert-Eaton myasthenic syndrome."²⁷ Evidence-based guidelines have shown that SFEMG may be used to assist in diagnosis and has shown positive in over 90% of patients with ocular myasthenia.⁴⁵

Myopathies

Chiodo²⁴ provides a review of the literature concerning acquired myopathies/dystrophies such as inflammatory myopathy and myositis (e.g., polymyositis, dermatomyositis, inclusion body myositis); congenital and hereditary dystrophic and nondystrophic myopathies, including myotonic muscular dystrophy; acquired myopathies (e.g., drug induced myopathy associated with statins, thyroid related) and metabolic myopathies (e.g., McArdle disease).

Evidence-based literature indicates that NEMG is beneficial in recognizing the presence of a myopathy by assessing motor units and their recruitment as well as detecting possible muscle necrosis and inflammation as implied by the presence of abnormal spontaneous activity. Electrodiagnosis is also valuable in ruling out other disorders that may mimic a myopathy by assessing the pattern of connection and by guiding the selection of location for a muscle biopsy. It may also be beneficial in assessing response to treatment.²⁴

NCS results are usually normal in myopathies though low compound muscle action potential amplitudes may exist if the myopathy is severe and/or affects distal musculature since distal muscles are generally utilized in NCSs. Sensory responses are typically normal, except in disorders that cause both a myopathy and neuropathy, such as critical illness neuromyopathy. Usually, at least one motor and one sensory NCS is conducted in the arm and in the leg, and the test expanded, contingent on those results. NEMG and/or NCS also permits differentiation between muscle disease and defects of neuromuscular transmission (both pre- and postsynaptic disorders).²⁴

Myotonic Dystrophy

Burakgazi²⁵ conducted a retrospective chart review for twelve patients with adult-onset myotonic dystrophy who were previously diagnosed with diabetes mellitus (DM)-type 1 and had EDX tests performed (average age 53.3 + 15.2 years). The goal of the study was to portray the common EDX results in DM patients and to evaluate the EDX sensitivity of muscles in the diagnosis of DM.

The NCS demonstrated that more than half of the patients had normal sensory and motor NCS results. In 11 of 12 patients, sensory NCSs were within normal limits. Only one patient displayed abnormal sensory responses. The most frequent abnormal NCS results were diminished amplitude of motor nerves with normal latency and normal conduction velocity possibly due to muscle wasting or motor axonal damage. The NEMG analysis proved more sensitive in detecting myotonic discharges in distal muscles of the extremities than in proximal muscles of the extremities. The author concluded that the NEMG study is essential in the diagnosis of myotonic disorders, especially in clinically elusive situations.²⁵

Anal or Urethral Sphincter Disorders

Wald et al³⁹ provides updated evidence-based clinical guidelines from the American College of Gastroenterology (ACG) for management of benign anorectal disorders. The guidelines include recommendations for defecatory disorders (DDs) and fecal incontinence (FI). A diagnosis of DD requires both symptoms of constipation and anorectal tests indicative of impaired rectal evacuation. A digital rectal examination (DRE) is recommended as part of the assessment to identify structural abnormalities (i.e., anal fissures, hemorrhoids, fecal impaction, descending perineum syndrome, or anorectal cancer) and evaluate anal sphincter function. Anorectal tests are needed as symptoms alone do not discriminate between DD and other causes of constipation. The diagnostic tests evaluate rectal sensation and anorectal pressures (manometry), rectal balloon expulsion (BET), external anal sphincter and pelvic floor muscle activity (with electromyography [EMG]), or rectal evacuation (barium or MRI defecography). These diagnostic tests have strengths and limitations, and there is no single gold standard. The recommendations for diagnostic assessment for defecatory disorders indicate that a diagnosis of DD be confirmed by at least two abnormal tests (i.e., anorectal manometry [ARM] and balloon expulsion).³⁹

The recommendations for FI include performing a physical examination to rule-out diseases to which FI is secondary, performing an anorectal examination (to identify rectal masses, gauge anal sphincter tone and pelvic floor motion at rest, during voluntary contraction of the anal sphincter and pelvic floor muscles, and during simulated defecation). A DRE should be done before referral for ARM. The recommendations for diagnostic testing for FI include ARM, BET and rectal sensation in patients who fail conservative treatment. Pelvic floor and anal canal imaging and anal EMG should be considered for patients with reduced anal pressures who have failed conservative therapy, particularly if surgery is being considered.³⁹

Winters et al⁴⁰ provides evidence-based guidelines from the American Urological Association (AUA) and the Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction (SUFU) for Adult Urodynamics. This guideline addresses the use of urodynamic tests for diagnosis, prognosis, guidance of clinical management decisions, and improvement of patient outcomes in patients with various urologic conditions. The authors noted the current literature is deficient in Level-1 evidence, which could elucidate the precise indications for urodynamic testing. Guideline statements for stress urinary incontinence (SUI)/prolapse include the following: A) Clinicians may perform multi-channel urodynamics in patients with both symptoms and physical findings of stress incontinence who are contemplating invasive, potentially morbid or irreversible treatments. Urodynamic studies (UDS) are not completely necessary as a component of the preoperative evaluation in uncomplicated patients. B) Multi-channel urodynamics can assess for the presence of detrusor dysfunction in women with SUI with high grade pelvic organ prolapse as some women with high grade pelvic organ prolapse may have an elevated post void residual or be in urinary retention. Guideline statements for neurogenic bladder (NGB) include the following: Clinicians should conduct EMG in combination with a cystometrogram, with or without pressure flow studies, in patients with a relevant neurologic disease at risk for a neurogenic bladder, or in patients with other neurologic diseases and an elevated post void residual or in patients with urinary symptoms.⁴⁰

Kobashi et al⁴³ provides evidence-based guidelines from the AUA and the SUFU for the surgical treatment of female SUI. Guideline statements regarding UDS include the following: A) Clinicians may omit urodynamic testing for the index patient desiring treatment when SUI is clearly established. B) Clinicians may perform urodynamic testing in non-index patients (Expert Opinion). The authors also note that all surgical interventions (e.g., midurethral slings [MUS], pubovaginal slings [PVS], colposuspension) to treat SUI have possible adverse outcomes, such as continued incontinence, voiding dysfunction, urinary retention, pain, and dyspareunia.

Ginsberg et al⁴¹ provides evidence-based guidelines from the AUA and the SUFU for adult neurogenic lower urinary tract dysfunction (NLUTD). The guideline statements regarding UDS include the following: A) For patients with low-risk NLUTD, at initial assessment, the clinician should not routinely obtain upper tract imaging, renal function evaluation, or multichannel urodynamics. B) For patients with unknown-risk NLUTD, at initial assessment, the clinician should obtain upper tract imaging, renal function assessment, and multichannel urodynamics. C) For patients with low-risk NLUTD and stable urinary signs and symptoms, the clinician should not obtain surveillance upper tract imaging, renal function assessment, or multichannel urodynamics. D) For patients with high-risk NLUTD and stable urinary signs and symptoms, the clinician should assess the patient with an annual focused history, physical examination and symptom evaluation; an annual renal function evaluation; an annual upper tract imaging; and multichannel UDSs, with or without fluoroscopy, which may be repeated when clinically indicated. E) For patients with moderate- or high-risk NLUTD who encounter a change in signs and symptoms, new complications (e.g., autonomic dysreflexia, urinary tract infections [UTIs], stones), or upper tract or renal function deterioration, the clinician may perform multichannel urodynamics. F) For NLUTD patients with recurrent UTIs and an unremarkable assessment of the upper and lower urinary tract, clinicians may perform urodynamic evaluation. G) For NLUTD patients with impaired storage parameters and/or voiding that put their upper tracts at risk, clinicians should repeat UDS at an appropriate interval following treatment. H) For follow-up and post treatment, clinicians may conduct urodynamics following sphincterotomy to evaluate outcome.⁴¹

Ginsberg et al⁴² provides evidence-based guidelines from the AUA and the SUFU for treatment and follow-up of adult NLUTD. This guideline provides recommendations for the appropriate assessment, diagnosis, and risk stratification of adult patients with NLUTD and the non-surgical and surgical treatment options available. Guideline statements concerning UDS include the following: A) Evaluation of bladder storage parameters with UDS are recommended to be conducted prior to any SUI procedure in patients with relevant NLUTD where bladder compliance may be worsened by an outlet procedure, resulting in elevated storage pressures and risk to the upper urinary tracts. B) Evaluation of bladder storage parameters with UDS should be conducted prior to any artificial urinary sphincter (AUS) placement in patients with relevant NLUTD where bladder compliance may be worsened by an outlet procedure, resulting in elevated storage pressures and risk to the upper urinary tracts. C) Evaluation of bladder storage parameters with UDS should be conducted in patients with relevant NLUTD where bladder compliance may be worsened by an outlet procedure such as bladder neck closure (BNC), resulting in elevated storage pressures and risk to the upper urinary tracts. D) Urodynamic studies should be repeated at an appropriate interval following treatment in NLUTD patients with impaired storage parameters and/or voiding that place their upper tracts at risk. E) In NLUTD patients with impaired storage parameters that place their upper tracts at risk and are refractory to therapy, clinicians should offer additional treatment. Stepwise treatment based on invasiveness is reasonable, providing repeated UDS are performed to evaluate efficacy at appropriate intervals. F) UDS is recommended following sphincterotomy to evaluate outcome. NLUTD patients may undergo non-surgical and surgical treatment options contingent on their level of risk, symptoms, and urodynamic findings. Proper follow-up, primarily based on their risk stratification, must be maintained after treatment.⁴²

Sandhu et al⁴⁴ provides evidence-based guidelines from the AUA and the SUFU for incontinence after prostate treatment (IPT). Guideline statements regarding UDS include the following: A) Clinicians may conduct urodynamic testing in a patient prior to surgical intervention for SUI in situations where it may facilitate diagnosis or counseling. B) Clinicians should assess patients with incontinence after prostate treatment with history, physical exam, and appropriate diagnostic modalities to categorize type and severity of incontinence and degree of bother. Confirmation of SUI can frequently be established by history or physical exam alone; however there are times when a clinician may choose advanced testing such as UDS.

Number of Studies/Tests

The table below summarizes the recommendations of the AANEM¹ regarding the reasonable maximum number of studies per diagnostic category necessary for a physician to arrive at a diagnosis for 90% of patients with that final diagnosis.

AANEM Recommended Number of Studies/Tests Per Date of Service

CTS: For suspected CTS, bilateral median motor and sensory NCSs are frequently indicated. The studies in the contralateral asymptomatic limb function as controls in cases where values are borderline and may determine the presence of bilateral CTS, which is a common finding. Two to four additional sensory or mixed NCSs can be contrasted to the median sensory NCSs to enhance the diagnostic sensitivity of the testing. The additional sensory NCSs and an additional motor NCS (usually ulnar) are indicated to rule-out a generalized neuropathy or multiple mononeuropathies.¹

If two sensitive sensory NCSs are conducted at the beginning, additional sensory testing on the same limb is seldom needed. For suspected bilateral CTS, bilateral median motor and sensory NCSs are indicated. Up to two additional motor and two additional sensory NCSs are frequently indicated. The extent of the NEMG assessment depends on the findings of the NCSs and the differential diagnosis considered in the individual patient.¹

Further testing may be indicated in patients with a differential diagnosis that involves peripheral neuropathy, cervical radiculopathy, brachial plexopathy, or more proximal median neuropathy.¹ Additional tests may be considered upon redetermination. In such circumstances, the rationale for the additional tests should be included in the medical record.

Radiculopathy: A minimal assessment for radiculopathy includes one motor and one sensory NCS and a NEMG assessment of the involved limb. However, the EDX testing can include up to three motor NCSs (in cases of an abnormal motor NCS, the same nerve in the opposite limb and another motor nerve in the ipsilateral limb can be studied) and two sensory NCSs. Bilateral tests are frequently needed to rule out a central disc herniation with bilateral radiculopathies or spinal stenosis or to differentiate between radiculopathy and plexopathy, polyneuropathy, or mononeuropathy. H-reflexes and F-waves can provide complementary information that is beneficial in the assessment of suspected radiculopathy and can add to the certainty of EDX information advocating a diagnosis of root dysfunction.¹

Radiculopathies cannot be diagnosed by NCS alone; NEMG must be performed to confirm a radiculopathy. Therefore, these studies should be performed together by one physician/qualified health care practitioner supervising and/or performing all aspects of the study.¹

Polyneuropathy/Mononeuropathy Multiplex: To characterize the nature of the polyneuropathy (axonal or demyelinating, diffuse or multifocal) and to rule-out polyradiculopathy, plexopathy, neuronopathy, or multiple mononeuropathies, it may be necessary to test four motor and four sensory nerves, consisting of two motor and two sensory NCSs in one leg, one motor and one sensory NCS in the opposite leg, and one motor and one sensory NCS in one arm. H-reflex studies and F-wave studies from two nerves may give additional diagnostic information. At least two limbs should be studied by a NEMG examination. Studies of related paraspinal muscles are indicated to rule-out some disorders such as polyradiculopathy.¹

Myopathy: To diagnose a myopathy, a NEMG study of two limbs is indicated. To help rule out other disorders such as polyneuropathy or neuronopathy, two motor and two sensory NCSs are indicated. Two repetitive motor nerve stimulation studies may be conducted to rule-out a disorder of neuromuscular transmission.¹

Motor Neuronopathy: To verify the diagnosis of motor neuronopathy (for example, ALS or Lou Gehrig’s disease) and to rule-out other disorders in the differential diagnosis, such as multifocal motor neuropathy or polyneuropathy, up to four motor nerves and two sensory nerves may be studied.¹

The NEMG assessment of up to four extremities (or three limbs and facial or tongue muscles) is frequently needed to document widespread denervation and to rule out a myopathy. One repetitive motor nerve stimulation test may be indicated to rule-out a disorder affecting neuromuscular transmission.¹

Plexopathy: To characterize a brachial plexopathy and to distinguish it from cervical radiculopathy and mononeuropathies, it is frequently necessary to assess all major sensory and motor nerves that can be easily evaluated in both upper extremities (radial, median, ulnar, and medial and lateral antebrachial cutaneous sensory; radial, median, ulnar, and possibly axillary and musculocutaneous motor) and to conduct a NEMG study in both upper extremities. To characterize the lumbosacral plexopathy and to distinguish it from lumbar radiculopathy and mononeuropathies, it is frequently necessary to assess all major sensory and motor nerves that can be easily evaluated in both lower extremities (superficial peroneal [fibular] and sural sensory; peroneal [fibular] and posterior tibial motor) and to conduct a NEMG study in both lower extremities. F-wave studies in the motor nerves and soleus H-reflexes also offer beneficial information.¹

NMJ: To reveal and characterize abnormal neuromuscular transmission, repetitive nerve stimulation studies should be conducted in up to three nerves and SFEMG in up to two muscles. If any of these are abnormal, up to two motor and two sensory NCSs may be conducted to rule out neuropathies that can be correlated with abnormal neuromuscular transmission. At least one motor and one sensory NCS should be conducted in a clinically involved limb, preferably in the distribution of a nerve studied with repetitive stimulation or SFEMG. At least one distal and one proximal muscle should be tested by a NEMG examination to rule-out a neuropathy or myopathy that can be associated with abnormal repetitive stimulation studies or SFEMG. At least one of the muscles should be clinically involved and both muscles should be in clinically involved limbs.¹

Frequency of Electrodiagnostic Testing in a Given Patient: The frequency for repeating EDX studies in a given patient by a given EDX provider for a given diagnosis per year can be reasonably limited. The following numbers of studies per 12-month period per diagnosis per physician are suitable: 1) Two studies for carpal tunnel-unilateral, carpal tunnel-bilateral, radiculopathy, mononeuropathy, polyneuropathy, myopathy, and NMJ disorders. 2) Three studies for motor neuronopathy and plexopathy. These limits should not apply if the patient requires assessment by more than one EDX provider (i.e., a second opinion or an expert opinion at a tertiary care center) in a given year or if the patient requires evaluation for a second diagnosis in a given year.¹

Repeat EDX studies are rare and should not be necessary in a 12-month period in 80% of all cases. In such circumstances, the rationale for the repeat study should be included in the medical record. Comparison with the previous study findings should be documented.¹

Procedures considered Experimental, Investigational, or Unproven

EDX testing with automated, noninvasive nerve conduction testing devices is considered investigational and not medically reasonable and necessary for all indications, including as an alternative method of performing NCSs.³

Screening testing for polyneuropathy of diabetes in patients without clinical deficits is not indicated. Testing for the sole purpose of monitoring disease intensity or treatment efficacy in this condition is not indicated.^3,20

Psychophysical measurements (electrical, vibratory or thermal perceptions), even though they may involve delivery of a stimulus, are not considered medically reasonable and necessary.³

Examination using portable hand-held devices, which are incapable of real-time waveform display and analysis, will be included in the evaluation and management (E/M) service.³

NEMG for the following situations is not considered medically reasonable and necessary: 1) Exclusive study of intrinsic foot muscles in the diagnosis of proximal lesions; 2) Definitive diagnosis based on paraspinal EMG in areas with scar from past surgeries (e.g., previous laminectomies); 3) Performing NEMG testing just after trauma occurs, before NEMG abnormalities would have reasonable time to develop; 4) SEMG and macro-EMGs; 5) Multiple uses of NEMG in the same patient at the same location of the same limb for the purpose of optimizing botulinum toxin injections.³

Based on evidence-based literature, the Professional Practice Committee (PPC) of the AANEM as part of the Choosing Wisely Initiative⁶⁰ recommends that the following procedures not be performed: 1) NEMG for isolated neck or back pain after a motor vehicle accident. NEMG for neck pain without arm pain, arm tingling, arm weakness, or arm numbness does not improve outcomes. The same is true of NEMG for back pain without lower limb pain, lower limb tingling, lower limb weakness, or lower limb numbness. 2) Dermatomal SEPs for a pinched nerve in the neck or back, as they are an unproven diagnostic procedure. Though methods such as NEMG and NCSs can be useful to diagnose pinched nerve in the neck (cervical radiculopathy) or back (lumbar radiculopathy), dermatomal SEP is of unproven worth for this purpose. There are several causes of neck, shoulder, and upper limb pain besides cervical radiculopathy. There are also several causes of back, hip, thigh, and lower limb pain other than lumbar radiculopathy. 3) NCSs without a NEMG for a pinched nerve in the neck or back. For diagnosis of a pinched nerve in the neck or back, NCSs alone cannot make the diagnosis. NEMG is essential to detect and characterize the disease process. 4) NCSs or NEMG for muscle pain without the presence of other abnormalities on examination or laboratory testing. Muscle pain or myalgias are widespread. The probability of discovering a muscle disease in an individual with muscle pain who has a normal neurologic exam and laboratory tests is quite low.

Dystonia

Albanese et al⁶⁵ provides the revised European Federation of Neurological Societies (NFNS) scientific task force committee guidelines on diagnosis and treatment of primary dystonias. This evidence-based guideline indicates neurophysiological tests are not normally recommended for the diagnosis or classification of dystonia. Though multiple simultaneous NEMG recordings from different muscles may add to the clinical assessment by displaying characteristic features of dystonia.⁶⁵

Overactive Bladder

Gormley et al⁶⁶ provides evidence-based guidelines from the AUA and the SUFU for the diagnosis and treatment of overactive bladder (OAB) (non-neurogenic) in adults. Guideline statements regarding UDS include the following: A) Urodynamics, cystoscopy and diagnostic renal and bladder ultrasound should not be utilized in the initial workup of the uncomplicated patient. For complicated patients or refractory patients who have failed multiple OAB treatments, the option of additional diagnostic tests depends on patient history and presentation and clinician judgment. B) In select cases, the clinician may elect to obtain further information with voiding diaries or symptom questionnaires, or may do further testing such as urodynamics to rule out other bladder pathologies or urethral dysfunction.

QST

Georgopoulos et al⁵⁴ performed a systematic review of the literature regarding the evidence for the capability of QST to predict pain, disability, and negative affect. Of the 37 studies included in the review (n = 3860 participants), 32 were prospective cohort studies and five were randomized controlled trials (RCTs). Pain was an outcome in 30 studies, disability in 11 and negative affect in three. Meta-analysis showed that baseline QST predicted musculoskeletal pain and disability. Baseline modalities quantifying central mechanisms such as temporal summation (TS) and conditioned pain modulation (CPM) were correlated with follow-up pain, whereas baseline mechanical threshold modalities were predictive of follow-up disability. The authors concluded that QST indicators of pain hypersensitivity might aid to develop targeted interventions aiming to enhance outcomes across a range of musculoskeletal conditions. However, this needs to be validated in further studies.⁵⁴

Shy et al⁵⁵ performed a systemic review of the literature to assess the clinical utility, efficacy, and safety of QST on behalf of the Therapeutics and Technology Assessment Subcommittee of the AAN. This review included 350 articles that employed computer operated threshold systems, manually operated threshold systems, and electrical threshold devices. The use of normal values and the degree of reproducibility between the same and different systems were evaluated. Because of variances between systems, normal values from one system cannot be transferred to others. Reproducibility of findings was also a significant concern, and there is no consensus on how it should be defined. There were no adequately powered class I studies found showing the effectiveness of QST in assessing any particular disorder. A few class II and III studies determined that QST is probably or possibly useful in identifying small or large fiber sensory abnormalities in patients with diabetic neuropathy, small fiber neuropathies, uremic neuropathies, and demyelinating neuropathy. The authors concluded that QST is possibly a useful tool for measuring sensory impairment for clinical and research studies. However, QST findings should not be the only criteria utilized to diagnose pathology. QST is not currently useful for the purpose of resolving medicolegal matters since malingering and other nonorganic factors can influence the test outcomes. Well-designed studies contrasting various QST devices and methodologies are necessary and should include patients with abnormalities detected solely by QST.⁵⁵

Katz et al⁵⁶ performed a systematic review of the literature to evaluate the use of QST methods to detect hyperalgesia in chronic pain patients on long-term opioids in clinical trials. Fourteen articles were involved in the review: one RCT, one prospective controlled trial, three prospective uncontrolled trials, and nine cross-sectional observation trials. Hyperalgesia measurement paradigms utilized cold pain, heat pain, pressure pain, electrical pain, ischemic pain, and injection pain. While none of the stimuli could detect patients' hyperalgesia, heat pain sensitivity indicated some encouraging findings. The authors concluded that none of the QST methods reviewed met the criteria of a definitive standard for the measurement of hyperalgesia. The authors indicate that further studies should be performed that use improved study design.⁵⁶

Marcuzzi et al⁵⁷ performed a systematic literature review to evaluate the prognostic value of QST measures in individuals with low back pain (LBP). Studies were included if they were prospective longitudinal in design, evaluated at least one QST measure in individuals with LBP, evaluated LBP status at follow-up, and reported the correlation of QST data with LBP status at follow-up. Statistical pooling of outcomes was unattainable due to heterogeneity between studies. Of the 6,408 articles screened after duplicates were removed, only three studies were included. None of these articles described a substantial association between the QST measures evaluated and the LBP outcome. Three areas at high risk of bias were recognized that possibly compromise the validity of these findings. The authors concluded that because of the lack of available studies and the methodological shortcomings detected, it remains unknown whether QST measures are predictive of outcome in LBP.⁵⁷

Wang et al⁶⁷ performed a systematic review of the literature to assess the diagnostic accuracy of monofilament tests for identifying diabetic peripheral neuropathy. A total of 19 comparative studies met the inclusion criteria and were part of the qualitative synthesis. Eight studies utilizing NCS as the reference standard were chosen for the meta-analysis. The pooled sensitivity and specificity of monofilament tests for identifying diabetic peripheral neuropathy were 0.53 and 0.88, respectively. The pooled positive likelihood ratio and negative likelihood ratio were 4.56 and 0.53, respectively. The authors concluded that monofilament tests had limited sensitivity for screening diabetic peripheral neuropathy. Based on currently available evidence, the clinical utilization of monofilament tests in the assessment of diabetic peripheral neuropathy cannot be supported.⁶⁷

SEMG

The AANEM⁶¹ performed a systematic review of the literature regarding the use of SEMG in the diagnosis and study of neuromuscular disorders. Evidence-based literature indicates: 1) SEMG may be helpful to identify the presence of neuromuscular disease. 2) The data are inadequate to establish the clinical efficacy of SEMG for differentiating between neuropathic and myopathic conditions or for identifying the more specific neuromuscular conditions of post-poliomyelitis syndrome, pathologic fasciculations, acquired demyelinating peripheral neuropathy, amyotrophic lateral sclerosis, myotonic dystrophy, and hypokalemic periodic paralysis. 3) The data are inadequate to address the question of disease severity detectable by SEMG. 4) The data are lacking to contrast the diagnostic effectiveness of SEMG with the established technologies of NEMG, NCS, and muscle ultrasonography. The authors concluded that the literature shows no added clinical efficacy for SEMG above the established NEMG as a diagnostic tool for detection and distinction of myopathic from neuropathic neuromuscular disease.⁶¹

Wang et al⁶² conducted a systematic review and meta-analysis of the literature to assess the significance of SEMG as a measure of trunk muscle activity in patients with spinal cord injury (SCI). The review included eleven case-control, cohort, and cross-sectional studies. The evidence revealed that trunk muscle activities for the sitting condition were greater in individuals with SCI than normal individuals. SEMG activity of trunk muscles for the sitting condition and posterior transfer was greater in individuals with high level (HL)-SCI contrasted to those with low level (LL)-SCI. Also, across studies, the level of trunk muscle activity for various difficulty settings was different for a given SCI group. The authors concluded that further research is needed to assess the efficacy of SEMG studies for trunk muscles for individuals with SCI.⁶² There is no evidence from this study that this information will affect patient management.

Halford et al⁶³ performed a prospective multicenter phase III study to assess the performance and tolerability in the epilepsy monitoring unit (EMU) of an investigational wearable SEMG monitoring system for the recognition of generalized tonic-clonic seizures (GTCSs). Study participants included 199 patients with a history of GTCSs who were admitted to the EMU in eleven level IV epilepsy centers for clinically indicated video-electroencephalographic monitoring and who received SEMG monitoring with a wearable device that was worn on the arm over the biceps muscle. All recorded SEMG data were processed at a central site utilizing a previously created detection algorithm. Detected GTCSs were contrasted to events confirmed by a majority of three expert reviewers. For all patients, the detection algorithm detected 35 of 46 (76%, 95% confidence interval [CI] = 0.61 - 0.87) of the GTCSs, with a positive predictive value (PPV) of 0.03 and an average false alarm rate (FAR) of 2.52 per 24 hours. For data recorded while the device was positioned over the midline of the biceps muscle, the system detected 29 of 29 GTCSs (100%, 95% CI = 0.88 – 1.00), with a detection delay averaging 7.70 s, a PPV of 6.2%, and a mean FAR of 1.44 per 24 hours. Mild to moderate adverse events were reported in 28% (55 of 199) of patients and led to study withdrawal in 9% (17 of 199). These adverse events generally involved skin irritation produced by the electrode patch that resolved without treatment. No serious adverse events were reported. The authors concluded that recognition of GTCSs using a SEMG monitoring device on the biceps is possible. However, improvements in the device are necessary to reduce the number of false-positive detections.⁶³

Physiologic Recording of Movement Disorder Symptoms

Heldman et al⁵⁹ evaluated the reliability and responsiveness of a portable kinematic system for quantifying Parkinson's disease (PD) motor deficits as compared to clinical ratings. Eighteen PD patients with subthalamic nucleus deep-brain stimulation (DBS) completed three tasks for assessing resting tremor, postural tremor, and finger-tapping speed, amplitude, and rhythm while wearing a wireless motion-sensor unit (Kinesia™) on the more-affected index finger. These tasks were repeated three times with DBS turned off and at each of ten distinctive stimulation amplitudes chosen to yield small changes in treatment response. Each task performance was video recorded for subsequent clinician rating in blinded, randomized order. Test-retest reliability was calculated as intraclass correlation (ICC), and sensitivity was calculated as minimal detectable change (MDC) for each DBS amplitude. The ICCs for Kinesia™ were substantially higher than those for clinician ratings of finger-tapping speed, amplitude, and rhythm, but were not significantly different for evaluations of resting or postural tremor. Likewise, Kinesia™ scores yielded a lower MDC as contrasted with clinician scores across all finger-tapping sub-scores but did not differ significantly for resting and postural tremor. The authors concluded that the Kinesia™ portable kinematic system may offer greater test-retest reliability and sensitivity to change than conventional clinical ratings for measuring bradykinesia, hypokinesia, and dysrhythmia in PD patients. However, the study did not substantiate the efficacy of such findings in improving care and outcome of patients. Additional studies are needed with robust evidence revealing consistent patient-relevant outcomes with the use of physiologic recording of movement disorder symptoms.⁵⁹

Automated Point of Care Nerve Conduction Tests

The results of preliminary trials for automatic or portable nerve conduction monitoring systems are encouraging; however, the studies are predominantly small case series contrasting portable nerve conduction monitoring systems with conventional NCSs or clinical examination in the same patient.^47-52 Additional studies are needed with robust evidence revealing consistent patient-relevant outcomes with the use of point of care nerve conduction tests.

Sharma et al⁵³ conducted a study to evaluate a point-of-care nerve conduction device (POCD) (NC-stat^®|DPNCheck™) in the assessment of diabetes polyneuropathy (DPN) and contrasted it with the LDI_FLARE that utilizes a laser Doppler imaging technique for early detection of small fiber dysfunction. Study participants included 162 patients with DM and 80 healthy controls (HC). Based on the 10-point Neuropathy Disability Score (NDS), DPN was categorized into none (< 2), mild (3 - 5) moderate (6 - 7), and severe (8 - 10). The correlations between POCD outcomes and the LDI_FLARE within the NDS categories were assessed utilizing regression analysis. In the HC and DM groups, the sural nerve conduction velocity (SNCV) and the sensory nerve action potential (SNAP) amplitude measured with the POCD correlated appreciably with the LDI_FLARE technique. Significance was also noted in all categories of DPN. The receiver operating characteristic (ROC) curves within each category of DPN indicated that the POCD was sensitive in the evaluation of DPN. The authors concluded that the NC-stat^®|DPNCheck™ system seems to have considerable potential for evaluating DPN in the clinical setting. According to the authors, the NC-stat may be limited as it is dependent on the presence of an accessible sural nerve that can be anatomically absent in up to 9% of healthy individuals.⁵³ Additional studies are needed with robust evidence revealing consistent patient-relevant outcomes with the use of point of care nerve conduction tests.

EDX studies are an extension of the clinical evaluation of patients with conditions of the peripheral and/or central nervous system. EDX studies are often vital in evaluating symptoms, arriving at a proper diagnosis, and in following a disease process and its response to therapy in patients with neuromuscular disorders.

Evidence-based guidelines and/or peer-reviewed literature indicate that NCSs and NEMG are beneficial when they are conducted and interpreted at the same time, on site, and in real time for the following conditions: 1) Plexopathy - including idiopathic, traumatic, inflammatory or infiltrative, radiation-induced,¹ brachial plexopathies (e.g., neuralgic amyotrophy, thoracic outlet syndrome) and lumbosacral plexopathies (e.g., diabetic, non-diabetic lumbosacral radiculoplexus neuropathy),⁴ 2) Focal neuropathies (e.g., entrapment neuropathies, or compressive lesions/syndromes such as carpal tunnel syndrome,^5-8 ulnar neuropathy,^9-10 tarsal tunnel syndrome,¹¹ femoral neuropathy, saphenous neuropathy, lateral femoral cutaneous neuropathy, peroneal (fibular) neuropathy, tibial neuropathies, sciatic neuropathy),^1,12-18 3) Generalized neuropathies such as metabolic (e.g., diabetic, uremic), toxic, hereditary or immune-mediated,^1,19-20 4) Motor neuron disease (e.g., ALS or Lou Gehrig’s disease),^1,21-22 5) Myopathy - including inflammatory myopathies such as polymyositis and dermatomyositis, congenital myopathies,²³ congenital and hereditary dystrophic and nondystrophic myopathies, including myotonic muscular dystrophy, acquired myopathies (drug induced myopathy associated with statins, thyroid related), metabolic myopathies (e.g., McArdle disease),^1,24 6) Myotonic disorders (e.g., drug induced myotonia),²⁵ 7) Neuromuscular junction disorders (e.g., myasthenia gravis, Lambert-Eaton myasthenic syndrome, botulism),^{1,26-27,34-35} 8) Polyneuropathies,^1,28-30 9) Radiculopathy - cervical,³¹ thoracic or lumbosacral,^1,32-33 10) Spinal cord disorders³¹ (i.e., myelopathy), 11) 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,¹ and 12) Traumatic nerve lesions, for diagnosis and prognosis.¹

Evidence-based guidelines and/or peer-reviewed literature demonstrate support for NMJ studies for the following conditions: 1) Botulinum toxicity,^1,3 2) Motor neuron disease (e.g., ALS or Lou Gehrig’s disease),¹ 3) Myopathy,^1,34 4) Myasthenia gravis,²⁷ and 5) Myasthenic syndrome (e.g., Lambert-Eaton myasthenic syndrome).^1,3

Evidence-based guidelines and/or peer-reviewed literature lend support for NCSs when performed without NEMG for the following situations: 1) Individuals treated with anticoagulants^35-36 such as warfarin (Coumadin), rivaroxaban (Xarelto), dabigatran (Pradaxa), apixaban (Eliquis), edoxaban (Lixiana), clopidogrel (Plavix), ticagrelor (Brilinta), ticlopidine (Ticlid), prasugrel (Effient), varapaxar (Zontivity), dipyridamole, cilostazol (Pletal), 2) Individuals with significant lymphedema in the affected extremity,³⁶ and 3) Individuals being evaluated for carpal tunnel syndrome or tarsal tunnel syndrome.^3,11

Evidence-based guidelines and/or peer-reviewed literature indicate that NEMG when conducted without NCSs is useful for the following situations: 1) Guidance for botulinum toxin treatment injections when it is difficult to isolate affected muscles,^1,37 2) Laryngeal neuropathy,³⁸ 3) Constipation,³⁹ 4) Fecal incontinence,³⁹ 5) Lower urinary tract symptoms,^40-44 and 6) Patients with risk factors for urinary retention.^40-44

Evidence-based guidelines recommend SFEMG for ocular myasthenia⁴⁵, myasthenia gravis,^27,34-35 and myasthenic syndrome (e.g., Lambert-Eaton myasthenic syndrome).²⁷

The quality of evidence in the literature is insufficient to support the following: 1) EDX studies where the interpretation is delayed and not completed at the time the study is performed.^2,8,46 The NCS must be performed and interpreted with the NEMG on site and in real time^1-2 2) EDX studies (NCS and NEMG) not performed in accordance with the CMS regulations defined for supervision for diagnostic tests. (Refer to the CMS IOM Pub 100-02, Medicare Benefit Policy Manual, Chapter 15, Section 80 Requirements for Diagnostic X-Ray, Diagnostic Laboratory, and Other Diagnostic Tests) 3) Non-invasive EDX studies using portable hand-held devices or automated point of care nerve conduction monitoring systems, which are incapable of real-time waveform display and analysis^3,47-53 4) Testing for polyneuropathy of diabetes in patients without clinical deficits or for the sole purpose of monitoring disease intensity or treatment efficacy^3,20 5) QST (e.g., hot-cold, touch, vibration)^54-58 6) NCSs accomplished with discriminatory devices that use fixed anatomic templates and computer-generated reports used as an adjunct to physical examination routinely on all patients¹ 7) Physiologic recording of movement disorder symptoms, including bradykinesia, dyskinesia, and tremor using wearable devices with accelerometers or gyroscopes⁵⁹ 8) NCSs or NEMG for muscle pain without the presence of other abnormalities on examination or laboratory testing⁶⁰ 9) NEMG for the following situations: a) Definitive diagnosis based on paraspinal NEMG in areas with scar from past surgeries (e.g., previous laminectomies)³ b) SEMG^3,61-63 c) Macro-EMG³, and d) NEMG for isolated neck or back pain after a motor vehicle accident.⁶⁰

Studies performed beyond the reasonable maximum number of studies recommended in the AMA CPT^® Codebook, Appendix J, Electrodiagnostic Medicine Listing of Sensory, Motor, and Mixed Nerves. These recommendations are supported by the AANEM.¹ Additional studies may be considered upon redetermination.

Evidence-based guidelines indicate that repeat EDX assessment may be needed in certain circumstances. The frequency for repeating EDX studies in a given patient by a given EDX provider for a given diagnosis per year can be reasonably limited. The following number of studies per 12-month period per diagnosis per provider are suitable: 1) Two studies for carpal tunnel-unilateral, carpal tunnel-bilateral, radiculopathy, mononeuropathy, polyneuropathy, myopathy, and NMJ disorders. 2) Three studies for motor neuron disease and plexopathy. These limits should not apply if the patient requires assessment by more than one EDX provider (i.e., a second opinion or an expert opinion at a tertiary care center) in a given year or if the patient requires evaluation for a second diagnosis in a given year.¹

Repeat EDX studies are rare and should not be necessary in a 12-month period in 80% of all cases.¹ Additional studies may be considered upon redetermination. In such circumstances, the rationale for the repeat study should be included in the medical record. Comparison with the previous study findings should be documented.

Please refer to the Local Coverage Article: Billing and Coding: Nerve Conduction Studies and Electromyography, A54095 for documentation requirements, utilization parameters and all coding information as applicable.

This bibliography presents those sources that were obtained during the development of this policy. The Contractor is not responsible for the continuing viability of Website addresses listed below.

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