Surface electromyography, a non-invasive procedure which records the summation of muscle electrical activity, has been investigated as a technique to evaluate the physiological functioning of the back. In addition, this has been studied as a technique to evaluate abnormal patterns of electrical activity in the paraspinal muscles in patients with back pain symptoms such as spasm, tenderness, limited range of motion, or postural disorders.

Identifying the pathogenesis of back pain is a challenging task, in part due to the complex anatomy of the back, which includes vertebrae, discs, facet joints, spinal nerve roots, and muscles. For example, back pain may be related to osteoarthritis, disc disease, subluxation, or muscular pathology, such as muscle strain or spasm. In addition, due to referred pain patterns, the location of the pain may not be anatomically related to the pathogenesis of the pain. For example, buttock or leg pain may be related to pathology in the spine. In addition to the diagnostic challenges of back pain is the natural history of acute back pain. As reported in the guidelines from the Agency for Healthcare Research and Quality (AHRQ, formerly the Agency for Health Care Policy and Research, AHCPR) for the management of acute low back pain, the majority of cases of acute low back pain will resolve without specific therapy and thus no specific workup is recommended, unless “red flag” warning signs are present or the pain persists for longer than 1 month. Conservative therapy consists of physical therapy and a continuation of normal activities within the limits permitted by the pain.

Aside from physical exam, diagnostic tests include imaging technologies, such as magnetic resonance imaging (MRI), designed to identify pathology (e.g., bulging discs), or tests such as discography to localize the abnormality by reproducing the pain syndrome. However, due to their lack of specificity, all diagnostic tests must be carefully interpreted in the context of the clinical picture. For example, 5% of asymptomatic patients will have bulging discs as identified by MRI. Therefore, the presence of a bulging disc may only be clinically significant if well correlated with symptoms. Assessment of the musculature may focus on range of motion or strength exercises.

In contrast to anatomic imaging, surface electromyography (SEMG), which records the summation of muscle activity from groups of muscles, has been investigated as a technique to evaluate the physiological functioning of the back. SEMG, a noninvasive procedure, is contrasted with needle electromyography, an invasive procedure, in which the electrical activity of individual muscles is recorded. Paraspinal SEMG, also referred to as paraspinal EMG scanning, has been explored as a technique to evaluate abnormal patterns of electrical activity in the paraspinal muscles in patients with back pain symptoms such as spasm, tenderness, limited range of motion, or postural disorders. The technique is performed using 1 or an array of electrodes placed on the skin surface, with recordings made at rest, in various positions, or after a series of exercises. Recordings can also be made by using a handheld device, which is applied to the skin at different sites. Electrical activity can be assessed by computer analysis of the frequency spectrum (i.e., spectral analysis), amplitude, or root mean square of the electrical action potentials. In particular, spectral analysis focusing on the median frequency has been used to assess paraspinal muscle fatigue during isometric endurance exercises. Paraspinal SEMG has been researched as a technique to establish the etiology of back pain and also has been used to monitor the response to therapy and establish physical activity limits, such as assessing capacity to lift heavy objects or ability to return to work.

Paraspinal SEMG is an office-based procedure that may be most commonly used by physiatrists or chiropractors. SEMG devices approved by the U.S. Food and Drug Administration (FDA) include those that use a single electrode or a fixed array of multiple surface electrodes. The following clinical applications of the paraspinal SEMG have been proposed:

• clarification of a diagnosis (i.e., muscle, joint, or disc disease)
• select a course of medical therapy
• select a type of physical therapy
• pre-operative evaluation
• postoperative rehabilitation
• follow-up of acute low back pain
• evaluation of exacerbation of chronic low back pain
• evaluation of pain management treatment techniques

Paraspinal surface electromyography (SEMG) is considered investigational as a technique to diagnose or monitor back pain.

There is no specific CPT code for surface EMG (other than 96002, dynamic surface electromyography, during walking or other functional activities, 1–12 muscles, which is part of the CPT coding for motion analysis). Existing codes for EMG (95860-95872) explicitly describe needle EMG, in which a needle is inserted into an individual muscle. Therefore, these codes do not describe surface EMG. 

One of the following nonspecific CPT codes might be used:

95999: Unlisted neurological or neuromuscular diagnostic procedure

97799: Unlisted physical medicine/rehabilitation service or procedure

99199: Unlisted special service, procedure, or report

There is a HCPCS code that is specific to surface EMG (S3900).

SEMG has been used as a research tool to further evaluate the performance of paraspinal muscles in patients with back pain and to further understand the etiology of low back pain. (1-5) However, validation of its use as a clinical diagnostic technique involves a sequential 3-step procedure as follows:

1. The technical performance of the test, including determination of test, retest reliability, positive and negative predictive values, compared to a gold standard

2. Data demonstrating how the results of the test may be used in the management of the patient

3. A determination of whether beneficial health outcomes occur as a result of the change in management

The following discussion focuses on these 3 steps.

1. Technical Performance of the Test

Several studies using different SEMG devices have suggested that paraspinal SEMG, in general, is a reliable technique, based on coefficients of variation or test retest studies. (2, 3) While reliability is an important initial diagnostic parameter, the reliability of a test does not necessarily relate to its clinical utility. A diagnostic test must be further evaluated against a gold standard. The gold standard for evaluating the electrical activity of muscles is needle electromyography. Ideally, one would like to see data comparing the results of SEMG, which tests groups of muscles, to needle electromyography, which evaluates individual muscles. No such articles were identified in a literature search, thus it is not known how, or if, the electrical activity of groups of muscles relates to any specific muscle pathology, as validated by needle EMG.

However, it is recognized that the pathology of individual muscles (i.e., radiculopathy, neuropathy, etc.) may represent a different process than the pathology of muscle groups (i.e., muscle strain, spasm, etc.), and thus SEMG may be considered by its advocates as a unique test for which there is currently no gold standard. Nevertheless, even if one accepts this premise, there are inadequate data to evaluate the diagnostic performance of SEMG. For example, no articles were identified in the published peer-reviewed literature that established definitions of normal or abnormal SEMG. In some instances, asymmetrical electrical activity may have been used to define abnormality, results may be compared to a “normative data base.” However, there was no published literature defining what degree of asymmetry would constitute abnormality or how a normative database was established. (4)

In the absence of a gold standard diagnostic test, correlation with the clinical symptoms and physical exam is critical. De Luca has published a series of studies investigating a type of SEMG called the Back Analysis System (BAS), consisting of surface electrodes and other components to measure the electrical activity of muscles during isometric exercises designed to produce muscle fatigue. (5) Using physical exam and clinical history as a gold standard, the author found that BAS was able to accurately identify control and back pain patients 84% and 91% of the time, respectively, with the values increasing to 100% in some populations of patients. (Accuracy is the sum of true positive and true negative results.) However, these studies were not designed as a clinical diagnostic tool per se, but were intended to investigate the etiology of back pain and to investigate muscular fatigue patterns in patients with and without back pain.

When used to monitor response to therapy, patients may have served as their own control. However, there are no data that analyze how changes in the SEMG correlate to clinical response, whether a clinical response in the face of persisting SEMG abnormalities suggests ongoing pathology, or whether persistent symptoms in the face of a normal SEMG represent malingering.

2. How Results of the Test Are Used in the Management of the Patient

Several articles describe the use of SEMG as an aid in classifying low back pain. (6, 7) Much of the research in this application has focused on the use of spectral analysis to assess muscle fatigability. However, it is unclear how this information may be used in the management of the patient. For example, while the innovators of the BAS system indicate that SEMG can suggest potential therapies by distinguishing deconditioning from muscle inhibition secondary to pain-related behavior, (6) no clinical studies describe the use of SEMG in suggesting therapy. In another application of SEMG, Arena and colleagues assessed the amplitude of SEMG recordings as a measure of paraspinal muscle tension in 66 patients and reported that the degree of muscle tension did not correlate with pain levels. These findings raised questions about the role of biofeedback, muscle relaxants, or other therapies designed to reduce muscle tension. (8) While SEMG may be used to objectively document muscle spasm or other muscular abnormalities, it is unclear how such objective documentation would supplant or enhance clinical evaluation, or how this information would be used to alter the treatment plan. Part of the difficulty in clinical interpretation is understanding to what extent the SEMG abnormalities are primary or secondary. In addition, as noted by the guidelines from the Agency for Healthcare Research and Quality (AHRQ, formerly the Agency for Health Care Policy and Research, AHCPR), no specific workup is recommended for acute low back pain without warning signs.

In terms of the use of SEMG to monitor response to treatment, there are no data to demonstrate how the results of SEMG compare to clinical assessment, such as determining recommended activity levels or ability to return to work. (9)

3. Whether Beneficial Health Outcomes Occur as a Result of the Change in Management

There are no data regarding the final health outcomes. For example, SEMG has been proposed as a technique to differentiate muscle spasm from muscle contracture, with muscle spasm treated with relaxation therapy, and contracture treated with stretching exercises. There are no data to validate that such treatment suggested by SEMG results in improved outcomes. (10, 11)

Conclusion

There are inadequate data regarding paraspinal SEMG to validate 3 key attributes of any diagnostic test, i.e., its performance compared to a gold standard, studies documenting how the test is used in the management of the patient, and studies validating that the changes in patient management result in an overall health benefit. The above discussion parallels a 1994 review of the chiropractic literature. (12)

2002-2006 Update

A review of the MEDLINE database from the period of 2002 through December 2005 did not identify any studies published in the peer-reviewed literature that would address the limitations noted in the discussion here. For example, the only studies identified on updated literature searches consist of uncontrolled case series. (13-15) Therefore, the policy statement is unchanged.

2007-2008 Update
A search of the MEDLINE database for the period of January 2006 to January 2008 did not identify any relevant studies. A review of spinal muscle evaluation in low-back pain patients indicates that the validity of SEMG remains controversial. (16) The authors note that although many studies show increased fatigability of the paraspinal muscles in patients with low back pain, it is not known whether these changes are causes or consequences of the low back pain. Also, “the considerable inter-individual variability and the absence of normative data complicate the description of normal or abnormal profiles, thereby limiting the diagnostic usefulness of SEMG.” These conclusions are similar to those reached above. The policy statement is unchanged.

2009 Update

A MEDLINE search was conducted for the period January 2008 through August 2009 to update this policy. None of the articles identified provide new relevant information that would impact the policy statement. The recent literature on SEMG describes studies that analyze muscle function in normal subjects; therefore, the policy statement remains unchanged.

References:

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EMG, Surface, Paraspinal
Paraspinal Surface EMG
Surface EMG, Paraspinal