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Electromyographic Evaluation of Cervical Radiculopathy
2224
DEPARTMENTS
Letters to the Editor Electromyographic Evaluation of Cervical Radiculopathy 1
We read with great interest the article by Dr Yaar regarding electromyographic evaluation for patients with suspected cervical radiculopathy. Unfortunately, the arguments presented were untested in clinical trials and do not support the contentions regarding what constitutes an optimal needle electromyography examination for evaluation of persons with suspected cervical radiculopathy. In his study, Dr Yaar used anatomic charts and a computational model to derive what he considers optimal electromyographic examinations for persons with suspected cervical radiculopathy based on myotomal innervation patterns. His extensive screens assess all roots and include enough muscles to identify the precise level when a radiculopathy is present. He suggests up to 11 upper limb muscles (one being the cervical paraspinals) without any clinical validation of this contention through prospective or retrospective studies. Without such validation in a clinical study, his recommendations remain only theoretical. The paradigm presented and the approach advocated fails to take into account the fact that most referrals will not have an electrodiagnostically confirmable radiculopathy. In the vast majority of cases, an entrapment such as carpal tunnel syndrome is present, the patient has a musculoskeletal disorder, or the patient has nonspecific neck pain without radiculopathy. Needle electromyography is a painful and anxiety-provoking procedure. In most cases, Dr Yaar’s screens will needlessly subject these patients to about twice as many muscles as is necessary. Previous retrospective and prospective clinical studies2,3 support a 2-stage process that uses an abbreviated, yet optimal screen, followed by expanded electromyographic testing if one of the screening muscles is positive. Such an approach minimizes discomfort for the majority of patients who will not have a cervical radiculopathy by electromyography, yet with a high degree of certainty identify those patients with an electrodiagnostically confirmable cervical radiculopathy. Over the last decade, our investigative team2-5 examined how many and which muscles constitute the optimal electromyographic evaluation. Our goal was to derive the minimal electromyographic screen that identified persons with an electrodiagnostically confirmable radiculopathy, yet minimized patient discomfort. Some radiculopathies such as those affecting only the sensory roots cannot be confirmed by needle electromyography no matter how many muscles are tested. A screening electromyographic evaluation involves determining whether the radiculopathy can be confirmed by electromyography. If the radiculopathy cannot be confirmed by electromyography, it is of no utility to add more muscles. The process of identification can be conceptualized as a conditional probability— given that a cervical radiculopathy can be confirmed by needle electromyography, what is the minimum number of muscles that must be examined in order to confidently recognize or exclude this possibility? The results of a multicenter study2 demonstrated that 6 muscles were sufficient, providing excellent detection (94%⫺99%) for an electrodiagnostically confirmable cervical radiculopathy. Six muscles representing all cervical root levels and including the cervical paraspinal muscles allow the examiner to confidently detect a cervical radiculopathy that can be confirmed through needle electromyography. Adding additional muscles was not useful for increasing identification. If 1 of the 6 muscles studied in the screen is positive, there is the possibility of confirming by electromyoArch Phys Med Rehabil Vol 86, November 2005
graphy that a radiculopathy is present. In this case, the examiner must study additional muscles to confirm this possibility, to determine the radiculopathy level, and to exclude mononeuropathy or polyneuropathy. If none of the 6 muscles are abnormal, the examiner can be confident of not missing the opportunity to confirm through electromyography that a radiculopathy is present and the examiner can curtail the painful needle exam. The patient may still have a radiculopathy, but other tests, such as magnetic resonance imaging, will be necessary to confirm this clinical suspicion. A large retrospective study3 likewise supported the concept of an abbreviated cervical screen. These studies clarified for electrodiagnosticians the point of diminishing returns, beyond which diagnostic certainty for detecting a cervical radiculopathy is not enhanced by examining more muscles. Six muscle screens are sufficient for assessing lumbosacral radiculopathies as well.4 In his article, Dr Yaar states that the remedy for missing a radiculopathy is to sample more muscles. This statement is incorrect and fails to take into consideration the fact that for persons with (1) sensory root involvement, (2) radiculopathies in which motor axonal loss is not occurring, or (3) radiculopathies in which the denervation is balanced by reinnervation, electromyography will not demonstrate fibrillation potentials. Studying additional muscles in these circumstances does not enhance the clinical assessment, yet adds substantially to patient anxiety and discomfort. Simply studying large numbers of muscles for all patients with suspected cervical radiculopathy is a simplistic and flawed strategy. Dr Yaar’s recommendations, absent any validation though clinical trials, do not represent evidence-based medicine. Electrodiagnostic medicine consultants should not adopt Dr Yaar’s recommendations and needlessly subject patients to excessive needle electromyographic testing in the misguided judgement that more muscles improve diagnostic yield. Timothy R. Dillingham, MD Medical College of Wisconsin Milwaukee, WI Tamara Lauder, MD Woodruff, WI References 1. Yaar I. The logical choice of muscles for needle-electromyography evaluation of cervical radiculopathy. Arch Phys Med Rehabil 2005; 86:521-6. 2. Dillingham TR, Lauder TD, Andary M, et al. Identification of cervical radiculopathies: optimizing the electromyographic screen. Am J Phys Med Rehabil 2001;80:84-91. 3. Lauder T, Dillingham TR. The cervical radiculopathy screen: optimizing the number of muscles studied. Muscle Nerve 1996;19:662-5. 4. Dillingham TR, Lauder TD, Andary M, et al. Identifying lumbosacral radiculopathies: an optimal electromyographic screen. Am J Phys Med Rehabil 2000;79:496-503. 5. Lauder T, Dillingham TR, Huston C, Chang A, Belandres PV. Lumbosacral radiculopathy screen: optimizing the number of muscles studied. Am J Phys Med Rehabil 1994;73:394-402.
doi:10.1016/j.apmr.2005.09.004
DEPARTMENTS
Letters to the Editor Electromyographic Evaluation of Cervical Radiculopathy 1
We read with great interest the article by Dr Yaar regarding electromyographic evaluation for patients with suspected cervical radiculopathy. Unfortunately, the arguments presented were untested in clinical trials and do not support the contentions regarding what constitutes an optimal needle electromyography examination for evaluation of persons with suspected cervical radiculopathy. In his study, Dr Yaar used anatomic charts and a computational model to derive what he considers optimal electromyographic examinations for persons with suspected cervical radiculopathy based on myotomal innervation patterns. His extensive screens assess all roots and include enough muscles to identify the precise level when a radiculopathy is present. He suggests up to 11 upper limb muscles (one being the cervical paraspinals) without any clinical validation of this contention through prospective or retrospective studies. Without such validation in a clinical study, his recommendations remain only theoretical. The paradigm presented and the approach advocated fails to take into account the fact that most referrals will not have an electrodiagnostically confirmable radiculopathy. In the vast majority of cases, an entrapment such as carpal tunnel syndrome is present, the patient has a musculoskeletal disorder, or the patient has nonspecific neck pain without radiculopathy. Needle electromyography is a painful and anxiety-provoking procedure. In most cases, Dr Yaar’s screens will needlessly subject these patients to about twice as many muscles as is necessary. Previous retrospective and prospective clinical studies2,3 support a 2-stage process that uses an abbreviated, yet optimal screen, followed by expanded electromyographic testing if one of the screening muscles is positive. Such an approach minimizes discomfort for the majority of patients who will not have a cervical radiculopathy by electromyography, yet with a high degree of certainty identify those patients with an electrodiagnostically confirmable cervical radiculopathy. Over the last decade, our investigative team2-5 examined how many and which muscles constitute the optimal electromyographic evaluation. Our goal was to derive the minimal electromyographic screen that identified persons with an electrodiagnostically confirmable radiculopathy, yet minimized patient discomfort. Some radiculopathies such as those affecting only the sensory roots cannot be confirmed by needle electromyography no matter how many muscles are tested. A screening electromyographic evaluation involves determining whether the radiculopathy can be confirmed by electromyography. If the radiculopathy cannot be confirmed by electromyography, it is of no utility to add more muscles. The process of identification can be conceptualized as a conditional probability— given that a cervical radiculopathy can be confirmed by needle electromyography, what is the minimum number of muscles that must be examined in order to confidently recognize or exclude this possibility? The results of a multicenter study2 demonstrated that 6 muscles were sufficient, providing excellent detection (94%⫺99%) for an electrodiagnostically confirmable cervical radiculopathy. Six muscles representing all cervical root levels and including the cervical paraspinal muscles allow the examiner to confidently detect a cervical radiculopathy that can be confirmed through needle electromyography. Adding additional muscles was not useful for increasing identification. If 1 of the 6 muscles studied in the screen is positive, there is the possibility of confirming by electromyoArch Phys Med Rehabil Vol 86, November 2005
graphy that a radiculopathy is present. In this case, the examiner must study additional muscles to confirm this possibility, to determine the radiculopathy level, and to exclude mononeuropathy or polyneuropathy. If none of the 6 muscles are abnormal, the examiner can be confident of not missing the opportunity to confirm through electromyography that a radiculopathy is present and the examiner can curtail the painful needle exam. The patient may still have a radiculopathy, but other tests, such as magnetic resonance imaging, will be necessary to confirm this clinical suspicion. A large retrospective study3 likewise supported the concept of an abbreviated cervical screen. These studies clarified for electrodiagnosticians the point of diminishing returns, beyond which diagnostic certainty for detecting a cervical radiculopathy is not enhanced by examining more muscles. Six muscle screens are sufficient for assessing lumbosacral radiculopathies as well.4 In his article, Dr Yaar states that the remedy for missing a radiculopathy is to sample more muscles. This statement is incorrect and fails to take into consideration the fact that for persons with (1) sensory root involvement, (2) radiculopathies in which motor axonal loss is not occurring, or (3) radiculopathies in which the denervation is balanced by reinnervation, electromyography will not demonstrate fibrillation potentials. Studying additional muscles in these circumstances does not enhance the clinical assessment, yet adds substantially to patient anxiety and discomfort. Simply studying large numbers of muscles for all patients with suspected cervical radiculopathy is a simplistic and flawed strategy. Dr Yaar’s recommendations, absent any validation though clinical trials, do not represent evidence-based medicine. Electrodiagnostic medicine consultants should not adopt Dr Yaar’s recommendations and needlessly subject patients to excessive needle electromyographic testing in the misguided judgement that more muscles improve diagnostic yield. Timothy R. Dillingham, MD Medical College of Wisconsin Milwaukee, WI Tamara Lauder, MD Woodruff, WI References 1. Yaar I. The logical choice of muscles for needle-electromyography evaluation of cervical radiculopathy. Arch Phys Med Rehabil 2005; 86:521-6. 2. Dillingham TR, Lauder TD, Andary M, et al. Identification of cervical radiculopathies: optimizing the electromyographic screen. Am J Phys Med Rehabil 2001;80:84-91. 3. Lauder T, Dillingham TR. The cervical radiculopathy screen: optimizing the number of muscles studied. Muscle Nerve 1996;19:662-5. 4. Dillingham TR, Lauder TD, Andary M, et al. Identifying lumbosacral radiculopathies: an optimal electromyographic screen. Am J Phys Med Rehabil 2000;79:496-503. 5. Lauder T, Dillingham TR, Huston C, Chang A, Belandres PV. Lumbosacral radiculopathy screen: optimizing the number of muscles studied. Am J Phys Med Rehabil 1994;73:394-402.
doi:10.1016/j.apmr.2005.09.004