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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 39  |  Issue : 3  |  Page : 132-137

Significance of pure sensory manifestations in estimating electromyography results in cervical radiculopathy


1 Department of Neurology, Gazi Mustafa Kemal Occupational and Environmental Diseases Hospital, Ankara, Turkey
2 Department of Neurology, Clinical Neurophysiology Division, Faculty of Medicine, Gazi University, Ankara, Turkey

Date of Submission14-Jan-2022
Date of Decision20-Jun-2022
Date of Acceptance03-Jul-2022
Date of Web Publication30-Sep-2022

Correspondence Address:
Merve Bahar Ercan
Gazi Mustafa Kemal Occupational and Environmental Diseases Hospital, Silahtar Avenue, Yenimahalle, Ankara
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/nsn.nsn_10_22

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  Abstract 


Background: The sensitivity of electromyography (EMG) in cervical radiculopathy (CR) is reportedly higher in patients with objective neurological findings, but many patients are sent to the EMG laboratory with only pain and paresthesias. Aims: We aimed to assess the diagnostic contribution of EMG in patients with sensory manifestations without objective neurological deficits. Settings and Design: The files of patients with neck pain radiating to the shoulder and arm on the same side referred to the EMG Laboratory were retrospectively evaluated. EMG findings of those with pure sensory manifestations were compared with the results obtained from patients with objective neurological deficits. Subjects and Methods: Patients with subjective sensory manifestations were separated into two groups according to the specificity of the presenting symptoms, who were compared with subjects with neurological findings in the upper extremity. Clinical diagnoses of the patients were compared with the electrodiagnostic testing results. Statistical Analysis: Categorical variables were analyzed with multi-span Chi-square test, while individual groups were compared utilizing Fisher's exact test. One-way analysis of variance was employed to assess the significance of group differences for quantitative values. Results: EMG rarely confirmed CR in patients with purely sensory symptoms. Some of these patients were found to have unexpected peripheral neuropathy syndromes. Both paraspinal and limb muscle EMG abnormalities indicative of CR were not only more common, but also helpful in localization in patients with objective clinical findings. Conclusions: CR patients presenting only with pain and paresthesias even in a specific dermatomal distribution usually demonstrate no abnormalities in EMG examination. However, some of these patients harbor unsuspected entrapment neuropathies.

Keywords: Cervical radiculopathy, electromyography, neck pain, paresthesia, spinal segment


How to cite this article:
Ercan MB, Kuruoglu HR. Significance of pure sensory manifestations in estimating electromyography results in cervical radiculopathy. Neurol Sci Neurophysiol 2022;39:132-7

How to cite this URL:
Ercan MB, Kuruoglu HR. Significance of pure sensory manifestations in estimating electromyography results in cervical radiculopathy. Neurol Sci Neurophysiol [serial online] 2022 [cited 2022 Dec 2];39:132-7. Available from: http://www.nsnjournal.org/text.asp?2022/39/3/132/357497




  Introduction Top


Cervical radiculopathy (CR), a significant cause of disability and morbidity, is a frequent problem among the general population. The disease manifests as neck, shoulder, and upper extremity pain, accompanied by paresthesias and in some instances weakness due to damage of individual nerve roots, while the diagnosis is usually made with clinical examination. Apart from these features in history, neurological examination may reveal loss of deep tendon reflexes, as well as dermatomal sensory defects and myotomal weakness in the upper extremities. Electromyography (EMG) is a useful tool in confirming the presence of a segmental neurogenic involvement brought about by the structural defects of the cervical spine.[1],[2],[3] Furthermore, in some situations, the differential diagnosis from motor neuron disease, plexus lesions or focal neuropathies proves difficult by clinical examination alone, which calls for an electrodiagnostic testing.[4] Among heterogeneously affected patients with findings varying from pure sensory symptoms to objective neurological deficits, the sensitivity of conventional EMG examination in detecting CR has been reported to range between 50% and 71%.[5],[6] On the other hand, the sensitivity is reportedly between 61% and 84%, when cases with objective neurological findings are assessed.[7],[8] In daily clinical practice, patients suspected of having CR are indiscriminately referred to the EMG laboratory, some with only pain and paresthesias; others with additional motor or reflex loss. Our previous experience with radiculopathies in general and reported findings on CR led us to think that the contribution of EMG to the diagnosis is poor in individuals with a normal neurological examination.[6],[7],[8] By comparing the EMG findings of referred patients with purely sensory symptoms to those with neurological deficits, we aimed to demonstrate objectively that our observation holds true.


  Subjects and Methods Top


Subjects

The EMG files of patients with neck pain radiating to the shoulder and arm on the same side referred with a diagnosis of CR to the Clinical Neurophysiology Laboratory between January 2006 and August 2012 were retrospectively evaluated. The study was approved by the Institutional Review Board (Date: October 17, 2012, No: 347). From a total of 402 subjects, those with clinical findings clearly indicative of another neuromuscular disorder, motor neuron disease, brachial plexopathies, as well as patients who had previously undergone surgery for CR and not giving consent to needle EMG studies were excluded (n = 222). The remaining 180 patients were categorized into three groups. While Group 1 consisted of subjects with nonspecific pain and paresthesias, Group 2 included patients with radicular pain and paresthesias that could be ascribed to a specific segmental dermatome. Neither Group 1 nor Group 2 patients exhibited power or deep tendon reflex loss, but some were found to have subjective sensory loss in nondermatomal distribution on neurological examination. Subjects in Group 3 had at least one neurological finding in the upper extremity (weakness, sensory loss in a segmental dermatomal distribution or an impaired deep tendon reflex). Following the neurological examination, a clinical diagnosis was made, which was compared with the electrodiagnostic testing results.

Electromyography studies

Electrodiagnostic examinations were conducted with Neuropack Σ MEB-5504K (Nihon Kohden, Tokyo, Japan), and Counterpoint (Dantec, Skovlunde, Denmark) devices. Upper extremity nerve conduction and needle EMG studies on the affected side were performed. Motor and sensory nerve conduction studies of the median and ulnar nerves were performed. Compound muscle action potentials were recorded from the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles, respectively. Amplitude was measured from peak to peak. Supramaximal stimulation was delivered with a pulse duration of 100 μs. Median nerve was stimulated at the wrist and the elbow. Ulnar nerve was stimulated at the wrist, below and above elbow and axilla levels. Therefore, motor nerve conduction velocities of the elbow and above elbow to axilla segments of the ulnar nerve, as well as forearm segments of the median and ulnar nerves were calculated. Sweep speed and sensitivity was 5 ms and 2 mV per division, respectively. Terminal and F-wave latencies were also obtained. Sensitivity was increased to 200 μV per division for F-wave studies. Amplifier bandpass filters were set at 20–10000 Hz. Sensory nerve conduction studies of the finger-wrist segments of the median (digit II) and ulnar (digit V) nerves were carried out orthodromically with superficial recording electrodes. Sweep speed and sensitivity were 1 ms and 10 μV per division respectively, with a bandpass filter of 20–2000 Hz. The compound nerve action potential amplitudes were measured from peak to peak. Latency measurements were made from the negative peak to calculate sensory nerve conduction velocities. Findings were evaluated using the normal values of our laboratory.

Needle EMG was performed with concentric needle electrodes utilizing a bandpass filter of 10–10000 Hz. A sweep speed of 10 ms per division was employed for spontaneous activity and motor unit potential (MUP) analysis, with sensitivities of 100 and 200 μV, respectively. Both C5 to C8 paraspinal and extremity muscles which consisted of deltoid, biceps brachii, triceps brachii and either APB or ADM were examined. At times other upper extremity muscles were also added to the study to confirm myotomal distribution of abnormalities. Fibrillation potentials or positive sharp waves in the paraspinal muscles confirmed the diagnosis of radiculopathy. Alternatively, high amplitude (>3 mV) or long duration (>15 ms) (HALD) MUPs, as well as fibrillation potentials or positive sharp waves in at least 2 extremity muscles innervated by the same spinal segment, but different peripheral nerves were required for a definite diagnosis of CR. These abnormal findings, not ascribed to peripheral neuropathy, observed in only one extremity muscle without involvement of the paraspinals, were considered “compatible” with the diagnosis of radiculopathy. In cases where the electrodiagnostic examination revealed the presence of a sensory-motor polyneuropathy or entrapment neuropathies of the median or ulnar nerves, limb EMG abnormalities or findings in muscles innervated by the affected nerves were not taken into consideration in the evaluation of CR.

Statistical analysis

Statistical analyses were performed with an SPSS program version 20. Satistical package for Social Sciences (SPSS, Inc., Chicago, IL). A P < 0.05 was considered statistically significant. Categorical variables were analyzed with multi-span Chi-square test, while individual groups were compared utilizing Fisher's exact test. One-way analysis of variance was employed to assess the significance of group differences for quantitative values.


  Results Top


Subjects

Our cohort consisted of 129 (71.5%) female and 51 (28.5%) male patients with a mean age (standard deviation) of 47.6 (12.2) ranging from 20 to 79. Data regarding the demographic features of the patients assigned to the groups are demonstrated in [Table 1]. There was no significant difference in terms of age (F = 0.87, P = 0.42) and pain duration (F = 0.66, P = 0.52) among the groups. Male patients predominated in the group of patients having neurological deficits, while females were in majority in the remaining groups presenting only with pain and paresthesias (Pearson x2 = 20.61, P = 0.00).
Table 1: Demographic features of the patients with cervical radiculopathy

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In Group 2 patients, pain and paresthesias were restricted to C6, C7 and C8 dermatomes in 6, 2 and 4 individuals, respectively. The remaining 13 patients had two or more dermatomal involvement ranging from C5 to C8 dermatomes. In subjects with abnormal neurological findings (group 3), 5 were found to have weakness in deltoid, biceps, or triceps muscles. Two subjects had motor deficits in both forearm and intrinsic hand muscles. Power loss was restricted to either forearm or intrinsic hand muscles in two patients, while another had involvement of both arm and forearm muscles. Loss of deep tendon reflexes affected both biceps and brachioradialis, triceps or finger flexor reflexes in one patient each. Reflexes were unobtainable in the upper extremities in another patient. Three patients demonstrated dermatomal sensory loss of the neighboring C6 and C7 segments and in one, loss of sensation was observed in C6-C8 spinal segments. Furthermore, 3 other patients revealed sensory loss localized to C6, C7, and C8 dermatomes, respectively [Table 1].

Electrodiagnostic findings

Results of the EMG examination are summarized in [Table 2] and [Table 3]. Carpal tunnel syndrome was diagnosed in 20, 3 and 1 patients in Groups 1, 2 and 3, respectively. The group 3 patient with carpal tunnel syndrome had a confirmed C5 radiculopathy. One patient was diagnosed as ulnar neuropathy at the elbow in Group 2. No difference was detected in the occurrence of entrapment neuropathies among the studied groups (Pearson x2 = 0.31, P = 0.86). There were 3 subjects found to have diffuse sensory-motor neuropathy on electrodiagnostic examination in Group 1. The diagnosis in these patients was confirmed with nerve conduction studies and needle EMG in the lower extremities. In Group 1, two patients with carpal tunnel syndrome demonstrated F-wave abnormalities. F-wave was unobtainable in one, the other had F-wave prolongation. Two patients in Group 3 with C8 radiculopathy demonstrated median and ulnar F-wave latency prolongation, respectively.
Table 2: Findings in electromyography examination

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Table 3: Diagnosis of cervical radiculopathy in patients with different clinical characteristics

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On needle EMG examination [Table 2], the diagnosis of CR was confirmed in 3 Group 1 patients, by the findings of fibrillation potentials and positive sharp waves in paraspinal muscles, in contrast to Group 2 patients in whom none showed an abnormality despite having specific sensory symptoms. Paraspinal muscles of Group 3 patients demonstrated significantly more fibrillation potentials and positive sharp waves compared to other groups (Pearson x2 = 46.61, P = 0.00). No difference was found in the incidence of paraspinal spontaneous activity between groups 1 and 2 (P = 1). Fibrillation potentials and positive sharp waves confined to the limb muscles were observed in two patients of Group 1. Fibrillations and positive sharp waves restricted to the limb muscles were also seen in three Group 3 patients, additionally, one patient had only HALD MUPs in the limb muscles, while another three patients in Group 3 demonstrated abnormalities both in the form of spontaneous potentials as described above, along with HALD MUPs. Although limb muscle abnormalities were significantly more common in Group 3 (Pearson x2 = 75.5, P = 0.00), no difference was found between groups 1 and 2 (P = 1). In conclusion, of 16 CR patients with EMG abnormalities, 6 (37.5%) had spontaneous activity confined to the paraspinal muscles, 8 (50%) had exclusive findings in limb muscles and 2 (12.5%) had both paraspinal and limb muscle abnormalities on EMG testing. Abnormal findings favoring CR on EMG examination were more common in Group 3 patients (Pearson x2 = 120.41, P = 0.00). However, there was no difference in the rate of confirmation of CR by EMG studies between Groups 1 and 2 (P = 1).

We also checked how well the clinical findings matched the EMG results in confirmed cases of CR. While in Group 3, 10 out of 11 patients demonstrated EMG results that confirmed clinical findings, no such correlation was found in Group 1 (P = 0.00).


  Discussion Top


It is clear from our findings that electrodiagnostic examination is most useful in confirming CR in individuals with neurological deficits. In more than 90% of our patients with abnormal neurological findings, a definite diagnosis was possible on EMG testing. On the contrary, <3% of the cases with nonspecific neck and upper extremity pain or paresthesias demonstrated unequivocal results. Surprisingly, all patients with dermatomal symptoms had negative EMG findings. Consistent with our results, a review on CR reported that almost all patients with loss of power had abnormalities in needle EMG, while clinically asymptomatic myotomes were rarely abnormal.[6] In a study by Hong et al., 80 patients with unilateral and 28 patients with bilateral CR were evaluated examining a total of 680 root levels.[7] Abnormal needle EMG findings were detected in 32 (97%) of the 33 cervical root levels with motor weakness and 79 (29%) of the 275 root levels with sensory abnormalities. In another study, patients with neurological deficits demonstrated a 2.5-fold increased likelihood of diagnosis of CR, while the rate of detecting abnormal EMG findings showed a 4-fold increase compared to patients with normal neurological examination. The authors concluded that the abnormal neurological findings were highly specific for the diagnosis of CR, which increased the sensitivity of EMG examination to 84%.[8] Additionally, Lauder and Dillingham reported that of 175 CR patients diagnosed by EMG, 83% had demonstrated objective neurological deficits.[9] Furthermore, in Nardin et al.'s series, 25 out of 47 CR patients showed abnormal neurological findings.[10] EMG confirmed the diagnosis in 18 (72%) of them. It is known that the sensitivity of EMG in the diagnosis of CR is closely related to patient selection. Moreover, motor weakness increases the likelihood of detecting EMG abnormalities.[6],[7]

Similar to these reports a substantial majority (91%) of our patients with neurological deficits had muscle weakness, accompanied by either sensory or deep tendon reflex loss. Sensory symptoms such as pain and paresthesias or numbness are less sensitive indicators for EMG abnormalities. In the presence of lesions affecting the sensory roots, the needle EMG is normal, while nerve conduction studies fail to demonstrate abnormalities due to the preganglionic localization of the involvement. Another confounding factor is the coincidental presence of a peripheral neuropathy syndrome such as an entrapment neuropathy. It is remarkable that 14% of the patients with nonspecific pain and paresthesias also had carpal tunnel syndrome, despite the fact that no significant difference existed between the groups in terms of occurrence of entrapment neuropathies. Whether the high incidence of entrapment neuropathies, carpal tunnel syndrome in particular can be explained on the basis of double-crush syndrome, is open to speculation, because the presence of CR could not be confirmed in most of them. Otherwise, nerve conduction abnormalities were not helpful in the diagnosis of CR.

Paraspinal fibrillations and positive sharp waves were the most important EMG findings, as these findings by themselves without accompanying limb muscle findings enabled a definite diagnosis of CR in 43% of 14 patients. One could argue that paraspinal abnormalities are reported in asymptomatic individuals as well, but in a situation where neck pain radiates to the upper extremity or pain is accompanied by neurological findings, they have a crucial importance in diagnosis. These findings are also helpful in localization because EMG abnormalities correlated nicely with clinical findings in patients with neurological abnormalities. Therefore, there is a general agreement in the literature that paraspinal EMG significantly increases the sensitivity of EMG examination and is an indispensable part of the examination.[4],[8],[11],[12] Abnormalities confined to the limb muscles in definite CR were found in only 43% of the patients, which shows the importance of performing paraspinal muscle EMG examination for the diagnosis of CR. It is stated that a 6-muscle screen is optimal for the evaluation of CR.[13] In our study the number of the examined muscles were 8 including the paraspinals and extra muscles was added in some instances to confirm the myotomal distribution of abnormalities, which should be more than sufficient to identify CR. Moreover, symptom duration has no relation with the needle EMG abnormalities in the paraspinal muscles that adds to its value both in the subacute and chronic use in the diagnostic process.[12]

Male gender predominated in our 16 cases found to have EMG abnormalities supportive of CR; 62.5% of the cases were male and 37.5% were female. Interestingly male predominance is also reported in the literature. In a study, 75% of the CR cases were reported to have male gender,[9] while another study found that 59% of their cases were male, the remaining 41% were composed of female patients.[8] Mean age of our 16 patients diagnosed with EMG was 54, corresponding to the peak age range of 50–54 previously reported in the literature.[6]

Because of the retrospective nature of our study, the majority of our patients are grouped in nonspecific pain and paresthesia and number of patients assigned to our groups are unequal. However, our results are compatible with the findings of other studies as discussed above. In addition, we demonstrated that pain and paresthesias in specific dermatomal distribution are not good indicators of an abnormal EMG in CR. It is important to note that in the absence of neurological deficits where intractable pain is the main reason for referral to surgery, the clinician should not be guided solely by the EMG results. In this kind of situation, other factors should also be taken into account, as EMG abnormalities would be scarce. On the contrary, abnormal examination findings, especially motor deficits usually localize the lesion clinically, confirmed by EMG results. It is advisable to keep in mind that in patients with pure sensory manifestations, the existence of an unexpected peripheral neuropathy syndrome is a possibility.


  Conclusion Top


Neurological examination findings are important in CR patents referred to the EMG laboratory to confirm the diagnosis and lesion localization, whereas in cases with pure sensory symptoms even in a specific dermatomal distribution the sensitivity of the examination is low. This distinction is important, because the prognosis, especially surgical outcomes of CR are more favorable with EMG confirmation.[12]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Plastaras CT, Joshi AB. The electrodiagnostic evaluation of radiculopathy. Phys Med Rehabil Clin N Am 2011;22:59-74.  Back to cited text no. 1
    
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Wilbourn AJ, Aminoff MJ. AAEM Minimonograph 23: The electrodiagnostic examination in patients with radiculopathies. Muscle Nerve 1998;21:1612-31.  Back to cited text no. 2
    
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Oh SJ. Principles of Clinical Electromyography: Case Studies. Baltimore: Williams & Wilkins; 1998. p. 215-21.  Back to cited text no. 3
    
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Tsao B. The electrodiagnosis of cervical and lumbosacral radiculopathy. Neurol Clin 2007;25:473-94.  Back to cited text no. 4
    
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American Association of Electrodiagnostic Medicine. Practice parameter for needle electromyographic evaluation of patients with suspected cervical radiculopathy: Summary statement. Muscle Nerve 1999;22 Suppl 8:S209-11.  Back to cited text no. 5
    
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American Association of Electrodiagnostic Medicine. The electrodiagnostic evaluation of patients with suspected cervical radiculopathy: Literature review on the usefulness of needle electromyography. Muscle Nerve 1999;22 Suppl 8:S213-21.  Back to cited text no. 6
    
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Hong CZ, Lee S, Lum P. Cervical radiculopathy. Clinical, radiographic and EMG findings. Orthop Rev 1986;15:433-9.  Back to cited text no. 7
    
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Lauder TD, Dillingham TR, Andary M, Kumar S, Pezzin LE, Stephens RT, et al. Predicting electrodiagnostic outcome in patients with upper limb symptoms: Are the history and physical examination helpful? Arch Phys Med Rehabil 2000;81:436-41.  Back to cited text no. 8
    
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Lauder TD, Dillingham TR. The cervical radiculopathy screen: Optimizing the number of muscles studied. Muscle Nerve 1996;19:662-5.  Back to cited text no. 9
    
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Nardin RA, Patel MR, Gudas TF, Rutkove SB, Raynor EM. Electromyography and magnetic resonance imaging in the evaluation of radiculopathy. Muscle Nerve 1999;22:151-5.  Back to cited text no. 10
    
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Dillingham TR, Lauder TD, Andary M, Kumar S, Pezzin LE, Stephens RT, et al. Identification of cervical radiculopathies: Optimizing the electromyographic screen. Am J Phys Med Rehabil 2001;80:84-91.  Back to cited text no. 11
    
12.
Dillingham TR, Annaswamy TM, Plastaras CT. Evaluation of persons with suspected lumbosacral and cervical radiculopathy: Electrodiagnostic assessment and implications for treatment and outcomes (Part II). Muscle Nerve 2020;62:474-84.  Back to cited text no. 12
    
13.
Dillingham TR, Annaswamy TM, Plastaras CT. Evaluation of persons with suspected lumbosacral and cervical radiculopathy: Electrodiagnostic assessment and implications for treatment and outcomes (Part I). Muscle Nerve 2020;62:462-73.  Back to cited text no. 13
    



 
 
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  [Table 1], [Table 2], [Table 3]



 

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