Correlation between Elbow Flexor Muscle Strength and Needle Electromyography Parameters after Musculocutaneous Nerve Injury / 法医学杂志

OBJECTIVES@#To explore the changes of elbow flexor muscle strength after musculocutaneous nerve injury and its correlation with needle electromyography (nEMG) parameters.@*METHODS@#Thirty cases of elbow flexor weakness caused by unilateral brachial plexus injury (involving musculocutaneous nerve) were collected. The elbow flexor muscle strength was evaluated by manual muscle test (MMT) based on Lovett Scale. All subjects were divided into Group A (grade 1 and grade 2, 16 cases) and Group B (grade 3 and grade 4, 14 cases) according to their elbow flexor muscle strength of injured side. The biceps brachii of the injured side and the healthy side were examined by nEMG. The latency and amplitude of the compound muscle action potential (CMAP) were recorded. The type of recruitment response, the mean number of turns and the mean amplitude of recruitment potential were recorded when the subjects performed maximal voluntary contraction. The quantitative elbow flexor muscle strength was measured by portable microFET 2 Manual Muscle Tester. The percentage of residual elbow flexor muscle strength (the ratio of quantitative muscle strength of the injured side to the healthy side) was calculated. The differences of nEMG parameters, quantitative muscle strength and residual elbow flexor muscle strength between the two groups and between the injured side and the healthy side were compared. The correlation between elbow flexor manual muscle strength classification, quantitative muscle strength and nEMG parameters was analyzed.@*RESULTS@#After musculocutaneous nerve injury, the percentage of residual elbow flexor muscle strength in Group B was 23.43% and that in Group A was 4.13%. Elbow flexor manual muscle strength classification was significantly correlated with the type of recruitment response, and the correlation coefficient was 0.886 (P<0.05). The quantitative elbow flexor muscle strength was correlated with the latency and amplitude of CMAP, the mean number of turns and the mean amplitude of recruitment potential, and the correlation coefficients were -0.528, 0.588, 0.465 and 0.426 (P<0.05), respectively.@*CONCLUSIONS@#The percentage of residual elbow flexor muscle strength can be used as the basis of muscle strength classification, and the comprehensive application of nEMG parameters can be used to infer quantitative elbow flexor muscle strength.

Optimization of muscle selection for needle electromyography in amyotrophic lateral sclerosis / 西安交通大学学报(医学版)

Objective: To compare the diagnostic sensitivity of muscles in different regions on electromyography (EMG) to optimize and the muscle selection of needle electromyography in amyotrophic lateral sclerosis (ALS). To compare the diagnostic performance of revised El Escorial criteria (rEEC) and Awaji criteria (AwC) in ALS. Methods: Totally 198 ALS patients were recruited from ALS Clinic of The First Affiliated Hospital of Xi'an Jiaotong University and diagnosed with rEEC and AwC diagnostic criteria. Needle EMG was detected in muscles of bulbar, cervical, thoracal, and lumbosacral regions. Results: The muscle sensitivity in ALS regions (with or without clinical involvement) was consistent with that in the regions without clinical involvement. The diagnostic sensitivity of muscles were presented as follows: tongue (54.7% vs. 39.2%), trapezius (44.2% vs. 30.2%), lower orbicularis oris (33.2% vs. 20.7%), sternocleidomastoid (20% vs. 13.2%) in bulbar region, the first dorsal interosseus (93.8% vs. 77.3%), abductor pollicis brevis (92.8% vs. 72.7%), biceps (82% vs. 50%), deltoid (82% vs. 45.4%) in cervical region, thoracic paraspinal muscle 10 (86.5% vs. 85.3%) and rectus abdominis (49.5% vs. 49.3%) in thoracal region, the tibialis anterior (74.6% vs. 46.3%), and gastrocnemius (53.4% vs. 19.7%) in lumbosacral region. The diagnostic rate at AwC standard (75.3%) was significantly higher than that at rEEG standard (24.2%) (McNemar test P<0.001). Conclusion: The muscles of clinical affected region should be detected first, followed by the non-affected region in clinically suspected ALS. The tongue in bulbar region, the first dorsal interosseus in cervical region, thoracic paraspinal muscle 10 in thoracal region, tibialis anterior in lumbosacral region are recommended to detect in EMG protocol. The AwC criteria are suggested in ALS clinical diagnosis.

Diagnosis of Zygomaticus Muscle Paralysis Using Needle Electromyography With Ultrasonography

A 22-year-old woman visited our clinic with a history of radiofrequency volumetric reduction for bilateral masseter muscles at a local medical clinic. Six days after the radiofrequency procedure, she noticed a facial asymmetry during smiling. Physical examination revealed immobility of the mouth drawing upward and laterally on the left. Routine nerve conduction studies and needle electromyography (EMG) in facial muscles did not suggest electrodiagnostic abnormalities. We assumed that the cause of facial asymmetry could be due to an injury of zygomaticus muscles, however, since defining the muscles through surface anatomy was difficult and it was not possible to identify the muscles with conventional electromyographic methods. Sono-guided needle EMG for zygomaticus muscle revealed spontaneous activities at rest and small amplitude motor unit potentials with reduced recruitment patterns on volition. Sono-guided needle EMG may be an optimal approach in focal facial nerve branch injury for the specific localization of the injury lesion.

The Effect of Cold Spray on Reducing Pain during Needle Electromyography

OBJECTIVE: To examine the effect of cold spray (Ethyl chloride) on reducing pain during needle electromyography (EMG). METHOD: Seventy-six adults, who had experienced needle electromyographic examination, were studied. They were randomly assigned to either experimental or control group. In experimental group, cold spray was applied to needling point of examining muscles before each needle examination. In control group, needle examination was performed without pre-treatment. The intensity of pain was assessed by the Visual analogue scale (VAS) and Verbal rating scale (VRS). Denial to re-examination was evaluated after EMG study. RESULTS: The VAS, VRS and denial to re-examination were significantly lower in experimental group (p<0.05). CONCLUSION: The application of cold spray before needle examination decreased the intensity of pain and denial to re-examination.

Diagnostic Usefulness of Dermatomal Somatosensory Evoked Potentials by Low Intensity Stimulation in Lumbar Radiculopathy

OBJECTIVE: To investigate diagnostic usefulness of dermatomal somatosensory evoked potentials (DSEP) in the evaluation of lumbar radiculopathy using stimulation intensity lower than conventional stimulation intensity. METHOD: Fifty-seven patients with low back pain were studied with DSEP and needle electromyography (EMG). The radiculopathy was diagnosed by lumbar MRI or operative findings. The DSEP study was performed with stimulation intensity of 1.0x, 1.5x, 2.5x sensory threshold, respectively. We compared the sensitivity and specificity of DSEP and needle EMG in the evaluation of L5 radiculopathy. RESULTS: Radiological and operative findings revealed unilateral herniated disc and L5 root compression in 38 patients (66.7%). Nineteen patients had no significant L5 root compression. The sensitivity and specificity of abnormality were 68.4% and 78.9% in 1.0x sensory threshold stimulation; 71.1%, 78.9% in 1.5x sensory threshold stimulation; and 44.7%, 84.2% in 2.5x sensory threshold stimulation, respectively. Whereas they were 55.2% and 100% in needle EMG. CONCLUSION: DSEP using low stimulus intensity showed higher sensitivity in the diagnosis of L5 radilculopathy, and DSEP might provide additional diagnostic usefulness in the evaluation of patients with suspected L5 radiculopathy.

Optimal Sampling of Muscles to Detect Lumbosacral Radiculopathy

OBJECTIVE: To determine the optimal number of muscles to detect lumbosacral radiculopathies. METHOD: Electrodiagnostic data of 152 patients who had been diagnosed as lumbosacral radiculopathy with the findings of operative record were obtained retrospectively. The findings of needle electromyography were reviewed and the frequency of abnormal spontaneous activities in L5 and S1 myotomes was investigated. We selected 8 individual muscles which had high sampling rate. These muscles were combined into different muscle screens and the detection rates were calculated that the frequency with which one or more muscles in the screen displayed abnormal spontaneous activity was divided by the total number of radiculopathies. RESULTS: The detection rates of lumbosacral radiculopathy were compared according to the number of muscle screens. Including paraspinal muscle, the detection rate of 6 muscle screens was higher than 5 muscle screens (p<0.05), but there was no significant difference of detection rate between 6 muscle screens and 7 muscle screens. The detection rates of each muscle screens without paraspinal muscle were lower than those including paraspinal muscle for all screens (p<0.05). CONCLUSION: Although there is controversy about selection of muscles, six muscle screen including paraspinal muscles may be optimal number for detecting lumbosacral radiculopathy.

Dose-dependent Responses to Botulinum Toxin A Injection on Compound Muscle Action Potential Amplitude and Electromyography: Local and Distant Effects

OBJECTIVE: The purpose of this study was to investigate the dose-dependent responses to botulinum toxin A (BTX-A) injection on compound muscle action potential (CMAP) amplitude and needle electromyography (EMG) in local and distant muscles. METHOD: The BTX-A (Botox , Allergan Co.) was injected to the left tibialis anterior (TA): 2, 4, 6, 8 U for each 4 Sprague-Dawley rats; 5, 10, 15, 20 U for each 2 rats. The sciatic nerve conduction and needle EMG were performed in the right and left TA immediately before BTX-A injection, on 2 days after injection, weekly for 1 to 10 weeks, and then monthly for 4 months. RESULTS: The range of dose-dependent maximal paralysis of the injected muscle was from 94% to 99.2% on 7 days after injection. With the lapse of time, the amplitudes in the left sciatic nerve conduction recovered, the abnormal spontaneous activities disappeared, and the power in spectral analysis of motor unit action potential increased. The range of dose-dependent reductions of the CMAP amplitude of the right TA was from 41.8% to 69.9% in the distant muscle, but there was no abnormal spontaneous activity in needle EMG study. As higher doses of BTX-A were injected, the degree of amplitude reduction became larger and the duration of amplitude reduction became longer in both local and distant TA muscles. CONCLUSION: We observed the dose-dependent muscle paralysis with injection of BTX-A. The systemic effects by local injection were induced and the durations of local and systemic effects were proportional to the BTX-A dosage.

Value of Needle Electromyography for the Diagnosis of Amyotrophic Lateral Sclerosis

BACKGROUND AND PURPOSE: For the diagnosis of amyotrophic lateral sclerosis(ALS), symptoms and signs of upper motor neuron(UMN) and lower motor neuron(LMN) involvement should be confirmed. The electromyography(EMG) studies are known to be essential for the demonstration of LMN involvement. The authors assessed the value of the EMG in the diagnosis of ALS. METHODS: The authors collected 51 patients (M:F=31:20, age:51.9?12.0 years) who were diagnosed and followed up at Seoul National University Hospital from 1994 to 1996. Diagnosis of ALS was based on the El Escorial diagnostic criteria. They were classified to be definite in 5, probable in 23, and possible in 23. On view of the affected area of onset, they consisted of 12 bulbar and 39 spinal form of ALS. The needle EMG studies were performed in limb, thoracic paraspinal and tongue muscles. RESULTS: Of 51 cases, it was possible to demonstrate widespread denervations at the initial needle EMG tests in 46(90.2%); 5 of 5 definite, 21 of 23 probable, and 20 of 23 possible ALS. Among 30 spinal form ALS without bulbar symptoms, the initial EMG evaluation showed the widespread denervation processes in three limbs in 13(43.3%) and in two limbs in 17(56.7%). Of 17 patients with denervation in only two limbs, the thoracic paraspinal and tongue muscles were found to be involved in 7 and 5 cases, respectively. The other 5, who initially showed abnormal EMG in limited muscles without abnormal EMG finding in thoracic paraspinal and tongue muscles, were confirmed to have ALS by the clinical and EMG follow-up. Nine patients of spinal onset ALS with bulbar symptoms and 12 patients of bulbar onset showed widespread denervation features at the tongue and limb muscles. In 6 ALS cases, difficult to be differentiated from spondylotic myeloradiculopathy, the abnormal EMG features in thoracic paraspinal and bulbar muscle were helpful to diagnose ALS. CONCLUSION: The authors could diagnose ALS in most cases(90.2%) at the time of initial EMG evaluation. The needle EMG study with the regular follow-up is useful to diagnose ALS. Moreover, the needle EMG study on thoracic paraspinal and tongue muscle is much helpful to differentiate ALS from spondylotic myeloradiculpathy.