Estimation of Median Nerve Axonal Degeneration without Needle Electromyography

Background and Aim: The present study aimed to use the median nerve Compound Muscle Action Potential (CMAP) amplitude by stimulation at the palm instead of Abductor Pollicis Brevis (APB) needle Electromyography (EMG) for determining axonal loss in patients with Carpal Tunnel Syndrome (CTS). Methods and Materials/Patients: This study was performed on 180 patients with CTS referred to the Electrodiagnostic (EDX) Center, Poursina Hospital, Guilan Province, Iran, in 2018-19. In this study, the APB needle EMG diagnostic test was used as the gold standard, and median nerve CMAP amplitude with stimulation at the palm and wrist were used to compare the two nerve stimulation tests. Results: All of the cases with abnormal amplitude loss detected by median nerve stimulation at the palm also had an axonal loss in the needle EMG of APB. So this test could be a good indicator of axonal loss if there is an abnormality (sensitivity: 73%, specificity: 100%). The results with wrist stimulation were not as accurate as of the palm stimulation, and some cases with decreased CMAP amplitude of median nerve had normal needle EMG of APB muscle (sensitivity: 86.6%, specificity: 94.9%). Conclusion: In cases with CTS, the abnormally decreased amplitude of the median nerve detected by stimulation at the palm could be a good indicator of axonal loss.

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THUMB OPPOSITION IN SEVERE CARPAL TUNNEL SYNDROME WITH UNDETECTABLE APB-CMAP

Hand Surgery ◽

10.1142/s0218810414500208 ◽

2014 ◽

Vol 19 (02) ◽

pp. 199-204 ◽

Cited By ~ 5

Author(s):

Tatsuki Ebata ◽

Katsumi Imai ◽

Susumu Tokunaga ◽

Yuji Takahasi ◽

Yoshihiro Abe

Keyword(s):

Carpal Tunnel Syndrome ◽

Muscle Atrophy ◽

Carpal Tunnel ◽

Compound Muscle Action Potential ◽

Abductor Pollicis Brevis ◽

Thenar Muscle ◽

Needle Electromyography ◽

Muscle Action Potential ◽

Muscle Innervation ◽

Tunnel Syndrome

Thumb opposition does not always represent the function of the median nerve due to variations in thenar muscle innervation. One hundred and thirty hands of 109 idiopathic carpal tunnel syndrome (CTS) patients with an undetectable compound muscle action potential of the abductor pollicis brevis (APB-CMAP) were classified into one of four groups; Type 1 (86.2%) had thenar muscle atrophy and could not perform thumb opposition; Type 2 (10.8%) had thenar muscle atrophy but could perform thumb opposition; Type 3 (2.3%) did not have thenar muscle atrophy and could perform thumb opposition, but needle electromyography of the APB showed neurogenic changes and Type 4 (0.8%) had no thenar muscle atrophy, could perform thumb opposition, and needle electromyography showed no neurogenic changes. Over 10% of severe CTS patients have mild or no muscle atrophy and intact thumb opposition. The purpose of this study was to investigate the variations in thenar muscle innervation in patients with severe CTS.

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ADDITIONAL METHOD FOR DIAGNOSIS OF CARPAL TUNNEL SYNDROME: VALUE OF THE SECOND LUMBRICAL-INTEROSSEI TEST (2L-INT)

Hand Surgery ◽

10.1142/s0218810413500093 ◽

2013 ◽

Vol 18 (01) ◽

pp. 49-52 ◽

Cited By ~ 1

Author(s):

Tomoo Inukai ◽

Kenzo Uchida ◽

Chikara Kubota ◽

Takaharu Takamura ◽

Hideaki Nakajima ◽

...

Keyword(s):

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Nerve Conduction Velocity ◽

Compound Muscle Action Potential ◽

Sensory Nerve ◽

Standard Test ◽

Additional Method ◽

Abductor Pollicis Brevis ◽

Muscle Action Potential ◽

Tunnel Syndrome

We examined 57 hands referred with suspected carpal tunnel syndrome (CTS) using the second lumbrical-interossei nerve test (2L-INT) as well as standard test. Sensory nerve conduction velocity (SCV) was detectible in 67% of patients (38/57), the abductor pollicis brevis-compound muscle action potential (APB-CMAP) in 84% (48/57), 2L-CMAP in 96% (55/57) and the first interossei palmares muscle (INT-CMAP) in 100% (57/57). ABP-CMAP was not recorded in patients in whom severe atrophy of the abductor pollicis brevis muscle was evident. As 2L-CMAP is maintained even in the most severe cases of CTS, the 2L-INT method is a valuable test for improving the accuracy of preoperative diagnosis in the electrophysiological diagnosis of CTS.

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Pseudomyopathic Changes in Needle Electromyography in Lambert-Eaton Myasthenic Syndrome

Case Reports in Neurological Medicine ◽

10.1155/2013/369278 ◽

2013 ◽

Vol 2013 ◽

pp. 1-2 ◽

Cited By ~ 2

Author(s):

Teppei Komatsu ◽

Kota Bokuda ◽

Toshio Shimizu ◽

Tetsuo Komori ◽

Reiji Koide

Keyword(s):

Nerve Stimulation ◽

Compound Muscle Action Potential ◽

The Other ◽

Motor Unit Potential ◽

Muscle Action ◽

Repetitive Nerve Stimulation ◽

Needle Electromyography ◽

Muscle Action Potential ◽

Myasthenic Syndrome ◽

Myopathic Changes

Lambert-Eaton myasthenic syndrome (LEMS) is a rare presynaptic disorder of the neuromuscular junction in association with cancer and subsequently in cases in which no neoplasm has been detected (O’Neill et al., 1988). The diagnosis of LEMS is based on the combination of fluctuating muscle weakness, diminished or absent reflexes, and a more than 60% increment of compound muscle action potential (CMAP) amplitude after brief exercise or 50 Hz stimulation for 1 s in a repetitive nerve stimulation (RNS) test (Oh et al., 2005). On the other hand, needle electromyography (EMG) findings related to LEMS have not been well described. Here, we report a case of LEMS, which showed apparent myopathic changes in needle EMG findings. Furthermore, we retrospectively examined the needle EMG findings in 8 patients with LEMS. In six of the 8 patients, the EMG findings showed myopathy-like findings. Although the findings of needle EMG indicated myopathic changes at a glance, the motor unit potential (MUP) returned to normal after a sustained strong muscle contraction. We propose the name “pseudomyopathic changes” for this phenomenon.

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