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Rehabilitation Practice and Science

Translated Title

斜方肌反射：一個雙側動作調控的新反射

Abstract

Close links between the bilateral trapezii are essential for the stability and coordination of neck and shoulder movements. However, there is no direct neurophysiological evidence to support such a bilateral motor control mechanism. Our study is the first to use an electrodiagnostic method to prove the existence of this reflex. In this study, we have identified a new uniform or standardized technique, named the trapezius reflex (TR), which is able to evaluate proximal shoulder motor function. The TR is defined as an electrically elicited reflex that originates from the synchronized activation of both trapezii by electric stimulation of the accessory nerve on just one side.To confirm the existence of TR, ten healthy male volunteers (all right-handed) with a mean age of 24.8±4.1 (19-31) years old were investigated. Electrical stimulation of the accessory nerve on one side should evoke a motor response, namely a compound muscle action potential (CMAP), on ipsilateral upper trapezius muscle called the M wave. In addition, another CMAP, named the T wave, should occur simultaneously and be picked up on the contralateral side. The accessory nerve was stimulated just above the midpoint of the posterior border of the sternocleidomastoid muscle. An active electrode was placed on the upper trapezius at the midpoint between the acromion and the spinous process of the seventh cervical vertebra together with a reference electrode on the acromion. The ground electrode was placed beside these two. The electrodes were arranged as a symmetric array on both sides of the shoulders. Bilateral CMAPs were simultaneously recorded using a two channel EMG apparatus. The sum of the electrophysiological data suggests there was no left-right difference in the bilateral M and T waves. Thus, we combined the data of the right and left sides to obtain values for the mean onset latency, amplitude and duration of the M wave as 2.09± 0.12 ms, 11.56±3.79 mV and 33.64±2.47 ms, respectively and the T wave as 13.67±1.56 ms, 346.50±169.59 μV and 32.60±2.96 ms, respectively. Consequently, the TR is a very stable motor response and is regularly obtained in healthy male volunteers. The trapezius reflex is an easily applied electrodiagnostic technique and it could play an objective role in the electrophysiological diagnosis and assessment of bilateral trapezii control. The components of the TR should be able to provide a measure than can assess the functional integrity of central nerve system in terms of possible lesions, as well as detecting lesions within the peripheral accessory nerve and trapezius muscles. The importance of this study is that it presents the characteristics of the TR. Further work to correlate TR with possible clinical applications is obviously necessary, and is currently underway.

Language

Traditional Chinese

First Page

79

Last Page

85

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