Novel method of repetitive nerve stimulation in trapezius muscle; middle trapezius muscle recording method

Abstract

Repetitive nerve stimulation study is one of the useful electrodiagnostic test in the evaluation of the patients with suspected neuromuscular junction disorders. The diagnostic yield increases with stimulation of proximal nerves. Although repetitive nerve stimulation for spinal accessory nerve is preferred, proximal stimulation has some technical problems. Isometric electrode position is essential for the test. Minimizing shoulder movement is difficult in upper trapezius muscle recordings. We use the middle trapezius muscle in repetitive nerve stimulation test for minimizing the effect of shoulder movements. The fluctuation of compound muscle action potential is evaluated by using the mean value of continuous difference (MCD). MCD is often used for calculating jitter in single fiber electromyography. Our method using the middle trapezius muscle recording without fixation of shoulder at sitting positon has lowest MCD values in the repetitive nerve stimulation test for spinal accessory nerve. This means middle trapezius muscle recording without fixation of shoulder for spinal accessory nerve stimulation is suitable for isometric electrode position, and is one of the useful methods.