American Society for Peripheral Nerve

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Novel Method of Repetitive Nerve Stimulation in Trapezius Muscle : Middle trapezius method
Miho Kanda, MT1; Hitoshi Mori, MD2
1Clinical Laboratory, Kurashiki Central Hospital, Kurashiki,Okayama, Japan; 2Neurology, Kurashiki Central Hospital, Kurashiki,Okayama, Japan

Introduction: Nerve conduction study of upper trapezius muscle is difficult because of motion artifact of upper trapezius muscle. Repetitive nerve stimulation (RNS) of upper trapezius muscle is more difficult due to the proper immobilization of the recording electrode over the muscle. The middle trapezius muscle recording has less motion artifact, we propose the middle trapezius recording methods for repetitive nerve stimulation.

Methods: In the 12 normal subjects, 24 upper trapezius recordings of RNS with traditional fixation and 24 middle trapezius recordings of RNS without fixation were recorded. 3Hz slow RNS were performed at accessory nerve on the side neck. The compound muscle action potential (CMAP) amplitude decrements (%) were measured in the both group, then we calculated the mean consecutive difference (MCD) of individual decrements.

Results: MCD were 1.7±0.7%(Mean ±SD) in the upper trapezius recording with muscle fixation group, 1.2±0.5% in the middle trapezius recording without muscle fixation group. The latter group has small MCD (p=0.015). Small MCD means less fluctuation and is considered suitable recordings.

Conclusions: Middle Trapezius recording without muscle fixation for RNS is novel and suitable recording.

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