Contribution of anti-ryanodine receptor antibody to impairment of excitation-contraction coupling in myasthenia gravis

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• 作者：Tomihiro Imai^a ; ^{toimai@sapmed.ac.jp} ; Emiko Tsuda^a ; Takayoshi Hozuki^a ; Hiroaki Yoshikawa^b ; Rika Yamauchi^a ; Masaki Saitoh^a ; Shin Hisahara^a ; Masakatsu Motomura^c ; Jun Kawamata^a ; Shun Shimohama^a
• 关键词：Myasthenia gravis ; Excitation&ndash ; contraction coupling ; Ryanodine receptor ; Repetitive nerve stimulation ; Masseter ; Bite force
• 刊名：Clinical Neurophysiology
• 出版年：2012
• 期刊代码：61_13882457
• 类别：med
• 出版时间：June, 2012
• 卷：123
• 期：6
• 页码：1242-1247
• 文件大小：241 K

摘要

Objective

The aim of this study was to elucidate the relationship between the impairment of excitation-contraction (E-C) coupling and anti-ryanodine receptor (RyR) antibody in patients with myasthenia gravis (MG).

Methods

Masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRPs) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The E-C coupling time (ECCT) was calculated as the latency difference between CMAP and MRP. For each patient, we selected a representative data set when there was no abnormal decrement in response to repetitive nerve stimulation. The 26 data sets were divided into an anti-RyR-positive group (n = 12) and an anti-RyR-negative group (n = 14).

Results

Masseteric ECCT was significantly longer (p = 0.017) in anti-RyR-positive group (median, mean, range; 3.6, 3.8, 3.0-5.9 ms) than in anti-RyR-negative group (3.1, 3.1, 2.7-4.0) although there were no significant differences in masseteric CMAP amplitude and%decrement between the two groups. The bite force was significantly lower in anti-RyR-positive group than in normal controls.

Conclusions

Presence of anti-RyR antibodies is associated with significantly prolonged masseteric ECCT compared to absence of the antibodies in MG.

Significance

Anti-RyR antibody contributes to E-C coupling impairment in the masseter muscle in patients with MG.