title: Contribution of anti-ryanodine receptor antibody to impairment of excitation-contraction coupling in myasthenia gravis.
abstract: 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.
  
  
  CONCLUSIONS
  Anti-RyR antibody contributes to E-C coupling impairment in the masseter muscle in patients with MG.
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan. toimai@sapmed.ac.jp
authors.forename: Tomihiro
authors.initials: T
authors.lastname: Imai
authors.forename: Emiko
authors.initials: E
authors.lastname: Tsuda
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Hozuki
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Rika
authors.initials: R
authors.lastname: Yamauchi
authors.forename: Masaki
authors.initials: M
authors.lastname: Saitoh
authors.forename: Shin
authors.initials: S
authors.lastname: Hisahara
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Motomura
authors.forename: Jun
authors.initials: J
authors.lastname: Kawamata
authors.forename: Shun
authors.initials: S
authors.lastname: Shimohama
mesh_terms: D000200:Action Potentials / Q000276:immunology; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D001732:Bite Force; D056966:Excitation Contraction Coupling / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000276:immunology / Q000503:physiopathology*; D009157:Myasthenia Gravis / Q000276:immunology / Q000503:physiopathology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D019837:Ryanodine Receptor Calcium Release Channel