title: Impaired post-tetanic potentiation of muscle twitch in myasthenia gravis.
abstract: OBJECTIVE
  The aim of this study was to evaluate post-tetanic potentiation of muscle twitch in myasthenia gravis (MG).
  
  
  METHODS
  Post-tetanic potentiation was evaluated by recording the compound muscle action potential (CMAP) of abductor pollicis brevis and movement-related potential (MRP) of the thumb using an accelerometer after tetanic stimulation of the median nerve at the wrist. After baseline recording, tetanic stimulation was delivered to the median nerve at a frequency of 10 Hz for 10s. The CMAP and MRP were successively recorded at baseline and at 5, 10, 30, 60, 90 and 120 s after tetanic stimulation. The chronological changes of CMAPs and MRPs were recorded bilaterally in 11 patients with MG, 9 patients with myopathies (disease controls), and 25 healthy control subjects.
  
  
  RESULTS
  Maximal acceleration of MRP was significantly elevated during 10s after tetanic stimulation without any CMAP changes in all groups. However, statistical analysis detected a significant decrease in post-tetanic potentiation of maximal acceleration of MRP in MG patients only compared to healthy controls, but not in myopathy patients, which may imply impairment of excitation-contraction coupling in MG.
  
  
  CONCLUSIONS
  Post-tetanic potentiation of muscle twitch is significantly diminished in MG, suggesting impaired excitation-contraction coupling.
  
  
  CONCLUSIONS
  Measurement of post-tetanic potentiation using an accelerometer is a simple and sensitive method to detect impairment of excitation-contraction coupling in MG.
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamamoto
authors.affiliation: Department of Occupational Therapy, Sapporo Medical University School of Health Sciences, Sapporo, Japan. Electronic address: toimai@sapmed.ac.jp.
authors.forename: Tomihiro
authors.initials: T
authors.lastname: Imai
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Tsuda
authors.affiliation: Sapporo Shirakabadai Hospital, Sapporo, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Hozuki
authors.affiliation: Department of Neurology, Sunagawa City Medical Center, Sunagawa, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Yamauchi
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Hisahara
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kawamata
authors.affiliation: Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Shimohama
mesh_terms: D061725:Accelerometry / Q000379:methods; D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D056966:Excitation Contraction Coupling / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology*; D012032:Refractory Period, Electrophysiological / Q000502:physiology; D055815:Young Adult
keywords: Excitation–contraction coupling; Muscle fatigue; Myasthenia gravis; Post-tetanic potentiation; Staircase phenomenon