Myasthenie.com

Lu sur :https://www.ncbi.nlm.nih.gov/pubmed/29040921

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Effect of local cooling on excitation-contraction coupling in myasthenic muscle: Another mechanism of ice-pack test in myasthenia gravis.
Yamamoto D1, Imai T2, Tsuda E1, Hozuki T3, Yamauchi R4, Hisahara S1, Kawamata J1, Shimohama S1.
Clin Neurophysiol. 2017 Sep 22;128(11):2309-2317. doi: 10.1016/j.clinph.2017.08.030. [Epub ahead of print]


Abstract

• OBJECTIVE:
  
  The ice-pack test is a convenient diagnostic testing procedure for myasthenia gravis (MG). We investigated the underlying mechanism of the ice-pack test performed on bilateral masseters.
  
• METHODS:
  
  We performed trigeminal repetitive nerve stimulation (RNS), excitation-contraction (E-C) coupling assessment (Imai's method) and bite force measurement before and after cooling of the masseters in MG patients and normal controls. After placing the ice-pack on the masseters for 3min,
• serial recordings of the three tests were performed at various time intervals during 10min after cooling.
  RESULTS:
  
  The bite force increased significantly after cooling in ice-pack-positive MG patients. The acceleration and acceleration ratio (acceleration at a given time to baseline acceleration) of jaw movement increased significantly after cooling of the masseters in ice-pack-positive MG patients compared to ice-pack-negative patients and normal controls. The prolonged effect of cooling continued until the end of recording even though decremental response to RNS had returned to baseline value.
  
• CONCLUSIONS:
  
  Cooling of myasthenic muscle may induce two effects. One is relatively short effect on electrical synaptic transmission at the endplate, and another is prolonged effect on E-C coupling in the muscle.
  
• SIGNIFICANCE:
  
  The ice-pack test induces a prolonged effect of ameliorating impaired E-C coupling in MG.
  

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