Study of Myasthenic Crisis in China

Inclusion Criteria: * clinical history and signs of fluctuating weakness and fatigability; * seropositivity forAChR/MuSKantibodies; * If negative or the tested antibodies, positive repetitive nerve stimulation(RNS) at low frequency(2-5Hz) is required; * Crisis: a serious, life-threatening, rapid worsening of MG requiring intubation or noninvasive ventilation to avoid intubation. * Impending crisis: rapid clinical worsening of MG that, in the opinion of the treating physician, could lead to crisis in the short term (days to weeks) with blood gases suggest hypoxia (oxygen saturation \<95%) or elevated carbon dioxide (paco2\>50mmHg). Exclusion Criteria: * the RNS had over 100% increase after high frequency stimulation or R2 repeats,to differentiate from lambert-Eaton syndrome and congenital MG. * except when intubation or noninvasive ventilation are employed during routine postoperative management.