Diagnostic Value Of Single Fiber Lectromypography Of Orbicularis Oculi Muscle In Myasthenia Gravis

Myasthenia gravis(MG) is a autoimmune neuromuscular junction disorder.MG presents with fluctuating,fatigable weakness involving specific muscle groups.MG remains one of the most challenging medical diagnoses due to its fluctuating character and to the similarity of its symptoms to those of other disorders.Prevalence rates for MG have increased over time.Recent prevalence rates approach 1/5000,this likely due to improvements in diagnosis.This topic performed a series of research works on electrophysiological results in MG patients.The research works include three parts,each focusing on the value of SFEMG of orbicularis oculi muscle(OO) in the diagnosis of MG,the ability of SFEMG to predict the development of generaliZed myasthenia gravis(GMG) patients presenting with OMG,thesensitivity of SFEMG and RNS in the diagnostic yield and the effect of multiple potential on caiculations of jitter in single-fiber electromyography.We performed SFEMG of OO in 44 patients with MG.The abnormality was defined as mean jitter exceeding 50μs or 10%or more of potential pairs having jitter exceeding 55μs or blocking.We evaluated the jitter of SFEMG in ocular and generalized MG patients.There were remarkable increases of jitter in MG.The mean jitter ranged(72.18±20.67)μs,the ratios of jitter＞55μs were(63.65±24.99)%and blocking were(38.79±23.90)%.There was a significant difference between MG and the controls.SFEMG of OO shows higher sensitivity for the diagnosis of MG.We found difference between the mean jitter of OMG and GMG group,but the results Of EDC suggested that there was no difference between OMG and GMG.Twenty-seven patients presenting with OMG underwent SFEMG of the orbicularis oculi muscle(OO) and/or the extensor digitorum communis(EDC).All patients were followed prospectively for six months to one year.Eleven remained with pure OMG for the entire follow-up period and sixteen developed GMG.We found that in SFEMG of OO the jitter in GMG were more abnormal than in OMG. SFEMG of the orbicularis oculi muscle is more sensitive for the diagnosis of OMG than of the extensor digitorum communis,but the absolute value of jitter can not be used to predict the development of GMG.The younger age at onset is associated with a better outcome.Low rate repetitive nerve stimulated(RNS)was performed in orbicularis oculi muscle(OO) in 44 MG patients,we compared the sensitivity of SFEMG and RNS in the diagnostic yield.A decrement of 15%or more of the amplitude of the compound muscle action potentials was considered abnormal.The ratio of abnormal SFEMG was 82.50%(33/40) and RNS was 35%(14/40),SFEMG was more sensitive than RNS in diagnosing neuromuscular transmission disorder.Receiver operating characteristic(ROC) curves were constructed to define maximal sensitivity and specificity of two technique.The "gold standard" was a positive pharmacologic testing and the clinical diagnosis.The sensitivity of MCD was 84.1%(95% confidencd interval 93.7～101.0%),with no false-positive results.The percentage of decrement of RNS was negatively correlated with SFEMG parameters,but jitter observed in SFEMG was not completely corresponding to the decrement in RNS.