Abstract: Objective To study and estimate the value of SFEMG of the frontalis muscle in the diagnosis of ocular myasthenia gravis(OMG),comparing the sensitivity of the SFEMG of the frontalis muscle,repetitive nerve stimulation(RNS),blood concentration of antibody to the acetylcholine receptor(AchR-Ab) and neostigmine test.Methods In insulated room of 25 ℃,we performed SFEMG of the frontalis muscle in 27 patients with OMG who attended Beijing Tongren Hospital from August 2006 to January 2007 and 12 controls.RNS,AchR-Ab titration and neostigmine test were also performed.Results 1) Eighteen of twenty seven patients had abnormal recordings in SFEMG of the frontalis muscle,the mean jitter ranged from 20 to 97 us(average 45.4±21.0 μs),the ratio of jitter >55 μs was(24.2±24.5)% and percentage of blocks was(1.9±4.4)%,in the controls,the mean jitter ranged from 19 to 40 μs average(27.4±6.6 μs);9 of 27 patients were abnormal in low frequencies of RNS,among which 7 patients had abnormality in facial nerve,one in facial and axillary nerve and one in axillary nerve;AchR-Ab titersns were increased in 8 patients;23 of 27 patients were positive in neostigmine test.2) Sensitivities of ACh-Ab titration(29.6%) in patients with OMG were remarkably lower than SFEMG of the frontalis muscle,sensitivity of RNS(33.3%),neostigmine test(85.2%) was not different from SFEMG of the frontalis muscle.Conclusion SFEMG of the frontalis muscle shows higher sensitivity for the diagnosis of OMG than RNS and AchR-Ab titration.

Key words: ocular myasthenia gravis, single fiber electromyography of the frontalis muscle, jitter