Study of repeated nerve stimulation in myasthenia gravis

AIM:To investigate normal value range of low-frequent repeated nerve stimulation(RNS):whether different low-frequent stimulation and different muscles have different normal value range.METHODS:Low-frequent (3c /s and 5c /s)RNS of 30healthy people and 27myasth enia gravis(MG)patients were test.RESULTS:Superior limit of amplitude of wave a ttenuation value of low-frequent RNS(x±2.5s)of different muscles(orbicularis oculi muscle,deltoid muscle and abductor muscle of little finger)of healthy people was 5.45%-7.55%.According to our normal value standard,RNS positive rate of MG group was 85%;according to the current criteria(amplitude of wave attenuation value >10%),positive rate of MG group was 70%,th ere was no apparent difference in RNS positive rate(P>0.1).Some labs adopted the criteria that amplitude of wave attenuation value >15%,ac-cording to this criteria,positive r ate of MG group was 51%.Compared with positive rate(85%)obtained according to our criteria,there was apparent difference(P<0.01).CONCLUSION:Each labs should establish their own normal value standard according to difference muscle and different f re-quent.If adopt universal standard,amplitude of wave attenuation value8%or 10%was suggested.