Findings of repetitive nerve stimulation test in myasthenia gravis: A case-control study

ABSTRACT

Authors had perforrned repetitive nerve stimulation tests on orbicularis oculi, flexor carpi ulnaris, and abductor digiti quinti muscles in 21 myasthenic patients and 40 normal controls using conventional Oh's rnethod and analysed statistically in detail. The results were as follows: 1) There were no significant statistical differences in CMAP and postexercise potentiation between normal controls and myastheic patients, but there were statistically significant decremental responses in both low-and high-rate of stimulation in myasthenic patients, with characteristic posttetanic potentiation and posttetanic exhaustion. 2) There were no statistical differences among Desmedt's, Stalberg's, and Oh's methods in determining the decremental ratio in low-rate of stimulation. 3) The proximal muscles showed more prominent decremental responses than distal muscles in myasthenic patients, and in three myasthenic patients, (14.3%) there were no statistically significant decremental responses in all tested muscles in spite of postivie edrophonium responses. 4) The gerleralized type myasthenic patients showed more prominent decremental responses than oclular type myasthenic patients. 5) Among the myasthenic patients, the oclular type myasthenic patients showed no statistically significant decremental response in both low-and high-rate of stimulation performed on flexor carpi ulnaris and abductor digiti quinti muscles.