Clinical Significance of Axonal Stimulation Single Fiber Electromyography
in Patients with Myasthenia Gravis

J Korean Neurol Assoc > Volume 18(4); 2000 > Article

Journal of the Korean Neurological Association 2000;18(4): 425-430.

중증 근 무력증 환자에서 축삭 자극 단일 근섬유 근전도 검사의 임상적 의의

김대성, 박규현

부산대학교 의과대학 신경과학교실

Clinical Significance of Axonal Stimulation Single Fiber Electromyography in Patients with Myasthenia Gravis

Dae-Seong Kim, M.D., Kyu-Hyun Park, M.D.

Department of Neurology, College of Medicine, Pusan National University

Abstract

Background : The axonal stimulation single fiber electromyography (S-SFEMG) is a relatively new electrophysio-logical technique and has several advantages over conventional voluntarily activated single fiber electromyography (V-SFEMG). This study was performed in patients with myasthenia gravis (MG) in order to analyze their neuromuscular transmission defects and thus to verify the usefulness of the S-SFEMG technique. Methods : In 44 patients with MG, S-SFEMG was performed on the extensor digitorum communis muscle. The repetitive nerve stimulation test (RNST) on orbicularis oculi, trapezius, flexor carpi ulnaris, and abductor digiti quinti muscles was also performed at the same time. The results of the RNS and S-SFEMG were then analysed in detail. Results : The S-SFEMG was found abnormal in 84.1%, while RNST was found abnormal in 75.0% of the patients tested. The normal S-SFEMG result was observed exclusively among 7 ocular type MG patients. The mean of the mean consecutive difference (MCD) value, % of fibers with blocking and % of fibers with abnormal jitter, was more increased in patients with generalized type MG than those with ocular type MG. This difference was statistically significant (P<0.01) in all 3 variables. C o n c l u s I o n s : The S-SFEMG is a highly sensitive and useful diagnostic tool in MG. Although it demands more strict technical consideration than V-SFEMG, it is less time-consuming and applicable to uncooperative patients including children. Our study shows S-SFEMG to be especially useful in patients with ocular type MG whose RNST results do not show definite decremen-tal responses. J Korean Neurol Assoc 18(4):425~430, 2000 Key Words : Myasthenia gravis, Axonal stimulation single fiber electromyography, Repetitive nerve stimulation test, Neuromuscular transmission, Clinical usefulness