Laboratory Tests and Their Significances in Myasthenia Gravis

J Korean Neurol Assoc > Volume 12(4); 1994 > Article

Journal of the Korean Neurological Association 1994;12(4): 694-701.

중증근무력증에서 제반 검사법의 진단적 의의

서대원, 주인수,이광우

서울대학교 신경과.

Laboratory Tests and Their Significances in Myasthenia Gravis

Dae Won Seo, M.D., In Soo Joo, M.D., Kwang Woo Lee, M.D.

Department of Neurology, Seoul National University College of Medicine

Abstract

Sometimes it is not easy to make the diagnosis of myasthenia gravis (MG). The aim of our study was to understand the diagnostic sensitivities of tensilon, repetitive nerve stimulation (RNS), single fiber EMG (SFEMG) tests, acetylcholine receptor (AChR) antibodies (Ab), and to know their comparative significances for making diagnosis of MG. Those tests were safely completed in 40 myasthenia gravis, which consisted of 17 ocular, 21 generalized, 1 acute severe, 1 late severe MG. In all 40 subjects at least one of the tests was abnormal. The positive rates of tensilon, RNS tests, SFEMG, AChR Ab were 92.5%, 65.0%, 90.0%, and 82.5% respectively. The sensitivities of each tests were high in severe MG group, compared with those in mild MG group, because the positive rates were decreased from 100.0% to 89.2% in tensilon tests, from 83.3% to 57.1% in RNS test, from 100.0% to 89.2% in SFEMG tests and 91.7% to 78.6% in AChR Ab test. The positive results of RNS test was increased from 32.5% on abductor digiti quinti (ADQ) to 65.0% on orbicularis oculi (OOC). Among 3 cases with negative tensilon test, the RNS test in 1 case, the SFEMG tests were positive in all 3 cases, and the AChR Ab assay 1case. Among 3 cases with negative SFEMG, the tensilon tests were positive in 3 all cases, the RNS test in 1case and the AChR Ab assay in 1 cases. Among 5 cases, with negative RNS teses and negative AChR Ab assay, the tensilon tesrs wre positive in 3 cases and the SFEMG tests in 3 cases. Therefore we conclude that tensilon and SFEMG tests were more sensitive than RNS tests and AChR Ab assay. SFEMG test would be indicated to diagnose MG, especially in those mild MG cases with negative stensilon test. Also AChR Ab assay could improve diagnostic yields.