Diagnostic Sensitivity of Repetitive Nerve Stimulation Test in Myasthenia Gravis

J Korean Neurol Assoc > Volume 11(2); 1993 > Article

Journal of the Korean Neurological Association 1993;11(2): 195-201.

중증근무력증의 유형별 반복신경자극검사의 진단적 감수성 비교

이상암, 권기한,선우일남

연세대학교 신경과.

Diagnostic Sensitivity of Repetitive Nerve Stimulation Test in Myasthenia Gravis

Sang-Ahn Lee, M.D., Ki-Han Kwon, M.D., Il-Nam Sunwoo, M.D.

Department of Neurology, College of Medicine Yonsei University

Abstract

Repetitive nerve stimulation (RNS) test was systematically performed in proximal and distal muscles of 142 cases with myasthenia gravis (MG) and 45 norrnal controls and then analyzed qualitatively. Diagnostic sensitivity was 75% based on abnorrnal decremental response in at least one muscle. The sensitivity increased from 56% in ocular MG to 96% in type Iib MG according to severity of disease. Higher diagnostic yield was noted in the orbiculans oculi in ocular MG and in the trapezius in gereralized MG. RNS test on proximal muscle showed a higher positive rate than that on distal muscles. When distal muscle testing was negative, there was an additional increase of 24% in proximal muscle testing. The posttetanic exhaustion (PTE) enhanced diagnostic sensitivitY as much as 8% in generalized MG. The posttetanic facilitation(PTF) and PTE were observed in 50% and 38% of generalized MG and were most prominent in MG with moderate severity. Five patterns on RNS findings were classified according to test paramcters. The most common response was the pattern which showed normal arnplitude of compound muscle action potential, decremental response at low rate stimulation, and PTF without PTE