신경-근 접합부 질환에서의 전기생리검사

Abstract

Electrodiagnostic studies are valuable in confirming the diagnosis of a disorder of neuromuscular transmission. They are used to distinguish presynaptic and postsynaptic abnormalities. These studies provide an objective measure of the severity of the illness and may be useful in assessing the response to therapy. This article reviews the electrodiagnostic techniques that are commonly used today and highlights their specificity, sensitivity, and pitfalls. Repetitive nerve stimulation test (RNST) and single-fiber electromyography (SFEMG) are the most available electrophysiologic test in the diagnosis of neuromuscular junction disorders. RNS showing 10% decrement in amplitude from the first to fourth or fifth intravolley waveform while stimulating at 2~5 Hz is valid for the diagnosis of MG. The degree of increment needed for the diagnosis of LEMS is at least 25% but most accurate when greater than 100%. Abnormal jitter or impulse blocking are the appropriate criteria for diagnosis of NMJ disorders when using SFEMG. SFEMG is more sensitive than RNS for the diagnosis of disorders of neuromuscular transmission, especially in MG but may be less specific or may not be available.