Repetitive nerve stimulation as a predictor of treatment response in myasthenia gravis

Abstract

Background and objectives. The clinical course of myasthenia gravis (MG) varies and may adversely affect quality of life and limit daily activities. Repetitive nerve stimulation (RNS) can be used to diagnose MG and may predict disease progression. We aim to establish the correlation between RNS and pharmacological treatment response. Materials and methods. We conducted a cross-sectional study evaluating the correlation between RNS result and pharmacological treatment response as evaluated using the Myasthenia Gravis-Activities of Daily Living (MG-ADL). Results. RNS positive patients possess greater severity on pre-treatment (9 [5-11] vs. 4 [2-5], p<0.001) and post-treatment (2 [1-4] vs. 1 [0-2], p=0.007) MG-ADL scores. ΔMG-ADL was also significantly greater in RNS positive patients (-6[-7 - -3) vs. -2 [-5 - -1], p=0.004). Spearman’s rank-order correlation conducted evaluating the correlation between RNS and ΔMG-ADL demonstrates a significant moderate positive correlation between RNS and ΔMG-ADL (rs=0.495, p<0.001). Conclusions. A moderate significant correlation was found between RNS and pharmacological treatment response. RNS positive patients are more responsive towards treatment compared to RNS negative patients. Higher fatigability in muscles translates to greater RNS decrements and clinical severity, lending itself to a greater opportunity for improvement following pharmacological. However, this must not be confused with long-term prognosis.