부산대학교 도서관

INTRODUCTION Myasthenia Gravis (MG) is an autoimmune disorder that affects neuromuscular transmission in skeletal muscles (1). The autoimmune process is caused by autoantibodies mostly against acetylcholine receptors (AChR), located at [...]
Objective: To investigate the effect of voluntary contraction at low frequency repetitive nerve stimulation (RNS) as a sign of presynaptic compensation in patients with Myasthenia Gravis (MG). Material and Method: Thirty-five patients with MG were included. RNS at 3 Hz, recorded from the abductor digiti minimi, trapezius, nasalis, and orbicularis oculi muscles were performed. In muscles with more than 10% decrement, RNS at 1 Hz with 20-90 stimuli was applied after 10-second maximal isometric voluntary muscle contraction (MIVMC). Progressive decremental pattern was considered when decrement values were increasing until the last response. Facilitation after MIVMC was determined by dividing the amplitude of motor response in resting state by the amplitude of the motor response recorded just after contraction. Results: Among 15 patients having RNS at 1 Hz, nine had facilitation after MIVMC. In the muscle with facilitation, there was a significant positive correlation between the increment ratio and the progressive decrement difference between responses 1-4 and 1-9 (correlation coefficient 0.730, p=0.026). Although not statistically significant, muscles showing facilitation following decrement tended to have a progressive decremental pattern. Conclusion: During RNS, facilitation after MIVMC followed by progressive decremental pattern may be related to presynaptic compensation of neuromuscular transmission failure in MG. Keywords: Myasthenia Gravis, repetitive nerve stimulation, low frequency stimulation, post-exercise facilitation, decrement Amac: Bu calismada, Myasthenia Gravis (MG) hastalarinda presinaptik kompansasyonun bir gostergesi olarak maksimal istemli kasi sonrasinda ardisik sinir uyarim testinde (ASU) degisikliklerin incelenmesi amaclandi. Gerec ve Yontem: Otuz bes MG hastasi calismaya dahil edildi. Bu hastalara abduktor digiti minimi, trapez, nazalis ve orbikularis okuli olmak uzere 4 kastan 3 Hz ASU incelemesi yapildi. Dekrement orani %10 uzerinde olan kaslarda 10 saniye izometrik maksimal kasi sonrasinda 1 Hz ASU incelemesi tekrarlandi. Bu kaslarda kasi sonrasi fasilitasyon ve progresif dekrement paterni varligi degerlendirildi. Progresif dekrement paterni, ASU incelemesinde dekrement oraninin son uyariya kadar artmasi olarak belirlendi. Progresif dekrement farki ise 1-4 ve 1-9 ile 1-4 ve 1-son uyari ile kaydedilen dekrement degerlerinin birbirinden cikartilmasi ile hesaplandi. Fasilitasyon ise kasi sonrasi ve istirahatte kaydedilen motor yanit amplitudlerinin birbirine oranlanmasi ile belirlendi. Bulgular: Istemli kasi sonrasi 1 Hz ASU yapilan 15 hastanin 9'unda fasilitasyon saptandi. Fasilitasyon izlenen kaslarda inkrement orani ile progresif dekremet farki (1-4 ve 1-9 uyari arasi) istatistiksel olarak anlamli pozitif bir korelasyon gosterdi (korelasyon katsayisi 0,730; p=0,026). Istatistiksel olarak anlamli olmamakla birlikte ilk 9 uyarida progresif dekrement paterni varligi dekrementi takiben fasilitasyon izlenen kaslarda daha fazlaydi. Sonuc: Izometrik kasi sonrasinda dusuk frekansli ASU incelemesi MG hastalarinda presinaptik kompansasyonu gosterebilir. Anahtar Kelimeler: Myasthenia Gravis, ardisik sinir uyarimi, dusuk frekansli uyarim, egzersiz sonrasi fasilitasyon, decrement