EVALUATION OF REPETITIVE NERVE STIMULATION WITH DIFFERENT STIMULATION FREQUENCIES IN PATIENTS WITH MYASTHENIA GRAVIS

Abstract

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.

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MYASTHENİA GRAVİS HASTALARINDA FARKLI UYARI FREKANSLARI İLE ARDIŞIK SİNİR UYARIM TESTİNİN İNCELENMESİ

Abstract

Amaç: Bu çalışmada, Myasthenia Gravis (MG) hastalarında presinaptik kompansasyonun bir göstergesi olarak maksimal istemli kası sonrasında ardışık sinir uyarım testinde (ASU) değişikliklerin incelenmesi amaçlandı. Gereç ve Yöntem: Otuz beş MG hastası çalışmaya dahil edildi. Bu hastalara abdüktör digiti minimi, trapez, nazalis ve orbikülaris okuli olmak üzere 4 kastan 3 Hz ASU incelemesi yapıldı. Dekrement oranı %10 üzerinde olan kaslarda 10 saniye izometrik maksimal kası sonrasında 1 Hz ASU incelemesi tekrarlandı. Bu kaslarda kası sonrası fasilitasyon ve progresif dekrement paterni varlığı değerlendirildi. Progresif dekrement paterni, ASU incelemesinde dekrement oranının son uyarıya kadar artması olarak belirlendi. Progresif dekrement farkı ise 1-4 ve 1-9 ile 1-4 ve 1-son uyarı ile kaydedilen dekrement değerlerinin birbirinden çıkartılması ile hesaplandı. Fasilitasyon ise kası sonrası ve istirahatte kaydedilen motor yanıt amplitüdlerinin birbirine oranlanması ile belirlendi. Bulgular: İstemli kası sonrası 1 Hz ASU yapılan 15 hastanın 9’unda fasilitasyon saptandı. Fasilitasyon izlenen kaslarda inkrement oranı ile progresif dekremet farkı (1-4 ve 1-9 uyarı arası) istatistiksel olarak anlamlı pozitif bir korelasyon gösterdi (korelasyon katsayısı 0,730; p=0,026). İstatistiksel olarak anlamlı olmamakla birlikte ilk 9 uyarıda progresif dekrement paterni varlığı dekrementi takiben fasilitasyon izlenen kaslarda daha fazlaydı. Sonuç: İzometrik kası sonrasında düşük frekanslı ASU incelemesi MG hastalarında presinaptik kompansasyonu gösterebilir.

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