Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology · 2010
Correlation of bite force with excitation-contraction coupling time of the masseter in myasthenia gravis.
Сравнительное исследованиеСтатьяПоддержка исследования: вне правительства СШАНазвание и аннотация: Перевод пока не подготовлен
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Tsuda Emiko, Imai Tomihiro, Hozuki Takayoshi, Yamauchi Rika, Saitoh Masaki, Hisahara Shin, Yoshikawa Hiroaki, Motomura Masakatsu, Shimohama Shun
Аннотация
OBJECTIVE: The aim of this study was to elucidate the relationship between the impairment of excitation-contraction (E-C) coupling of masseter and the bite force in patients with myasthenia gravis (MG).
METHODS: In 20 patients with MG, masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRP) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The E-C coupling time (ECCT) was calculated by the latency difference between CMAP and MRP. Bite force was measured using a pressure-sensitive sheet. Serial assessments of % decrement in masseteric repetitive nerve stimulation (RNS), ECCT, and bite force were performed before and after corticosteroid therapy alone or in various combinations with FK506, cyclosporin A, intravenous immunoglobulin and immunoabsorption.
RESULTS: Percent amplitude decrement in RNS and ECCT decreased significantly accompanying an increase in bite force after treatment. Simple regression analysis demonstrated a linear correlation among % decrement, ECCT and bite force. However, ECCT shortening accompanying bite force recovery without reduction in % decrement was observed in 4 patients.
CONCLUSIONS: Masseteric E-C coupling is impaired in some MG patients, and functional recovery of E-C coupling contributes at least in part to the increase in bite force after treatment.
SIGNIFICANCE: Impaired E-C coupling contributes to muscle weakness in patients with MG.
METHODS: In 20 patients with MG, masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRP) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The E-C coupling time (ECCT) was calculated by the latency difference between CMAP and MRP. Bite force was measured using a pressure-sensitive sheet. Serial assessments of % decrement in masseteric repetitive nerve stimulation (RNS), ECCT, and bite force were performed before and after corticosteroid therapy alone or in various combinations with FK506, cyclosporin A, intravenous immunoglobulin and immunoabsorption.
RESULTS: Percent amplitude decrement in RNS and ECCT decreased significantly accompanying an increase in bite force after treatment. Simple regression analysis demonstrated a linear correlation among % decrement, ECCT and bite force. However, ECCT shortening accompanying bite force recovery without reduction in % decrement was observed in 4 patients.
CONCLUSIONS: Masseteric E-C coupling is impaired in some MG patients, and functional recovery of E-C coupling contributes at least in part to the increase in bite force after treatment.
SIGNIFICANCE: Impaired E-C coupling contributes to muscle weakness in patients with MG.