بررسي ميزان پاسخ دهي عضله تراپزيوس به تحريكات مغناطيسي كورتكس موتور همان سمت و سمت مقابل مغز در افراد داوطلب نرمال

Bilateral responses of trapezius muscle to transcranial magnetic stimulation in normal subjects

Introduction: Motor evoked potentials (MEPs) can be elicited in trapezius and other axial muscles by ipsilateral transcranial magnetic stimulation (TMS).The purpose of this study is to compare the relative amplitudes and latencies of ipsilateral versus contralateral responses to TMS from trapezius muscle of normal subjects. Materials and Methods: MEPs were bilaterally recorded during complete relaxation and voluntary contraction from upper trapezius muscle in 40 healthy right handed subjects by TMS in right and left hemispheres. Base-to-peak amplitude and latency of MEP were measured for each muscle on both sides. Results: At rest, a contralateral response was obtained in 45 trapezius muscles. Ipsilateral responses were observed in II muscles (latency contra-lateral and ipsilateral 9.8ms and 15.5 ms, respectively, P <0.001). During contraction ipsilateral MEPs could be evoked in 37 muscles. Contralateral MEPs were obtained in 76 experiments on 40 subjects (latency contralateral and ipsilateral8.5ms and 12.6 ms, respectively, P <0.001). Conclusion: MEPs can be readily evoked by TMS over the ipsilateral motor cortex in a variety of proximal muscles, such as trapezius. Ipsilateral MEPs have a later onset and lower amplitude than contralateral responses. It is considered that oligosynaptic connections may be a common feature of axial muscles, such as trapezius. These patterns of connections are discussed in relation to the contrasting bilateral functional roles of this muscle.