P24-F Medium latency Soleus reflex responses induced by transcranial magnetic and peroneal nerve stimulation

Abstract

Background Sudden foot dorsiflexion generates medium and long latency responses in soleus muscle which are thought to be the stretch reflex and have a spinal origin. Peroneal nerve stimulation results in foot dorsiflexion and produces a medium latency reflex in soleus muscle (SOL-MLR). Similarly, transcranial magnetic stimulation (TMS) of motor cortex corresponds to the leg area evokes a response analogous to SOL-MLR, referred to as soleus motor evoked potential 80 (SOL-MEP 80). Material and methods In this study, the origin of SOL-MLR and SOL-MEP 80 were investigated in 15 healthy volunteers using surface electromyography. SOL-MEP 80 was evoked by non-invasive TMS of leg area of motor cortex on the scalp using a round coil. On the other hand, SOL-MLR was obtained through electrical stimulation of the peroneal nerve during the foot was slightly dorsiflexed. Given that the contraction of the tibialis anterior (TA) muscle results in foot dorsiflexion, so, the stretch reflex in the soleus muscle. Therefore, the latency of SOL-MLR and SOL-MEP 80 was compared with the muscle action potential generation in TA muscle with similar methodology, TA direct motor response and TA MEP. Results The latency difference between SOL-MLR and TA direct motor response was 64.0 ± 4.0 ms while the difference was 61.4 ± 5.6 ms between SOL-MEP 80 and TA-MEP. Conclusions Comparable latency features and similar behavior pattern of the responses propose that SOL-MLR and SOL-MEP 80 may have a related origin. This project (3135) supported by Akdeniz University Scientific Research Unit .