Fujii M, Yamada T, Aihara M, Kokubun Y, Noguchi Y, Matsubara M, Yeh M H
Department of Neurology, University of Iowa, College of Medicine, Iowa City 52242.
Electroencephalogr Clin Neurophysiol. 1994 Nov;92(6):518-26. doi: 10.1016/0168-5597(94)90136-8.
We examined the effect of stimulus rates on the somatosensory evoked potential (SEP) amplitude following stimulation of the median nerve (MN) and the ulnar nerve (UN) at the elbow or wrist, and the radial nerve (RN) at the wrist in 12 normal subjects. We measured the amplitude of frontal (P14-N18-P22-N30) and parietal peaks (P14-N20-P26-N34) at a stimulus rate of 1.1, 3.5 and 5.7 Hz. The amplitude attenuation was found at frontal P22 and N30 and to a lesser degree at parietal N20 and P26 peaks with an increasing stimulus rate from 1.1 to 5.7 Hz. The amplitude attenuation was greatest at the elbow when compared to the wrist stimulation for both MN and UN. The attenuation was least for wrist stimulation for the RN. The UN block by local anesthesia just distal to the stimulus electrode at the elbow abolished the amplitude attenuation caused by the fast stimulus rate. The observed amplitude attenuation with the faster stimulus rate is probably due, in part, to interference from the "secondary" afferent inputs. The secondary afferent inputs arise from peripheral receptor stimulation (muscle, joint and/or cutaneous) as a subsequent effect of efferent volleys initiated from the point of stimulation. The greater number of peripheral receptors being activated as more proximal sites of stimulation in a mixed nerve would result in greater attenuation of the SEP recorded from scalp electrodes. We postulate that the attenuation of frontal peaks by the fast stimulus rate is due to the frontal projection of interfering "secondary" afferent inputs.
我们在12名正常受试者中，研究了刺激频率对在肘部或腕部刺激正中神经（MN）和尺神经（UN）以及在腕部刺激桡神经（RN）后体感诱发电位（SEP）幅度的影响。我们在1.1、3.5和5.7Hz的刺激频率下测量了额部峰（P14 - N18 - P22 - N30）和顶叶峰（P14 - N20 - P26 - N34）的幅度。随着刺激频率从1.1Hz增加到5.7Hz，发现额部P22和N30以及顶叶N20和P26峰的幅度衰减，且顶叶幅度衰减程度较小。对于MN和UN，与腕部刺激相比，肘部刺激时幅度衰减最大。对于RN，腕部刺激时衰减最小。在肘部刺激电极远端进行局部麻醉阻断UN，消除了快速刺激频率引起的幅度衰减。观察到的快速刺激频率下的幅度衰减可能部分归因于“次级”传入输入的干扰。次级传入输入源于外周感受器刺激（肌肉、关节和/或皮肤），是刺激点发出的传出冲动的后续效应。在混合神经中，随着刺激部位更靠近近端，更多外周感受器被激活，这将导致从头皮电极记录的SEP衰减更大。我们推测，快速刺激频率引起的额部峰衰减是由于干扰性“次级”传入输入的额部投射。
