Stegeman D F, Gootzen T H, Theeuwen M M, Vingerhoets H J
Department of Clinical Neurophysiology, University of Nijmegen, The Netherlands.
Electroencephalogr Clin Neurophysiol. 1994 Apr;93(2):81-90. doi: 10.1016/0168-5597(94)90070-1.
A comprehensive volume conductor study of single fiber needle EMG (SF EMG) has been made. The electrode shaft is described as a passive inhomogeneity in the volume conductor. The most important observation is a substantial increase in single fiber action potential (SFAP) amplitude (up to 70%) for muscle fibers observed from a short distance. For SFAPs from muscle fibers located on the back of the SF electrode a shadow effect occurs which can result in a maximal amplitude decrease of 50%. SFAP wave form changes were observed only in situations without practical consequences or beyond physical reality. The presence of the needle shaft causes an anisotropy-like behavior of the relation between leading-off point to muscle fiber distance. The observed amplification due to the presence of the needle cannula decreases faster in the direction parallel to the cannula than in the direction normal to it: due to the amplification of SFAPs from muscle fibers observed from a short distance, the maximal distance from which SFAPs are included in fiber density measurements (amplitude greater than 0.2 mV) is raised from 380 microns to 460 microns. Also, the consequences of the formation of an edematous layer around the needle cannula have been studied. It was shown that the effect of high conductive fluid around the needle electrode can counteract the effects caused by the presence of the electrical double layer.
已对单纤维针电极肌电图（SF EMG）进行了全面的容积导体研究。电极轴被描述为容积导体中的一个无源不均匀性。最重要的观察结果是，从近距离观察到的肌肉纤维的单纤维动作电位（SFAP）幅度大幅增加（高达70%）。对于来自SF电极背面肌肉纤维的SFAP，会出现阴影效应，这可能导致最大幅度降低50%。仅在没有实际影响或超出物理现实的情况下才观察到SFAP波形变化。针轴的存在导致引出点与肌肉纤维距离之间的关系呈现出类似各向异性的行为。观察到由于针套管的存在而产生的放大效应，在与套管平行的方向上比在垂直于套管的方向上下降得更快：由于近距离观察到的肌肉纤维的SFAP放大，纤维密度测量中包含SFAP的最大距离（幅度大于0.2 mV）从380微米增加到460微米。此外，还研究了针套管周围水肿层形成的后果。结果表明，针电极周围高传导性流体的作用可以抵消双电层存在所引起的影响。
