Dumitru D, Walsh N E, Ramamurthy S
Department of PM&R, University of Texas Health Science Center, San Antonio 78284-7798.
Arch Phys Med Rehabil. 1989 Jul;70(7):537-40.
A small waveform precedes the compound muscle action potential evoked from the thenar eminence with median nerve stimulation with high amplifier gains. This potential is believed to emanate from fibers destined to innervate the volar aspect of the first digit. It has been suggested recently that the source of the premotor potential is the palmar cutaneous branch of the median nerve. In this study, the palmar cutaneous branch of the median nerve was blocked at the wrist. A localized zone of anesthesia was observed over the proximal midpalm, not the thenar eminence, and the premotor response remained unchanged as did a midpalmar potential. The median nerve was then blocked at the base of the thenar eminence; only then did the premotor potential disappear. The palmar cutaneous branch of the median nerve innervates only a small portion of the medial aspect of the thenar eminence and does not produce the thenar premotor potential. Additionally, because of the close proximity of the main median nerve to its palmar cutaneous branch, volume conduction of stimuli and responses precludes an electrophysiologic technique which exclusively localizes the palmar cutaneous branch of the median nerve.
在高放大增益下通过正中神经刺激诱发的鱼际隆起复合肌肉动作电位之前会出现一个小波形。该电位被认为源自注定要支配第一指掌侧的纤维。最近有人提出运动前电位的来源是正中神经的掌皮支。在本研究中，正中神经的掌皮支在腕部被阻断。在手掌近端中部观察到一个局限性麻醉区域，而非鱼际隆起处，并且运动前反应和掌中部电位均保持不变。然后在鱼际隆起基部阻断正中神经；只有到那时运动前电位才消失。正中神经的掌皮支仅支配鱼际隆起内侧的一小部分，并不会产生鱼际运动前电位。此外，由于正中神经主干与其掌皮支紧邻，刺激和反应的容积传导排除了专门定位正中神经掌皮支的电生理技术。
