title: Far-field recording of compound muscle action potentials produced during brachial plexus stimulation.
abstract: In 15 normal subjects, compound muscle action potentials (CMAPs) produced during electrical stimulation of the brachial plexus were obtained at a distance (far field) from their sources (upper-limb muscles). These far-field CMAPs were recorded at the forehead, neck, and tip of the middle finger and were referred to a relatively inactive region (contralateral forearm or knee). At the proximal recording site (neck or forehead), the far-field CMAPs were generally triphasic in appearance when all of the muscles of the upper limb were activated during brachial plexus stimulation. The initial component was a negative wave; this was followed by a positive component which terminated in a negative potential. At the distal recording site (tip of middle finger), the far-field CMAPs usually had a biphasic appearance, with an initial positivity followed by a period of negativity. The contours of the major components of the far-field CMAPs were frequently interrupted by a series of small amplitude negative and positive peaks or inflections.
authors.affiliation: Department of Neurology, University of Mississippi Medical Center, Jackson.
authors.forename: A S
authors.initials: AS
authors.lastname: Wee
authors.forename: R A
authors.initials: RA
authors.lastname: Ashley
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001132:Arm; D001917:Brachial Plexus / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D009132:Muscles / Q000502:physiology*