Precise orientation of brachialis muscle branch in the spinal nerve roots in rats

Abstract

Objective To compare the efficacy of retrograde tracing and electrophysiologic localization in precise orientation of brachialis muscle branch in the spinal nerve roots in a rat model, and discuss the feasibility of electrophysiological orientation of brachialis muscle branch of the musculocutaneous nerve in human. Methods Adult Sprague Dawley rats were used. Retrograde tracing of brachialis muscle branch or brachialis muscle in various combinations of nerve root transection-preservation was done. Compound muscle action potentials of brachialis muscle were recorded while various roots of the brachial plexus were stimulated. Results Brachialis muscle in rat received dual innervation from the musculocutaneous nerve and radial nerve. The former was mainly from C5 and C6 spinal nerve roots and the latter from C7 spinal nerve root. The results of retrograde tracing agreed with the results of electrophysiologic testing. Conclusion Both retrograde tracing and electrophysiologic testing could be used in precise localization of spinal nerve root origin of forelimb muscles. Electrophysiological studies could be employed in precise orientation of brachialis and its motor branches in human. Key words: Brachial plexus; Nerve transfer; Musculocutaneous nerve; Electrophysiology; Neuron tracing