Electrophysiological and functional analysis of peripheral nerve regeneration enlargement and compensation in rhesus monkey

Abstract

Objective To establish a model of peripheral nerve fiber enlargement and compensation in rhesus monkey and conduct electrophysiological analysis. Methods Right ulnar nerve and musculocutaneous nerve of 8 rhesus monkeys were cut at 4 cm below the pectoralis major muscle and repaired with small gap bridging by using a degradable and biocompatible conduit (inner diameter 4 mm,length 10 mm) that left 2 mm distance between nerve ends. At the proximal end of the conduit was the proximal ulnar nerve end,and at the distal end of the conduit both ulnar nerve and musculocutaneous nerve were sutured in. Before the surgery,baseline conduction velocities of both nerves were collected. The electrophysiological evaluation and histological analyze were performed after 3 and 6 months respectively. Results The electrophysiological results at 3 months showed that there was action potential recorded at biceps and hypothenar muscles when the proximal ulnar nerve was stimulated. However,motor nerve conduction velocity between proximal ulnar nerve and distal musculocutaneous nerve was (14.62±0.53)mm/s,which was much lower compared to the baseline (34.17±0.93)mm/s. And the conduction velocity between proximal and distal ulnar nerve was (20.99±1.71)mm/s,which was less than 1/2 of the baseline (48.84±1.89)mm/s value. During the functional evaluation,there were no elbow flexion and finger separation and closing movement.Electrophysiologic evaluations at 6 monthsshowed conductive velocity of (18.47±0.86) mm/s and (27.03±1.19) mm/s for ulnar to musculocutaneous nerve and ulnar to ulnar nerve,respectively. Slight movement of the elbow and figures were observed. Conclusion The injured peripheral nerve fibers of rhesus monkey are enlargeable and have compensatory effects. It is possible that the regenerated nerve fibers from injured proximal ulnar nerve could integrate with distal ulnar nerve and musculocutaneous nerve and complete the pathway that could lead to partial functional restoration. Key words: Peripheral nerves; Nerve regeneration; Neural enlargement; Neural compensation