Experimental study on changes of the motor cortex plasticity following median nerve injury and repair

Abstract

Objective To investigate changes of plasticity of the motor cortex at different intervals following median nerve injury and repair.Methods Thirty-five adult Sprague Dawley rats were randomly divided into 7 groups：normal group and 1 day，1，4，8，12，16 weeks group after median nerve repair，with 5 each.The median nerve of the left side was transected 2 cm distal to the medial cord and sutured immediately.Intracortical microstimulation technique was used to quantitatively evaluate the changes of plasticity of the corresponding left forelimb motor region. Results The area of finger and wrist flexion zone at the motor cortex was[(0.85±0.1)mm2，-x±s，下同].The zone of finger and wrist flexion was occupied by the sites of the radial nerve.musculocutaneous nerve and axillary nerve 1 day and l week postoperatively.There were no unresponsive sites.Unresponsive sites appeared at 4，8 and 16 weeks postoperatively in the motor cortex.The sites of finger and wrist flexion presented in the contralateral hemispheres 8 and 12 weeks postoperatively，and there was signifieant difference in area when compared to the normal group(P＜0.05).Sixteen weeks postoperatively there Was no significant difference compared to the normal group(P＞0.05).Condusion The motor cortex of the adult rat has plasticity following median nerve injury and repair.It is a dynamical procedure.Its meehanism need to be further studied. Key words: Peripheral nerves; Wounds and injuries; Intracortical microstimulation; Plasticity