Reorganization in motor cortex after brachial plexus avulsion injury and repair with the contralateral C7 root transfer in rats

Abstract

The purpose of our study was to establish the profile of cortical reorganization in whole BPAI on rats and evaluate changes of cortical reorganization after repair of the median nerve with the contralateral C7 root transfer. Forty adult SD rats underwent whole roots avulsion of left brachial plexus, among them 20 received contralateral C7 root transfer to the injured median nerve. Intracortical microstimulation was performed in primary motor cortex (M1) at intervals of 3, 5, 7, and 10 months, postoperatively. The maps of motor cortical responses were constructed. Five normal rats were used as the control. Results showed that stimulating right M1 elicited motion of left vibrissae, submaxilla, neck, back, and left hindlimb after left BPAI, among them neck representation area replaced the forelimb area throughout the reorganization process. The left forelimb representation area was found in the left motor cortex 5 months after the contralateral C7 root transfer and existed in both motor cortexes at 7th postoperative month. The left forelimb representation area was detected only in right motor cortex at 10th month, postoperatively. In conclusions, after the contralateral C7 root transfer for repair of the median nerve in BPAI, the cortical reorganization occurred in a time-dependent reorganization. The findings from this study demonstrate that brain involves in the functional recovery after BPAI and repair with nerve transfer and suggest that efforts to improve the results from nerve repair should address the peripheral nerve as well as the brain.