Brachial plexus repair by peripheral nerve grafts directly into the spinal cord in rats. Behavioral and anatomical evidence of functional recovery.

Over the years, peripheral nerve grafts, a favorable environment for the support of axonal elongation, have attracted interest as a possible means of promoting spinal cord repair. In the experiments described here, rats underwent an avulsion injury of the brachial plexus, and the musculocutaneous nerve was repaired by direct insertion of peripheral nerve grafts into the spinal cord. After varying postoperative periods, the rats were submitted to a series of behavioral tests to evaluate forelimb and hindlimb function. They also underwent retrograde double-labeling studies. Nerve grafts were harvested and processed for electronic microscopy. The biceps muscle was removed and weighed and its histology studied. After surgery, central axons effectively regenerated about 65 mm along the peripheral nerve grafts, restoring normal active elbow flexion. Forelimb movements were well coordinated in both voluntary and automatic activities. Clinical investigations showed that there were no side effects in the ipsilateral forepaw, contralateral forelimb, or either hindlimb. Regenerating axons stemmed from original motoneurons, foreign motoneurons, and even antagonist motoneurons, but this did not impair function. Ganglionic neurons from adjacent roots also sent processes to the peripheral nerve grafts.