The fate of motoneurons in the spinal cord after peripheral nerve repair: a quantitative study using the neural tracer horseradish peroxidase.

Abstract

This study assessed the changes that occurred in the spinal motoneuron pool after the repair of a specific peripheral nerve by means of several clinically appropriate surgical techniques: nerve graft, muscle graft, and epineurial suture. The motoneuron pool relating to a single muscle was assessed at 50, 100, 200, and 300 days after repair via retrograde axonal transport of the neural tracer horseradish peroxidase. The results indicate that although a small portion of the motoneuron population dies following peripheral nerve surgery, this is not a significant number. The majority of the anterior horn cells appear to have the ability to both survive nerve transection and form new functional connections with the regenerated nerve after repair. The degree of cell loss is influenced by the nature of the injury and the method of repair implemented. Injuries involving neurotmesis result in the loss of a greater proportion of the cell population than less severe injuries involving axonotmesis. A greater proportion of the motoneuron population is preserved when the severed nerve has been repaired using a direct epineurial suture than when repair is achieved by means of a graft. The two methods of grafting produced comparable results, although the muscle graft tended to result in the preservation of a greater number of cells than the nerve graft, making it an acceptable alternative method for the surgical repair of short gaps in peripheral nerves.