Experimental surgery in spinal cord lesions by connecting upper motoneurons directly to peripheral targets

This research was aimed at assessing the possibility to connect central motoneurons with skeletal muscles through PNS segments bypassing a lesion of the spinal cord. The investigation was performed in 20 non-human primates (Macaca fascicularis). The surgical paradigm consisted of anastomosing the lateral bundle of the spinal cord directly with the sciatic nerve of the right hindlimb, using the peroneal nerve as a graft. The animals were followed-up clinically for 18 months; at the end of this observation period, they underwent electrophysiological examinations before being killed. Specimens were taken from the spinal cord, graft, sciatic nerve and potentially reinnervated muscles, and processed for routine light microscopy and immunohistochemistry. Postoperative mortality was fairly high (six monkeys), yet the overall outcome was regarded as very good because the animals were neither restrained nor intensively cared for. Five of the surviving monkeys showed clinical, electrophysiological and histological evidence of successful reinnervation. This research demonstrated that upper CNS motoneurons are potentially capable of elongating neuritic processes into the endoneural tubes of a connecting graft, up to reaching a peripheral nerve (sciatic), and restoring functional connections with the relevant skeletal muscles.