Direct neurotization of muscles by presynaptic motoneurons

The spinal cord cannot heal after severance because the central nervous sys tem is "non-permissive" to the advancement of axons that regrow from presyn aptic motoneurons. With the aim of overcoming paraplegia, the author has ca rried out extensive experimental research since 1980, first in rats and sub sequently in monkeys, severing the cord and connecting its cephalad stump w ith the muscular nerve branches by means of peripheral-nerve grafts, and us ing various surgical protocols. Functional connections were established, as certained by physical, electrophysiologic, and histologic examinations. In this reported study, it is demonstrated that presynaptic motoneurons are also able to reconstruct the cytoskeleton of peripheral neurons, as well a s motor end-plates. The possibility of elongation of the axons of presynapt ic motoneurons into the peripheral nerve up to the muscle had not previousl y even been hypotheized. This possibility, which has now been validated, ca n open the door to new surgical techniques for spinal-cord lesions. In addi tion, the author presents preliminary results from a single human case, uti lizing the surgical procedures of the preceding animal experiments.