Rerouting peripheral nerves for spinal cord lesions.
To provide control of paralyzed limb muscles following spinal cord lesions, peripheral nerves containing motor axons from motoneurons located above a spinal cord lesion could potentially be rerouted to nerves containing motor axons located below the spinal cord lesion. To test this hypothesis in rats, the distal end of a cut tibial nerve, innervated by the L4-6 spinal level, was anastomosed or rerouted to the central end of the cut femoral nerve, innervated by the L3-4 spinal level. Appropriate controls were used. Recovery of lower hind limb motor function was followed at regular intervals, measuring the twitch tension of toe flexion (innervated by the tibial nerve) induced by transcutaneous stimulation of nerve rootlets exiting the spinal cord. After 4-6 months, 54% of motor function returned in the experimental group. Retrograde transport of horseradish peroxidase from the gastrocnemius muscles to spinal motoneuron cell bodies confirmed that the innervation of this group was at a higher level. Furthermore, after an L4 spinal transection, twitch tension responses to spinal cord outlet stimulation remained only in the experimental group. Therefore, a peripheral nerve containing motor axons from above the lesion was rerouted to a distal peripheral nerve to control muscles that would have otherwise been denervated.