Functional evaluation of regenerated and misrouted axons to glabrous and hairy skin of the rat hind foot after sciatic neurotomy and suture

Functional evaluation of regenerated and misrouted low threshold mechanoreceptors and polymodal nociceptors in the skin of rat hindfeet after crush lesions to the sciatic nerve

Tracer studies on motor axons after nerve crush injuries have indicated that misrouting may occur even when the endoneurium is intact. Misrouting of regenerated polymodal nociceptive C-fibres and low threshold mechanoreceptive axons have been studied functionally in 50 rats three months after unilateral crush lesions to the sciatic nerve. Two weeks before evaluation the tibial fascicle (or the peroneal fascicle) above the lesion was cut and tied off. In this way only functional regeneration of misrouted axons was tested. Misrouted low threshold mechanoreceptive axons and polymodal nociceptor C-fibres were found after regeneration in both glabrous and hairy skin. We conclude that functional misdirection of both myelinated and unmyelinated sensory axons innervating either glabrous or hairy skin can occur after a crush lesion to a peripheral nerve in rats.

Inferior functional sensory regeneration after suture of sciatic neurotomy in newborns compared with mature rats

It is generally believed that nerve injuries in children regenerate better than those which occur in adults. However, there are no functional experimental studies that support this belief. This study evaluates the functional regeneration of polymodal C-fibres after nerve regeneration in newborn and mature rats 3 months after unilateral sciatic nerve neurotomy and suture. The distribution of polymodal C-fibres was tested by measuring the Evans blue-stained area in the skin after antidromic nerve stimulation. In the newborn group of regenerated animals showed that functional C-fibres were present in a significantly (P < 0.05) smaller area than found in the adult group. We conclude that the functional regeneration of C-fibres is superior in mature rats compared with newborns, 3 months after regeneration.

Selective restoration of sensation by peripheral nerve grafts directly implanted into the contralateral C7 dorsal root ganglion: an experimental study in rat brachial plexus

OBJECTIVE

In brachial plexus injuries, when the dorsal root ganglion (DRG) is avulsed from the spinal cord there is no possibility of direct repair. Therefore, in the present report the median nerve was connected directly to the contralateral C7 DRG, to restore forepaw sensation.

METHODS

The ulnar nerve was sectioned, and a 15-mm segment of nerve was removed. The median nerve was sectioned, transposed dorsally, and repaired using a sural nerve graft directly implanted into the C7 contralateral DRG. Rats were then assessed 6 and 12 months later by behavioral, histological, and plasma extravasion techniques.

RESULTS

All animals recovered sensation in the forepaw. Retrogradely labeled sensory neurons were demonstrated in the C7 DRG, and the whole forepaw was labeled after plasma extravasion induction by median nerve antidromic stimulation. Several myelinated and positively neurofilament-stained fibers were demonstrated in the grafted median nerve.

CONCLUSION

The surgical strategy proposed might be a useful alternative to selective sensory repair in the emerging field of brachial plexus reconstruction by direct spinal cord surgery.

Functional regeneration of C-fibres inside a silicone tube after sciatic neurotomy in rats

Peripheral nerve lesions are often complicated by difficulties in approximating the nerve stumps without tension. The aim of the present study was to evaluate C-fibre function after nerve regeneration in rats in which the nerve had been lengthened by leaving a 5 mm gap inside a silicone tube (n = 5). The outcome was compared with nerve regeneration after epineural end-to-end suture (n = 5). The innervated skin territory was defined by Evans blue extravasation after antidromic nerve stimulation. Five rats acted as controls. After three months, there was similar functional reinnervation in both experimental groups, which indicates that silicone tubes may reduce tension over a nerve repair with no adverse effects.