Functional recovery and mechanisms in end-to-side nerve repair in rats

Comparison of muscle force after immediate and delayed reinnervation using nerve-muscle-endplate band grafting

BACKGROUND

Because of poor functional outcomes of currently used reinnervation methods, we developed novel treatment strategy for the restoration of paralyzed muscles-the nerve-muscle-endplate band grafting (NMEG) technique. The graft was obtained from the sternohyoid muscle (donor) and implanted into the ipsilateral paralyzed sternomastoid (SM) muscle (recipient).

METHODS

Rats were subjected to immediate or delayed (1 or 3 mo) reinnervation of the experimentally paralyzed SM muscles using the NMEG technique or the conventionally used nerve end-to-end anastomosis. The SM muscle at the opposite side served as a normal control.

RESULTS

NMEG produced better recovery of muscle force as compared with end-to-end anastomosis. A larger force produced by NMEG was most evident for small stimulation currents.

CONCLUSIONS

The NMEG technique holds great potential for successful muscle reinnervation. We hypothesize that even better muscle reinnervation and functional recovery could be achieved with further improvement of the environment that favors axon-end plate connections and accelerates axonal growth and sprouting.

Influence of breaching the connective sheaths of the donor nerve on its myelinated sensory axons and on their sprouting into the end-to-side coapted nerve in the rat

The influence of breaching the connective sheaths of the donor sural nerve on axonal sprouting into the end-to-side coapted peroneal nerve was examined in the rat. In parallel, the effect of these procedures on the donor nerve was assessed. The sheaths of the donor nerve at the coaptation site were either left completely intact (group A) or they were breached by epineurial sutures (group B), an epineurial window (group C), or a perineurial window (group D). In group A, the compound action potential (CAP) of sensory axons was detected in ~10% and 40% of the recipient nerves at 4 and 8 weeks, respectively, which was significantly less frequently than in group D at both recovery periods. In addition, the number of myelinated axons in the recipient nerve was significantly larger in group D than in other groups at 4 weeks. At 8 weeks, the number of axons in group A was only ~15% of the axon numbers in other groups (p<0.05). Focal subepineurial degenerative changes in the donor nerves were only seen after 4 weeks, but not later. The average CAP area and the total number of myelinated axons in the donor nerves were not different among the experimental groups. In conclusion, myelinated sensory axons are able to penetrate the epiperineurium of donor nerves after end-to-side nerve coaption; however, their ingrowth into recipient nerves is significantly enhanced by breaching the epiperineurial sheets at the coaptation site. Breaching does not cause permanent injury to the donor nerve.

Facial--hypoglossal nerve end-to-side neurorrhaphy: anatomical study in rats

End-to-side neurorrhaphy (ESN) is presented as a sort of surgical technique for nerve repair that has the aim to obtain a good reinnervation of the recipient nerve and function preservation of the donor nerve. Several problems regarding this technique remain to be solved. Even if ESN could find some indications in particular cases of peripheral nerve surgery, we do not think that this technique can be first choice surgery for repairing a damaged facial nerve because of the complexity of the function of facial muscles and the necessity to offer an adequate number of motoneurons from the donor nerve for reinnervation of the recipient nerve.So, despite some reports about the clinical use of facial-hypoglossal nerve ESN, we studied experimentally such technique in the rat, having as recipient the facial nerve and as donor the hypoglossus. The purpose was to establish the number of motoneurons with which the donor hypoglossal nerve innervates the recipient facial nerve, and to compare the result with that obtained after facial-hypoglossus end-to-end neurorrhaphy (EEN). Beside other interesting findings, the key point of the obtained results was that motoneuron contribution given from the donor hypoglossus to the innervation of the recipient facial nerve was limited in ESN as compared to the classic EEN.

Nerve fiber transfer by end-to-side coaptation

To bring some light into the ongoing controversy concerning end-to-side coaptation in brachial plexus surgery, the authors organized a symposium in 2006 titled How To Improve Peripheral Nerve Surgery. The authors sought the participation of experienced surgeons and researchers who had made personal contributions to the field. This article contains information collected at this symposium and presents the authors' clinical results and ideas illustrating the potential of nerve fiber transfer by end-to-side coaptation.