REPAIR OF THE MANDIBULAR BRANCH OF THE RAT FACIAL-NERVE THROUGH TRANSMEDIAN GRAFTING IN ONE OR 2 STAGES - FUNCTIONAL-EVALUATION

A previous study examined the morphological outcome of axonal regenera tion in the mandibular branch (ramus marginalis mandibulae) of the rat facial nerve after transmedian nerve grafting in one or two stages. T he present study supplements the morphological data with a functional evaluation. Recordings of the force of tetanic muscle contractions eli cited through stimulation of the mandibular branch showed that upper a nd lower lip data obtained from animals grafted in one stage did not d iffer significantly from control data. However, animals grafted in two stages exhibited significantly lower muscle forces compared to one-st age data and to control data. Electromyographic recordings of the M-re sponse showed multiple prolonged potential fluctuations with subnormal amplitudes in grafted cases. In both groups of grafted rats, the mean voltage amplitudes recorded from the upper lip were weaker than the a mplitudes seen at the angle of the mouth or the lower lip. The two-sta ge cases exhibited the most obvious deficit. In conclusion, the presen t results show that, with respect to the functional restoration achiev ed three months after nerve injury, repair through transmedian graftin g in one stage gives better results than repair in two stages. This fi nding, which conforms with previous morphological data, suggests that the one-stage procedure should be considered for clinical use.