EFFECT OF DELAYED FACIAL-FACIAL NERVE SUTURE ON FACIAL-NERVE REGENERATION - A HORSERADISH-PEROXIDASE TRACING STUDY IN THE RAT

In clinical practice, the lesioned facial nerve is usually restored by facial-facial nerve anastomosis (FFA) with some delay. The optimal ti me-point for facial nerve reconstruction is still unknown. This study, using rats, compared the effects of immediate and delayed FFA, i.e. F FA 7-56 days after interruption of the facial nerve. Muscle reinnervat ion was studied 42 days after nerve suture by counting all retrogradel y labelled facial motoneurons after injection of horseradish peroxidas e (HRP) into the whiskerpad of the rats. Immediate FFA caused a local hyperinnervation of the target muscle, i.e. the projection of more neu rons into the whiskerpad muscles than under normal conditions. FFA del ayed for 7 days resulted in a significant suppression of this hyperinn ervation, whereas longer delay times of 10-56 days showed no differenc e from immediate FFA.