Experimental study on facial nerve regeneration with or without geniculate ganglionectomy.

OBJECTIVE To investigate regeneration of the distal facial nerve following nerve grafting within the tympanic segment with geniculate ganglion preservation or dissection. DESIGN Randomized controlled trial. SUBJECTS Twenty-three adult New Zealand albino rabbits were used in this study. INTERVENTIONS A 2-mm tympanic segment of the facial nerve was removed, and the greater auricular nerve was harvested for grafting in all animals. In group 1 (10 rabbits), the geniculate ganglion was preserved. In group 2 (13 rabbits), the geniculate ganglion was dissected. Mastoidal and extratemporal segments of the facial nerve were harvested 3 months postoperatively for histological examination by electron microscopy. RESULTS The number of myelinated axons in normal facial nerves was 1819.6 +/- 535.6. In group 1, the number of myelinated axons was 123.6 +/- 31.1, and, compared with normal facial nerves, the diameter of the regenerative axons was decreased and the sheath thickness in the regenerative fiber was diminished. In group 2, the number of myelinated axons was 515.1 +/- 103.1, while the myelin sheath thickness was proportionate to axon diameter. (Data are given as mean +/- SD.) CONCLUSION Geniculate ganglionectomy may improve motor axon regeneration.