Abstract:

Objective　To explore the effects of facial nerve ischemia on facial nerve and facial nucleus, and provide references for parotidectomy.  Methods　Rabbits were used to simulate parotidectomy in this study. The facial nerve and facial nucleus on one side of each rabbit was taken as experimental side randomly, and another side as control side. For experimental side, the capillary net of facial nerve was separated and damaged, following the resection of parotid gland   under operation microscope. The rabbits survived 4 weeks after operation, and the following indexes were observed and detected: ①The conduction velocity, CMAP wave amplitude and latency period of buccal branch of facial nerve on experimental and control sides. ②The ultrastructure of the trunk of facial nerve outside the stylomastoid foramen on two sides. ③Choline acetyltransferase (CHAT) expression and telomerase activity of the facial nucleus of bilateral sides.  Results　①The conduction velocity of buccal branch of facial nerve on experimental side was obviously lower than that on control side, as well, the CMAP wave amplitude; while the CMAP latency was obviously longer (P＜0.01, P＜0.05). ②The ultrastructure of facial nerve on experimental side changed remarkably, with mainly the axonal degeneration: hyperplasied and fractured microfilamen in neuraxon, swelled mitochondria and broken cristae, dissolved degenerated neuraxon. ③CHAT expression and telomerase activity of facial nucleus on experimental side were significantly lower than that on control side (P＜0.01, P＜0.05).   Conclusions　Dissociating of facial nerve and damaging of its' capillary net during parotidectomy can induce obvious changes of the ultrastructure of facial nerve, the decrease of neural conduction function and acetylcholine synthesis in facial nucleus and the increase of neurons apoptosis in facial nucleus. It is necessary to protect capillary net of facial nerve as far as possible during parotidectomy for avoiding the happen of facial paralysis after the operation.

Key words: Facial nerve;　Facial nucleus;　Ischemia;　Parotidectomy