1Professor, Ankara, Turkey/2ENT Resident, Ankara, Turkey/3Associate Professor, Ankara, Turkey/4Assistant Professor, Ankara, Turkey/5Assistant Professor, Ankara, Turkey/6Assistant Professor, Ankara, Turkey

■ OBJECTIVES: To investigate experimentally and to compare the time dependent changes of latency, amplitude, threshold of neural response and histopathology in injured rat facial nerve in a nerve-cut and nerve-crush trauma model.

■ METHODS: Ninety Wistard rats (10 for control) weighing 220- 280 g (12-16 week), were grouped for permanent and transient nerve injury during time course analysis of electrophysiological and histopathological changes at 1st week, and 1st, 3rd and 6th months. For the nerve-crush group, facial nerve was pressed by vascular clamps for 40 minutes without disturbing the nerve integrity. Evoked EMG recordings were obtained at each time interval. For the nervecut group, Schwann and inflammatory cells in neural specimens from free and peripheral endings of the nerve at each time interval group in which the facial nerve was cut and a 5-mm part was removed before were counted under light microscope. Measurements were compared with Variance-analysis and Student’s T-tests.

■ RESULTS: In the nerve-crush group, recovery of the latency from 1st week to 1st month (0.029, p≤0,05) and excitability thresholds in 1st week was statistically significant (p≤0,05) as compared to the control.  ecovery of the reduced amplitude at consecutive intervals was not statistically significant. In the nerve-cut group, the number of Schwann and inflammatory cells was statistically higher at the distal free end of the nerve in 1st week. Cell count at peripheral end of the facial nerve was significant for consecutive intervals (p≤0,05). However, significant increase was found in the 6th month.

■ CONCLUSION:Excitability threshold and latency were found to be more reliable than the amplitude in the follow-up of electrophysiological changes of traumatic injury of the facial nerve in rats. Early repair of neural cut is favorable since histopathology demonstrated distal progression of the degeneration and increase of inflammation after 3 months.