Int. Adv. Otol. 2011; 7(1) 24-30

Time dependent electrophysiological changes in nerve-crush traumatic facial nerve injury in rats. 
Erkan Kahraman, Sertac Yetiser,  Fatih Ozdag. 
Gulhane Medical Academy, Medical Faculty, Otolaryngology Department, Ankara, Turkey. drerkan76@yahoo.com

Objective: To investigate experimentally the time dependent changes of latency, amplitude, threshold of neural response in injured rat facial nerve in a nerve-crush trauma model.

Materials and Methods: Thirty Wistar rats weighing 220-280 g (12-16 week), were grouped for permanent and transient nerve injury during time course analysis of electrophysiological 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 (10 rats). For the nerve-cut group, the facial nerve was cut and a 5-mm part was removed (10 rats). 10 rats with intact facial nerve served as control. CMAP (compound muscle action potantial) recordings were obtained at each time interval. Measurements were compared with Variance-analysis.

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. Recovery of the reduced amplitude at consecutive intervals was not statistically significant. In the nerve-cut group, no electrical response was obtained throughout the follow-up.

Conclusion: In the follow-up of electrophysiological changes of traumatic injury of the facial nerve in rats, the results appear to indicate that parameters “latency and threshold” may reflect the different aspect of injured nerve condition from the parameter “amplitude”. Amplitude comparison alone could bring some problems in the clinical setting. These findings suggest complete measurement of all parameters to outline the prognosis of traumatic facial paralysis