Investigation of the Effects of the Timing of Decompression and Topical Mitomycin-C Application on Nerve Regeneration in a Rat Model of Bell's Palsy.

Objective: The timing of facial nerve (FN) decompression (FND) for Bell's palsy is controversial. Intraneural fibrosis is one of the factors affecting post-traumatic nerve regeneration. This study aimed to investigate the effects of decompression timing and antifibrotic agent topical mitomycin-C (MMC) on nerve regeneration in rats in which a Bell's palsy model was created.

Methods: Bell's paralysis model was created by ligating the subjects' FN trunk. A total of 25 subjects were divided into five groups of five each. Group 1 was not decompressed. The FN was decompressed after one week in Groups 2,3 and after three weeks in Groups 4,5. Topical MMC was applied after decompression on the nerves of the rats in Groups 3,5. Clinical, electrophysiological and histopathological evaluations were performed at three weeks after compression in Group 1 and after decompression in the other groups.

Results: The median total clinical score in Group 1 was statistically significantly lower than the other groups (p=0.001). There were no statistically significant differences between Groups 2-5 (p>0.05). The mean left (operated)/right (undamaged) amplitude values of the subjects in Group 1 were statistically lower (p=0.006), while no statistically significant differences were found among Group 2-5 (p>0.05). It was observed that while axonal degeneration, macrovacuolization and myelin morphology disruption was more severe in subjects in Group 1 (adjusted p<0.05), there were no statistically significant differences between Group 2-5 (p>0.05).

Conclusion: FND can be effective in patients with total paralysis, even when performed in the late stages after allowing a period of recovery. Also, topical MMC applications aiming to reduce intraneural fibrosis have no effect on nerve regeneration.