The Effects of Aminoguanidine, Methylprednisolone, and Melatonin on Nerve Recovery in Peripheral Facial Nerve Neurorrhaphy

Background: The medications may enhance the recovery after nerve paralysis. We aimed to evaluate the effects of aminoguanidine (AG), melatonin, and methylprednisolone on peripheral facial nerve neurorrhaphy. Methods: The buccal branch of the facial nerve was transected and autografted in 32 New Zealand rabbits. Subjects were divided into 4 groups equally (AG, melatonin, methylprednisolone, and control). After the medical treatment latency and amplitude were measured with nerve conduction study at 3, 6, and 10 weeks. Then, coapted segments of nerve were examined microscopically. The groups were compared with each other. Results: The latent period was shortened, and the amplitudes were increased in the AG group; the latent period was shortened, and the amplitudes did not show significant change in the melatonin group with the time. There were no significant differences between the amplitudes at 3 to 6 and 3 to 10 weeks in the methylprednisolone group, and the latent period was shortened. There was no significant difference between the amplitude values at 3, 6, and 10 weeks in the control group. In the histological examination, AG had the best influence on preventing myelin degeneration and reducing the accumulation of myelin debris. Considering the increase in collagen fibers, the best results were achieved in the melatonin group. The degree of myelin-axonal degeneration was higher in the methylprednisolone group. The degree of collagen fiber increase, axonal degeneration, myelin degeneration, and the accumulation of myelin debris were detected quite high in the control group. Conclusions: Aminoguanidine and melatonin alone achieved an increase in regeneration after peripheral facial nerve neurorrhaphy, but methylprednisolone did not. The best healing was determined in the AG group.