Intratympanic Insulin-like Growth Factor-1 Administration Via the Otic Bulla in a Severe Facial Paralysis Model.

Hypothesis: We investigated the treatment effect of intratympanic insulin-like growth factor-1 (IGF-1) on severe facial paralysis in guinea pigs.

Background: The use of regenerative medicine involving growth factors has been reported in the treatment of peripheral nerve diseases. IGF-1 plays a crucial role in nerve regeneration.

Methods: We performed the following procedures on guinea pigs. In the normal group (n = 7), no procedure was performed. In the saline (n = 7) and IGF-1 (n = 7) groups, facial paralysis was induced by freezing of the facial canal. Subsequently, in the saline and IGF-1 groups, a gelatin hydrogel impregnated with 100 μL saline and 400 μg/100 μL IGF-1, respectively, was placed in the facial canal. Facial nerve functions were evaluated using three test batteries: facial movement observation, electrophysiological testing, and histological assessment.

Results: At 10 weeks postoperatively, the facial movement scores for the IGF-1 group were improved compared to those in the saline group. The conductive velocity was significantly faster in the IGF-1 group than in the saline group. There was a significant between-group difference in the nerve fiber number and myelin thickness.

Conclusion: Intratympanic IGF-1 administration improved facial nerve regeneration. This novel method could provide prompt ambulatory regenerative treatment and reduce the incidence of poor recovery in patients with severe facial paralysis.