Facial nerve stimulation at the internal auditory canal: An animal model and experimental assessment

Objectives: The main objective was to evaluate a canine model as a reliable animal model for the experimental study of the facial nerve at the internal auditory canal. The study also sought to begin testing the limits of facial nerve stimulation regarding electrically induced nerve damage. Study Design: Experimental and clinical analysis of facial nerve function after exposure and electrical stimulation in a canine model. Methods: Using a posterior fossa approach, the intracranial portion of the facial nerve was exposed from the brainstem to the internal acoustic meatus in 10 mongrel dogs. The nerve was then stimulated with variable frequency and amperage. The subjects were clinically examined for 2 weeks for evidence of facial nerve dysfunction. Both facial nerves were then harvested in each subject and histologically compared using light microscopy. Results: The canine model allowed for reliable exposure of the facial nerve at the internal auditory canal in all subjects (n = 10). The results also showed no functional or histopathological deficits in a canine facial nerve electrically stimulated at up to 50 stimulations of 1 mA per stimulation when stimulated at the internal auditory canal. Conclusions: The reported canine model is a reliable animal model for the study of the facial nerve at the internal auditory canal. The canine facial nerve can tolerate at least 50 stimulations at 1 mA and still remain functionally and histopathologically normal.