Delayed facial palsy in a patient with a bifid facial nerve lending support for viral theory of facial palsy

OBJECTIVE: To describe the level of neurologic impairment in a case of delayed facial palsy occurring after cochlear implantation surgery. PATIENT: A 58-year-old man undergoing cochlear implantation who was found intraoperatively to have congenital bifurcation of the facial nerve just distal to the second genu. INTERVENTION: Cochlear implantation was performed through a facial recess approach. RESULTS: The lateral branch of the nerve impinged on the posterior tympanotomy slot and was uncovered during the procedure, rendering it vulnerable to direct thermal or mechanical injury or to the effects of local tissue injury products. The patient developed facial palsy 9 days later, affecting all facial muscle groups equally. CONCLUSION: Theories regarding the cause of delayed facial palsy after cochlear implantation include direct thermal or mechanical injury to the nerve, local effects of blood breakdown products or other mediators causing vasospasm, and reactivation of latent herpes virus, leading to neural inflammation and neuropathy of the geniculate and labyrinthine segments of the nerve. The fact that the patient developed weakness that affected all facial muscle groups equally suggests that the level of neurologic impairment was proximal to the nerve bifurcation, so distant to the actual site of surgery. This finding lends support for the viral hypothesis of delayed nerve palsy.