Reinnervation by the contralateral facial nerve in patients with peripheral facial palsy

Abstract

Introduction: Reinnervation activity is triggered after complete unilateral peripheral facial palsy (PFP).

Methods: In 27 patients with PFP we recorded electromyographic activity with a concentric needle electrode inserted 1 cm lateral to the oral commissure of the affected side. We applied electrical stimuli to the unaffected (contralateral) facial nerve from the tragus to the mid-lower lip and measured the response latency variability and segmental conduction velocity.

Results: Responses to electrical stimulation of the unaffected facial nerve were found in all patients. Mean conduction velocity was 49.6 ± 6.2 m/s between tragus and oral commissure, and 6.0 ± 1.9 m/s between oral commissure and mid-lower lip. Latency variability was 0.27 ms to facial nerve stimulation and 0.08 ms to oral commissure stimulation.

Conclusion: Short distance sprouting of axons that innervate muscle fibers, which originate from the unaffected facial nerve, results in propagation of impulses to muscle fibers in the midline.