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

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.