Contralateral reinnervation in patients with facial nerve palsy.

OBJECTIVE: To demonstrate a phenomenon of contralateral reinnervation in facial nerve palsy patients.

METHODS: Retrospective case review of 9 patients whose facial muscles were electrophysiologically proven to be reinnervated contralaterally.

RESULTS: The duration from symptom onset spanned from 3 to 114 months. All subjects had moderate-to-severe facial palsy initially. Contralateral reinnervation was observed in both traumatic and idiopathic causes, also in both complete and incomplete palsies. Cross-innervation is more frequently reported in muscles near the midline; however, this is the first report demonstrating evidence of cross-innervation in muscles far from the midline--the frontalis, the orbicularis oculi, and the zygomaticus.

CONCLUSION: Although contralateral reinnervation after facial nerve palsy is a common observation, it has not gained appropriate attention. Without recognition of this phenomenon, misinterpretation of the electromyography may mislead the proper timing of nerve repair or reanimation procedure. Therefore, routine examination of motor action potential by contralateral stimulation during electromyography, especially in patients with moderate-to-severe palsy, would provide accurate assessment of the injured nerves and would help in appropriate decision making for further treatment.