Static syndrome after cross-facial nerve transplantation.

A cross-facial nerve graft connected to buccal branches of the healthy facial nerve may carry axons destined for the orbicularis oris muscle as well as axons destined for elevators and abductors of the corner of the mouth. If this nerve graft innervates a pedicled or free muscle flap, contractions of the flap or part of it will also occur when the patient purses his lips. This results in immobilization of the corner of the mouth. On the other hand, smiling may lead to simultaneous contraction of other erroneously reinnervated muscle fibers, equally immobilizing the corner of the mouth. Electromyography in these cases shows well-reinnervated musculature. The only solution to prevent this so-called static syndrome is to transplant smaller nerves connected at more peripheral levels to smaller facial nerve branches with more specific functions.