Dual innervation method using one-stage reconstruction with free latissimus dorsi muscle transfer for re-animation of established facial paralysis: simultaneous reinnervation of the ipsilateral masseter motor nerve and the contralateral facial nerve to improve the quality of smile and emotional facial expressions

Abstract

Background: One-stage microneurovascular free muscle transfer is a common surgical procedure for re-animation of established facial paralysis. However, innervation of the transferred muscle by the contralateral facial nerve prevents smile and other facial expressions on one side, and reinnervation requires about 7 months. To overcome these drawbacks, we report a dual innervation method using one-stage reconstruction with free latissimus dorsi muscle transfer.

Methods: Three patients were treated with the dual innervation method, which is based on the one-stage method with some modifications: the soft tissue present over the ipsilateral masseter muscle and the hilum where the thoracodorsal nerve proceeds into the muscle segment is removed; the muscle is harvested to locate the hilum in the cranial one-third of the segment; and the muscle is transferred to the malar pocket of the paralysed face such that the hilum contacts the masseter muscle.

Results: On average, muscle movement was recognised on voluntary biting at 3.4 months and on spontaneous smiling at 5.9 months after surgery. A dual innervation sign was recorded on electromyographs 6.4 months after surgery. The patients developed a spontaneous symmetrical smile and facial expressions on one side with minimum synkinesis after postoperative mirror rehabilitation.

Conclusions: The advantages of the dual innervation method include faster reinnervation of the transferred muscle compared to one-stage options; achievement of spontaneous smile and voluntary smile on each side; augmentation of neural signals to the muscle for more symmetrical smiling; minimum synkinesis of the transferred muscle on biting for eyelid closure and emotional facial re-animation through a learning program to enhance cerebral cortical reorganisation.