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

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. 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. 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. 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.