Laryngeal Synkinesis: A Viable Condition for Laryngeal Pacing.

Laryngeal synkinesis as a form of defective healing is the rule rather than the exception in persistent vocal fold paralysis. It typically occurs 4-6 months after the onset of the recurrent laryngeal nerve paralysis. The incidence is up to 85%. Not all laryngeal muscles need to be equally affected. Reliable evidence can only be provided by a laryngeal electromyography. Physiological co-activation of the laryngeal muscles during antagonistic maneuvers must be considered. Although synkinesis undeniably worsens the prognosis for a motion recovery, it protects the muscle fibers from degeneration. A differentiation is required between favorable synkinesis (type I according to Crumley), which does not always require further therapy in the case of unilateral paralysis, and unfavorable forms of synkinesis (type II-IV) according to Crumley, which are associated with a functionally relevant malposition of the vocal fold(s) or with vocal fold jerks. Particularly when bilateral vocal fold motion does not return, type I synkinesis can be a good prerequisite for new dynamic therapy approaches, such as laryngeal pacing. The rarely occurring type II-IV synkinesis should, whenever possible, be transformed into a more favorable type I synkinesis by selective or non-selective reinnervation at an early stage of the disease. The latter applies to expected muscle atrophy with insufficient regrowth of nerve fibers.