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.