Electromyographic laryngeal synkinesis alters prognosis in vocal fold paralysis.

OBJECTIVES/HYPOTHESIS: Synkinesis, or misdirected reinnervation, is likely a confounder when predicting return of function of an immobile vocal fold. Currently, no information exists on the incidence of synkinesis in unilateral vocal fold immobility (UVFI) or the effect synkinesis has on prognosis and treatment. Our objective was to examine a vocal fold adductor synkinesis screening protocol using diagnostic laryngeal electromyography (LEMG). We aim to determine the effect of synkinesis on prognosis of recovery of purposeful vocal fold motion.

STUDY DESIGN

Retrospective review of LEMG data and patient charts from laryngology practice.

METHODS

A standardized LEMG analysis method to diagnose vocal fold adductory synkinesis was performed in 124 consecutive laryngeal electromyographic exams.

RESULTS

Synkinesis testing was positive in 12/124 patients (9.7%). Post hoc quantitative analysis of electromyographic recordings to compare motor unit potential amplitude in the thyroarytenoid/lateral cricoarytenoid complex during sustained phonation to those in the same muscle during a "sniff" revealed a significant difference in motor unit potential amplitude ratio for control subjects (0.32), those who recovered purposeful vocal fold motion (0.40), and those with vocal fold paralysis (0.96) (P = .001). The presence of synkinesis in patients with UVFI improved the negative predictive value of LEMG from 53% to 100% and the sensitivity from 56% to 100%.

CONCLUSIONS

Presence of laryngeal synkinesis using motor amplitude ratio criteria, in the setting of good voluntary motor unit recruitment and UVFI, downgrades a patient's prognosis to one that is poor for recovery. We propose this screening protocol as an adjunct to diagnostic LEMG.