Complete and incomplete recurrent laryngeal nerve injury after thyroid and parathyroid surgery: Characterizing paralysis and paresis.

BACKGROUND

Injury of the recurrent laryngeal nerve and consequent disorder of vocal fold movement is a typical complication in thyroid and parathyroid surgery. During postoperative laryngoscopy we observed not only a complete standstill (vocal fold paralysis), but also a hypomobility (paresis). In this prospective study, we investigated the difference in incidence and prognosis as well as risk-factors, intraoperative neuromonitoring, and symptoms between vocal fold paralysis and vocal fold paresis.

METHODS

Data were prospectively collected and analyzed in a single high-volume thyroid center between 2012 and 2016. Vocal fold paresis was defined as hypomobility in abduction or adduction, a reduction in range and speed of vocal fold movement. Vocal fold paralysis was defined as asymmetry and missing purposeful vocal fold movement.

RESULTS

The study included 4,707 surgeries and 7,992 at-risk nerves at risk. Vocal fold paralysis was diagnosed in 374 patients (4.68% of 7,992 nerves at risk) and vocal fold paresis in 114 patients (1.43%). Exclusively in the paralysis group, 36 patients (0.45%) developed permanent loss of vocal fold function (P < .001). In follow-up, vocal fold paresis patients regain normal vocal fold function significantly earlier than vocal fold paralysis (mean duration: 6.96 ± 6.506 vs 10.77 ± 7,827 weeks) and presented with significantly less symptoms like hoarseness, diplophonia, dysphagia, and dyspnea (68.8% vs 95.9 %). In intraoperative neuromonitoring, vocal fold paresis showed a significantly higher postresectional N. vagus amplitude than vocal fold paralysis patients (0.349 mV vs 0.114 mV, P < .001).

CONCLUSION

After thyroidectomy, vocal fold paresis must be distinguished from vocal fold paralysis and should be implemented as a separate outcome parameter in the postoperative quality assessment.