Differential recurrent laryngeal nerve palsy rates after thyroidectomy

Abstract

Introduction: Recurrent laryngeal nerve (RLN) palsy is a devastating complication of thyroidectomy. Although neurapraxia is thought to be the most common cause, the underlying mechanisms are poorly understood. The objectives of this study were to examine the differential palsy rates between the left and right RLNs, and the role of intraoperative nerve swelling as a risk factor of postoperative palsy.

Methods: Thyroidectomy data were collected, including demographics, change in RLN diameter, and RLN electromyographic (EMG) reading. Left and right RLNs, as well as bilateral and unilateral subgroup analyses were performed.

Results: A total of 5,334 RLNs were at risk in 3,408 thyroidectomies in this study. The overall RLN palsy rate was 1.5%, greater on the right side than the left for bilateral cases (P = .025), and greater on the left side than the right for unilateral cases (P = .007). In a subgroup of 519 RLNs, the diameter and EMG amplitude were measured. The RLN diameter increased by approximately 1.5-fold (P < .001), and corresponded to increased EMG amplitude (P = .01) during the procedure. The diameter of the right RLN was larger than the left RLN, both at the beginning and end of the dissection (P = .001).

Conclusion: The right-left differential rates of post-thyroidectomy RLN palsy seemed to be due in part to differential RLN diameters, with stretch having a more deleterious effect on RLNs with a smaller diameter; also, edema as a result of stretch might be an underlying mechanism for postoperative neurapraxia and palsy. Thyroid surgeons should be aware of the different vulnerabilities of each RLN and develop practices to avoid iatrogenic injury.