The predictors of postoperative laryngeal nerve paresis in patients undergoing thyroid surgery: a pilot study

The objective of this study was to evaluate the factors predictive of postoperative laryngeal nerve paresis (LNP) in patients undergoing thyroid surgery. We also assess the implications of preoperative LNP on postoperative vocal fold status.

Case series with retrospective chart review.

Charts of 17 patients who underwent thyroid surgery and had pre- and postoperative laryngeal electromyography (LEMG) were reviewed. LEMGs were ordered routinely in all patients undergoing thyroid surgery, not just in those with clinical findings suggestive of paresis. We collected data relating to pre- and postoperative laryngeal and thyroid evaluations and the details of the surgical procedure. We analyzed the prevalence of preoperative LNP and relationship of thyroid diagnoses, size of thyroid mass, and type of surgery performed with respect to the outcome of the LNP.

All the 17 patients had a mild to moderate degree of unilateral or bilateral LNP preoperatively. However, only seven (41.2%) had vocal symptoms. After surgery, only five of these seven patients had voice complaints, and there were no patients with voice complaints among the group that had been asymptomatic preoperatively. Thyroid diagnoses included 11 cases of benign disease (64.7%) in which LNP improved in two, worsened in four, and remained the same in five; and six cases of malignant disease (35.3%) in which LNP improved in none, worsened in two, and remained the same in four. Predictors of worsening postoperative LNP on LEMG included the diagnosis of goiter (P=0.0005) and size of mass greater than 5cm (0.032).

This study supports the notion that there is an intrinsic relationship between benign thyroid diseases and LNP that is probably related to local effects of the disease on the laryngeal nerves. All patients with the postoperative diagnosis of goiter worsened, and all patients with the postoperative diagnosis of adenoma showed no change on postoperative electromyography (EMG). Similarly, all patients with the diagnosis of thyroiditis alone improved, and there were no cases of improvement outside this group. Of the six cases of malignancy, four exhibited no change on EMG and only two worsened. The only reliable predictors of worsening paresis postoperatively are mass size greater than 5cm and diagnosis of goiter.