Hypothesis: Recurrent laryngeal nerve paralysis after thyroidectomy can be unrecognized without routine laryngoscopy, and patients have a good potential for recovery during follow-up.

Design: A prospective evaluation of vocal cord function before and after thyroidectomy. Periodic vocal cord assessment was performed until recovery of cord function. Persistent cord palsy for longer than 12 months after the operation was regarded as permanent.

Setting: A university hospital with about 150 thyroid operations performed by 1 surgical team per year.

Patients: From January 1, 1995, to April 30, 1998, 500 consecutive patients (84 males and 416 females) with documented normal cord function at the ipsilateral side of the thyroidectomy were studied.

Main outcome measures: Vocal cord paralysis after thyroidectomy.

Results: There were 213 unilateral and 287 bilateral procedures, with 787 nerves at risk of injury. Thirty-three patients (6.6%) developed postoperative unilateral cord paralysis, and 5 (1.0%) had recognizable nerve damage during the operations. Complete recovery of vocal cord function was documented in 26 (93%) of 28 patients. The incidence of temporary and permanent cord palsy was 5.2% and 1.4% (3.3% and 0.9% of nerves at risk), respectively. Among factors analyzed, surgery for malignant neoplasm and recurrent substernal goiter was associated with an increased risk of permanent nerve palsy. Primary operations for benign goiter were associated with a 5.3% and 0.3% incidence (3.4% and 0.2% of nerves at risk) of transient and permanent nerve palsy, respectively.

Conclusions: Unrecognized recurrent laryngeal nerve palsy occurred after thyroidectomy. Thyroid surgery for malignant neoplasms and recurrent substernal goiter was associated with an increased risk of permanent recurrent nerve damage. Postoperative vocal cord dysfunction recovered in most patients without documented nerve damage.