Rates of RLN and SLN injury : Data from national quality registries and the literature

The impact of thyroid surgery on voice is a key performance indicator of surgical quality. This chapter discusses factors that can impact on the incidence of both recurrent and external laryngeal nerve (external branch of superior laryngeal nerve-EBSLN) injury. The literature is reviewed and reported incidence of nerve palsy following thyroid surgery is presented. Particular reference is made to the British and Scandinavian database registries. The present evidence supports that the true injury rate is underreported. Factors that might influence nerve injury are presented in an evidence-based manner. A centrally important dynamic in this area of study is that there is clear positive correlation between the rate of postoperative vocal cord examination and palsy. Overall, 10 % of patients can sustain a temporary laryngeal palsy following thyroidectomy. Permanent voice problems are common and the true incidence of permanent palsy remains unknown. There is little doubt, however, that the literature grossly underestimates its true incidence. Thirty percent of patients with a known vocal palsy may not complain of voice symptoms which again endorses the importance of routine post- operative vocal cord examination. Voice change secondary to EBSLN injury is also common and again the true incidence remains unknown. This situation prevails due to the difficulty of precise diagnosis with extant non- invasive methods of cord examination. The importance of surgical volume to patient outcomes is emphasized. Surgery for cancer particularly when involving nodal dissection has been identified as a significant and higher risk for nerve palsy as have been revision and more extensive thyroid surgery. Similarly, higher rates of nerve injury are reported with retrosternal goitres. The literature is unclear as to whether the side of thyroidectomy is a risk factor or whether certain benign pathology such as Graves' disease confers a higher risk of injury