AB128. SOH24AB₀56. The non-recurrent laryngeal nerve in an Irish thyroid surgery population: an 11-year experience

Background: The non-recurrent laryngeal nerve (NRLN) is a rare anatomical variant of the recurrent laryngeal nerve (RLN). It occurs where abnormalities of the aortic arch are present, such as aberrant right subclavian artery, and may be associated with higher risk of iatrogenic injury during thyroid surgery. The presence of NRLN can be detected pre-operatively by ultrasound or volumetric imaging and intra-operatively by direct observation or intra-operative nerve monitoring. To our knowledge, no data has been published on this anomaly in an Irish population. The objective of this study was to ascertain the prevalence of NRLN in a cohort of patients undergoing thyroid surgery in a major head and neck centre in Ireland over an eleven-year period. Methods: This is a retrospective review of 301 patients in a single-centre undergoing thyroid and parathyroid surgery who underwent pre-operative volumetric imaging of the neck between 2008 and 2019. Patients were identified from a prospectively kept operative database of a single surgeon. Patient imaging and reports were reviewed to identify NRLN, calculate its prevalence and calculate the relative risk of nerve injury in patients with this anomaly. Results: A total of 1,127 patients were identified from the database, of whom 301 met the inclusion criteria. Three cases of NRLN were identified (n=3) giving a prevalence of 0.99% in this population. No statistically significant difference in nerve injury rates was found for patients with NRLN versus RLN. Conclusions: The prevalence of NRLN in this population is consistent with international studies and meta-analysis. Although rare, the NRLN represents a clinically important variant of the RLN and one which surgeons operating in the neck should be mindful of. Further data are needed to assess whether NRLN increases relative risk of vocal cord injury.