Initial experience of vocal cord evaluation using grey-scale, real-time, B-mode ultrasound

Background: To evaluate whether grey-scale, real-time, B-mode ultrasound (US) is a reliable alternative to nasopharyngoscopy for assessing vocal cord function post-thyroid and post-parathyroid surgery. Methods: A prospective validation study was undertaken comparing grey-scale, real-time, B-mode vocal cord US with the standard of nasopharyngoscopy in 100 consecutive patients undergoing thyroid and parathyroid surgery between 1 February 1999 and 31 August 1999, with seven patients with known cord palsy. The sensitivity and specificity of grey-scale, real-time vocal cord US for the detection of vocal cord palsy when compared to the standard of nasopharyngoscopy was analysed. Results: In the postsurgical group, there were six nerves (3.2% of the nerves at risk) transient and no permanent vocal cord palsies. US identified four of six transient palsies and reported two false negatives and three false positives. US identified four of seven cord palsies in the non-surgical group with known cord palsy. Analysis of the 107 combined patients showed US had sensitivity of 62% (8/13), specificity of 97% (91/94), a positive predictive value of 73% (8/11) and a negative predictive value of 95% (91/96) for detecting cord paralysis compared to the standard of nasopharyngoscopy. Conclusion: Despite the enthusiasm of earlier reports, our initial experience with grey-scale, real-time, B-mode US suggests it is not a reliable alternative to nasopharyngoscopy for assessing vocal cord function post-thyroid and post-parathyroid surgery. Further recruitment of patients with known vocal cord palsy is required to confirm or refute these initial impressions.