Indication and validity of ultrasonographic evaluation for assessment of vocal fold mobility before and after thyroid surgery

Abstract

Background: Evaluating recurrent laryngeal nerve function before and after thyroid surgery is important. Although laryngeal electroendoscope is the most reliable tool for evaluating vocal fold (VF) mobility, ultrasonography (US) may offer a non-invasive alternative. The aim of this study is to evaluate the validity and limitation of US evaluation for the assessment of VF mobility.Methods: This was a study for diagnostic testing of US in a single center. One hundred and one patients who underwent thyroid surgery between February 2011 and August 2011 were enrolled to this study. Observation of the VF mobility using a B-mode US scanner was performed before and after thyroid surgery, through the thyrohyoid membrane, thyroid notch, and cricothyroid membrane. The results of US were compared with those of electroendoscopic examination which was performed on the same day but after the US.Results: First we excluded one case that could not be observed by electroendoscopic examination before surgery. After excluding the cases which the VF mobility was invisible by US, we analyzed 89 out of the 100 patients before thyroid surgery and 89 out of the 101 patients after surgery. The sensitivity and specificity of US were 87.5%, 100% for before and 94.4%, 100% for after surgery, respectively. It was significantly more difficult to assess the VF mobility by US among patients who were men (odds ratio [OR] 24.7, 95% confidence interval [CI] 4.9-124.2), 65 years old or more (OR 3.5, 95% CI 1.0-11.9), and have past history of thyroid surgery (OR 7.9, 95% CI 2.1-29.2). Being obese was also a significant factor (OR 10.5, 95% CI 1.7-64.8) among younger patients (less than 65 years).Conclusion: US evaluation can be used for the assessment of recurrent laryngeal nerve function before and after thyroid surgery. This is a safe and non-invasive diagnostic tool which may be performed as a first-line method.

Functional analysis of vocal folds by transcutaneous laryngeal ultrasonography in patients undergoing thyroidectomy

“…Quantitative variables were compared by Mann‐Whitney U Test while the strength of association was assessed by Spearman's rank correlation test. Presence of hoarseness, age, gender and weight have reported and biologically plausible effect on VFDV of vocal fold movement …”

“…Flexible laryngoscopy (FL) for visualisation of vocal folds (VF) in patients undergoing thyroidectomy is an unpleasant experience for patients even with good topical anaesthesia …”

“…Thus, a reliable, non‐invasive, readily available, and easy to learn technique is desired which would clearly outline the anatomical structures of laryngeal inlet and functionally analyse the VF movement. Unsurprisingly, transcutaneous laryngeal ultrasound (TCLUS) is gaining popularity as an alternative to FL for vocal fold assessment is still lacking due to variable reported diagnostic sensitivity and specificity to distinguish disabled VFs.…”

“…However, universal acceptance is still lacking due to variable reported diagnostic sensitivity and specificity to distinguish disabled VFs. In most studies, TCLUS has been performed by otolaryngologists, endocrine surgeons, or radiologist, but none by the anaesthesiologist. Although anaesthesiologists have been performing airway ultrasound for assessing difficult airway, measurement of tracheal diameter for selection of the appropriate size of double lumen tube, identifying cricothyroid membrane for surgical securement of airway but functional analysis of VF by TCLUS is relatively unexplored.…”

“…Transcutaneous laryngeal ultrasound can assess functionality of VFs by evaluating mobility of true or false VFs subjectively or by quantification of vocal fold displacement velocity (VFDV) . Neither technique has proven superiority over the other for reliable identification of disabled VF.…”