Surgeon- Performed Laryngeal Ultrasound Can Be Used to Screen for Vocal-Cord Palsy before Thyroid Surgery
Cheng SP, Lee JJ, Liu TP, Lee KS, Liu CL. Preoperative ultrasonography assessment of vocal cord movement during thyroid and parathyroid surgery. World J Surg 2012;36:2509-15.
SUMMARY • • • • • • • • • • • • • • • • • • • • • • • •
Iatrogenic recurrent laryngeal-nerve (RLN) injury is a rare but well recognized and dreaded complication of thyroid or parathyroid surgery. The presence or absence of dysphonia is not a reliable predictor of vocal-cord function in the preoperative setting. Routine preoperative and postoperative laryngoscopy has been advocated by some experts, but remains controversial. Because laryngoscopy can be an invasive and uncomfortable procedure, a noninvasive method of screening patients for impaired vocal-cord mobility is desirable. A sonographic method to evaluate vocal-cord mobility would be an ideal inexpensive, painless, and noninvasive screening method. There is a paucity of data on the utility of transcutaneous ultrasound examination of the larynx as a screening tool to identify laryngeal dysfunction. This study was designed to evaluate the utility of ultrasound as a screening tool for the detection of impaired vocal-cord movement before thyroid or parathyroid surgery.
This was a single institution prospective study. In the first 6 months (first phase), patients scheduled for thyroid or parathyroid surgery underwent both routine preoperative laryngoscopy by experienced independent otolaryngologists and laryngeal ultrasonography. In the second 6 months of the study (second phase), all patients scheduled for thyroid or parathyroid surgery underwent laryngeal ultrasound first, and only some of these patients were then selectively evaluated by laryngoscopy. Patients with either abnormal vocal-cord movement on laryngeal ultrasound, with dysphonia despite apparently normal laryngeal ultrasound, or whose vocal-cord movement could not be assessed sonographically underwent laryngoscopy. Laryngeal ultrasound was performed by endocrine surgeons and not radiologists. Normal vocal-cord movement was defined as “symmetrically abductive and adductive motion of the true vocal cords during quiet respiration.” The results of the laryngeal ultrasound were compared with the findings from laryngoscopy.
In the first phase, 114 patients were evaluated preoperatively. Vocal-cord movement could be assessed sonographically in 82% (n = 93). In 2 of 93, patients the vocal-cord movement was determined to be abnormal on the ultrasound exam, and laryngoscopy revealed a unilateral vocal-cord palsy in both patients. In the second phase, vocal-cord motion was successfully evaluated in 349 of 415 patients (84%). Four patients with abnormal vocal-cord movement were identified sonographically, and each underwent laryngoscopy, which revealed unilateral vocal-cord palsy. For 66 of 415 patients (16%), vocal-cord movement could not be evaluated sonographically. Only 45 of these patients went on to laryngoscopy, and one vocal-cord palsy was identified.
The preoperative recognition of vocal-cord palsy can alert the surgeon to the possibility of an invasive malignancy and might also alter intraoperative management of the central neck. The routine use of preoperative laryngoscopy remains controversial. The selective use of preoperative laryngoscopy might be more cost-effective than routine laryngoscopy. In this study, it was possible for surgeons to sonographically evaluate vocal-cord movement in 84% of preoperative patients. The authors state that physicians who perform cervical ultrasound can easily and quickly learn to perform laryngeal ultrasound and that it can be performed in the office in 1 minute. The authors estimated that nearly two thirds of preoperative laryngoscopies could be avoided by the use of preoperative screening laryngeal ultrasound.
ANALYSIS AND COMMENTARY • • • • • •
The preoperative identification of vocal-cord dysfunction may impact surgical decision-making and alter the operative approach for benign and malignant disease. Unfortunately, vocal-cord dysfunction is not reliably ruled out by the absence of dysphonia. This has led some experts to recommend laryngoscopy for all patients who are about to undergo thyroid surgery, regardless of preoperative or postoperative voice quality. This recommendation has been met with some opposition because fiberoptic laryngoscopy is an invasive and costly procedure that is not performed by all surgeons, and it has a fairly low likelihood of identifying vocal-cord dysfunction in the nondysphonic population.
In this study, the success rate for documenting vocal-cord movement was 84%, and only 1.8% of preoperative patients in phase 1 (1.3% overall) were found to have a vocal-cord palsy. The authors postulated that laryngeal ultrasound would be cost-effective and easily adopted by endocrine surgeons. They estimated that approximately two thirds of preoperative laryngoscopies could be avoided by the use of screening laryngeal ultrasound.
Laryngeal ultrasound has been proposed as an alternative to fiberoptic laryngoscopy by these authors and others because it is inexpensive, rapid, noninvasive, and painless and generates an image that can be stored in the medical record. Laryngeal ultrasound to evaluate vocal-cord movement is not widely used, however. The greatest enthusiasm for this technique was historically in the pediatric population, in whom laryngoscopy is not tolerated without anesthesia (1, 2). The widespread adoption of this technique in the adult population has not occurred largely because of concerns regarding false negative results or the inability to sonographically image the vocal folds.
Several studies have had favorable findings, contributing to enthusiasm for laryngeal ultrasound in the adult population. Dedecjus et al. evaluated vocal-cord movement in 50 thyroidectomy patients during the preoperative and postoperative periods with both ultrasound and laryngoscopy. They found that the sonographic findings correlated with the laryngoscopy and concluded that it was a minimally invasive and reproducible method for the identification of postoperative vocal-cord dysfunction (3). Ooi et al. evaluated color Doppler imaging of the vocal cords and determined that it was just as accurate as laryngoscopy in the identification of vocal-cord palsy or paresis (4). Wang et al. evaluated 705 patients with laryngeal ultrasound and found that vocal-cord motion could be assessed in 87% of patients. Interestingly, they found laryngeal ultrasound to be more successful and accurate in female patients. They concluded that laryngeal ultrasound would be an alternative for the evaluation of vocal-cord movement in over 90% of women and about 50% of men (5). Not all studies have shared enthusiasm for laryngeal ultrasound, however. Sidhu et al. evaluated 100 postoperative patients with laryngeal ultrasound in 1999 and found that sensitivity was 62%, specificity was 97%, positive predictive value was 73%, and negative predictive value was 95%; they concluded that the false positive and false negative rates were too high to use ultrasound as an alternative to nasopharyngoscopy (6).
There is an increasing demand from patients that medicine be practiced through minimally invasive low-risk procedures. The economics of health care delivery demand that we identify lower-cost alternatives to meet or exceed the standard of care. The culture of safety surrounding health care providers, and surgeons in particular, requires us to document our outcomes and complications. The findings of Cheng et al. suggest that laryngeal ultrasound might be an expedient, noninvasive, inexpensive, reproducible, and accurate method to interrogate and document vocal-cord mobility in most patients. With the increased availability of compact high-resolution ultrasound machines in the offices of thyroid surgeons, the use of laryngeal ultrasound to evaluate vocal-cord motion is certain to gain momentum. When used correctly, laryngeal ultrasound could accurately screen patients and direct patients who have a higher pretest probability of vocal-cord dysfunction for laryngoscopy.
- Friedman EM. Role of ultrasound in the assessment of vocal cord function in infants and children. Ann,Otology Rhinol Laryngol 1997;106:199-209.
- Garel C, Hassan M, Legrand I, Elmaleh M, Narcy P. Laryngeal ultrasonography in infants and children: pathological findings. Pediatr Radiol 1991;21:164-7.
- Dedecjus M, Adamczewski Z, Brzezinski J, Lewinski A. Real-time, high-resolution ultrasonography of the vocal folds—a prospective pilot study in patients before and after thyroidectomy. Langenbecks Arch Surg 2010;395:859-64. Epub July 20, 2010.
- Ooi LL, Chan HS, Soo KC. Color Doppler imaging for vocal cord palsy. Head Neck 1995;17:20-3.
- Wang CP, Chen TC, Yang TL, Chen CN, Lin CF, Lou PJ, et al. Transcutaneous ultrasound for evaluation of vocal fold movement in patients with thyroid disease. Eur J Radiol 2012;81:e288-e291. Epub October 22, 2011.
- Sidhu S, Stanton R, Shahidi S, Chu J, Chew S, Campbell P. Initial experience of vocal cord evaluation using grey-scale, real-time, B-mode ultrasound. ANZ J Surg 2001;71:737-9.
CLINICAL THYROIDOLOGY • MAY 2013 VOLUME 25 • ISSUE 5• © 2013