Possibilities of ultrasound scanning for assessment of vocal fold mobility in patients with thyroid disease

Introduction. Ultrasound examination of the larynx is now increasingly becoming an alternative to laryngoscopy in determining the perioperative mobility of the vocal folds in patients with thyroid disease. However, it is not always possible to visualize vocal folds and arytenoid cartilages in a patient. Age and male gender are factors leading to ossification of the thyroid cartilage as a window for scanning. The exact age of onset of limitations in the use of diagnostic ultrasound and other factors that cause early ossification of cartilage currently represent open questions. Purpose of the study. To determine the possibilities of ultrasound scanning in the vocal fold mobility assessment in patients with thyroid disease depending on age, sex, and smoking status. Material and methods. Ultrasound examination of the larynx and thyroid gland in B-mode and color Doppler Imaging was performed at the Irkutsk Regional Oncological Dispensary in 55 patients aged 10 to 90 years with the following thyroid diseases: cancer (2 patients), diffuse toxic goiter (2), nodular goiter (49). Forty-six (83.6%) women and 9 (16, 4%) men were examined using a Toshiba Viamo 10 MHz linear scanning transducer. There were 6 female smokers and 5 male smokers. The transducer was placed in transverse or oblique transverse position in the projection of the lower third of the anterior surface of the thyroid cartilage, the mobility of the vocal folds was determined during breathing and phonation of vowel sounds “a” and “e”. With significant ossification of the thyroid cartilage, visualization of the vocal fold movements was difficult. We determined the dependence of laryngeal cartilage ossification on age, gender, smoking, and occupation. Statistical processing of the results was carried out using contingency tables and the Fisher’s exact test, odds ratio, and ROC analysis using the Statistika 7.0 and MedCalc software. Results. Upon examination, the patients were divided into 2 groups. Group 1 (n=27) consisted of 25 women (57.0±16.4 years) and 2 men (49.0±21.2 years). They had their VFs visualized, and their FV mobility could be assessed by US: there was no calcinosis of thyroid cartilage. In this group, only one woman was a smoker, and laryngeal paresis was present in one case. The second group (n=28) with ossification of laryngeal cartilages consisted of 21 women (65.0±8.8 years) and 7 men (64.0±8.1 years), 5 women and 5 men were smokers, 18 were nonsmokers. In this group, visualization of the internal structures of the larynx was difficult. According to Fisher’s two-sided test, group 2 patients were more likely to be smokers (p=0.0052), aged over 50 years (p=0.0001), without any association with gender (p=0.1430) or occupation. The odds for calcinosis were 14 times higher in smokers compared with non- smokers (95% confidence interval — CI 1.988-394.405). The age above which the probability of cartilage ossification increased was determined by ROC analysis — 57 years (sensitivity 55.6%, specificity 82.1%). Conclusions. Laryngeal ultrasound is informative for the VF mobility assessment in nonsmoking patients with thyroid disease up to 57 years of age. In smokers over 57 years of age, this method is highly likely to be less informative due to ossification of the laryngeal cartilage. Key words: ultrasound scanning of the larynx, color Doppler ultrasound, thyroid disease, vocal folds, vocal fold paralysis diagnostics, laryngeal cartilage calcification, smoking Conflicts of interest. The authors have no conflicts of interest to declare. Funding. There was no funding for this study