Transcutaneous laryngeal ultrasonography in vocal fold assessment before and after thyroid surgery in light of recent studies

Abstract

Transcutaneous laryngeal ultrasonography (TLUS) has become a cheap, convenient, and novel method in vocal fold (VF) assessment. The gold standard method of VF examination is laryngoscopy. It requires ear, nose, and throat specialist consultation and additional equipment. Moreover, laryngoscopy causes distress to patients, and during the COVID-19 pandemic it is a high-risk, aerosol-producing procedure. The aim of the paper was to review publications on the role of TLUS in VF evaluation. Considered aspects included VF visibility, factors affecting them, and different variables measured during TLUS examination. The visibility of VFs in TLUS ranged from 72.8 to 100%. Among men it was significantly lower (17-100%) in comparison to women (83-100%). All but 2 authors concluded that TLUS is a viable tool that can be an alternative to laryngoscopy in diagnosing VFs. Obesity, age, male gender, height, calcified thyroid, and incision close to the thyroid cartilage were independent factors for inaccessible vocal folds. VF displacement velocity (VFDV) is the most objective parameter measured by Doppler, and it is proportional to the velocity of the wave causing the vibrations of the VFs. After VF paralysis, this parameter is reduced. Valsalva manoeuvre, low-frequency transducer, and different transducer positions can improve images obtained on USG. TLUS in a majority of cases can adequately assess whether the function of the VFs is intact or paresis/paralysis has occurred. It is noninvasive and rapid, it adds no extra cost, and it can be a part of the preoperative examination of the thyroid gland. TLUS can usually be a convenient alternative to laryngoscopy.