Translaryngeal ultrasound in thyroid surgery: state of the art review

Clinical voice assessment prior to thyroid and parathyroid surgery is essential, but the paradigm of indirect laryngoscopy (IDL), when indicated, has been challenged by the risk of aerosolised SARS-Cov-2 during endoscopy of the aerodigestive tract. Translaryngeal ultrasound (TLUS) to assess the vocal cords has been proposed as a safe, non-invasive and sensitive alternative. The aim of this review was to verify TLUS as a viable tool for perioperative laryngeal assessment.

A literature review was performed using Medline, Embase, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials and Scopus with the following search strategy: (vocal cord OR vocal fold OR glottic OR glottis OR vocal ligaments OR rima glottidis) AND (ultras* OR sonograph* OR echography OR echotomography).

Fifteen studies were included in this review. All studies compared TLUS to IDL in visualizing the vocal cords in adults. Ten studies compared pre-operative TLUS to IDL where 50.6-100% of vocal cords were successfully visualized. Nine studies compared post-operative TLUS to IDL and reported visualization between 39.6% and 100%. Pre- and post-operative negative predictive values ranged from 60% to 100%.

Whilst promising, successful visualization of the cords is limited by inter-user variability, older age and male gender. Thus, we see the role of TLUS as an alternative to IDL in the post-operative setting in the young patient following uncomplicated surgery with a normal voice on clinical examination, to confirm recurrent laryngeal nerve integrity while minimizing the risk of aerosolization.