Utility Of Ultrasound In The Assessment Of Swallowing And Laryngeal Function: A Rapid Review And Critical Appraisal Of The Literature

Background Ultrasound (US) is not widely used as part of the speech and language therapy (SLT) clinical toolkit. The COVID-19 pandemic has intensified interest in US as an alternative to SLT instrumental tools such as the videofluoroscopic swallowing study (VFSS), fibreoptic endoscopic evaluation of swallowing (FEES) and endoscopic evaluation of the larynx (EEL) as a non-invasive, non-aerosol-generating procedure that can be delivered at the bedside to assess swallowing and/or laryngeal function. To establish the appropriacy of routine US use, and in response to a national professional body request for a position statement, a group of expert SLTs conducted a rapid review of the literature.Aim To explore critically the clinical utility of US as an assessment tool for swallowing and laryngeal function in adults.Methods & Procedures A rapid review of four databases was completed to identify articles using US to assess swallowing and/or laryngeal function in adults compared with reference tests (VFSS/FEES/EEL/validated outcome measure). Screening was completed according to predefined inclusion/exclusion criteria and 10% of abstracts were rescreened to assess reliability. Data were extracted from full texts using a predeveloped form. The QUADAS-2 tool was used for quality ratings. Information from included studies was summarized using narrative synthesis and visual illustration.Outcomes & Results Ten papers used US to assess swallowing, and 13 to assess laryngeal function. All were peer-reviewed primary studies across a range of clinical populations and with a wide geographical spread. Four papers had an overall low risk of bias, but the remaining 19 had at least one domain where risk of bias was judged as high or unclear. Applicability concerns were identified in all papers. The papers that used US to assess swallowing varied widely in terms of the anatomical structures assessed and methodology employed. The papers assessing laryngeal function were more homogenous in their methodology. Sensitivity and specificity data were provided for 12 of the laryngeal function papers with ranges of 64.3-100% and 48.5-100%, respectively.Conclusions & Implications There is burgeoning evidence to support the use of US as an adjunct to SLT clinical assessment of swallowing and laryngeal function. However, the current literature does not support its use as a tool in isolation. Further research is required to establish reliability in US assessment as well as clear SLT-driven protocols and training.What this paper adds What this paper adds to existing knowledgeWhat is already known on the subjectWhat are the potential or actual clinical implications of this work?US has demonstrated potential as an assessment tool for objective parameters of swallowing. Its use for laryngeal assessment (gross vocal fold movement) is also widely recognized within the literature. This review appraised the literature related to US as an alternative or adjunctive tool for the assessment of swallowing and laryngeal function.This paper identifies that the current evidence base for US as a swallowing or laryngeal assessment tool is heterogenous and of variable quality. No study combined the assessment of swallowing and laryngeal function, and only two studies assessed more than one parameter of swallowing, limiting the clinical application of the results.This review shows that US is a non-invasive accessible tool that can offer a detailed focal assessment of swallowing and laryngeal function, such as hyoid displacement and vocal fold mobility. With the development of protocols, training packages and competency standards, US has the potential to be used as an adjunct to SLT assessment of swallowing and laryngeal function. There is not currently enough evidence to support the use of US as a stand-alone tool for SLT assessment of swallowing or laryngeal function.