Vol.:(0123456789) 1 3 Dysphagia https://doi.org/10.1007/s00455-018-09968-3 ORIGINAL ARTICLE The Association of 3‑D Volume and 2‑D Area of Post‑swallow Pharyngeal Residue on CT Imaging Rachel W. Mulheren 1,2,3  · Yoko Inamoto 4,5  · Charles A. Odonkor 2  · Yuriko Ito 5  · Seiko Shibata 5  · Hitoshi Kagaya 5  · Marlis Gonzalez‑Fernandez 2  · Eiichi Saitoh 5  · Jeffrey B. Palmer 2 Received: 30 April 2018 / Accepted: 31 December 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Pharyngeal residue, the material that remains in the pharynx after swallowing, is an important marker of impairments in swallowing and prandial aspiration risk. The goals of this study were to determine whether the 2D area of post-swallow residue accurately represents its 3D volume, and if the laterality of residue would affect this association. Thirteen patients with dysphagia due to brainstem stroke completed dynamic 320-detector row computed tomography while swallowing a trial of 10 ml honey-thick barium. 3D volumes of pharyngeal residue were compared to 2D lateral and anterior–posterior areas, and a laterality index for residue location was computed. Although the anteroposterior area of residue was larger than the lateral area, the two measures were positively correlated with one another and with residue volume. On separate bivariate regression analyses, residue volume was accurately predicted by both lateral (R 2 = 0.91) and anteroposterior (R 2 = 0.88) residue areas, with limited incidence of high residuals. Half of the sample demonstrated a majority of pharyngeal residue lateralized to one side of the pharynx, with no effect of laterality on the association between areas and volume. In conclu- sion, the area of post-swallow pharyngeal residue was associated with volume, with limitations in specific cases. Direct measurement of pharyngeal residue volume and swallowing physiology with 3D-CT can be used to validate results from standard 2D instrumentation. Keywords Pharynx · Dynamic computed tomography · Brainstem stroke · Residue · Deglutition · Deglutition disorders Introduction Approximately 16 million people are treated for dyspha- gia in the United States annually [1, 2]. Dysphagia is asso- ciated with risk of aspiration pneumonia, malnutrition and dehydration, high morbidity and mortality of stroke patients, deterioration in quality of life, and increased healthcare costs [3–5]. Pharyngeal residue, the material that may remain in the pharynx after swallowing, is an important marker of impairments in swallowing and prandial aspiration risk. Res- idue may result from weak or uncoordinated oropharyngeal musculature during bolus propulsion, disrupted sensation, or limited opening of the upper esophageal sphincter (UES), and is associated with several etiologies, including brainstem stroke [6, 7]. Previous reports suggest that risk of aspira- tion is directly associated with the presence and amount of pharyngeal residue [8–10]. To date, pharyngeal residue has been assessed by percep- tual, semi-quantitative, and quantitative methods. Percep- tual measures categorize residue by its absence/presence, * Yoko Inamoto inamoto@fujita-hu.ac.jp 1 Department of Psychological Sciences, Case Western Reserve University, Cleveland, OH, USA 2 Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA 3 Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, USA 4 Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, 1-98 Dengakugakubo, Kutsukake, Toyoake, Aichi 470-1192, Japan 5 Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan