Soft palate angle and basihyoid depth increase with tongue size and with body condition score in horses.

Background: Obesity has been associated with human obstructive sleep apnoea and canine brachycephalic obstructive airway syndrome. To the authors’ knowledge the effect of body condition score (BCS) on structures of the oropharynx , nasopharynx and upper airway of the horse has not been investigated. Objectives: To investigate the effect of BCS on tongue area and height, soft palate angle and basihyoid depth in the horse. Study Design: Retrospective, analytical, cross-sectional. Methods: Computed tomographic (CT) images of the head of 44 horses were assessed. DICOM viewing software was used to measure head length, basihyoid-skin depth, soft palate angle (SPA), midline tongue area and dorsoventral height (DVH) of the tongue in two locations. BCS were assigned at the time of CT examinations. Results: Increased BCS led to an increased mean SPA (mean difference=2.56 ˚ ; P=0.019) and increased median basihyoid depth (mean difference=0.246cm; P=0.006). Following adjustments made for the effect of head length on tongue measures, significant correlation was identified between SPA and tongue area (Spearman’s r=0.544; P=0.007); SPA and DVH of the tongue at the level of the hard palate (Spearman’s r=0.562; P=0.004) and SPA and DVH of the tongue at the lingual process of the basihyoid bone (Spearman’s r=0.690; P<0.001). No significant correlation was identified between variables with sex or age of horses. Conclusions: Increased BCS increases SPA and basihyoid bone depth. Increases in tongue size measurements increase SPA. Results from this study warrant further investigation into the clinical significance of the effects of BCS on the upper airways of the horse.