Computed tomographic study of the effect of a tongue-tie on hyoid apparatus position and nasopharyngeal dimensions in anesthetized horses

Objective-To determine the effect of manual tongue protrusion on the dimens ions of the hyoid apparatus, nasopharynx, and oropharynx in anesthetized ho rses. Animals-5 adult horses. Procedure-Horses were anesthetized and positioned in sternal recumbency for 2 sequential computed tomographic (CT) scans. Images were acquired with th e tongue in a natural position inside the mouth. Then, the tongue was pulle d rostrally and secured, and a second CT scan was performed. Dorsoventral l ength of the hyoid apparatus and angles of the basisphenoid, basihyoid, and ceratohyoid were measured on 3-dimensional reconstructed CT images. Cross- sectional diameters and areas of the nasopharynx and oropharynx were determ ined on reformatted images in the transverse and longitudinal planes, using osseous landmarks for consistency. Results were tested between the 2 group s to determine significant differences. Results-We were unable to detect a significant difference between any of th e lengths or angles of the hyoid apparatus measured with or without rostral protrusion of the tongue. Similarly, nasopharyngeal and oropharyngeal diam eters and cross-sectional areas were not significantly different with or wi thout rostral protrusion of the tongue. Conclusions and Clinical Relevance-Tying the tongue rostrally out of a hors e's mouth did not influence the position of the hyoid apparatus or dimensio ns of the nasopharynx or oropharynx in anesthetized horses. Currently, no d ata suggest that application of a tongue-tie is effective for maintaining s tability and patency of the nasopharyngeal or orolaryngeal airways in horse s during races.