CT volumetric analysis permits comparison of tongue size and tongue fat in different canine brachycephalic and mesaticephalic breeds

Ava Song, Heidi Phillips, Cintia R. Oliveira, Annette M. McCoy

Background: This article discusses the problem of brachycephalic obstructive airway syndrome (BOAS) in dogs with shortened craniofacial conformation, which can cause chronic and fatal respiratory distress. One of the components of BOAS is macroglossia, or enlarged tongue, which can obstruct the airway. The authors note that tongue fat is a major contributor to macroglossia and obstructive sleep apnea (OSA) in people, and suggest that it may also play a role in BOAS in dogs.

Study: The purpose of this study was to describe and compare the volumetric dimensions of the tongue and tongue fat in brachycephalic (BC) and mesaticephalic (MC) dogs using multiplanar CT images and specialized volumetric software. The authors hypothesized that BC dogs would have greater tongue volume and fat deposition than MC dogs, and that fat would be concentrated at the tongue base.

Methods: The authors selected 35 dogs that had pre- and postcontrast CT of the head and neck performed between 2009 and 2019, including 17 BC dogs and 18 MC dogs. They used manual image segmentation to trace the tongue and its boundaries in all CT planes, and calculated the total tongue volume (TTV), tongue fat volume (TFV), and tongue muscle volume (TMV) using a greyscale threshold to differentiate fat from other tissues. They also divided the tongue into rostral and caudal regions to assess the topographical distribution of fat. They used three normalization indices to adjust for differences in size among dogs: area of intermandibular space (IMS), skull length × skull width (LW index), and body weight (BW). They performed statistical analyses to compare volumetric measurements between BC and MC dogs, and to evaluate the effects of conformation, age, sex, and weight on TFV.

Results: The authors found that BC dogs had greater TTV and TMV than MC dogs when normalized to IMS and BW, but not to LW index. They also found that BC dogs had greater TFV than MC dogs when normalized to BW, but not to IMS or LW index. The proportion of TTV attributable to fat was not different between groups. In regression analysis, both BC conformation and weight were significant predictors of TFV, indicating that BC dogs had more tongue fat per kilogram BW, and heavier dogs had more tongue fat regardless of conformation. They also found that more fat was localized in the caudal tongue in both groups, but BC dogs tended to have more fat in the rostral tongue than MC dogs.

Limitations: The authors acknowledged several limitations of their study, such as the retrospective nature, the lack of body condition scores, the uncertainty of normalization indices, the static modality of CT, and the heterogeneity of BC breeds. They suggested that future studies should use direct methods of body composition assessment, validated craniofacial indices, histological and biochemical analysis of tongue fat, and prospective and breed-specific designs to further investigate the role of tongue fat in BOAS and sleep-disordered breathing in BC dogs.

Conclusions: The authors concluded that their study provided evidence that BC dogs have greater tongue volume and fat than MC dogs, and that tongue fat deposition was the greatest caudally in both groups, but some BC dogs had increased fat in the rostral tongue. They proposed that CT volumetry of the tongue may help to identify regions of fat that may be targeted for treatment in BC dogs with BOAS10.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.