Three-dimensional volumetric magnetic resonance imaging (MRI) analysis of the soft palate and nasopharynx in brachycephalic and non-brachycephalic dog breeds

Abstract

The purpose of this study was to use magnetic resonance imaging (MRI) to compare the volumes and three-dimensional configurations of the soft palate and nasopharynx in non-brachycephalic and brachycephalic dogs with different body weights, and infer which factors influence nasopharyngeal volume. This was a retrospective observational study. The brain MRI medical records of all dogs referred to the Veterinary Medical Center, Chungbuk National University, between 2013 and 2016, for evaluation of intracranial disease were reviewed. There was a significant difference in the two-dimensional parameters including soft palate length/skull length ratio (P<0.01) and maximum soft palate thickness (P<0.01), and three-dimensional parameters which included soft palate volume (P<0.01), nasopharyngeal volume (P<0.01), soft palate/total upper airway volume ratio (P<0.01), and nasopharyngeal volume/total upper airway volume ratio (P<0.01), between brachycephalic and non-brachycephalic dog breeds. Nasopharyngeal volume correlated positively with the maximum soft palate thickness and body weight in all breeds. The three-dimensional morphologic grades of soft palate were significantly different between the two groups. In brachycephalic breeds, Grade 3 was observed in 33% of cases but was absent in non-brachycephalic breeds, where Grade 1 was present in 85% of the cases. We can conclude that three-dimensional morphology and upper airway volume are significantly different between brachycephalic and non-brachycephalic breeds, and body weight and maximum soft palate thickness are the key factors associated with a decreased nasopharyngeal volume.

Dynamic computed tomography evaluation of the nasopharynx in normal Beagle dogs

“…There are several diagnostic imaging modalities to evaluate the anatomic or dynamic changes of the upper airway in dogs especially in brachycephalic breeds including radiography, rhinoscopy, fluoroscopy, static CT, and magnetic resonance imaging (MRI) [ 10 , 12 , 15 , 16 , 18 , 21 , 23 , 24 ]. Among these modalities, fluoroscopy has been used in dogs with obstructive airway syndrome because it has the feasibility of real-time assessment of the dynamic profile of the upper airway and can be used without general anesthesia using an endotracheal tube [ 23 , 24 ].…”

“…In this study, various locations were selected to evaluate nasopharyngeal CSA and collapsibility at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and the caudal end of the soft palate. These anatomical levels for nasopharyngeal evaluation were chosen based on previous studies on brachycephalic dogs, and on their easiness to find that could be used in landmarks on CT [ 12 , 15 , 16 , 25 ].…”

Aspectos anatômicos e clínicos da síndrome braquicefálica: revisão de literatura

“…Um estudo recente realizou ressonância magnética do crânio de cães braquicefálicos e não braquicefálicos, comparando seu volume e as imagens tridimensionais, e confirmando que os cães braquicefálicos apresentam o palato com volume e espessura maior que o dos cães mesaticefálicos, o que influencia diretamente a redução do espaço nasofaríngeo, favorecendo a ocorrência de um colapso nasofaríngeo (Kim et al, 2018).…”

“…Alterações secundárias do palato mole podem surgir em função do edema e da inflamação causados por microtraumas secundários ao aumento da turbulência na região da orofaringe, pela elevação da pressão negativa e pelo consequente aumento do esforço inspiratório, levando a alterações fibromusculares e aumentando a intensidade dos sinais clínicos (Kim et al, 2018).…”

“…A eversão é um achado comum nas raças braquicefálicas, reconhecida em 40 a 60% dos exemplares (Gianella et al, 2019). Em estudo recente da nasofaringe de cães braquicefálicos, revelou que 85% dos cães analisados apresentavam colapso laríngeo no grau I, e 33% no grau 3 (Kim et al, 2018). Essas alterações impactam diretamente o prognóstico e o tratamento do paciente (Cantatore et al, 2012), pois dificultam significativamente a passagem do ar pela laringe, podendo intensificar a apresentação clínica da doença .…”