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Brachycephalic syndrome in dogs

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Stenotic nares and elongated soft palates seem to be the initiating events of brachycephalic syndrome in dogs. As a result of increased negative pressure during inspira-tion, the soft tissues of the upper airway are sucked into the lumen, aggravating the condition. The most common signs of brachycephalic syndrome are stress and heat intolerance, inspira-tory stridor, and asphyxia. Severely affected animals are prone to life-threatening attacks. Sur-gical corrections include wedge resection of stenotic nares, shortening of the soft palate, and removal of laryngeal saccules. B rachycephalic breeds tend to have respiratory problems that come under the term brachycephalic syndrome. The typical anatomic abnormalities are stenotic nares, enlarged tonsils, elongated soft palate, everted lateral saccules of the lar-ynx, narrowed rima glottidis, and collapse of the larynx and trachea. 1 These findings occur singularly or in various combinations and degrees in each dog. These abnor-malities narrow the lumen of the upper respiratory tract, thereby restricting breath-ing, which often leads to asphyxiation and collapse during excitement or heat result-ing from the weather or activity. This article provides a review of the predisposition and anatomic and pathophysiologic particularities of the respiratory tract in connec-tion with brachycephalic syndrome.
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... Brachycephalic dogs have become increasingly popular as companion animals, mainly because they are docile and require less space in their homes [7,8]. These dogs usually have brachycephalic syndrome (BS), in which several congenital anatomical changes lead to obstruction of the airways [18,20]. This obstruction resulted in resistance to airflow and increased intraluminal negative pressure, generating secondary changes that perpetuate the cycle of obstruction and soft tissue injury, aggravating respiratory symptoms [1,9]. ...
... When classifying the clinical manifestations of the dogs in the study, more than half of the animals included had severe manifestations of BS, since at least one of the signs that were considered severe (syncope, cyanosis, dyspnea at rest) was observed in each of these animals [13,16]. Therefore, it is possible to believe that even in young animals, the disease can cause damage to the quality of life and even the risk of death [20,31]. ...
... Although no evident relationship of in severity was observed, more than half of the dogs presented had some alterations in the trachea, between among congenital and acquired alterations [20,23,24]. This finding suggests that, in the dogs of the present study, BS may be the cause of tracheal alterations, as well as a consequence of these findings [5]. ...
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Background: Brachycephalic dogs have several abnormalities in the airways, which generate clinical manifestations that impair the quality of life of these animals. Primary alterations promote airflow obstruction and increase intraluminal negative pressure, causing secondary alterations due to a cycle of inflammation with consequent obstruction. With the onset of inflammation and other alterations in the airways, clinical manifestations can be observed, such as snoring, reverse sneezing, coughing, dyspnea, cyanosis, syncope, and vomiting. Endoscopic examination of the airways allows visualiza-tion and diagnosis of morphological changes in these animals. This study aimed to evaluate the endoscopic findings of the airways and determine the quantitative and qualitative assessment of the severity of clinical manifestations in 14 dogs with brachycephalic syndrome (BS). Materials, Methods & Results: Historical and anamnesis data and clinical, respiratory, and digestive manifestations were collected from the owners' reports. The clinical manifestations were classified as mild, moderate, or severe. All animals were subjected to endoscopy of the airways, and image findings were grouped according to the anatomical site where they were observed, then the abnormalities were correlated with the severity of the clinical manifestations. When comparing the frequency of endoscopic abnormalities with the severity of clinical manifestations, it is interesting to observe that animals with severe disease more frequently presented the following alterations: prolongation and thickening of the soft palate, laryngeal changes, presence of hyperemia, lymphoid hyperplasia and polyps in the nasopharynx, hypoplasia and presence of tracheal secretion and thickening of the dorsal tracheal muscle; bronchial collapse, hypoplasia of the main bronchi and bronchial hyperemia and the presence of aberrant nasal turbinates. Comparison between the means of nonparametric variables was performed using the Mann-Whitney test, with a 5% significance level. Discussion: A higher frequency of French Bulldog dogs included in the study was observed, probably due to their greater popularity, although any brachycephalic dog may be affected by BS. Considering that nostril stenosis is a congenital alteration , which is usually diagnosed early, and since the animals included in the study were dogs referred for the rhinoplasty procedure the higher frequency of young dogs in the study was not surprising. The results revealed a significant difference in the endoscopic findings with the severity of the clinical manifestations in different variables, such as prolongation and thickening of the soft palate, eversion of the laryngeal saccules, presence of laryngeal inflammation and collapse, presence of polyps or lymphoid hyperplasia in the nasopharynx, thickening of the dorsal muscle of the trachea, polyps in the trachea and hypoplasia in addition to bronchial hyperemia. The larynx was the most affected anatomical site, with alterations present in 92.8% of the evaluated dogs. Based on these findings, it can be concluded that airway obstruction caused by primary alterations can cause secondary alterations, with consequent clinical manifestations in brachycephalic dogs it is possible to suggest that dogs with this syndrome may present severe manifestations of the disease, regardless of age. Furthermore, it can be concluded that in this study, dogs with BS had frequent laryngeal alterations and that alterations in the main bronchi were present in all animals with severe manifestations of the disease.
... Brachycephaly often leads to the well-known respiratory disease of the upper airway tract, the Brachycephalic Obstructive Airway Syndrome (BOAS) [20][21][22][23][24]. Affected dogs may present a variety of clinical signs, from mild respiratory symptoms such as noisy breathing up to dyspnea and severe impairment of physical fitness and heat intolerance [25,26]. ...
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Background Echocardiographic measurements may be influenced by breed-specific characteristics. Therefore, this study aims to establish reference values for standard echocardiographic measurements in pugs by investigating the influence of age, sex, heart rate, body weight and Brachycephalic Obstructive Airway Syndrome (BOAS). Sixty-two privately owned pugs underwent physical examination, blood sample collection, non-invasive blood pressure measurements and echocardiography. Influences of independent variables on echocardiographic measurements were examined using a multiple linear regression analysis model. For the entire study population, 95% prediction intervals were generated. Further, reference ranges for subcategories of clinical severities of BOAS were provided. Selected echocardiographic measurements of pugs were compared to reference values of previous studies generated from various breeds. Results In the study, a total of fifty-one privately owned pugs aged between two and 10 years were included for establishing reference ranges. Mainly body weight, but also age, sex and heart rate had influence on several echocardiographic parameters. The clinical grading of BOAS was conducted in 42 pugs. Except for pulmonic peak velocity (Pvel), which declined with increasing severity of BOAS, clinical symptoms of upper airway disease did not have significant impact on echocardiographic measurement results. Significant deviations, however, of left ventricular (LV) internal dimension (LVID), interventricular septum (IVS), LV posterior wall (LVPW), and tricuspid annular plane systolic motion excursion (TAPSE) compared to interbreed reference values were observed. Conclusions Breed-specific reference ranges for echocardiographic values with special regard to BOAS are provided to enable a more accurate assessment of cardiac health in pugs.
... This results in a distinctive short and very often flattened dorso-ventral snout. This is a result of deliberate efforts by breeders to select dogs for breeding so that they develop local chondrodysplasia and generate individuals with an even more shortened facial skeleton [90,91]. In recent years, there has been a significant increase in the popularity of brachycephalic breeds. ...
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Dogs are a good starting point for the description and anatomical analysis of turbinates of the nose. This work aimed at summing up the state of knowledge on the shape of the nasal cavity and airflow in these domestic animals and dealt with the brachycephalic syndrome (BOAS) and anatomical changes in the initial airway area in dogs with a short and widened skull. As a result of artificial selection and breeding concepts, the dog population grew very quickly. Modern dog breeds are characterized by a great variety of their anatomical shape. Craniological changes also had a significant impact on the structure and physiology of the respiratory system in mammals. The shape of the nasal cavity is particularly distinctive in dogs. Numerous studies have established that dogs and their olfactory ability are of great importance in searching for lost people, detecting explosives or drugs as well as signaling disease in the human body. The manuscript describes the structure of the initial part of the respiratory system, including the nasal turbinates, and compares representatives of various animal species. It provides information on the anatomy of brachycephalic dogs and BOAS. The studies suggest that further characterization and studies of nasal turbinates and their hypertrophy are important.
... 6,10,11 Several studies consider a combination of both theories. 5,7,11 Unfortunately, tonsil enlargement and/or eversion can lead to additional airway obstruction. 8 As a consequence, further exacerbation of clinical breathing problems associated with increased airway resistance is conceivable. ...
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Objective: Investigation of the MRI characteristics of the palatine tonsil in brachycephalic dogs in 3T high-field system. Material and methods: Eighty-five brachycephalic dogs and 37 normocephalic dogs were divided into five groups: group 1 French bulldogs (FBs) with neurological clinical signs (n = 37), group 2 FBs with brachycephalic obstructive airway syndrome (BOAS) (n = 22), group 3 pugs with neurological clinical signs (n = 17), group 4 pugs with BOAS (n = 9) and group 5 normocephalic dogs (n = 37). Cross-sectional area and volume measurements were performed, and tonsillar margination and contour, shape, signal intensity and homogeneity/heterogeneity of the palatine tonsils were evaluated and compared. Results: Cross-sectional area and volume measurements of the tonsils showed no significant differences between brachycephalic and normocephalic dogs with the exception of the dogs of group 2 (FB BOAS), which showed relatively high volume and large cross-sectional area in comparison to other groups. In 87% of the brachycephalic animals, the tonsils were well defined. A smooth contour was detectable in 91.8% and a rounded shape in 94.7% of brachycephalic dogs. Signal intensity was assessed as hyperintense in relation to the musculature and iso- to hyperintense to the soft palate. Heterogeneous appearance was described in 86.9% of the brachycephalic animals. Conclusions: The MRI characteristics of the tonsils of brachycephalic dogs do not differ considerably from those of normocephalic dogs. In FBs with distinct clinical signs of obstructive airway syndrome, increase in cross-sectional area and volume of the tonsils was detected.
... Many studies have shown that exaggerated breeding for brachycephaly leads to pronounced malformations in many areas other than the head [1][2][3][4], particularly the upper respiratory tract. Furthermore, several structures in the head itself are impaired in both form and function by this pathological head shape. ...
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Objectives This study aimed to investigate and compare the anatomical features of the nasolacrimal drainage system (NDS) in three brachycephalic dog breeds with those of normocephalic dogs, taking into account how the NDS was related to the malformed brachycephalic head. Animals Fifty-one brachycephalic dogs were examined, comprising 23 Pugs, 18 French Bulldogs, and 10 English Bulldogs. Six normocephalic dogs of different breeds served as a comparison. Methods Computed tomographic dacryocystography was performed. Parameters such as length, angulation, and gradient were determined. Crossing of the nasolacrimal duct (NLD) beneath the maxillary canine root, as well as the incidence of an accessory opening, were also analyzed. Results and conclusions In all three brachycephalic breeds, the NDS was grossly malformed. We regard this as a further consequence of exaggerated breeding for a short head conformation. While the length of the NLD was substantially reduced by 41 to 57 percent in brachycephalic dogs, their lacrimal canaliculi were two to three times as long as those of normocephalic dogs. Varying parts of the nasolacrimal drainage system followed an inverse direction in short-headed dogs, giving the entire nasolacrimal apparatus an anomalous U- or V-shaped appearance. The NLD exhibited a three to five times steeper alignment in brachycephalic dogs than in normocephalic ones. Obviously, this strong slope did not cause clinical symptoms only because there was an aberrant outflow pathway. The brachycephalic dogs consistently exhibited an accessory opening, through which most of fluid escaped into the posterior nasal cavity instead of through the common route into the nasal vestibule via the nasolacrimal ostia.
... More recent studies have repeatedly assigned the Boxer to the brachycephalic group (Bannasch et al., 2010;Koch et al., 2003;Koch & Sturzenegger, 2015;Sturzenegger, 2011) using different kinds of measurement such as the Square Index (SI), the Length-Width Index (LWI) or the Craniofacial Angle. ...
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Excessive breeding of dogs has led to a disadvantageous morphology in some breeds, for example extreme brachycephaly, which is responsible for many health issues. We hypothesize that alterations of the mimic muscular system are present in brachycephalic dogs and could contribute to behavioural problems due to a restricted mimic display. Therefore, the purpose of this paper was to compare the mimic muscular systems of brachycephalic with dolichocephalic dogs. Mimic muscles were measured and set in ratio to measurements of the head and calculated indices. When bringing the length of the muscles m(x) in proportion to the length of the head, highly significant differences (p < .0001) and significant difference (p < .05) were found in all but two of the examined muscles. Calculations of the m(x) divided by the cranial index and the square index showed significant differences for all muscles. For example, the musculus (m.) levator nasolabialis was morphologically different from the one of dolichocephalic dogs. Muscle fibres of the m. levator nasolabialis were localized in the fold over the nasal bridge of brachycephalic dogs. The raphe of the m. orbicularis oris was not always apparent in brachycephalic dogs. The proportions of the muscle lengths and the length of the eye slots to the size of the skull have shifted considerably in brachycephalic dogs. We conclude that many alterations contribute to the strong shift in the proportions of the head of brachycephalic dogs versus that of dolichocephalic dogs. Our findings suggest that brachycephalic dogs have reduced mimic skills that can lead to ambiguous communication.
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Despite efforts of veterinarians and breeders, brachycephalic obstructive airway syndrome (BOAS) is still a common problem in pugs, underlining the need for objective tests to identify and prevent breeding with affected dogs. In the current study, a submaximal, treadmill-based fitness test was evaluated as a tool to identify signs of airway obstruction not recognisable under rest conditions. In addition to this, different body conformation and measurements were assessed regarding their association with BOAS. A total of 62 pugs and 10 mesocephalic dogs trotted with an individual comfort speed on a treadmill for 15 min. Before and during the examination, dogs were examined for signs of respiratory distress, and a functional BOAS grading was applied. The influence of body conformation on BOAS grading was tested in a univariable and multivariable logistic regression model. During exercise, more respiratory noises were observed, and existing respiratory noises became more apparent in comparison to when at rest. In the multivariable logistic regression model, no factor had a statistically significant influence on BOAS classification. Submaximal fitness testing helped to identify signs of respiratory distress not apparent under resting conditions, and could be a valuable addition for identifying dogs with BOAS. Performing testing on a treadmill facilitates continuous observation of the patients, and enables standardisation of the test regarding the test environment, as well as provides an uninterrupted, steady workload.
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Dogs presenting with brachycephalic obstructive airway syndrome suffer from multilevel obstruction of the airway as well as secondary structural collapse. Stenotic nares, aberrant turbinates, nasopharyngeal collapse, soft palate hyperplasia, macroglossia, tonsillar hypertrophy, laryngeal collapse, and left bronchial collapse are described as the most common associated anomalies. Rhinoplasty and palatoplasty as well as newer surgical techniques and prudent preoperative and postoperative care strategies have resulted in significant improvement even in middle-aged dogs.
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Objectives Periodontal disease is a frequent diagnosis of dogs and can have severe negative impacts on welfare. It was hypothesised that breeds with skull shapes that differ most in conformation from the moderate mesocephalic skull shape have higher odds of periodontal disease. Materials and Methods The cohort study included a random sample of dogs under primary veterinary care in 2016 from the VetCompass Programme database. Risk factor analysis used random effects multivariable logistic regression modelling. Results The study included a random sample of 22,333 dogs. The 1-year period prevalence for diagnosis with periodontal disease was 12.52% (95% CI: 12.09 to 12.97). Eighteen breeds showed increased odds compared with crossbred dogs. Breeds with the highest odds included Toy Poodle (odds ratio 3.97, 95% confidence intervals 2.21 to 7.13), King Charles Spaniel (odds ratio 2.63, 95% confidence interval 1.50 to 4.61), Greyhound (odds ratio 2.58, 95% confidence interval 1.75 to 3.80) and Cavalier King Charles Spaniel (odds ratio 2.39, 95% confidence interval 1.85 to 3.09). Four breeds showed reduced odds compared with crossbreds. Brachycephalic breeds had 1.25 times the odds (95% confidence interval 1.11 to 1.42) of periodontal disease compared with mesocephalic breeds. Spaniel types had 1.63 times the odds (95% confidence interval 1.42 to 1.87) compared with non-spaniel types. Increasing adult bodyweight was associated with progressively decreasing odds of periodontal disease. Clinical Significance The high prevalence identified in this study highlights periodontal disease as a priority welfare concern for predisposed breeds. Veterinarians can use this information to promote improved dental care in predisposed dogs, especially as these dogs age.
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Synopsis “Brachycephaly” is generally considered a phenotype in which the facial part of the head is pronouncedly shortened. While brachycephaly is characteristic for some domestic varieties and breeds (e.g., Bulldog, Persian cat, Niata cattle, Anglo-Nubian goat, Middle White pig), this phenotype can also be considered pathological. Despite the superficially similar appearance of “brachycephaly” in such varieties and breeds, closer examination reveals that “brachycephaly” includes a variety of different cranial modifications with likely different genetic and developmental underpinnings and related with specific breed histories. We review the various definitions and characteristics associated with brachycephaly in different domesticated species. We discern different types of brachycephaly (“bulldog-type,” “katantognathic,” and “allometric” brachycephaly) and discuss morphological conditions related to brachycephaly, including diseases (e.g., brachycephalic airway obstructive syndrome). Further, we examine the complex underlying genetic and developmental processes and the culturally and developmentally related reasons why brachycephalic varieties may or may not be prevalent in certain domesticated species. Knowledge on patterns and mechanisms associated with brachycephaly is relevant for domestication research, veterinary and human medicine, as well as evolutionary biology, and highlights the profound influence of artificial selection by humans on animal morphology, evolution, and welfare.