Definition/Overview

The term brachycephalic syndrome (BS), also previously named brachycephalic airway obstructive syndrome (BAOS), refers to a disorder resulting from multiple anatomic abnormalities commonly found in brachycephalic breeds of dogs, mainly the English and French bulldog and the pug. It is also recognized in Persian cats. This syndrome causes respiratory and digestive symptoms and is a frequent cause of respiratory distress in brachycephalic dogs.¹

Etiology

Conformational anomalies in brachycephalic dogs are related to breeding selection of ‘hypertypes,’ which leads to progressive shortening of the face and nose, with subsequent shortening of the bony structures of the skull without concurrent reduction in surrounding soft tissues.²

Pathophysiology

Primary inherited abnormalities include stenotic nares, elongated/thickened soft palate, hypoplastic trachea, and, sometimes, protrusion of nasal turbinates into the nasopharynx, namely caudal aberrant turbinates.³ In some dogs, the soft palate can be too long in addition to being exceptionally thick; macroglossia can also occur. Secondary lesions develop as a probable consequence of increased pressures on the pharyngeal, laryngeal, and intrathoracic structures during breathing. These lesions include everted laryngeal saccules, progressive laryngeal collapse, and probably bronchial collapse (mainly collapse of the left main bronchus). Besides, subepiglottic cysts, severe edema of the dorsal aspect of the laryngopharynx, and laryngeal granulomas ‘kissing lesions’ all further narrow the air passage at the laryngeal inlet.⁴ The severity and the combination of these abnormalities will vary. To complicate matters even further, these dogs can have various accompanying gastrointestinal abnormalities involving the distal esophagus, stomach, and duodenum, including inflammatory disease with coexisting functional or anatomic anomalies (cardial atony, gastroesophageal reflux, gastric retention, pyloric mucosal hyperplasia, and pyloric stenosis).^5,1

Clinical Presentation

The abnormalities associated with the BS impair airflow through the upper airways and cause clinical signs of upper airway obstruction including noisy respiration, strider, stertor, exercise, and heat intolerance, respiratory distress, cyanosis, syncope, gagging and retching, and sometimes sleep apnea. The clinical signs are exacerbated by exercise, excitement, and high environmental temperatures. As a result, some dogs can be presented with life-threatening clinical signs of airway obstruction. Digestive signs such as regurgitation and vomiting are common. Secondary aspiration pneumonia is also a common associated finding and must be addressed.

Diagnosis

A tentative diagnosis can be based on the breed and clinical signs. Laryngoscopy and thoracic radiography are essential diagnostics. Thoracic radiographs are preferably performed before anesthesia, in order to detect possible associated aspiration pneumonia, tracheal and cardiac sizes, presence of vertebral anomalies, and hiatal hernia. Bronchoscopy and gastroscopy are necessary in order to assess the full scope of the existing abnormalities and are helpful in providing an accurate prognosis and the best treatment recommendation. However, selection of the diagnostic procedures should be based on each animal’s condition. It is important to recognize and treat accordingly those dogs that are susceptible to quickly developing life-threatening airway obstruction and collapse, possibly before the end of the examination. Indeed, in some dogs with strongly impaired oxygenation, manipulation is dangerous, and sedation if not anesthesia is required before starting diagnostic tests. Recovery from anesthesia should be closely monitored.

Management

Animals presented with life-threatening upper airway obstruction should be cooled, oxygenated, sedated, and in severe cases, anesthesia and intubation are immediately required. A tracheotomy might be indicated in the case of severe upper airway occlusion. In somewhat less critical cases, sedation, cooling, and oxygen are hence needed before starting complementary tests. In other less severe cases, medical therapy consisting of anti-inflammatory doses of short-acting glucocorticoids (prednisone 0.5 mg/kg q 12 h) will suffice and allows the owners to make an appointment for surgical treatment in better conditions. One should remember that apparently stable patients are susceptible to worsen suddenly, especially if the temperature is elevated, if the dog is stressed or excited. Some owners appear surprisingly abnormally confident (while you are not!), just because their pet has never been breathing “normally.” According to the results of a structured questionnaire, it appears that the extent and severity of clinical signs and their impact on quality of life greatly exceed our expectations.⁶

Therefore, most dogs require careful attention for the whole duration of the visit to your clinic.

Widening of stenotic nares, surgical removal of excessive soft palate, and everted laryngeal saccules are strongly advised surgical procedures,¹ at least in the absence of severe laryngeal and tracheal hypoplasia, which would make any treatment less successful. Novel elegant approaches, including removal of nasal conchae using laser-assisted turbinectomy (LATE) using a diode laser as part of a multilevel surgery, have more recently been described.⁷ Corrective surgical procedures should best be done as early in life as possible in order to decrease the consequences of long-term negative pressure on the airway structures. Once severe laryngeal dysfunction occurs, successful management is much more difficult. If tracheal hypoplasia with its associated ventilator impairment is still severe after reaching adult size (at 1 year of age), there is nothing else that can be done to remedy the situation. Stress, excitement, and weight gain must be avoided in these animals.

Digestive tract medical treatment combined with upper respiratory surgery appears to decrease the complication rate and improve the prognosis of dogs presented with upper respiratory syndrome.^1,8 Those treatments are widely used. In brachycephalic dogs, it is probable that regular microaspiration occurs, aggravating the inflammation of the mucosa of the laryngeal/nasopharyngeal areas. Accordingly, any possible cause of macro- or microaspiration, such as esophagitis or sliding hiatal hernia, should be addressed.

Prognosis

Prognosis depends on the severity of the abnormalities and the ability to surgically correct them.

A combination of primary and secondary changes can progress to life-threatening laryngeal collapse in many brachycephalic dogs. Early recognition of the primary anatomic abnormalities is essential since it allows the clinician to make early recommendations for medical and surgical management, which can improve the quality of life in affected animals. Factors that may increase the risk and further complicate the condition include obesity, overexcitement, and exercise.

Take Home Message

Some owners strongly underestimate the degree of breathing impairment in their pet. It is important to keep in mind that even apparently stable patients are susceptible to worsen suddenly in your practice.

The major impact that selective breeding for extreme brachycephalic features has on animal welfare should be emphasized.

References

1.  Dupre G, Heidenreich D. Brachycephalic syndrome. Vet Clin North Am Small Anim Pract. 2016;46(4):691–707.

2.  Packer RMA, Hendricks A, Tivers MS, Bum CC. Impact of facial conformation on canine health: brachycephalic obstructive airway syndrome. PLoS One. 2015;10(10):e0137496.

3.  Oechtering GU, Pohl S, Schlueter C, Lippert JP, Alef M, Kiefer I, et al. A novel approach to brachycephalic syndrome. 1. Evaluation of anatomical intranasal airway obstruction. Vet Surg. 2016;45(2):165–172.

4.  Bernaerts F, Talavera J, Leemans J, Hamaide A, Claeys S, Kirschvink N, et al. Description of original endoscopic findings and respiratory functional assessment using barometric whole-body plethysmography in dogs suffering from brachycephalic airway obstruction syndrome. Vet J. 2010;183(1):95–102.

5.  Poncet CM, Dupre GP, Freiche VG, Estrada MM, Poubanne YA, Bouvy BM. Prevalence of gastrointestinal tract lesions in 73 brachycephalic dogs with upper respiratory syndrome. J Small Anim Pract. 2005;46(6):273–279.

6.  Roedler FS, Pohl S, Oechtering GU. How does severe brachycephaly affect dog’s lives? Results of a structured preoperative owner questionnaire. Vet J. 2013;198(3):606–610.

7.  Oechtering GU, Pohl S, Schlueter C, Schuenemann R. A novel approach to brachycephalic syndrome. 2. Laser-assisted turbinectomy (LATE). Vet Surg. 2016:45(2):173–181.

8.  Poncet CM, Dupre GP, Freiche VG, Bouvy BM. Long-term results of upper respiratory syndrome surgery and gastrointestinal tract medical treatment in 51 brachycephalic dogs. J Small Anim Pract. 2006;47(3):137–142.