Introduction

Clinical signs of upper respiratory syndrome in the brachycephalic dogs (BD) usually include snoring, inspiratory dyspnea, exercise intolerance and stridor, cyanosis or even syncopal episodes in more severe cases. These problems usually aggravate with stress, exercise or heat. Vomiting or saliva regurgitation are also frequently encountered.

Anatomic Anomalies and Functional Consequences

Several anatomic abnormalities can be found in the brachycephalic dogs (BD). The cartilaginous skeleton of the external nares is usually shorter, thicker and medially displaced, secondarily obstructing the nostrils. The size, shape and position of the conchae are modified, leading to potential intra-nasal stenosis. The soft palate which normally extends to the top of the epiglottis can extend up to 1 to 2 cm beyond. On a radiographic examination or CT, one can readily see that in many cases, the soft palate is not only overlong but also over-thick. A hyperplastic tongue is also frequently encountered. In many BD, laryngeal ventricles can be seen protruding into the laryngeal lumen. Finally, the trachea of some brachycephalic dogs (mainly English Bulldogs) is hypoplastic, which further decreases the air flow. These anatomical anomalies are responsible for a multifocal obstruction of the upper airways which has secondary functional consequences on laryngeal function. Given their narrowed nostrils and nasal passages, brachycephalic dogs must produce higher negative pressure to breathe properly. This can be clinically observed on the nostrils but also on the larynx. The cuneiform and corniculate cartilages are drawn into the glottal opening following increased inspiratory efforts causing laryngeal collapse. In these cases, an inspiratory stridor and even suffocation can be observed. In such patients, the laryngeal ventricles are usually everted into the laryngeal lumen. Many owners describe signs of regurgitation or vomiting when their BD becomes excited or suffers of respiratory distress. In these instances, signs of respiratory distress are usually relieved when the dog vomits or regurgitates large packs of "foam". In one study on 73brachycephalic dogs suffering from upper airway syndrome, respiratory and digestive signs were graded as minimal (grade 1), moderate (grade 2), or severe (grade 3) according to their frequency and severity. A correlation between gastric and severity of respiratory signs was demonstrated (p = 0,059).

Diagnostic

Diagnosis is based on breed, age and clinical signs. Radiographic, CT, or MRI examinations are used to assess the length and thickness of the soft palate, as well as other mucosal hyperplasia or nasal anomalies. Thoracic radiographs can be recommended in order to diagnose stenotic trachea, aspiration pneumonia and secondary right-sided heart failure. Endoscopy should be conducted as a basic diagnostic work-up: after removal of the endotracheal tube, the motion of the arytenoid cartilages and position of the ventricles are evaluated. In some specific breeds, antegrade and retrograde rhinoscopy are recommended to evaluate the presence of abnormal conchae. During the same procedure, upper gastro-intestinal endoscopy is usually recommended if digestive signs are present.

Surgical Treatment

Several techniques of rhinoplasty have been developed. They all aim at opening the lateral wings of the nostrils. Removing this part actually increases the diameter and contributes to improvement of the nasal flow. However, a new vestibuloplasty technique is under investigation and seems to alleviate the obstruction more distally.

Current techniques for treatment of elongated soft palate involve resection of the overlong part. A new technique "The folded flap palatoplasty" has been developed in order to address both the pharyngeal and the laryngeal obstruction. This technique achieves a marked reduction of the soft palate thickness, thereby relieving the nasopharynx and oropharynx from obstruction.

An endoscopic laser removal of abnormal caudal conchae has been proposed and actually relieves the intra-nasal obstruction, should it be present.

Since it is postulated that laryngeal collapse and ventricular eversion are more likely secondary events due to increased respiratory depression, relief of proximal obstruction should alleviate signs of laryngeal collapse. In cases where clinical signs are not improved after rhinoplasty and palatoplasty, lateralization of one of the arytenoid cartilages can be attempted if the cartilages are stiff enough. Laser removal of the ventricles as well as laser "laryngoplasty" seems to carry promising results in patients with a flaccid larynx.

Concurrent medical treatment of gastro-esophageal signs should be proposed as it has been shown to improve the overall prognosis.

References

1.  Findji L, Dupré G (2008) Folded flap palatoplasty for treatment of elongated soft palates in 55 dogs Wien.Tierärztl.Mschr.95:56-63.

2.  Oechtering TH, Oechtering GU, Noeller (2007) Structural characteristics of the nose in brachycephalic dog breeds Tierarzt Prax 35:177-187.

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

4.  Poncet CM, Dupre GP, Freiche VG, et al. (2005) Long-term results of upper respiratory syndrome surgery and gastrointestinal tract medical treatment in 51 brachycephalic dogs. J Small Anim Pract 47(3):137-142.