Feline Brachycephalic Airway Syndrome – NAVLE Study Guide

Overview and Clinical Importance

Brachycephalic Obstructive Airway Syndrome (BOAS) is a chronic, progressive condition affecting flat-faced cat breeds characterized by upper airway abnormalities that cause respiratory obstruction. Unlike dogs, BOAS in cats is underdiagnosed and often presents with stenotic nares as the predominant primary abnormality. Persian, Himalayan, Exotic Shorthair, Scottish Fold, and Burmese cats are most commonly affected.

The syndrome results from selective breeding for shortened skull bones (brachycephaly) without corresponding reduction in soft tissue volume, leading to constricted nasal passages and potential obstruction of the pharynx and larynx. Understanding this condition is essential for the NAVLE as it tests your ability to recognize breed-specific presentations, differentiate primary from secondary abnormalities, and select appropriate diagnostic and therapeutic interventions.

Etiology and Pathophysiology

Genetic and Conformational Basis

Brachycephaly results from early ankylosis of basicranial epiphyseal cartilage, causing chondrodysplasia of the longitudinal skull axis. This skeletal shortening occurs without corresponding reduction in soft tissue volume, creating a mismatch that leads to airway obstruction. The degree of brachycephaly correlates with the severity of clinical signs.

Predisposed Breeds

Primary Anatomical Abnormalities

Stenotic Nares (Most Common in Cats)

Stenotic nares are abnormally narrowed nostrils that restrict airflow to the lungs. In cats, stenotic nares are often the predominant or sole abnormality, unlike in dogs where multiple abnormalities typically coexist.

Other Primary Abnormalities

Elongated Soft Palate: The soft palate extends beyond the epiglottis, partially obstructing the tracheal entrance. Rarely documented in cats but can cause severe respiratory distress and non-cardiogenic pulmonary edema.

Hypoplastic Trachea: A trachea with smaller than normal diameter, reducing total air volume per breath. Variable prognosis; cannot be surgically corrected.

Nasopharyngeal Turbinates: Aberrant extension of nasal turbinate tissue into the nasopharynx, increasing airway resistance.

Secondary Abnormalities

Everted Laryngeal Saccules: Chronic increased respiratory effort causes negative pressure, pulling the laryngeal saccules into the airway lumen and further obstructing airflow.

Laryngeal Collapse: Progressive weakening and collapse of laryngeal cartilages due to chronic airway obstruction. Indicates advanced disease.

Clinical Signs and Presentation

Respiratory Manifestations

Non-Respiratory Manifestations

Gastrointestinal Signs: Vomiting, regurgitation, and aerophagia are common due to chronic negative intrathoracic pressure. BOAS has been linked to hiatal hernia in 29% of affected cats.

Otologic Signs: Cats with nasal disease have significantly higher risk of bulla effusion and middle ear disease due to Eustachian tube dysfunction.

Ocular Signs: Chronic epiphora (tear staining) due to nasolacrimal duct obstruction from dorsorotation of facial bones.

Cardiovascular: Echocardiographic abnormalities have been documented in all brachycephalic cats studied, likely due to chronic hypoxia and increased cardiac workload.

Diagnosis

Diagnostic Approach

Diagnosis of feline BOAS is primarily based on breed, clinical signs, and physical examination. Stenotic nares can be diagnosed via visual inspection in awake patients. Assessment of the soft palate, larynx, and pharynx requires heavy sedation or general anesthesia.

Physical Examination Findings

• Visual identification of narrowed nostrils (stenotic nares)
• Medial collapse of alar wings during inspiration
• Increased respiratory noise (stertor/stridor)
• Open-mouth breathing or increased respiratory effort
• Chronic epiphora and facial fold dermatitis

Diagnostic Testing

Treatment

Medical Management

Medical management is palliative only and does not correct underlying anatomical abnormalities. It is appropriate for mild cases or as stabilization before surgery.

Surgical Treatment

Surgery is the treatment of choice when anatomical abnormalities interfere with breathing. Early intervention prevents progression to secondary abnormalities and provides better outcomes.

Stenotic Nares Correction (Rhinoplasty)

Soft Palate Resection (Staphylectomy)

Surgical shortening of an elongated soft palate to prevent obstruction of the tracheal entrance. Rarely needed in cats compared to dogs. The palate is shortened to the level of the epiglottis using scissors, electrosurgery, or laser.

Laryngeal Saccule Resection

Removal of everted laryngeal saccules to eliminate laryngeal obstruction. Performed when secondary changes are present.

Post-Operative Care and Monitoring

• Flow-by oxygen during recovery
• Close monitoring for airway swelling (highest risk in first 24 hours)
• Elizabethan collar for 10-14 days to prevent self-trauma
• Pain management (opioids, NSAIDs)
• Soft diet following soft palate surgery
• Suture removal at 10-14 days if non-absorbable sutures used

Prognosis

Memory Aids

BOAS in Cats = "SNORE"

S - Stenotic nares (PRIMARY abnormality in cats)

N - Nasal breathing obligate (open-mouth breathing NEVER normal)

O - Obesity worsens symptoms

R - Rhinoplasty is treatment of choice

E - Early surgery = better prognosis

Feline vs. Canine BOAS = "VENT vs. WING"

Cats: VENTral skin fold obstruction at nasal floor

Dogs: Alar WING deviation and thickening