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.