BACKGROUND

Brachycephalic dog breeds have multiple skull malformations which may lead to anatomical changes in the external auditory canal. It is our frequent observation that in the otoscopic examination of the external ear in these breeds we are unable to visualise the tympanic membrane as a consequence of extreme narrowing of the proximal ear canal. Additionally brachycephalic dogs reportedly are predisposed to otitis externa (OE) and otitis media.

OBJECTIVES

To characterizse the transition of the cartilaginous ear canal to the bony meatus acusticus externus using computed tomography (CT) and to investigate a possible association with OE in brachycephalic dogs.

MATERIALS AND METHODS

Seventy-five client-owned dogs [pugs (n = 20), French bulldogs (n = 55)] were included and assessed for OE using an owner questionnaire and otoscopic and cytological examinations. In dorsal plane CT scans, the diameter of the porus acusticus externus was measured using novel methodology. The results were compared with a normocephalic control group without preexisting otological disorders.

RESULTS

Brachycephalic dogs had a significantly smaller porus acusticus externus diameter (2.6 mm) than normocephalic dogs (5.0 mm). Of the brachycephalic dogs, 32% had OE yet this was not statistically significantly related to the diameter of the porus acusticus externus. Middle ear effusion (44%) and narrowing of the external ear canal (82.6%) were significantly more frequent in brachycephalic dogs. Only five of 150 eardrums could be visualised otoscopically.

CONCLUSIONS AND CLINICAL RELEVANCE

Malformation of the porus acusticus externus causes severe stenosis of the proximal ear canal in brachycephalic dogs. A connection between stenosis of the external auditory canal and OE could not be confirmed.