Prevalence of computed tomographic findings compatible with middle ear disease in brachicephalic dogs : a retrospective study (2012-2022)

Abstract

Brachycephalic dog breeds such as French and English Bulldogs, Pugs, Boxers or even Cavalier King Charles Spaniels are well known for their congenital health issues in relation to their shorter skull bones. The most obvious entity is the Brachycephalic Airway Obstruction Syndrome, but they also are predisposed to clinical otitis externa and media. Otitis media is an inflammation of the middle ear characterized by modifications of the tympanic bulla (TB) wall such as thickening and irregularity, lysis, or the presence of effusion within the lumen. It is of multifactorial pathogenesis, including the brachycephalic pattern. Recent studies have shown these breeds to have subclinical changes of the external auditory canal and tympanic cavity, incidentally found in cross sectional imaging, and all measured high prevalence of middle ear effusion and tympanic bulla thickening. However, it is still unclear if these modifications in brachycephalic breeds are physiological or secondary to early stages of otitis media. The aim of this study is to compare a subpopulation of Belgian brachycephalic dogs with non-brachycephalic breeds, to assess the presence or not of subclinical middle ear disease in computed tomography (CT), and to try to find a link between these middle ear anomalies and the brachycephalic pattern. A retrospective, observational study was conducted at the Clinique Veterinaire Universitaire of the University of Liege (ULiege). A total of 53 dogs presented for CT examination of the head without any history of ear disease were included and divided into two groups. The presence of soft tissue attenuating material/fluid in the tympanic bullae was estimated subjectively and the thickness of the ventral tympanic bulla wall, the soft palate and the cranium wall were measured. Brachycephalic dogs had a significantly thicker tympanic bulla (with or without effusion), thicker soft palate and thicker cranium wall. In addition they showed significantly more effusion than non-brachycephalic breeds and their TB were significantly thicker when effusion was observed. This study shows that incidental middle ear anomalies found on CT in brachycephalic dogs are on one hand due to their breed conformation, as previously described, but also seem aggravated by a higher prevalence of middle ear diseases.