Computed tomographic morphometry of tympanic bulla shape and position in brachycephalic and mesaticephalic dog breeds

Abstract

Anatomic variations in skull morphology have been previously described for brachycephalic dogs; however there is little published information on interbreed variations in tympanic bulla morphology. This retrospective observational study aimed to (1) provide detailed descriptions of the computed tomographic (CT) morphology of tympanic bullae in a sample of dogs representing four brachycephalic breeds (Pugs, French Bulldogs, English Bulldog, and Cavalier King Charles Spaniels) versus two mesaticephalic breeds (Labrador retrievers and Jack Russell Terriers); and (2) test associations between tympanic bulla morphology and presence of middle ear effusion. Archived head CT scans for the above dog breeds were retrieved and a single observer measured tympanic bulla shape (width:height ratio), wall thickness, position relative to the temporomandibular joint, and relative volume (volume:body weight ratio). A total of 127 dogs were sampled. Cavalier King Charles Spaniels had significantly flatter tympanic bullae (greater width:height ratios) versus Pugs, English Bulldogs, Labrador retrievers, and Jack Russell terriers. French Bulldogs and Pugs had significantly more overlap between tympanic bullae and temporomandibular joints versus other breeds. All brachycephalic breeds had significantly lower tympanic bulla volume:weight ratios versus Labrador retrievers. Soft tissue attenuating material (middle ear effusion) was present in the middle ear of 48/100 (48%) of brachycephalic breeds, but no significant association was found between tympanic bulla CT measurements and presence of this material. Findings indicated that there are significant interbreed variations in tympanic bulla morphology, however no significant relationship between tympanic bulla morphology and presence of middle ear effusion could be identified.

Skin and ear health in a group of English bulldogs in Finland – a descriptive study with special reference to owner perceptions

“…It is known that narrow conformation of the ear canals may predispose to otitis, but an abnormal OTIS‐3 score was a surprisingly rare finding in the dogs in our study. Previous studies have demonstrated a higher prevalence of subclinical middle ear effusion in brachycephalic dogs of various breeds . However, only a small number of dogs in these studies were EBs.…”

“…Brachycephalic dog breeds, such as the EB, have a congenitally flattened facial anatomy. This conformation is associated with several malformations of the head and neck and also has been shown to affect the structure of the ear . Brachycephalic dogs have been reported to possess a significantly thicker tympanic bulla wall and a lower tympanic bulla volume than nonbrachycephalic dogs .…”

“…This conformation is associated with several malformations of the head and neck and also has been shown to affect the structure of the ear. [12][13][14] Brachycephalic dogs have been reported to possess a significantly thicker tympanic bulla wall 12 and a lower tympanic bulla volume 12,13 than nonbrachycephalic dogs. 12,13 Fluid accumulation in the middle ear as an incidental finding appears to be more common in brachycephalic breeds.…”

“…[12][13][14] Brachycephalic dogs have been reported to possess a significantly thicker tympanic bulla wall 12 and a lower tympanic bulla volume 12,13 than nonbrachycephalic dogs. 12,13 Fluid accumulation in the middle ear as an incidental finding appears to be more common in brachycephalic breeds. [12][13][14] Narrow horizontal ear canals, possibly due to conformational abnormality, are a common anecdotal finding in clinical practice and may be a predisposing factor for otitis.…”

“…12,13 Fluid accumulation in the middle ear as an incidental finding appears to be more common in brachycephalic breeds. [12][13][14] Narrow horizontal ear canals, possibly due to conformational abnormality, are a common anecdotal finding in clinical practice and may be a predisposing factor for otitis. 15 Skin and ear conditions may affect not only the wellbeing of the dog but also the quality of life (QoL) of the dog's owner.…”