Vertebral Vascular Canal Dysplasia in Three Brachycephalic Breeds and Its Relationship With BOAS Grade.

The relationship between vertebral vascular canal dilation and raised intra-abdominal and intrathoracic pressures has been observed in humans. Vertebral vascular canal dysplasia (VVCD) has recently been reported as a vertebral anomaly in brachycephalic dogs. This retrospective, single-institutional study aimed to estimate the prevalence of VVCD number and type in thoracic vertebrae of three brachycephalic breeds and a non-brachycephalic control group, and to correlate the findings with the brachycephalic obstructive airway syndrome (BOAS) functional grading. Thoracic CT studies of French Bulldogs, English Bulldogs, and Pugs that had previously undergone BOAS assessment were retrospectively reviewed. Non-brachycephalic dogs that underwent a thoracic CT scan were matched by weight with the BOAS group and randomly selected to be part of the control group. The prevalence of VVCD involving ≥1 thoracic vertebra was 20% (6/30) in the control group, 56.9% (136/239) in French Bulldogs, 95.3% (41/43) in English Bulldogs, and 87.3% (55/63) in Pugs. French Bulldogs had significantly fewer vertebrae affected than the other brachycephalic breeds (p < 0.001). BOAS grade III dogs had more affected vertebrae; however, this was not statistically significant on multivariable analysis. The difference between the VVCD type and BOAS grades was not significant (p = 0.33). As BOAS severity was not correlated with either the presence or type of VVCD, no evidence was found to support a causative link between BOAS grading and the degree of vertebral vascular canal dilation. The potential role of raised intrathoracic or intra-abdominal pressures in the development of VVCD therefore remains hypothetical.