Thoracic Vertebral Canal Stenosis Associated with Vertebral Arch Anomalies in Small Brachycephalic Screw-Tail Dog Breeds

Objective The aim of this study was to describe clinical and imaging features of thoracic vertebral canal stenosis secondary to the hypertrophy of the vertebral lamina and articular processes in screw-tail brachycephalic dog breeds, to evaluate the prevalence of the malformation in a large group of screw-tail dog breeds and to determine if degree of stenosis is associated with presence of neurological signs. Study Design This is a retrospective multicentric study. Materials and Methods Clinical records of 185 screw-tail brachycephalic dogs (French Bulldogs, English Bulldogs, Boston Terriers) and Pugs were reviewed. Ten dogs with neurological deficits secondary to thoracic vertebral canal stenosis diagnosed on magnetic resonance imaging were identified (Group 1). Neurologically normal dogs (n = 175) of the same breeds underwent computed tomographic imaging of the thoracic vertebral column for other medical reasons (Group 2). Cross-sectional measurements were used to calculate a stenotic ratio. Results Group 1 consisted of three French Bulldogs, six English Bulldogs and one Pug. Eight were males. Most dogs presented with progressive non-painful pelvic limbs ataxia and paresis. Twenty stenotic sites were identified with the most common being T4-T5. Three of ten dogs were treated surgically and all had a good long-term outcome. In Group 2, 33 of 175 dogs had one or more stenotic sites with the most common being T2-T3. The degree of the stenosis was significantly higher in Group 1 (p = 0.019). A stenotic ratio of 0.56 had sensitivity and specificity of 67% to differentiate between dogs with and without neurological signs. Conclusion Cranial thoracic vertebral canal stenosis is observed predominantly in young male Bulldogs, but not all stenoses are clinically relevant.