Abstract
Background: A retrospective case series study was undertaken to describe the magnetic resonance imaging (MRI)findings in Pug dogs with thoracolumbar myelopathy and concurrent caudal articular process (CAP) dysplasia. Electronic clinical records were searched for Pug dogs who underwent MRI for the investigation of a T3-L3 spinalcord segment disease with subsequent confirmation of CAP dysplasia with computed tomography between January 2013 and June 2017. Clinical parameters age, gender, neuter status, body weight, urinary or faecal incontinence, severity and duration of clinical signs were recorded. MRI abnormalities were described. Univariablenon-parametric tests investigated the association between the clinical parameters and evidence of extra- or intra-dural spinal cord compression on MRI. Results: 18 Pug dogs were included. The median age was 106 months with median duration of clinical signs 5months. All presented with variable severity of spastic paraparesis and ataxia; 50% suffered urinary/faecalincontinence. In all cases, MRI revealed a focal increase in T2-weighted signal intensity within the spinal cord at anintervertebral level where bilateral CAP dysplasia was present; this was bilateral aplasia in all but one case, whichhad one aplastic and one severely hypoplastic CAP. MRI lesions were associated with spinal cord compression in allbut one case; intervertebral disc protrusion resulted in extra-dural compression in 10 (56%) cases; intra-duralcompression was associated with a suspected arachnoid diverticulum in 4 (22%) cases and suspected pia-arachnoidfibrosis in 3 cases (17%). There was no association between clinical parameters and a diagnosis of intra-dural vsextra-dural compression. CAP dysplasia occurred at multiple levels in the T10–13 region with bilateral aplasia atT11–12 most often associated with corresponding spinal cord lesions on MRI. Conclusions: All Pugs dogs in this study were presented for chronic progressive ambulatory paraparesis;incontinence was commonly reported. Although intervertebral disc disease was the most common radiologic diagnosis, intra-dural compression associated with arachnoid diverticulae/fibrosis was also common. Bilateral CAPaplasia was present in all but one Pug dog at the level of MRI detectable spinal cord lesions. A causal relationship between CAP dysplasia and causes of thoracolumbar myelopathy is speculated but is not confirmed by this study.