Abstract
BackgroundA 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 spinal cord 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. Univariable non-parametric tests investigated the association between the clinical parameters and evidence of extra- or intra-dural spinal cord compression on MRI.Results18 Pug dogs were included. The median age was 106 months with median duration of clinical signs 5 months. All presented with variable severity of spastic paraparesis and ataxia; 50% suffered urinary/faecal incontinence. In all cases, MRI revealed a focal increase in T2-weighted signal intensity within the spinal cord at an intervertebral level where bilateral CAP dysplasia was present; this was bilateral aplasia in all but one case, which had one aplastic and one severely hypoplastic CAP. MRI lesions were associated with spinal cord compression in all but one case; intervertebral disc protrusion resulted in extra-dural compression in 10 (56%) cases; intra-dural compression was associated with a suspected arachnoid diverticulum in 4 (22%) cases and suspected pia-arachnoid fibrosis in 3 cases (17%). There was no association between clinical parameters and a diagnosis of intra-dural vs extra-dural compression. CAP dysplasia occurred at multiple levels in the T10–13 region with bilateral aplasia at T11–12 most often associated with corresponding spinal cord lesions on MRI.ConclusionsAll 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 CAP aplasia 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.
Highlights
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
Pug dogs with constrictive myelopathy were diagnosed with intra-dural spinal cord compression associated with fibrous adhesions originating from the dura mater that adhere to the pia; chronic, low-grade vertebral instability associated with CAP dysplasia has been proposed to contribute to arachnoid fibrosis [4]
Information from medical records retrieved for analysis included patient age, sex, neutering status, duration of clinical signs, severity of neurologic deficits using a 15-point functional scoring system previously published elsewhere [10] that was assigned at the time of examination, the presence or absence of urinary and/ or faecal incontinence and whether the Super-Oxide Dismutase (SOD)-1 genetic test was performed and the result thereof
Summary
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. ‘Constrictive myelopathy’ is a spinal cord disease previously described in Pug dogs, which appears to be associated with caudal articular process (CAP) dysplasia of the post-diaphragmatic thoracic vertebrae [4]. In a recent study utilising CT examinations from neurologically normal Pug dogs, a greater tendency for CAP aplasia (as opposed to hypoplasia) in the post-diaphragmatic region of the thoracic spine in comparison to other similar dog breeds, was identified [9]. This could result in an increased likelihood of CAP dysplasia being clinically relevant in this breed
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