Clinical features and MRI characteristics of presumptive constrictive myelopathy in 27 pugs

Constrictive myelopathy has been described in pugs with paraparesis and is characterized by fibrous connective and granulation tissue within the dura mater causing spinal cord compression and focal gliosis. An association between constrictive myelopathy and caudal articular process (CAP) dysplasia is suspected; however, some studies have reported CAP dysplasia as an incidental finding. The imaging appearance of constrictive myelopathy is currently limited to a small number of cases. The aim of this multicenter, retrospective, descriptive study was to detail the magnetic resonance imaging (MRI) characteristics and to correlate these with clinical signs of presumptive constrictive myelopathy in pugs. Medical databases from five veterinary referral hospitals were reviewed to identify pugs with pelvic limb ataxia and paresis, that had a complete record of signalment, neurological examination, and MRI of the thoracolumbar spinal cord. The exclusion criteria were pugs with other conditions, such as unequivocal subarachnoid diverticula, hemivertebrae causing vertebral canal stenosis, intervertebral disc extrusions/protrusions, and multifocal/diffuse lesions. Twenty-seven pugs met the inclusion criteria. All cases were ambulatory with paraparesis and ataxia. Nearly 60% were incontinent. Magnetic resonance imaging revealed a focal myelopathy in all cases showing one or more of the following lesions: CAP dysplasia (25/27), focal subarachnoid space irregular margination (26/27) with circumferential or dorsal contrast enhancement (10/12), and a symmetric V-shaped ventral extradural lesion (23/27). This study describes specific MRI features of pugs with presumptive constrictive myelopathy, which authors hypothesize to be a consequence of chronic micro-motion. Our results may help in diagnosing and subsequently treating this condition, which may warrant vertebral stabilization.