Congenital Spinal Malformation in a Pug

02/Sep/2013


Written by Dr Andrew Dunn  BVSc (Hons), MACVSc,

Bubba, a four-month old male neutered Pug, presented with a history of worsening pelvic limb incoordination and weakness over several weeks, with recent onset mild faecal and urinary incontinence. Conservative management with confinement and anti-inflammatory doses of prednisolone for several weeks prior to referral had not caused a halt to the neurologic deterioration.

On presentation there was marked ambulatory paresis, exaggerated pelvic limb spinal reflexes and absent pelvic limb proprioceptive paw placing.  There was obvious mid thoracic spinal kyphosis. Plain radiographs revealed hemivertebra at T8 and T9 with a kyphosis of 95 degrees. CT myelogram (figures 1 and 2) confirmed marked ventral extradural compression over the deformed T8 and T9 vertebral bodies, and subluxation of the T7-8, 8-9, and 9-10 facet joints.

Bubba's owners decided to go ahead with decompressive surgery, in order to give him the best chance at a normal life. The goals of surgery were to decompress the spinal cord and prevent repeated spinal microtrauma and pain associated with the deranged vertebrae and luxated facets.

A dorsal laminectomy was performed, extending from T7-T9. Spinal stabilisation was performed with positive profile threaded 2mm pins placed bilaterally in vertebral bodies T7-10, bonded with PMMA cement (Figure 3).  Risks of surgery include poor purchase in vertebral bodies, pneumothorax, aortic perforation by threaded pins and difficulty closing skin over the mass of cement.

Surgery went to plan and Bubba was ambulatory the following morning. By day 20, there had been a marked reduction in paresis and improvement in faecal and urinary continence. Bubba continued to gradually improve and at a recent contact (nine months post surgery), the owner confirmed that Bubba's physical activity is at a normal level. He is even able to jump onto chairs!

Congenital vertebral malformations occur sporadically in Pugs and have been reported in many other small breeds and the occasional large breed. Age at presentation varies from four months to eight years, with the majority presenting in the first year of life. The thoracic spine is most often affected. Aikaw (2007 Vet Surg) reported on nine cases of congenital vertebral malformations. On presentation, three of these were paraplegic, two had non ambulatory paresis and four dogs had ambulatory paresis. Eight of the nine returned to or maintained the ability to ambulate long term (forty month follow-up) with the majority ambulating within seven days of surgery. Whilst there are no reports of outcomes with conservative management, experience tells us that many clinically normal Pugs have vertebral malformations as an incidental finding on thoracic radiographs. Some of these develop mild to moderate clinical signs and cope well long term with conservative management, whilst others continue to deteriorate. This latter group are surgical candidates, and based on the limited published reports, the outcomes are usually favourable.  

Congenital vertebral malformations in pugs are likely to be heritable and effected dogs and their first degree relatives should not be bred.

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