Effectiveness of cervical hemilaminectomy in canine Hansen Type I and Type II disc disease: a retrospective study.

Medical records of 41 dogs, including 15 small breed dogs (<15 kg) and 26 large breed dogs (>15 kg), with cervical intervertebral disc disease (IVDD) that underwent a hemilaminectomy were reviewed. Dogs were diagnosed using myelography, computed tomography/myelography, or MRI, and dogs were classified as having either Hansen Type I disc extrusion or Hansen Type II disc protrusion located ventrally, ventrolaterally, or laterally within the cervical spinal canal. The most common clinical presentation was ambulatory tetraparesis and/or lameness (44%). The most affected sites for cervical IVDD were between the sixth and seventh cervical vertebrae (C6-C7; 78% of Hansen Type II discs) and C2-C3 (86% of Hansen Type I discs). Treatment was effective in 88% of dogs. Five large breed dogs (12%) did not improve. In dogs with a Hansen Type I disc extrusion, clinical signs improved in 96% of the cases. In dogs with a Hansen Type II disc protrusion, an excellent and good outcome was seen in 47% and 32% of cases, respectively. Outcome was significantly better for small breed dogs and dogs with Hansen Type I disc disease compared with large breed dogs and dogs with Hansen Type II disc disease.

Association of spinal cord compression seen on magnetic resonance imaging with clinical outcome in 67 dogs with thoracolumbar intervertebral disc extrusion.

OBJECTIVES: To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. METHODS: Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. RESULTS: Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219.7, range 14.3 to 84.9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. CLINICAL SIGNIFICANCE: The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study.

Hansen type I disk disease at T1-2 in a dachshund.

A 7-year-old Dachshund was presented with chronic left thoracic limb lameness and acute neurological deficits to the hind limbs following trauma. A lesion was suspected between C7 and T2 on the basis of neurological examinations. Radiography and myelography identified a calcified intervertebral disk at C7-T1 and an extradural unilateral compressive lesion at T1-2. Computed tomography scans of the cranial thoracic spine revealed extrusion of disk material from the T1-2 intervertebral space resulting in marked spinal cord compression. Intervertebral disk disease is rarely reported at this location. The neurological condition deteriorated after a second myelogram, which was done to examine the thoracolumbar spine. A modified dorsal decompression of T1-2 was performed. The dog was euthanased due to further neurological deterioration 8 days after surgery.

Incidence of contralateral versus ipsilateral neurological signs associated with lateralised Hansen type I disc extrusion.

Asymmetrical neurological signs were noted in 50 dogs presenting with Hansen type I thoracolumbar disc extrusion. Thoracolumbar myelograms and surgical decompression were performed in all cases. Dogs were divided into two groups (acute and chronic) based on the duration of clinical signs prior to presentation to the University of Georgia. Lateralising extradural cord compressive lesions were noted on all myelograms. In the acute group, 35 per cent of the dogs had asymmetrical neurological signs contralateral to the myelographic and surgical lesion, while in the chronic group only 11 per cent had neurological signs contralateral to the lesion. There was found to be no significant difference in frequency of contralateral asymmetrical clinical signs between the two groups (Fischer's exact test; P = 0.095). The high frequency of contralateral signs documents the importance of thoracolumbar myelography for accurate localisation of the disc material before decompressive surgery.