Surgical Options for Canine Disk Associated Cervical Spondylomyelopathy

I was fortunate to moderate this year’s ACVIM Neurology panel discussion at National Harbor in Washington, DC on the topic of surgical options for disk associated cervical spondylomyelopathy (DACSM) in dogs, generically known as Wobbler’s disease. Each year a controversial topic is chosen for presentation at the neurology specialty day portion of the conference. The purpose is to provide a forum to stimulate open discussion on a topic between American and European diplomates, trainees and students.

Our panel this year included three experts in the field of neurosurgical approaches to DASCM: Dr. Filippo Adamo from East Bay Veterinary Specialists, Dr. Robert Bergman from Carolina Veterinary Specialists, and Dr. William Thomas from the University of Tennessee. Each one presented a specific case example with different surgical approaches as a springboard to the discussion.

As part of the presentation, the following questions were posed to help focus our discussion. As you would expect, there were divergent opinions but also commonalities.

Here is a summary of some of the questions that we addressed on disk associated cervical spondylomyelopathy (DACSM) in dogs:

• Clinical signs:

  • Is there a standardized clinical assessment and scoring system being used?
    A standardized neurological assessment and scoring system is currently not being used in the literature. However, a functional scoring system has been validated for use by Olby et al (Am J Vet Res. 2001 Oct;62(10):1624-8) that would be helpful to compare results between studies.
  • Is there breed specific pathophysiology resulting in differences in onset and progression of signs?
    Breed specific pathophysiology is likely present in the giant breed dogs (eg Great Danes), where rapid bone growth early in the first year of life has been associated with cervical stenosis due to articular facet hypertrophy. Controversy exists on whether this is a hereditary problem or enhanced by high protein diets fed to young dogs, or both.
  • What are best objective parameters to correlate to clinical signs and prognosis?
    The best objective parameters to correlate clinical signs with prognosis appear to be age of onset, severity of signs, rapidity of progression, and initial response to treatment. Mature dogs with slower progression of signs and that are ambulatory prior to surgery are deemed to have the better prognosis with surgery.

• Diagnosis

  • What is the best diagnostic method?
    MRI scanning is the recommended diagnostic test of choice. Both static (neutral position) and dynamic (distracted) sagittal and axial views of the cervical spine are recommended.

• Treatment

  • What are the parameters for decision on medical versus surgical approach?
    The question of when to recommend surgery versus medical management is quite controversial. A wide range of clinical response to medical management ranging from 38 to 81% has been reported. (Table 1). However, dogs that do not respond within the first month of treatment had a guarded prognosis for improvement, and euthanasia was most likely to occur within the first year of treatment in 85% of dogs in one study.
    The panel was in general agreement that if neurologic deficits were present associated with lesion on MRI scans, then surgery is their treatment recommendation over medical management.
  • Why do some dogs tolerate spinal decompression better than others?
    Decompressive cervical surgery, either ventral slot or dorsal laminectomy, does not address the instability aspect of this disease process. An excellent case example was presented that demonstrated resolution of disk -associated spinal compression but with progression of spinal cord damage, as noted by serial MRI scans.
  • When is decompression recommended?
    In general, a decompressive surgery is recommended when a static compressive lesion of the cervical spine is present that does not improve with simulated distraction, extradural disk rupture is present, or stenosis is present from facet and/or bone lesions.
  • When is stabilization is recommended?
    In general, cervical stabilization is recommended when a dynamic compressive lesion is observed on MRI scanning demonstrating improvement with simulated distraction and/or presence of moderate intramedullary T2W hyperintensity (associated with gliosis).
  • What is the preferred method of stabilization?
    Several methods of cervical stabilization are currently being used in veterinary medicine. No evidence currently exists that one method is superior in regards to outcome. Decision making is dictated by surgical preference and experience, cost of the procedure, patient size, and single or multiple sites to be surgically addressed.
    A newer technique of cervical disk arthroplasty (artificial disk replacement) was presented by Dr. Adamo that appears promising, as this procedure is less invasive, allows for quicker post-operative recovery, and multiple affected sites can be surgically addressed at one surgery.

• Prognosis

  • How can we best advise owners on short and longer-term prognosis?
    A review of the published literature of 235 cases treated with surgical intervention had a surprising close range of 70-72% listed as a successful outcome. However, there was a relative large degree of variability in the criteria of success, duration of observation, and when the paper was published (1 to 30 years).

In general, the panel agreed that there is a strong probability that surgery will improve the clinical outcome in dogs affected by DACSM provided that they are treated in the early stage of the disease with ambulatory function preserved.

Table 1. Summary of clinical outcome with medical management in dogs with DASCM.

Table 2. Summary of clinical outcome with surgical management in dogs with DASCM from literature review.