In the June issue of JAVMA, you can find a promising clinical trial that found percutaneous/intradiscal injections of chondroitinase to be safe and effective for the treatment of acute onset paraparesis and paraplegia in 54 small dogs, presumptively resulting from acute intervertebral disk extrusion, including those with and without intact pain perception. This clinical trial addresses the fact that, currently, nonsurgical treatment is “widely considered to fall short of the standard of care.” Thus, to meet ethical animal welfare standards, the participants of this study were limited to dogs whose owners had financial constraints that eliminated cross-sectional imaging and decompressive surgery as treatment options. One of the authors, Dr. Nick Jeffery, a professor of neurology at Texas A&M School of Veterinary Medicine & Biomedical Sciences, shares with us some of his thoughts about this study.
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What is the most important takeaway from this clinical trial?
Dr. Jeffery: A nonsurgical therapy can lead to successful recovery of ambulation in a large proportion of dogs that become nonambulatory after acute thoracolumbar disk herniation.
Did any findings surprise you?
Dr. Jeffery: I think we were all a bit surprised that the results were so similar to those obtained following traditional decompressive surgery.
Recognizing that randomized controlled trials are necessary to assess the effectiveness of this nonsurgical intervention compared to surgery, will you be pursuing that next?
Dr. Jeffery: Yes, in general, I would hope so; but there are several potential obstacles that we need to address. The first question is whether, in the views of relevant stakeholders, there is clinical “equipoise”— i.e., widespread acceptance that there is sufficient uncertainty about comparative outcomes that a trial to determine whether one is superior needs to be run. This will partly depend on how convinced people are when they read our study! However, an important step in this direction is acceptance by the Royal College of Veterinary Surgeons in the UK (one of the study’s principal investigators is based in the UK) that intradiscal chondroitinase injection can be considered a viable treatment option for acute thoracolumbar disk herniation. There are also some more practical questions. For instance, there is a considerable cost disparity between this method of chemonucleolysis and conventional cross-sectional imaging and surgery, which impedes easy randomization. At present, we have taken the route of offering the 2 options to clients. We present the results of our study, a summary of the outcomes for standard imaging and decompressive surgery, along with the cost of each, and allow clients to decide which they prefer. While this is not a truly randomized study, each client will not be able to predict the outcome for their dog during their decision process.
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What should a general practitioner know about injectable chondroitinase as a potential future referral treatment option?
Dr. Jeffery: Unfortunately, because of the current status of this product, this procedure is only available at Texas A&M University (and University of Cambridge in the UK); so, clients would need to be reasonably close to one of these centers to receive the therapy. Our vision is that this product will become more widely available to general practitioners to administer to suitable dogs in the future, although general practitioners may prefer to use ultrasound-guided injections (rather than fluoroscopy).
There is not a product that has been approved by the FDA for this intended use in animals, but do you foresee that happening in the near future?
Dr. Jeffery: Yes, the manufacturer of the enzyme is currently working to acquire FDA approval. It is also plausible that a similar product used in humans in Japan will become available in the U.S., although it is likely to be expensive, perhaps prohibitively so for use in dogs.
Is there anything else you would like our readers to know that has not been mentioned?
Dr. Jeffery: We have considered the possibility that a future trial on the efficiency of chondroitinase therapy should include 3 arms (solely conservative treatment, chondroitinase injection, or decompressive surgery) because the comparative value of surgery versus conservative therapy has not been formally examined. Our study also strengthens the importance of veterinarians stressing that owners should allow plenty of time for nonambulatory dogs to spontaneously recover after acute thoracolumbar disk herniation.
The Study
Percutaneous enzymatic chemonucleolysis of intervertebral disks appears safe and effective in treatment of acute-onset paraparesis and paraplegia in small dogs.
Freeman P, Atiee G, Donoghue EM, Jeffery ND. JAVMA.
doi:10.2460/javma.24.12.0790