‘Canine degenerative myelopathy’, also known as CDRM or ‘chronic degenerative radiculomyelopathy’ is a disease that affects your dog’s spinal cord, resulting in hind limb weakness and paralysis. The human equivalent most similar is amyotrophic lateral sclerosis (ALS), also known as ‘Lou Gehrig’s disease.’ If you have been unfortunate enough to care for a dog affected by CDRM, you may already be aware of the ins and outs of this progressive condition. This article will dive into the cause of CDRM, the clinical signs, diagnostic options and prognosis.
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What is CDRM?
CDRM is a non-painful progressive disease which ultimately leads to hind limb paralysis in dogs. I think of CDRM as being quite similar to motor neurone disease, as in CDRM cases they experience a failure of nerve signal transmission to and from the limbs. This transmission failure occurs due to death of the nerve cells carrying the signal to and from the limbs.
Do we know what causes CDRM?
CDRM has been discovered to be an inherited condition spread by a specific genetic mutation. I won’t explore this area in too much detail due to complicating factors, however, it is an autosomal recessive condition. This means that if their offspring receive one gene from the mother and one gene from the father, they are at a greater risk of developing CDRM when they are older. Interestingly, dogs which do not inherit this mutated gene may still develop this condition so they are not completely risk free.
The mutated gene plays a role in destroying ‘free radicals’ in the body. Free radicals exist naturally as part of the body’s natural defence system (Crisp et al, 2013). However, when free radicals are produced in large quantities, such as in CDRM patients, they lead to cell death and degeneration.
Which dogs are affected by CDRM?
This condition is over-represented in German Shepherd dogs. Previously, people used to refer to this condition as ‘German Shepherd Dog Disease’ simply because it occurred so commonly and it was first reported in this breed in 1973 (Neeves and Granger, 2015). CDRM is now recognised more and more in other breeds too including the Novia Scotia Duck Tolling Retriever. However, the condition is still seen more often in larger breed dogs and there are currently no sex predilections been identified.
CDRM usually shows its first presenting signs in patients between six and fourteen years of age.
What are the clinical signs in dogs?
Recognising this condition can prove quite challenging to Vets because the early clinical signs resemble the same characteristics as other conditions such as chronic osteoarthritis, hip dysplasia or intervertebral disc disease (IVDD). And of course, one of the most common causes of hind limb weakness in older dogs (especially German Shepherds) is arthritis and joint disease.
Below lists the most common clinical signs of CDRM (this list is not exhaustive):
- Loss of hind limb coordination/ataxia
- No identifiable areas of pain during the physical examination from your Vet. CDRM is usually associated with weakness rather than ‘pain.’ However, sometimes CDRM patients can appear painful if they are also arthritic.
- Crossing and knuckling of hind limbs
- Dragging paws
- Difficulty toileting or voiding urine – problems with bowel and bladder control usually only occur as the disease progresses
- Hind limb weakness or full paralysis (inability to move)
- Hind limb muscle wastage/atrophy
How is it diagnosed?
Diagnosis of CDRM is not as straightforward as it may seem. Diagnosis in CDRM patients is often via a diagnosis of exclusion. This means that diagnostics such as blood tests, testing of cerebrospinal fluid, radiographs and more advanced imaging such as MRI (magnetic resonance imaging) will be conducted in order to rule out other conditions including osteoarthritis, IVDD, toxicities and inflammatory diseases.
The incredible advancement of the field of Veterinary medicine now enables genetic testing for the CDRM gene in dogs. Additionally, it is extremely important to understand that this test will not guarantee that your dog will not develop CDRM, but it will evaluate your dog’s risk based on the presence of the affected gene.
Can CDRM be treated?
Sadly CDRM cannot be treated. CDRM is described as a ’progressive’ disease meaning that it will worsen and be fatal to your dog. Understandably, this can be very difficult for people to come to terms with. Following a diagnosis of CDRM, we will have an ultimate aim and goal to keep your dog as active, mobile, supported and happy for as long as this is possible and achieved.
Unfortunately, this disease will progress to complete hind limb paralysis (and sometimes fore limbs are affected too) and your dog will be unable to walk, a situation which is extremely distressing for both your canine friend and of course you as their caregiver. The overall prognosis for CDRM patients is poor.
Often, people will decide to follow the path of palliative and supportive care until this management plan is no longer successful due to natural disease progression. In some CDRM cases, hydrotherapy and physiotherapy sessions may be beneficial to keep their limbs moving and remain as supple as possible. Adaptations within their home environment may also be essential and sling support may be advised by your Veterinarian. Your Veterinarian will provide support and guidance into the most appropriate treatment options for your dog. Euthanasia is never an easy decision but once CDRM has progressed and has led to your dog irreversibly being unable to walk, this often sadly remains the kindest option for your beloved dog.
Conclusion
To conclude, I hope that this article has raised some awareness about this condition. There are thankfully not many conditions within Veterinary medicine which are not treatable at all, however, CDRM sadly remains one of these irreversible diseases. If you notice any of the above clinical signs in your dog please do not hesitate to contact your Vet to explore this further and remember that other conditions can also present in a similar way.
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