How can I talk about one of the most hopeless diseases of dogs without sounding hopeless? Like this:
Many cases of degenerative myelopathy are probably misdiagnosed
It starts with Google. Don’t get me wrong, I like Google. But put in either “weak back legs” or “dragging back legs” and you might only get the wikipedia page on degenerative myelopathy (DM).
You’ll see in a minute how wrong this is. Of course, vets don’t use Google, but they face their own major hurdles in getting an accurate diagnosis, as you’ll also see.
What Is Degenerative Myelopathy?
DM is a disease causing slowly progressive loss of neural tissue in the spinal cord. It starts with weakness or wobbliness (paresis or ataxia) in the back legs, eventually leading to complete paralysis. At this point the dog drags the back legs and cannot stand up on their own.
Further progression causes the same to occur in the forelimbs, plus urinary and faecal incontinence, and still further to respiratory failure. DM is now believed to be very similar to the human disease amyotrophic lateral sclerosis (ALS) or motor neurone disease.
The age of onset is late, with an average of 9 in large breed dogs and 11 in Pembroke Welsh Corgis. Large breed dogs diagnosed with DM go from mild signs to being unable to walk in 6 to 9 months. The same figure for smaller breeds might be slightly over 12 months.
Breeds Affected With DM
Degenerative myelopathy is now known to be a genetic disease. It was first described in the German Shepherd, and this remains the key dog breed we see with it. However, it can occur in almost any breed of dog, and especially these:
- Bernese Mountain Dog
- German Shepherd Dog
- Pembroke Welsh Corgi
- Finnish Lapphund
- Soft Coated Wheaten Terrier
- Cavalier King Charles Spaniel
- Rhodesian Ridgeback
- Boxer
Dogs usually only show the signs of DM after already breeding and passing it on. Therefore, although I am very critical of some breeding decisions, DM was nearly impossible to eradicate until the development of genetic testing.
Diagnosis Of Degenerative Myelopathy
Traditional diagnosis of DM has relied on identifying the signs in a dog of the right breed and age.
All affected dogs show at least some knuckling of the hind limbs (pictured here in a Cavalier King Charles). This is demonstrated by turning over the paw while supporting the body. An affected dog is unaware of the position of their paw and so does not return it, or does so slowly.
They will also often stumble and drag the hind legs. All these signs are typical of any spinal disease, such as:
- Intervertebral disc disease (type II)
- Lumbosacral stenosis
- Spinal tumours
It is often said that DM can be identified by a lack of pain, but this is very misleading. DM may be painless, but most dogs with severe chronic pain will display no signs. Therefore, I have also seen cases of severe hip dysplasia, cruciate ligament rupture or arthritis get mistaken for DM.
Degenerative myelopathy is described as a diagnosis by exclusion. The only way to prove it is to rule out all the other possibilities, which almost inevitably requires advanced imaging such as MRI. Sadly, this is unrealistic for most dog owners.
Does Misdiagnosis Matter?
My best clue that a dog doesn’t have degenerative myelopathy is when the disease progresses more slowly than expected. Getting the diagnosis wrong only matters if the other disease was treatable. This is certainly true for any painful condition.
Therefore, all dogs with suspected (but not confirmed) DM should at least go on a trial of pain medication. Even if they truly have DM, their signs may be caused by a mix of conditions including arthritis, and so some improvement is common.
The other neurological conditions are much harder to treat, but have possible positive outcomes with specialist surgery. The problem most dog owners face is that the investment in reaching the diagnosis is considerable, for such an uncertain outcome. That’s why, although I will offer referral as a best case, I won’t expect everyone to take it.
In 2020, here’s what I now recommend…
Genetic Testing For Degenerative Myelopathy
The genetic fault for most cases of DM is now well-understood and a commercial test is widely available around the world. Owners can even do it themselves. Here in Australia an SOD-1 swab costs under $100.
A positive test does not guarantee that a dog will be affected, but it’s a great tool for choosing which dogs to breed. That’s why I have hope for the future.
For dog owners facing the decision on whether to see a specialist it’s also potentially a great help. If a dog has a positive test, it makes the diagnosis of DM all the more likely. If on the other hand, the test is negative, or a dog has improved on a medication trial, then just maybe the disease is actually something that could be managed better if we knew what it was.
Treatment Of Degenerative Myelopathy
Even if your dog has DM, the outlook isn’t hopeless as long as you’re careful and know when to stop. They aren’t in pain so your big focus should be on maintaining quality of life.
I cannot stress this too many times: there is no treatment available for degenerative myelopathy. Not prednisolone or other corticosteroids, not vitamin E, not CBD oil. If you get a response to treatment, you should re-evaluate the diagnosis.
In the early phase of DM, much improvement in walking can be had just by adding more grip to slippery floors by the use of carpet runners etc. Then, as the back feet start to scuff on the ground, you need to prevent open sores from forming. There are plenty of people selling dog booties, or your vet can show you how to use products like ‘Vet Wrap’.
Negotiating stairs gets challenging so baby gates are a good idea. Special harnesses with back handles (such as the Rogz Explore®) are even available to help them go up and down or into cars. Physiotherapy and hydrotherapy have been shown to slightly prolong life.
As for the use of carts, my advice is to remember three important things:
- DM progresses quickly
- The front legs are affected not long after the back legs
- What you see on social media may not be the whole story
If you get a cart, you probably only have a short time before the front legs aren’t strong enough any more. I also worry a lot that the dogs aren’t always comfortable, so I ask owners to be very realistic and self-critical in using them.
Talking about euthanasia is a terrible place to finish, but it doesn’t have to be feared. Most dog owners who reach this point do so with their dogs retaining dignity and quality of life. They know they’re doing the right thing, and the actual event is much, much better than they ever expected or feared.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These blogs are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story!
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