Degenerative Myelopathy in Dogs

There are many different neurologic diseases that can affect dogs, and common problems such as intervertebral disc disease and Wobbler’s syndrome are disorders that many owners have heard of before. But there are also uncommon disorders like degenerative myelopathy that are insidious, predictable, and deadly. Therefore, it is important to know the signs and what to do if they occur.   

Degenerative myelopathy (DM) is a progressive disease that affects the spinal cord of middle-aged to older dogs with the latter group being the most affected. Large breed dogs such as German Shepherds, Bernese Mountain Dogs, Golden Retrievers, and Boxers have a higher risk for developing DM, but the disease has been documented in smaller breeds such as Pugs and Corgis.

Dogs with DM end up with progressive hind limb paralysis because part of the spinal cord known as thewhitematter will gradually degenerate over several months. While not as painful as orthopedic diseases, it can look like your pup is in pain because he will eventually stop running and playing.

Like in humans, your dog’s spinal cord is comprised of white matter, a special type of tissue from the nervous system that acts like wiring to conduct signals to the rest of the body. The fatty tissue surrounding it known asmyelin is white, hence the name. DM gradually destroys the fibers contained within white matter and willdemyelinate the fibers, thus removing the protective fatty layer. This process is similar to how Lou Gehrig’s Disease or ALS affects humans.

At this time, scientists do not know why degenerative myelopathy occurs. However, they have identified a genetic mutation known asSOD-1 which appears to be a major risk factor. This means that breeding dogs can pass the gene onto their offspring. Dogs who develop DM inherit one mutated gene from each parent, but there are still some cases where dogs with two mutated copies never develop DM at all.  

Early signs of DM can be subtle such as hind pawknuckling, which is when a dog cannot feel sensation in their hind paw so the paw drags across the floor with digits curled inward. Skin lesions can develop on the tops of the hind paws because this dragging can lead to abrasions.

Dogs may also suffer fromataxia which is when the hind limbs seem uncoordinated as they walk. Even when standing still, you may notice your dog’s hips sway back and forth. He may also fall over easily when bumped or pushed.

Over the following few months, your dog’s hind limb weakness may become full-blown paralysis, where he is completely unable to walk without assistance. The paralysis can move up the spinal cord until it affects the forelimbs as well. Most dogs who develop degenerative myelopathy eventually succumb to it within a year or a little longer.  

It can be difficult to diagnose DM because initial clinical signs can mimic those of orthopedic disorders such as hip dysplasia. Your veterinarian may recommend baseline blood and urine testing to rule out infection, and imaging such as x-rays or CT and MRI may be recommended to rule out other spinal cord issues such as intervertebral disc disease.

Specialized testing such as cerebrospinal fluid analysis is also recommended, especially if other diagnostics are inconclusive. Also, DNA testing for the SOD-1 mutation can be performed. If your dog has two copies of the mutated gene and all other diagnostics are normal, it makes a diagnosis of DM more likely.

There is currently no effective treatment for a cure for dogs with degenerative myelopathy. A veterinary neurologist in Gainesville, FL, Dr. Roger Clemmons, performed studies on the effects of acetylcysteine and aminocaproic acid in dogs with DM, and the studies suggested that these compounds can help slow the progression of the disease. Steroids and vitamin supplements may also be effective.

For all dogs with DM, it is important to focus on weight management and exercise. Overweightdogs will have more difficulty with their mobility, and rehabilitation therapies such as deep tissue massage and passive range-of-motion exercises can help some dogs as their hind limb mobility worsens. If a dog with DM develops skin lesions on his paws or bed sores on his limbs, your vet will prescribe treatments.

Dogs with DM will also require assistance when going to the bathroom. Special harnesses are available to support dogs from their bellies so that owners can pick up their dog’s hind end easier. Some dogs may also benefit from the use of a special cart or wheelchair for mobility.

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Degenerative myelopathy is a progressive and incurable disease in dogs. Over time, dogs with DM are unable to walk on their hind limbs without help from their owners. It can be tricky to diagnose, but once it is suspected, it usually progresses in the same manner for all dogs, making it very predictable. It is important to focus on keeping your pup as comfortable as possible. If you suspect that your dog has neurologic signs of any kind, be sure to talk to your veterinarian right away.

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