What is Degenerative Myelopathy in Dogs?
Degenerative Myelopathy (DM), is a condition of the spinal cord in dogs that eventually leads to loss of control of the hind end. This disease might not be as common as something like arthritis, but for affected pets, the symptoms are significant.
We understand that the underlying process of DM is a slow and progressive degeneration of the white matter of the spinal cord. White matter is found in both the brain and the spinal cord, and its primary job is to make sense of and send signals to other parts of the body.
Symptoms of Degenerative Myelopathy in Dogs
Degenerative Myelopathy typically has symptoms like loss of sensation, weakness, or even paralysis. Symptoms of Degenerative Myelopathy in dogs can include:
Ataxia in the hind end (wobbly or drunken-type gait)
Dragging the hind feet or catching the tops of the feet when walking
General hind limb weakness
Trouble standing or supporting weight for long periods of time
Swaying from side to side while standing
Falling over easily
Knuckling over on the back feet
Hind-end paralysis in advanced cases
Stages of Degenerative Myelopathy in Dogs
It’s not uncommon for DM to resemble other diagnoses in its early stages. This is because the symptoms can be similar to those of dogs with conditions like arthritis.
Dogs may look like they are having trouble getting up in the hind end, making owners think they are showing signs of pain. Later on, symptoms are progressive and make us more suspicious of something like DM (or other diseases of the spinal cord).
Over time, symptoms will unfortunately progress to the point where they will have a heavy impact on the pet's quality of life. This includes a decline in mobility and losing the ability to control their bladder and bowel.
What Causes Degenerative Myelopathy in Dogs?
We’ve been able to determine that there is a genetic component to developing DM. In particular, a mutation of the SOD-1 gene (superoxide dismutase) is known to play a role. Dogs that have two abnormal copies of this gene are at risk for developing the disease.
Which Dog Breeds are Prone to Degenerative Myelopathy?
By far the most commonly diagnosed breed is the German Shepherd and those crossed with them. There is also a higher incidence in Collies, Corgis, Poodles, and Boxers, among others.
DM is typically a disease of older dogs, usually over the age of eight years, though it can be diagnosed earlier.
How is Degenerative Myelopathy Diagnosed?
DM is a disease that doesn’t have an easy diagnostic path. A suggested diagnosis of DM requires ruling out several other issues along the way, in addition to reviewing the pet's history, physical exam results, and clinical symptoms.
Most often, veterinarians will start the process by performing a general blood panel to check overall organ function and blood cell counts. Basic imaging like x-rays will also likely be performed to look for signs of hip dysplasia, severe hip arthritis, or other bone changes such as tumors.
If these tests are normal, referral to a specialist (a veterinary neurologist) is the next step. Genetic testing for the SOD-1 gene mutation can be done as a suggestive piece of evidence for DM. For a pet to develop DM, they must have two copies of this mutated gene.
More advanced testing can include sampling of the cerebrospinal fluid, imaging with an MRI, and biopsies. Samples of the spinal cord are needed to confirm this diagnosis and are not performed often due to practical reasons (i.e. we do not take the samples in live animals). This means that typically a diagnosis of DM is presumptive (i.e., we consider it highly likely based on the pet's history, physical exam, blood tests, and genetic testing).
Can Degenerative Myelopathy in Dogs be Treated?
There isn’t any curative treatment for DM, so support for pets is typically provided through medical management. Luckily, most dogs with DM alone do not seem to be in pain as much as they are simply weak in the hind end.
That being said, we can see some cases of arthritis as well that do cause pain and require intervention (especially because more cases are in larger breeds of dogs).
Keeping dogs active and at a healthy body weight can potentially help slow the display and progression of symptoms. The longer we can help dogs keep a healthy muscle mass, the more strength they can gain in their back end. Some pets may benefit from physical therapy such as hydrotherapy or acupuncture. Supplements with vitamin E have also been proposed as beneficial.
While we can’t stop the progression of DM, we can do our best to provide a good quality of life for as long as possible.