Hey there, pet parents. Today we have to talk about a tough one. It's a heartbreaking and progressive disease of the spinal cord that affects older dogs, and it's called Degenerative Myelopathy (DM). It is essentially the canine equivalent of Amyotrophic Lateral Sclerosis (ALS) or Lou Gehrig's disease in people. Let's walk through what we know about this disease.
What is Degenerative Myelopathy?
Degenerative Myelopathy is a slowly progressive, non-painful disease of the spinal cord in older dogs. It results in a gradual loss of coordination and strength in the hind limbs, eventually leading to paralysis.
The disease is caused by a degeneration of the white matter of the spinal cord. The white matter contains the nerve fibers that are responsible for transmitting nerve impulses from the brain to the limbs. As these fibers degenerate, the dog slowly loses the ability to control its back legs.
We now know that DM is caused by a mutation in a gene called superoxide dismutase 1 (SOD1). A dog must have two copies of this mutated gene to be at risk for developing the disease.
Breeds at Risk
While it can affect many breeds, DM is most commonly seen in:
- •German Shepherds (it was first described in this breed)
- •Boxers
- •Corgis (both Pembroke and Cardigan Welsh Corgis)
- •Rhodesian Ridgebacks
- •Chesapeake Bay Retrievers
The signs usually start in dogs that are 8 years of age or older.
Spotting the Signs of DM
The onset of DM is very slow and gradual. The most important thing to know is that DM is not a painful condition.
- •Hind Limb Weakness and Ataxia: This is the first sign. The dog may seem wobbly or unsteady in the hind end. They may scuff their toenails or "knuckle over" and walk on the tops of their paws. The gait is often described as looking like a "drunken sailor."
- •Difficulty Rising: They will have trouble getting up from a lying position.
- •Muscle Atrophy: The muscles of the hind limbs will waste away from disuse.
- •Progressive Paralysis: Over a period of 6-12 months, the weakness will progress to a complete paralysis of the hind limbs.
- •Incontinence: Eventually, the dog will lose bladder and bowel control.
- •Front Limb Weakness: In the very late stages of the disease, the weakness can ascend the spinal cord and start to affect the front limbs.
How Vets Diagnose DM
Diagnosing DM can be challenging because it is a diagnosis of exclusion. There are many other conditions that can cause progressive weakness in the hind limbs of an older dog, such as a herniated disc (IVDD), a spinal tumor, or severe arthritis. The key difference is that most of these other conditions are painful, whereas DM is not.
Your vet will perform a thorough physical and neurological exam. They will likely recommend X-rays or an MRI of the spine to rule out other, more treatable causes of the weakness.
If other causes have been ruled out, a presumptive diagnosis of DM is made based on the breed and the classic, non-painful, progressive signs.
There is also a genetic test available for the SOD1 mutation. This test can tell you if your dog is clear (has no copies of the gene), a carrier (has one copy), or is at-risk (has two copies). It's important to know that not all dogs that are "at-risk" will go on to develop the disease. The genetic test is a tool that helps to support the diagnosis.
Treatment and Management
This is the heartbreaking part: there is no cure for Degenerative Myelopathy. There is no treatment that has been proven to stop or reverse the progression of the disease.
The management of DM is focused on supportive care and maintaining the dog's quality of life for as long as possible.
- •Physical Therapy: This is the cornerstone of management. Intensive physical therapy, including exercises and hydrotherapy (swimming or underwater treadmill), has been shown to prolong the length of time that a dog will remain mobile. The goal is to maintain muscle mass and "re-educate" the nerves.
- •Mobility Aids: As the disease progresses, you will need to use a sling or harness to help your dog get around. Eventually, a doggy wheelchair can be a great option to allow the dog to remain active.
- •Good Nursing Care: It's very important to prevent bedsores by providing soft bedding and to keep the dog clean and dry, especially once they become incontinent.
The decision of when to say goodbye is a very personal one. Many owners will elect for humane euthanasia when the dog is no longer able to support its own weight or becomes incontinent.
DM is a devastating diagnosis to receive. The slow, progressive nature of the disease is emotionally taxing for owners. The goal is to cherish the good time you have with your companion and to focus on their quality of life.
Sources & Further Reading:
- •VCA Animal Hospitals - Degenerative Myelopathy in Dogs
- 1American Kennel Club - Degenerative Myelopathy