Degenerative myelopathy is a slow, incurable disease of the spinal cord. It usually appears in older dogs, often around eight years of age or later, and it affects the dog's ability to walk and control its back legs [citation:2].
What it is
DM is a progressive condition of the spinal cord. The nerves that control movement slowly stop working, starting in the middle of the back and moving down and then up the spinal cord. There is no cure, and the changes cannot be reversed [citation:2].
Symptoms
The first signs are usually mild. One back leg may scuff or drag, and the dog may seem a little unsteady. Over time both back legs weaken, and the dog may struggle to rise or climb stairs. Muscle loss becomes visible. In the later stages, the front legs can be affected too, and the dog may lose control of bladder and bowels [citation:2][citation:13].
DM itself is not painful. The disease affects movement, not pain sensation. Any discomfort usually comes from secondary problems, such as pressure sores or arthritis [citation:10][citation:13].
How it is diagnosed
There is no single test that confirms DM in a living dog. Diagnosis is made by ruling out other spinal cord diseases, such as intervertebral disc disease, tumours or infections. A vet will usually do a neurological exam, blood work, and imaging such as MRI or CT. Spinal fluid may also be checked [citation:2][citation:13].
A DNA test can show whether a dog carries the SOD1 mutation linked to DM, but it does not confirm the disease. A dog with two copies of the mutation is at higher risk, but not every at-risk dog develops DM [citation:2][citation:7].
Care and treatment
There is no treatment that stops or reverses DM. What helps is keeping the dog mobile and comfortable for as long as possible [citation:2].
Regular physiotherapy can slow the loss of muscle and coordination. Swimming or hydrotherapy is often easier on the dog than walking. A belly sling or harness lets you support the back legs. Non-slip rugs and ramps around the house make daily life safer. Once weakness sets in, a two-wheel dog cart can keep the dog active and protect its quality of life [citation:2][citation:6].
Keeping the dog at a healthy weight is important. Extra weight makes movement harder and puts more strain on the body [citation:2].
Breeding advice
DM is linked to a mutation in the SOD1 gene. Dogs with two copies are considered at higher risk, though the disease does not develop in every dog with the mutation. Carriers have one copy and generally progress more slowly if they develop signs at all [citation:2].
Breeding decisions should not be based on DNA results alone. Removing every carrier from breeding would shrink the gene pool and could increase other health problems. The club encourages breeders to test, to be honest about results, and to weigh the whole picture when planning a litter [citation:7].
For data on the breed, Genomia reported in 2018 that among tested Coton de Tulear dogs, 92 percent were clear, 8 percent were carriers, and none were at-risk homozygotes [citation:21]. These numbers come from dogs that were tested, so they may not reflect the whole breed.
What the club recommends in 2026
As of 2026, DM DNA testing is part of the health screening the club encourages for breeding Cotons. If you are buying a puppy, ask whether the parents were tested and whether you can see the results. If you have questions about a test result, or you are not sure what it means for your dog, please write to us, call us, or come and visit us at a club event.
Sources: Cornell University College of Veterinary Medicine, AKC Canine Health Foundation, Genomia.
