Cause and Signs
Degenerative myelopathy is a progressive disease of undetermined cause that affects the spinal cord. It results in a loss of co-ordination of the hind legs, which progresses to weakness and then to paralysis of the hindquarters. What happens is that the structures within the spinal cord that are responsible for nerve impulses degenerate. In degenerative myelopathy, the myelin (the insulation around the nerve fibres) and the axons (the nerve fibres that carry signals to the muscles) are affected. While these changes can happen anywhere along the spinal cord, they usually happen in the lower back.
Typically, degenerative myelopathy isn’t seen in dogs under the age of five. The degeneration occurs slowly over a period of several months. Often the first signs noticed are difficulty getting up in the hind quarters. This awkwardness is most noticeable when the dog walks on a smooth surface. However, as the disease progresses, the dog becomes uncoordinated and will scuff or drag its rear feet, causing excessive wearing of the toenails.
Sometimes one side is more noticeably uncoordinated than the other. The disease can either wax and wane episodically or progress steadily. It usually takes a few months to a year after onset for a dog to become unable to walk.
There is no known cause for this disorder, although a genetic basis is presumed in German shepherds. Genetic, nutritional, and immune factors have been suggested, but none have been scientifically proven. While this is mostly a disease of middle-aged to older German shepherds, German shepherd mixes, Siberian huskies, collies, Corgis, and other breeds can also be affected. It is not thought to cause pain or discomfort because the spinal cord axons have no way to feel pain. Usually, affected dogs can still urinate and defecate on their own until the very late stages.
Diagnosis is a matter of eliminating other diseases, including spinal cord cancer, osteomyelitis (bone infection), and disk disease/injury. This elimination process usually involves radiographs of the spine, myelograms, or MRI (magnetic resonance imaging).
The disease can be managed, but it can not be cured.
One aspect of management involves finding ways to help your dog adjust to the gradual paralysis. You can help the dog walk and do business by using a towel (or one of the products on the market for this) as a sling to hold the dog’s hind end up, or you can use a cart designed for canine paraplegics. There are many products made for dogs that have hind end difficulties and can not walk. Which one is best depends on the dog and the level of paralysis.
Many veterinarians believe that stress can exacerbate the disease, so it’s helpful to avoid stress.
Exercise in the form of walking or swimming helps more than anything else as treatment. If the dog is old or has arthritis, be sure to build up to exercise rather than taking a “weekend warrior” approach. The most beneficial schedule is a day with regular exercise, followed by a day of rest. Specific exercise is best, not just running around in the backyard. Some owners feel that swimming helps the most. Dog spas, with trained therapists, are available in some locales.
Vitamin supplementation is sometimes helpful.
Your veterinarian can help you determine when/if euthanasia may be the kindest thing for you and your dog.
Prevention and Control
Affected dogs should never be bred. Because the disease is found in specific breeds, responsible breeding is the only way to prevent degenerative myelopathy. If you plan to get a purebred German shepherd puppy, ask the breeder about history of the disease in the kennel’s line. Clinical signs don’t develop until after sexual maturity, so be certain that a dog’s line doesn’t have degenerative myelopathy before you breed or buy.