By Christie Long
One of the most common complaints owners of older large-breed dogs cite is hind-end weakness. Most often, this weakness is due to pain from the effects of osteoarthritis.
Lots of dogs have hip dysplasia; some have knee problems or back pain; and all of these conditions make it difficult for them to rise and subsequently move around due to pain.
But there is another illness, albeit much rarer than osteoarthritis, that also results in hind-end weakness.
Known as degenerative myelopathy, or DM, is not painful and typically affects dogs between the ages of 8 and 14.
Assessing pain in animals is difficult, but veterinarians are can usually tell whether hind-end weakness is caused by a painful or nonpainful condition. DM attacks myelin, the protective cover around the spinal cord, making it difficult or impossible for muscles to receive the signals nerves are sending to move. Although DM can occur anywhere on the spinal column, it most commonly affects the mid- to lower portion.
Owners might first notice that it becomes more obviously difficult for their dog to get up from lying down and that, once walking, there is a pronounced sway to the gait. This usually progresses to scuffing or dragging the rear feet. With time, the muscles of the flank become noticably smaller, a condition known as atropy. The disease can wax and wane over time, but ultimately progresses to the point where the dog can no longer walk.
Differentiating DM from other conditions is extremely important, since DM has no effective treatment, while arthritis often can be successfully managed for some time. Finding pain on physical examination is an important factor, but x-rays can definitively diagnose arthritis. Other conditions such as cancer on the spinal column are more difficult to diagnose, and sometimes advanced imaging is required.
Scientists have determined dogs with DM have a specific gene mutation. A test has been developed to identify dogs that can be carriers of the disease. Dogs that have two copies of the mutated gene almost universally are affected. This test has become very important to breeders of dogs that are frequently affected by DM, such as German shepherds. Identification of potential carriers of the disease allows them to be removed from breeding programs.
Unfortunately, there is no effective treatment for DM, but studies have shown dogs that receive physical therapy have a better quality of life and may live longer than dogs that don’t. Determining the cause of hind-end weakness, helps to develop an effective treatment and establish a prognosis.
Christie Long is a veterinarian at the VCA Animal Hospital in Fort Collins, CO. Long left her job in software sales in 2000 to travel for 13 months. Along the way, she was touched by the plight of the animals she saw and somewhere in the Nepalese Himalayas she vowed to return to school to become a veterinarian. While she often finds end-of-life situations heart-wrenching, she considers herself blessed to be called upon as a trusted adviser to families during difficult times. Dr. Long’s family includes her husband and travel partner, Wiley, their 5-year-old son, Wiley IV, their dogs Pancake and Gizmo and cats Sneaky and Sidh.