Canine Degenerative Myelopathy: It's in the DNA
Degenerative myelopathy (DM) is a slowly progressive spinal cord disorder that resembles Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig’s Disease) in people. The inevitable result for dogs with DM is paraplegia—hind end paralysis.
Dogs at risk of degenerative myelopathy
DM affects primarily older dogs, with symptoms typically beginning at eight years of age or older. Back in the day (when I was just a pup) we referred to this disease as German Shepherd Myelopathy because we thought it was unique to this breed. We now know that DM occurs in many purebred and mixed breed dogs. The breeds most commonly affected include the German Shepherd, Pembroke Welsh Corgi, Cardigan Welsh Corgi, Boxer, Borzoi, Rhodesian Ridgeback, American Eskimo Dog, Bernese Mountain Dog, Golden Retriever, Great Pyrenees, Kerry Blue Terrier, Poodle, Pug, Shetland Sheepdog, Soft Coated Wheaten Terrier, Wire Fox Terrier, and Chesapeake Bay Retriever.
Symptoms of degenerative myelopathy
DM symptoms progress slowly over the course of months to even years. From beginning to end, DM affected dogs typically remain alert and animated. The symptoms typically progress as follows:
- Loss of coordination (ataxia) in the hind legs
- Dragging the hind feet causing wearing down of the toenails.
- Hind end weakness (difficulty climbing stairs, jumping up into the car, going for walks)
- Knuckling of hind feet (weight bearing on the tops of the feet rather than their undersides)
- Difficulty supporting weight with hind legs
- Inability to walk without support
- Urinary and/or fecal incontinence
- Paraplegia (paralysis of hind legs).
- Weakness in front legs.
Although this degenerative process is not painful, affected dogs can develop discomfort because of overuse of other body parts attempting to compensate for the hind end weakness.
Cause of degenerative myelopathy
DM causes degenerative changes within spinal cord axons, structures that transmit information back and forth between the brain and the rest of the body. These degenerative changes begin in the thoracolumbar region of the spinal cord, the portion that lines up with the end of the rib cage. This explains why the hind limbs are more severely affected. Given enough time, the disease progresses toward the head end of the body, causing loss of front leg function as well.
DM is an inherited disease. In 2008 a group of researchers reported through Texas A&M University that a genetic mutation on