related terms:  chronic degenerative radiculomyelopathy, German shepherd dog myelopathy

What is degenerative myelopathy?

This disorder affects dogs 5 years of age or older. There is a slowly progressive loss of coordination in the hind limbs, with increasing weakness. This occurs because of deterioration of structures in the spinal cord that are responsible for conduction of nerve impulses (specifically the loss of myelin and degeneration of axons in the white matter). Although the changes may be found anywhere in the spinal cord, they are most severe in the lower back (thoracolumbar) region.

The cause of these changes is not known. There is evidence that an inappropriate immune response (to a neural antigen) may be involved.

How is degenerative myelopathy inherited?

The mode of inheritance is not known.

What breeds are affected by degenerative myelopathy?

This condition is seen most often in the German shepherd and German shepherd crosses. Degenerative myelopathy has also been reported in other large and medium breeds, including the Kerry blue terrier, collie, Siberian husky, Belgian shepherd, old English sheepdog, Labrador retriever and Chesapeake Bay retriever.

For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.

What does degenerative myelopathy mean to your dog & you?

The condition is seen in dogs 5 years of age or older. The changes develop slowly and may initially be blamed on hip dysplasia. The first signs are weakness and lack of coordination in the hind limbs, which are more apparent when the dog is walking on a smooth surface. One side may be more severely affected than the other. The condition does not appear to be painful, and dogs retain the ability to control urination and defecation,  although as they become progressively weaker they will be unable to move to an appropriate spot or assume the necessary posture.

These signs gradually worsen until the dog is unable to walk, usually several months to a year after the neurologic problems are first noticed.

How is degenerative myelopathy diagnosed?

There are several conditions that can cause this kind of weakness in the hind end, in middle-aged medium to large breed dogs. Your veterinarian will do a thorough neurologic exam on your dog and x-rays, to rule out other causes.

For the veterinarian: Rule-outs include diskospondylitis, myelitis, intervertebral disc protrusion, and spinal neoplasia. Abnormalities on neurologic examination are consistent with an upper motor neuron lesion in the T3-L3 region, and include decreased proprioception and placing reactions in the hind limbs, normal to exaggerated patellar and hind limb withdrawal reflexes, normal anal sphincter tone, and sometimes crossed extensor reflexes in the pelvic limbs. Occasionally patellar reflexes are  depressed or absent in one or even both legs, but this is an afferent rather than an LMN lesion.

How is degenerative myelopathy treated?

Although there is no specific treatment for this condition, supportive care can generally be provided for several months.Your veterinarian will suggest ways to help you adjust to your dog's gradually increasing limitations, and to recognize the point at which euthanasia becomes the best option. This is usually within a year of the initial diagnosis, when your dog is no longer able to walk.

Some believe that treatment with a combination of increased exercise, vitamin supplementation and aminocaproic acid can slow the progression of this disease (see Clemmons below), but controlled studies have not been carried out that demonstrate this.

Breeding advice

Because clinical signs don't develop until well after sexual maturity, it is safest to avoid breeding any dogs from families where degenerative myelopathy has been diagnosed.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources

LeCouteur, R.A., Child, G. Diseases of the Spinal Cord. In S.J. Ettinger and E.C. Feldman (eds) Textbook of Veterinary Internal Medicine, pp.650-652. W.B. Saunders Co., Toronto.

Clemmons, R.M. 1992 Degenerative myelopathy. Vet Clin  North Am 22(4):965-971

Copyright 1998 Canine Inherited Disorders Database. All rights reserved.
Revised: October 30, 2001.

This database is a joint initiative of the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association.