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.
Chesapeakes needed for DM study. See the American Chesapeake
Club DM webpage at: www.amchessieclub.org/myelopathy.html
AKC Canine Health Foundation--DM Videos
Pictures of a Pembroke with DM at Canine Genetic Disease
website:
www.caninegeneticdiseases.net/dm/index.html
Chat room Spinal
Myelopathy:
Sponored by Dr Clemmons, University of Florida
Online
Resources:
WorkingDogs.com DM
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
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.
Copyright © 1998 Canine Inherited Disorders Database. All rights
reserved.
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