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Degenerative 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. Although the changes
may be found anywhere in the spinal cord, they are
most severe in the lower back region.
The cause of these changes
is not known. There is evidence that an inappropriate
immune response 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.
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