Adapted by Leslie Manis, Health/Genetics Chairman, ASTC
Note: This article is for informational purposes only.
DM has not been ideintified in the Sealyham Terrier
as a health problem. This article is an adaptation
of Degenerative Myelopathy--Disease Basics, published
at www.caninegeneticdiseases.net/DM/basicDM.htm
[Every effort has been made to ensure accuracy of information. However,
this is not a substitute for prompt veterinary care. Any similarity
to other publications is unintentional. Published online at Sealyhealthguard.org,
7/20/11]
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Degenerative myelopathy is a progressive disease of the spinal cord
in older dogs, usually beginning between 8 and 14 years of age. The
first sign is a loss of coordination in the hind legs; it can begin
in one leg and then the other. Within 6 months to a year, the
dog will become paraplegic. If signs continue to progress,
incontinence may occur and eventually weakness will develop in the
front legs.
The only way to confirm diagnosis is to examine the spinal cord
under the microscope after death. Any disease that affects
the spinal cord can cause similar signs of loss of coordination
and weakness. Many of these other diseases can be treated
effectively. The most common one is herniated intervertebral
disks. This can often affect short-legged, long-backed dogs. It
can usually be seen with X-rays of the spine and myelogram. Myelography
involves using a contrast medium and X-rays to examine the spinal
cord. More advanced imaging techniques like CT scan or MRI
may be used. A neurologist can aid in diagnosis, if necessary. Other
causes of weakness and loss of coordination include tumors, cysts,
infections, injuries and stroke. Degenerative myelopathy
is a diagnosis of elimination of these other possibilities.
DM begins in the white matter in the chest (thoracic) region of
the spinal cord. This white matter contains fibers that transmit
commands from the brain to the limbs, and feelings from the limbs
to the brain. There is loss of the fibers themselves as well
as the stripping away (demyelination) of the insulation of these
fibers. This interferes with communication between the brain
and limbs.
There are no treatments that have been clearly shown to stop or
slow the progression of DM. The dog's quality of life can
be improved by good care, physical rehabilitation, pressure sore
prevention, monitoring for urinary infections, and use of harnesses
or carts.
There is a DNA test available which clearly identifies dogs that
are clear (two normal copies of the gene, G-G), those that are carriers
(one normal copy of the gene, one mutated copy, G-A), and those
dogs at a much higher risk for developing degenerative myelopathy
(two mutated copies, A-A). Not all dogs with two mutated
copies develop DM. Researchers now seek to understand what
triggers the development of clinical symptoms in some, but not all
of these A-A dogs.
As of July 2008, researchers have found the mutation present in
43 breeds. It is possible that the genetic background that
predominates in some breeds prevents the development of symptoms
even in A-A dogs. At this time, they have the required evidence
that there's an association between DM symptoms and the mutation
in the following breeds: Boxer, Cardigan & Pembroke
Corgis, Chesapeakes, German Shepherds, Rhodesian Ridgebacks and
Standard Poodles. Of these breeds, G-G and A-G dogs have
never been confirmed to have degenerative myelopathy. All
dogs with DM have A-A (two mutated copies of the gene), but as stated
above, the reverse is not necessarily always true.
Now that the DNA test has been developed to identify dogs at risk
for developing degenerative myelopathy, researchers can work to
discover what triggers its development, and find ways to prevent
it. Until then, breeders can add this as a valuable tool
for informed, balanced breeding decisions.
For more info on the DNA test:
http://www.caninegeneticdiseases.net/DM/ancmntDM.htm
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