What is Degenerative Myelopathy?
Degenerative myelopathy (DM) is also known as chronic degenerative radiculomyelopathy (CDRM). It is a progressive disease that affects the spinal cord and eventually the brain stem and cranial nerves, which results in complete paralysis. If not euthanized, the pet will eventually succumb due to paralysis of the rib muscles and difficulty breathing.
The symptoms result from degeneration of the white matter of the spinal cord. The white matter contains the nerve fibers responsible for transmitting signals from the brain to the limbs and sensory information back to the brain. The fatty myelin sheath surrounding the nerve fibers is destroyed and eventually the nerve fibers also deteriorate. DM is similar to some of the forms of human amyotrophic lateral sclerosis (ALS) more commonly known as Lou Gehrig’s Disease.
One theory for the cause of DM is that the immune system itself attacks the nervous system causing the degeneration. But according to veterinary neurologist Dr. Joan R. Coates, one of the leading experts in this condition, DM is not an inflammatory disease. Degenerative myelopathy patients do not benefit from immunosuppressive drugs such as cyclophosphamide, prednisone, and azathioprine. She states that DM is similar to oxidative stress which characteristically has a release of free radicals resulting in cell degeneration.
A genetic mutation of SOD-1 (super oxide dismutase - a free radical scavenger found in abundance in the central nervous system) has been found in affected animals. DNA testing can be performed to determine whether a dog is at risk for the disease. Results are labeled as N for normal or DM for degenerative myelopathy. A result of N/N means the dog will not develop DM and cannot transmit it to their offspring. A result of N/DM means the dog will not have the disease, but is a carrier and can transmit this variant to 50% of their offspring. Breeding two carrier dogs has a predicted outcome of 25% DM-affected puppies. Dogs with DM/DM may develop the disease and will transmit the genes to all their offspring.
Which animals are affected by DM?
While cats can be affected by this disease, it is very rare. Breeds commonly affected include German Shepherds, Corgis, Siberian Huskies, Collies, Bernese Mountain Dogs, Boxers, Chesapeake Bay Retrievers, Golden Retrievers, Kerry Blue Terriers, Miniature Poodles, Rhodesian Ridgebacks, Standard Poodles, and Wirehaired Fox Terriers. Any breed can potentially be affected.
The disease generally starts in mid- to late-age, but dogs have been affected as young as four years old.
What are the symptoms of DM?
Symptoms may be subtle early in the disease. The disease affects the nerves to the hind legs first. Dogs may appear clumsy or be weak in the hind end; they may drag their feet causing the nails to wear down. They may sway when standing or cross the hind legs. As the disease progresses they will knuckle over or have trouble placing their feet when walking. The hind limbs may tremble and the muscles will start to atrophy or waste away. Disease progression continues until the dog is unable to stand or walk. Eventually they will become urine and fecal incontinent. The disease will progress to the forelimbs in later stages. Progression is slower in smaller breeds.
Affected dogs generally lose the ability to walk within six to twenty four months from diagnosis. Dogs with DM are not painful; weakness is the issue.
How is Degenerative Myelopathy Diagnosed?
This disease may be suspected on the basis of breed, medical history, physical examination, and diagnostic tests. The diagnosis is made by eliminating other causes of hind end weakness. Radiographs, CT scan, or MRI can be used to rule out problems such as hip dysplasia, intervertebral disc disease, spondylitis, cruciate tears, and chronic arthritis. If one of these other problems is also present, it can contribute to the patient's loss of function of the hindquarters. DNA testing is recommended for any at-risk breed displaying clinical signs consistent with DM. Biopsy of the spinal cord is the only way to definitively diagnose DM.
Management of DM
While there is no cure, diet and exercise appear to play key roles in slowing or halting disease progression. Studies have show that physical therapy increases average survival times in pets with DM. Underwater treadmill therapy is highly recommended if available. Dogs with arthritis or other painful disorders should be treated for pain. Other options that may help include:
- Toe Grips
- No-Knuckling Training Socks
- Resistance Bands
- Help Em Up Harnesses
- Chiropractic Adjustments
- Acupuncture, particularly electroacupuncture
- Vitamin E 2,000 IU per day
- Selenium 100 ug per day
- Vitamin C 1,000 mg twice a day
- Vitamin B complex 100 mg per day or 1 tablespoon nutritional yeast
- CoQ10 200 mg per day
- N-Acetylcysteine (NAC) 600 mg three times a day for dogs under 50 pounds, 1200 mg three times a day for dogs over 50 pounds for two weeks, then decrease to every other day
- Epsilon-aminocaproic acid (EACA) 500 mg twice a day, from Westlab pharmacy
- Omega 3 fatty acids - approximately 2500 mg twice daily for large dogs, 1200 mg twice daily for small dogs
- l-Carnitine 50 mg per pound body weight daily
- Whole food raw or gently cooked low-glycemic diet - avoid processed food, starchy foods, and overfeeding
In TCVM, muscles are associated with the Earth element and the tendons and ligaments with the Wood element. Since degenerative myelopathy causes weakness, incoordination, and muscle wasting, it is most commonly diagnosed in TCVM as Spleen Qi deficiency with Liver Yin deficiency. Other systems may also be out of balance.
Dogs that are down must be supported to avoid pressure sores. Frequent turning and inspection for any irritated areas must be performed. If the dog is unable to urinate or defecate on its own, the owner must learn to express the bladder and bowels. Incontinent animals must be kept immaculately clean. Getting the pet outside for environmental enrichment is a good idea.