myelopathy (mi″ә-lop´ә-the) any functional disturbance or pathological change in the spinal cord; often used to denote nonspecific lesions, as opposed to myelitis.
pathological bone marrow changes. adj., myelopath´ic., adj.
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Degenerative Myelopathy
What is it?
Degenerative Myelopathy (DM) of German Shepherds is an autoimmune disease. In autoimmune diseases, the patient's own immune system attacks some part of its body. In DM, the myelin and axons are attacked. (Myelin is the insulation around nerve fibers leaving the nerve cell. Axons are long nerve fibers that go from nerve cells to muscles and other parts. They carry the signals from the nerve to the muscles.) It is similar to Multiple Sclerosis in humans. Belgian Shepherds, Old English Sheep Dogs, Rhodesian Ridgebacks, Weimaraners and, probably, Great Pyrenees seem to suffer from the same problem, and can be helped by the same things that help German Shepherds. Many other breeds can suffer from myelopathy. Since we're not sure whether the cause is the same, we don't know if they can respond as well to these treatments.
DM is usually first seen in adult dogs between the ages of 5 and 14 years of age. It is diagnosed mainly by the clinical signs: a progressive weakness and ataxia of the hindquarters, which may come and go, or just get steadily worse. Muscles of the lower back and hindlegs are smaller than normal. Many dogs also have hip dysplasia and/or arthritis of the spine, which complicates the picture. Conventional treatment for these problems (such as Rimadyl or corticosteroids) may initially cause an improvement, but they don't necessarily help the myelopathy. DM begins in the spinal cord in the middle of the back, and is most severe there. It also affects other areas of the central nervous system, including the brain stem and sub-cortical white matter of the brain. The cause is most likely a combination of inherited weakness, plus environmental and toxic factors that lead to its development.
Due to some triggering factor, immune-complexes circulate. These immune-complexes lead to damage to the cells lining the blood vessels in the central nervous system. Later, fibrin is deposited in the spaces around the blood vessels. When it breaks down, inflammatory cells migrate into this area. (Aminocaproic acid helps decrease the breakdown.)
The inflammatory cells release prostaglandins and cytokines. These chemicals activate tissue enzyme, contributing to the formation of free radicals which, in turn, lead to tissue damage. Vitamins C and E help decrease prostaglandin and cytokine release. Anti-oxidants in general and acetylcysteine help decrease damage from the free radicals.
Conventional medicine has little to offer patients with DM. Use of exercise, certain vitamins and selected drugs have delayed or prevented progression of DM in many dogs. While these treatments are aimed at suppressing the clinical signs, little has been done to prevent the development of this autoimmune disease.
In DM, cerebrospinal fluid shows elevated protein in the lumbar area, and elevated acetylcholinesterase. There are no signs of myelopathy that can be detected in a plain X ray. A myelogram also will not show anything, and signs can worsen after it's done. An EMG will show the presence of spinal cord disease, but is not specific for myelopathy.
Treatment
The treatment of DM involves four basic approaches:
1) medication
2) exercise
3) supplements
4) other supportive measures
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