Degenerative Myelopathy

Degenerative myelopathy (progressive rear limb weakness or paralysis) was first described as a specific neurologic disease in 1973. The age at onset is five to fourteen years. It has been reported in almost all large breeds of dogs with the disease appearing with relative frequency in the German Shepherd.

The classic presentation is a painless, slowly progressive rear limb weakness or paralysis. There may be discomfort due to arthritis in the hip or lower lumbar (lower back) area, but this usually improves with activity. Over days, weeks, or months the dog becomes progressively weaker as is evidenced by shuffling of the rear limbs and lack of coordination. Finally, full paralysis coupled with fecal and urinary incontinence develops.

Diagnosis

A diagnosis of degenerative myelopathy is based on a history of progressive spinal ataxia and weakness that may be waxing or steadily progressive. The tentative diagnosis is supported by neurological findings of widespread thoracolumbar (back) spinal cord dysfunction. Laboratory findings are generally within normal limits except for an elevated cerebral spinal fluid (CSF) protein. A myelogram (contrast dye study of the spine) must be performed to differentiate degenerative myelopathy from disc disease, tumors, and other progressive neurologic diseases.

Current research points to an immune mediated basis for degenerative myelopathy. It is hoped that research involving the antigens present in the immune complexes formed in degenerative myelopathy will lead to a blood test for this condition.

Treatment

The treatment of degenerative myelopathy involves four basic approaches:

• Exercise
• Supportive measures
• Medication
• Minimization of stress

Exercise is extremely important in maintaining the well being of affected dogs, maximizing muscle tone, and maintaining good circulation and conditioning. This is best achieved by an increasing schedule of alternate day exercise. Since many dogs have lost muscle tone prior to their diagnosis, it is important to gradually build up their level of activity. The goal is to do aerobic exercise for thirty minutes twice a week and one hour once a week. This can begin with walking and gradually progress to a faster pace. While not all patients can reach this goal, it is important to strive to do so. Running loose on the owner’s property is not adequate exercise. Regular periods of programmed, continuous exercise are required. It is equally important that the patient with degenerative myelopathy be allowed to rest on the day exercise is not scheduled. This will allow strained muscles and tendons to heal and will increase muscle strength. The dogs do not have to be confined but merely discouraged from any strenuous exercise on days of rest. Consistent, controlled building of muscle tone through exercise will help delay the progression of degenerative myelopathy.

Vitamin support may be useful in delaying degenerative myelopathy symptoms. Some recommend that patients receive 200 IU of vitamin E daily and one high potency B vitamin (B-1) twice daily. Synthetic vitamins are cheaper and just as effective as natural vitamins. No other supplementation of a balanced diet is needed or indicated in the treatment of degenerative myelopathy. Because vitamin E at the levels recommended is a nonsteroidal antiinflammatory agent, concurrent use of aspirin-like drugs is not recommended. Should aspirin-like drugs be required to treat arthritis in degenerative myelopathy patients, daily vitamin E supplementation is reduced to 100 IU.

Aminocaproic acid (Amicar) may prevent progression or result in clinical remission of degenerative myelopathy in over 15 to 20% of patients. It is given orally at 500 mg every eight hours (three times daily). Since the pill form of Amicar has become expensive, we recommend giving aminocaproic acid as a solution using the generic product. The aminocaproic acid can be mixed with a vitamin/mineral supplement to provide a palatable solution for oral usage. The only side effects that have been attributed to aminocaproic acid have been occasional gastrointestinal irritation. This presents a problem in only a few patients, usually those with preexisting gastrointestinal problems. In some dogs, vitamin supplements can cause excessive flatulence, necessitating that they receive the aminocaproic acid solution without the vitamin/mineral supplement.

Prognosis

Degenerative myelopathy progresses at different rates in each animal. Stress plays a role in its advancement. Minimizing stressful situations is important. While anesthesia does not appear to cause problems with degenerative myelopathy, even minor invasive surgical procedures can result in a marked increase in clinical signs. Therefore, we recommend caution in considering major surgery in patients with degenerative myelopathy. The worsening caused by surgical stress can be irreversible.