Degenerative Myelopathy

Progressive Rear Limb Weakness or Paralysis

(Permission to reprint granted by The Southern California Surgical Group. This article is one of a series of pamphlets produced by this group.).

Degenerative myelopathy (DM) was first described as a specific, progressive, generative neurologic disease in 1973. Since then, much has been done to understand the processes involved in the disease and in the treatment of DM.

The age at onset is 5 to 14 years. Cases have been reported in almost all large breeds of dogs, with the disease appearing with relative frequency only in the German Shepherd. This suggests that there is a pre-disposition for German Shepherd dogs to develop DM. The work presented here and by others on the nature of DM has been performed in the German Shepherd, the Belgian Shepherd and the Old English Sheepdog. It is currently not known whether the same condition exists in all breeds of dogs or if subtypes of the condition occur.

The classic clinical presentation is a painless, slowly progressive real 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 patient 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.

A diagnosis of DM is made based on a history of progressive spinal ataxia and weakness that may be waxing and waning or steadily progressive. This tentative diagnosis is supported by the neurological findings of widespread thorocolumbar (back) spinal cord dysfunction. Laboratory findings are generally normal except for an elevated cerebral spinal fluid (CSF) protein. A Myelogram (a contrast dye study of the spine) must be performed to differentiate DM from Disc Disease, Tumors, or other Progressive Neurologic Diseases. The striking feature common to each syndrome is the reduction of rear limb muscle support.

Current research points towards an immune mediated pathogenesis of DM. This provides a logical explanation for the presence of immune abnormalities in German Shepherd dogs with DM. It is hoped that work in this area with the antigens present in the immune-complexes will lead to a major breakthrough in our understanding of DM and to an early blood test for this condition.

The treatment of DM involves four basic approaches:

1) Exercise

2) Supportive Measures

3) Medication

4) Minimalization 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 their level of activity. The goal is to do aerobic exercise for 30 minutes twice a week and one hour once a week. This can begin with walking and gradually build 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. Regular periods of programmed, continuous exercise are the most important. It is equally important that the patient with DM 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 these days of rest. It will be the consistent, controlled building of muscle tone through exercise that will help to delay the progression of DM.

Vitamin support is also useful in delaying DM symptoms. Some recommend patients receive 200 IU of Vitamin E daily and one high potency B vitamin (B-1) every 12 hours. Synthetic vitamins are cheaper and just as effective as "natural" vitamins in this regard. No other supplementation of a balanced diet is needed or indicated in the treatment of DM. Because Vitamin E, at the levels recommended, is a non-steroidal anti-inflammatory agent, concurrent use of aspirin-like drugs is not recommended. Should aspirin-like drugs be required to treat a DM patient, the daily Vitamin E supplementation is reduced to 100 IU daily.

Flea products should be restricted to carbamate and pyrethrin products. Heart-worm preventative should be limited to daily medication with a diethylcarbamazine product. Dogs with DM should not receive ivermectin (Heartgard), styrid caracide, or Filarbits Plus, as all may be associated with potential problems.

For the last decade, one medication has prevented progression or resulted in clinical remission of DM in over 15 to 20% of the patients. This medication is aminocaproic acid (Amicar). It is given orally at 500 mg every eight hours. Now that the "pill" form of medication has become expensive, we recommend giving aminocaproic acid as a solution, using the generic product. This product, while designed for injection, 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 gastro-intestinal irritation. This presents a problem in only a few patients, usually those who have pre-existing GI problems. In some dogs, vitamin supplements can cause excessive flatulence, necessitating that they receive the aminocaproic acid solution undiluted with the vitamin-mineral solution.

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