Degenerative Myelopathy

Summary

Also called "chronic degenerative radiculomyelopathy," and "German shepherd dog myelopathy," degenerative myelopathy (DM) is a relatively uncommon neurological disease characterized by progressive weakness and loss of normal function in the hind limbs of affected dogs.

In DM, the loss of myelin (the tissue surrounding the nerves) and the degeneration of axons (nerve endings) leads to the symptoms seen in this disease.

Ultimately, the origin of these symptoms is unknown but a genetic predisposition is assumed. An aberrant immune response may be responsible but is as yet merely hypothesized. The mode of inheritance is also unknown.

Sadly, the prognosis for affected dogs is uniformly poor. Most affected dogs will reach a non-ambulatory, end-stage disease state within months to a year of their diagnosis.

Symptoms and Identification

Affected dogs are typically 5 years old or older. A gradually progressive loss of coordination in the hind limbs is the hallmark sign. Weakness is evident in all cases. Signs are initially consistent with hip dysplasia but the lack of pain (sometimes so hard to discern in our stoic canines) eventually informs us of the disease's true nature.

DM patients may be affected neurologically in the hind end but they nonetheless manage to retain control of their urination and defecation. When they become progressively weaker, however, they're typically incapable of a variety of normal ambulatory/motor functions.

Diagnosis is achieved through basic physical examination and detailed neurological examination. X-rays and basic labwork are always undertaken to rule out any other obvious causes. Sometimes more advanced imaging (such as MRIs, CT scans and myelography are performed).

Affected Breeds

German Shepherd and Shepherd mixes seem most predisposed, but the disease has also been reported in a number of breeds including:

• Kerry Blue Terrier

• Collie

• Siberian Husky

• Belgian Sheepdog

• Old English Sheepdog

• Labrador Retriever

• Chesapeake Bay Retriever

Treatment

Supportive care is the fundamental approach to degenerative myelopathy as no definitive treatment options area available. Physical therapy, nutritional supplements and other alternative therapies (acupuncture, for example) may be of some palliative benefit in these cases.

Veterinary Cost

Because treatment options are so limited, veterinary cost is typically relegated to diagnosis, which normally includes X-rays and typically involves a neurologist's consultation. In some instances, expensive imaging studies may be employed to rule out diseases with similar signs. In these cases the cost of diagnosis may reasonably rise to $2,000 to $4,000.

Prevention

Though inheritance modalities have not yet been established it's considered advisable to refrain from breeding affected dogs and all possible relatives. Ideally, the entire line of dogs should be terminated by removing all its known members from the breeding pool.

References

LeCouteur, R.A., Child, G. Diseases of the Spinal Cord. In S.J. Ettinger and E.C. Feldman (eds) Textbook of Veterinary Internal Medicine, pp.650-652. W.B. Saunders Co., Toronto.

Clemmons, R.M. 1992 Degenerative myelopathy. Vet Clin North Am 22(4):965-971