Causes of Canine Degenerative Myelopathys
Canine degenerative myelopathy (DM) is a progressive, rare and usually fatal adult-onset disease that involves the degeneration of nerves in the central nervous system (brain and spinal cord). For many years, authorities thought that DM was an immune-mediated disorder similar to multiple sclerosis in people. Other experts suspected that toxicity, vitamin deficiency, oxidative stress and/or genetics were possible contributing causes to this disorder. Recently, however, researchers have discovered that degenerative myelopathy in dogs is caused by a specific mutation in the superoxide dismutase 1 (SOD1) gene. Mutations in the SOD1 gene have been shown to cause amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease, in people. Because degenerative myelopathy shows up most commonly in certain purebred dog breeds, there probably is a strong hereditary component to the condition. DM is thought to be spread by autosomal recessive inheritance.
Preventing Degenerative Myelopathy
Dogs that have been diagnosed with degenerative myelopathy should not be bred. Dogs that are carriers of the genetic mutation, which can be detected through a genetic test, also probably should not be bred, to prevent passing on of the mutated SOD1 gene. Otherwise, there is no realistic way to prevent DM in dogs. However, once a dog is diagnosed with DM, its owner can do a number of things to manage the consequences of the disease, which include urine retention (owners can manually express their dog’s bladder), urinary tract infection, weight gain from inability to ambulate and skin lesions from urine scalding. It is critically important that dogs affected by degenerative myelopathy receive meticulous supportive care and good hygiene, especially in their “rear end” area, to prevent accumulation of waste products, bed sores, urine scalding and secondary bacterial infection.
Diagnosis of degenerative myelopathy is made by veterinarians through a process of elimination. There is no cure or truly effective treatment for this disease. Owners must provide meticulous supportive and nursing care for affected dogs in an attempt to slow the progression of the disease and to help maintain the dog’s quality of life, especially once the dog can no longer stand and walk on its own. Slings, wheel carts, vitamins and other supplements, together with physical therapy, can be very helpful. Unfortunately, the long-term prognosis for dogs with DM is poor.