Affects: Dogs
Canine degenerative myelopathy, also known as chronic degenerative radiculomyelopathy, is an incurable, progressive disease of the canine spinal cord that is similar in many ways to amyotrophic lateral sclerosis (ALS). Onset is typically after the age of 7 years and it is seen most frequently in the German shepherd dog, Pembroke Welsh corgi, and boxer dog, though the disorder is strongly associated with a gene mutation in SOD1 that has been found in 43 breeds as of 2008, including the wire fox terrier, Chesapeake Bay retriever, Rhodesian ridgeback, and Cardigan Welsh corgi. Progressive weakness and incoordination of the rear limbs are often the first signs seen in affected dogs, with progression over time to complete paralysis. Myelin is an insulating sheath around neurons in the spinal cord. One proposed cause of degenerative myelopathy is that the immune system attacks this sheath, breaking it down. This results in a loss of communication between nerves in lower body of the animal and the brain.
Symptoms: Degenerative myelopathy initially affects the back legs and causes muscle weakness and loss, and lack of coordination. These cause a staggering effect that may appear to be arthritis. The dog may drag one or both rear paws when it walks. This dragging can cause the nails of one foot to be worn down. The condition may lead to extensive paralysis of the back legs. As the disease progresses, the animal may display symptoms such as incontinence and has considerable difficulties with both balance and walking. If allowed to progress, the animal will show front limb involvement and extensive muscle atrophy and paralysis. Eventually cranial nerve or respiratory muscle involvement necessitates euthanasia or long term palliative care.
Progression of the disease is generally slow but highly variable. The animal could be crippled within a few months, or may survive as long as three years or more.
Causes: The etiology of this disease is unknown. Recent research has shown that a mutation in the SOD1 gene is a risk factor for developing degenerative myelopathy in several breeds. Mutations in SOD1 are also associated with familial amyotrophic lateral sclerosis (Lou Gehrig's disease) in people. More than 100 SOD1 gene mutations are involved in human familial amyotrophic lateral sclerosis (ALS), and the pathologic spinal lesions of ALS are similar to those of canine DM, making canine DM a potentially useful animal model of ALS.
Known causes of spinal cord dysfunction should be excluded before accepting the diagnosis of degenerative myelopathy; disc disease (protrusions) or spinal cord tumors can cause compression of the spinal cord with similar signs to degenerative myelopathy.
Treatment: Degenerative myelopathy is an irreversible, progressive disease that cannot currently be cured. There are no treatments to currently stop the disease. Recent studies suggest that laser therapy can slow the progression of disease. More studies are needed, however, it may help alone with rehabilitation and acupuncture. https://www.dvm360.com/view/degenerative-myelopathy-does-laser-therapy-offer-new-hope
Prognosis: The prognosis for the disease is generally poor. Aggressive therapy may be used to combat the disease, but even this puts the life expectancy at only around 14 months. It is recommended to put the dog to sleep at around 12 months, to prevent unnecessary suffering that comes from the disease. Some dogs have lived for many years with the disease, with one female boxer even living for 11 years. Without treatment, survival is around 3 months. The disease progresses rapidly without treatment, but this option arguably comes with less suffering. The dog begins to realize it is ill during the late stages. Some dogs have even appeared to be combating the disease on their own, walking on their own and doing exercise. The record survival without treatment is 14 years.