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. DM 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 (making it easy for a vet to mi-diagnose as old age)
Progression of the disease is generally slow but highly variable. The animal could be crippled within a few months, or may survive up to three years or more. DM is a non-reversible, progressive disease that cannot be cured. There are no treatments that have been clearly shown to stop or slow progression.