Degenerative myelopathy (DM) is a poorly understood, progressive neurodegenerative disease seen in many dog breeds. Onset of the disease is typically is seen in dogs age 8 to 14.
Degenerative myelopathy begins with the spinal cord in the chest. The degeneration is two-fold: demyelination, i.e. the stripping away of the protective covering (myelin sheath) that surrounds nerve fibers in the spinal cord, and interference in the communication between the brain and the limbs.