Degenerative myelopathy (DM) is characterized by slowly progressive difficulty walking in the pelvic limbs. Degenerative myelopathy occurs predominantly in German shepherd dogs, Corgis and Boxers, but is seen in other breeds, including Rhodesian Ridgebacks, Chesapeake Bay Retrievers, Poodles and others.
Recent research has suggested that the disease may be due to mutation of the superoxide dismutase gene (SOD-1) in several breeds, although this is not the whole story, and other factors are likely to be involved in the pathogenesis.
DM generally occurs in dogs six years of age or older. Males are affected more often than females. It has been reported most commonly in German shepherd dogs and German shepherd mixed-breed dogs, although it does occur in other large and medium breeds of dog including collie and collie crosses, Labrador retrievers, Siberian huskies, Chesapeake Bay retrievers, and Kerry blue terriers.
Affected dogs usually are presented with a slowly progressive uncoordinated gait in their back legs. Although neurologic deficits are most often present bilaterally, they may be asymmetric. Signs progressively worsen so that most affected dogs become nonambulatory within several months to one year after neurologic deficits are first detected. Apparent pain or discomfort is not evident in affected dogs. Voluntary control of urination and defecation is retained, although affected dogs may not be able to urinate or defecate in an appropriate place owing to severe paraparesis or inability to assume a voiding posture. This is important, as some dogs are presented for apparent incontinence in the house, which may suggest a problem lower in the spinal cord.
Diagnosis of degenerative myelopathy is based on clinical findings, age and breed of the dog, and the ruling out of all other causes of a spinal cord problem in the middle part of the back.