IVDD can be caused by degeneration in the cervical (neck) or thoracolumbar (along the back) areas of the spinal column. Two primary forms of the disease occur in dogs, called Hansen Types I and II intervertebral disk disease. These both involve degeneration of intervertebral disks, but the mechanisms of degeneration and the predisposed breeds are different. Regardless of the form of disk disease, prompt treatment is needed to prevent further damage.
Types of Intervertebral Disk Disease
Hansen Type I intervertebral disk disease is a progressive disorder characterized by degeneration of the outer layer and mineralization (or hardening) of the inner layer of affected disks. The outer layer eventually ruptures acutely, letting the calcified inner layer press against the spinal cord, with resulting pressure, inflammation and nerve destruction. Multiple disks can be affected and degeneration usually begins at an early age, with clinical signs appearing by 3 years of age.
Type I IVDD typically occurs in chondrodystrophic breeds. These dogs have short, stubby legs and include the American Cocker Spaniel, Basset hound, Beagle, Corgi, Dachshund, French and other bulldogs, Shih-tzu and the Pekingese. Poodles also are predisposed. Type I IVDD usually comes on suddenly and is very painful.
Hansen Type II intervertebral disk disease involves a slower, more gradual degenerative process that leads to chronic bulging of inner disk material into the spinal canal, with subsequent pressure on and compression of the spinal cord. Type II IVDD usually affects older dogs between 8 and 10 years of age and comes on slowly, without the sudden, severe pain normally associated with Type I IVDD. Type II IVDD normally does not involve as many disks as does Type I.