CVI is a condition affecting the spinal cord in the neck region that in large and giant breed dogs that leads to pain, weakness, and paralysis. There are two types of CVI identified. In young dogs, developmental abnormalities lead to malformation of the vertebrae in the neck and pressure on the spinal cord. In older dogs, the condition is associated with intervertebral disk movement and pressure on the spinal cord. This may be due to vertebral joint instability.