Your dog's backbone consists of the spinal cord, which contains the nerves that allow the body to function, the vertebrae that protect the cord, and the intervertebral discs. These are made of an outer layer of firm fibrous cartilage with a soft, gel-like center and act as shock absorbers for the spine, as well as giving it flexibility. Intervertebral disk disease (IVDD) may occur when the intervertebral discs begin to degenerate either from an injury or as a dog ages.
Types of Intervertebral Disc Disease
Type I: In Type I IVDD, the firmer outer cartilage layer becomes brittle, weak, and can break open if it is put under sudden pressure, for example, when the dog jumps up or pulls on a lead. This most commonly occurs in the neck area and the symptoms can be sudden and dramatic.
Type II: In Type II, disc disease develops more slowly. As an intervertebral disc hardens and eventually starts to bulge out towards the spinal cord, the pressure it exerts stops the nerves from working properly.
Symptoms of Intervertebral Disc Disease
The symptoms of intervertebral disc disease develop when the burst or bulging disc puts pressure on the spinal cord. This is painful and stops the nerves from functioning properly. The firmer the pressure, the deeper the damage.
The nerves in the spinal cord are arranged in layers. The most superficial nerves link the limbs and the brain, coordinating your dog's gait and posture. Beneath this layer are other nerves that control limb movement. In the deepest layer of all are the pain receptors.
The initial symptoms of spinal cord disc disease are often 'paresis' or wobbly walking. This reflects the fact that the 'proprioceptive' or coordinating nerves are being damaged. The dog is also likely to be in pain. This pain is a protective response mechanism from the body to discourage them from moving around too much and causing more damage.
If the condition progresses, symptoms appear that reflect the deepening nerve damage, eventually leading to paralysis. Most often, this is just in the back legs but can include the front as well. If things worsen, the dog will eventually lose the ability to feel pain in their legs. They can also lose bowel and bladder control, either becoming incontinent or, in some cases, being unable to empty themselves without help.
Treatment of Intervertebral Disc Disease
In the early stages of IVDD, your vet is likely to advise strict rest, to lessen the pressure on the spine and to try to prevent the disc from bulging any further. They will also prescribe pain relief.
The next step is to image the spine to see exactly where the damage is and how severe it is. X-rays can be used, but because the discs are made of soft cartilage, they don't show up as well as bone; sometimes dye is injected into the spine to outline the spinal cord and show up any areas where it is under pressure. Often the best way to assess the discs fully is with either CT or MRI scans, which usually need to be carried out at a referral clinic.
In some cases, rest and pain relief are enough to settle the discs down and reduce the pressure on the spinal cord. However, many affected dogs require surgery to remove the disc material from the spinal cord. This is a highly specialized procedure and not without risks, but is often curative
It can be difficult to prevent IVDD but if you have a long-backed breed of dog, you should ensure they stay slim, active, and are fed a healthy diet. If you suspect your dog is suffering from IVDD, you should speak to your vet immediately.