Intervertebral Disc Disease in Canines

Dogs have little 'discs' between the bony vertebrae in the spine, and problems with these discs can put pressure on the delicate spinal cord. This causes a range of signs including pain, weakness, incoordination and potentially paralysis. Spinal surgery is sometimes needed to treat disc disease, but this is not required in all cases.

What are the discs in the spine?

The dog's spine is made of bony vertebrae. The vertebrae surround the spinal cord, which is a tubular structure made of lots of nerve fibres that run down from the brain to reach all the different parts of the body. Nerve impulses travelling through these fibres allow the brain to control the body and feel sensations.

Because the spinal cord is very delicate, it must be protected by the bony vertebrae. Between the vertebrae there are 'discs'that cushion the bones as they move in relation to each other. These discs have an outer fibrous layer called the 'annulus fibrosus', which surrounds a gel-like centre called the "nucleus pulposus'.

Animation on vertebral anatomy:

Dogs sometimes develop problems with their discs. There are two main types of disc disease in dogs: Type I and Type II.

What happens in Type I disc disease?

Type I disc disease is often called a 'slipped disc'. This is when the gel-like centre of the disc ruptures through the fibrous outer layer and this puts pressure on the spine.

Animation illustrating Type I disc disease:

Normally, this happens as a result of chronic degeneration of the disc. In this process the centre of the disc becomes harder, meaning it loses its flexibility and there is extra force on it when the dog moves. Eventually, this causes the disc to rupture.

Disc degeneration is most common in young to middle-aged small-breed dogs. Some breeds are particularly predisposed, including the Dachshund, Shih Tzu, Pekingese and Basset Hound.

While most discs that rupture are degenerate, it is also possible for a healthy disc to rupture as a result of severe trauma such as a road traffic accident.

What happens in Type II disc disease?

In Type II disc disease, the disc does not rupture but it bulges out and puts pressure on the spinal cord.

Animation illustrating Type II disc disease:

This most often affects medium to large breed dogs.

What are the signs of disc disease?

The symptoms of disc disease result from compression of the spinal cord. The nature of the signs depend on how much compression there is, how acutely it has developed, and where in the spine the problem is.

If the disc disease is in the neck, signs can affect all four limbs. Dogs with an acute disc herniation in this area may show marked neck pain and struggle to lift their head properly. They may also show weakness or incoordination in all limbs, though depending on which parts of the spinal cord are compressed most, the limbs may not be equally affected. In severe cases, the legs can be paralysed.

Chronic disc disease in the neck can have more subtle signs, with dogs being reluctant to move their neck fully. Often, they will develop a wobbly gait with hindlimb incoordination and short strides on their front limbs.

Problems with the discs in the middle of the spine will only affect the hindquarters rather than the forelimbs. Acute disc disease in this area can cause back pain and hindlimb weakness, incoordination and lameness. Hindlimb paralysis and urinary incontinence can develop in severe cases. Chronic problems are again more subtle and you may see that your dog struggling to stand up or jump.

How will my vet diagnose disc disease?

First, your vet will talk through your dog's signs and examine your pet, assessing the nerve reflexes and responses. If they suspect disc disease, they will probably suggest imaging to confirm this. X-rays can provide some indication of whether disc disease is present, but often advanced imaging such as CT or MRI scans is needed to diagnose the condition.

How is disc disease treated?

The best way to treat disc disease depends on a number of factors including how severe the problem is and the general health of your dog. Your vet will help you make the best decision for your pet.

If your dog only has mild signs, or if an operation would be a big risk for them, your vet may suggest you try conservative management with a period of rest and a course of anti-inflammatory painkillers. If you opt for this with your dog, it is very important to follow your vet's advice regarding how strictly and how long to rest your dog, as exercise can make the disc disease worse. Usually, strict rest is advised for several weeks, followed by a very gradual build-up to normal exercise.

If your dogs signs are more severe, particularly if they are paralysed or have lost pain sensation, your vet is more likely to advise surgery. There are various different surgical options and your vet will advise on which is best for your pet. Spinal surgery is a specialist procedure and your vet may recommend that your dog travels to a special referral hospital for the surgery.

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