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Intervertebral Disc Disease

Randy Walker DVM

About Intervertebral Disc Disease...

Intervertebral disc disease (sometimes also referred to as a "slipped disc" or "I.V. disc disease") is a disease of dogs (and rarely cats) in which one or more intervertebral discs (see attached diagram) ruptures and places pressure on the spinal cord.

Briefly, Describe The Normal Intervertebral Disc That Disc Is Changed During Intervertebral Disc Disease.

In the normal spinal column (also called the back bone) the spinal cord lies within the hollow centers of the vertebrae (the bones of the spine). Normally these vertebrae are separated by discs of cartilage material (see the attached diagrams) which keep the bones evenly spaced and aligned with each other. In a case of intervertebral disc disease one or more of these discs have protruded or "slipped" so that they place pressure on the spinal cord. This usually happens in the mid to lower back but can also happen in the neck on occasion.

What Are The Clinical Symptoms Of The Dog With I.V. Disc Disease?

The dog with a slipped disc will usually experience varying degrees of pain, loss of control over the rear quarters, and paralysis depending on how severe the damage to the back is. Dogs with I.V. disc disease will fall on a spectrum with the most mildly affected dog (at one end of the spectrum) experiencing only back pain. The dog toward the middle of the spectrum has back pain and mild incoordination and loss of sensation on the rear limbs. Finally, the dog on the other end of the spectrum has complete paralysis of the hind quarters. As the disc initially presses against the spinal cord, intense pain results in this area. This is nature's way of telling the dog that a serious problem has occurred here and that activity should be limited. If the slippage is severe, it will impinge upon the spinal cord to the point of interfering with the transmission of nervous impulses to the rear quarters. This results in loss of coordination (stumbling) and weakness and loss of feeling in the rear limbs. In the most severe case, enough interference with conduction of nervous impulses occurs to cause complete paralysis of the rear limbs, bladder and anus.

What Causes I.V. Disc Disease?

Most cases of intervertebral disc disease result from degeneration of the disc as the patient ages. This degeneration often results in progressive weakness of the disc which the dog can usually cope with. Eventually, however, the forces upon the weakened disc will cause it to prolapse, resulting in immediate onset of back trouble. In some other cases the damage to the disk can result from an injury.

Which Dogs Are Most Likely To Get I.V. Disc Disease?

The most common breed affected is the Dachshund, followed by the Cocker spaniel, miniature poodle, and other small breed dogs. Dogs can inherit the tendency for intervertebral disc disease so if a given dog has a history of I.V. disc disease in their family tree, they will be more likely to experience a back problem. It should be remembered, however, that its possible for I.V. disc disease to happen to any dog or cat at any age and of any breed.

How Is I.V. Disc Disease Treated?

This depends on how far the disease has progressed before treatment. In those cases where back pain with or without mild loss of rear limb coordination is the only clinical sign, then medical therapy is all that is indicated. This medical therapy usually consists of medications to reduce the swelling and inflammation around the spinal cord and also muscle relaxants to decrease tension in the back. As a general rule, medical therapy is preferred in those cases where the patient still has rear limb mobility. In those cases where complete paralysis of the rear limbs has occurred, then emergency surgery is indicated. As a general rule, the I.V. disc syndrome patient who is completely paralyzed on the rear limbs must receive surgery within 12 hours (and sooner is better) in order to have a reasonable chance of regaining function of the rear quarters. The surgery performed on these patients consists of removing the tops of the vertebrae in order to relieve the pressure. After surgery has been performed we still need several weeks (usually) of physical therapy to regain full use of the limbs. As noted above, the patient with paralysis of the rear limbs must have surgery as soon as possible (at least within the first 12 hours) in order to regain function of the rear limbs.

What Is The Prognosis For The Patient With I.V. Disc Disease?

Here again, this depends on how severe the problem is and how long it goes on before therapy. Each case is different. Usually those cases with only back pain have the best overall chance of complete recovery. Those with back pain and moderate rear limb weakness and incoordination have a poorer prognosis but most of these respond well to medical care. As noted above, the dog with complete paralysis of the rear limbs is the most serious situation and, of these dogs, the ones who don't receive surgery have a very poor prognosis for a return to proper function. If your dog has complete paralysis of the rear limbs you must contact your regular veterinarian or an emergency veterinary clinic immediately since even a few hours can make a difference in recovery potential.

- Randy Walker DVM
Sun Lakes Animal Clinic
May 16,2004

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