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Dogs' Disc Problems can be Treated

Pet Column for the week of August 23, 2004

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

The "herniated disc" is a common back injury in people who take a fall or strain their backs. Likewise, dogs can suffer from herniated vertebral discs that can lead to severe pain or paralysis. Dr. Dianne Dunning, veterinary surgeon formerly at the University of Illinois Veterinary Teaching Hospital in Urbana, explains that though these injuries can be serious, there are effective treatments, such as physical rehabilitation and surgery.

Between each pair of vertebrae there sits an intervertebral disc, which Dr. Dunning compares to a jelly donut. "An outer fibrous ring called the annulus fibrosis is like the cake donut, and it is filled with a dense, shock-absorbing material called the nucleus pulposus, which is like the jelly."

If the "jelly" becomes calcified and hard, it loses its shock-absorbing capacity. Pressure or trauma can cause the calcified material to bulge or explode into the nearby spinal canal, which houses the spinal cord, a process called herniation. The resulting pressure on the spinal cord can result in clinical signs ranging from pain to complete loss of feeling and function of the limb.

Classically, there are two types of disc herniation: "disc extrusion" occurs when the nucleus pulposus explodes into the spinal canal and "disc bulging" is when the nucleus pulposus protrudes into the spinal canal. This latter type is the type commonly suffered by people.

Some dog breeds, particularly "dwarf" breeds with long bodies and short legs (such as Basset hounds, dachshunds, and Pekingese), are prone to disc extrusion as they experience a condition know as chondroid metaplasia, where the discs begin to deteriorate and calcify as early as one year of age. Large breed dogs (such as Labradors, German shepherds, and Doberman Pinschers) are more prone to disc protrusion, similar to what is seen in people.

The clinical signs stemming from the disc herniation depend upon the location of the injury; a disc injury in the lower back can cause problems only in the hind limbs, whereas an injury in the neck can cause dysfunction in all limbs. Dr. Dunning explains that with spinal injuries, neurological function is lost in a specific order, and the chance for recovery is greatly influenced by seeking prompt medical attention.

In the first stage an animal loses proprioception, or its ability to know where its limbs are. When this happens, an animal will display a "drunken" walk, known as ataxia. If the problem worsens, the animal will lose its ability to move its legs. In the last stage of paralysis an animal loses its ability to feel it legs. Paralysis can be progressive, going from bad to worse, so an animal displaying any of these signs should be seen by a veterinarian immediately.

The treatment for disc herniation depends on the degree and duration of neurological dysfunction. For mild disc injuries with no loss of strength or voluntary movement, a veterinarian will prescribe rest and limited activity, just as a human doctor advises against heavy lifting or other activity that may stress the spine.

For animals that have not responded to conservative management or who have had multiple relapses of clinical signs of disc disease or have paresis or weakness of the limbs, surgery is a likely recommendation. Before surgery, diagnostic imaging such as an MRI, myelogram, or CT scan will be performed to confirm the cause and location of problem.

Decompression surgery can relieve pressure on the spinal cord caused by disc debris. The veterinarian creates a hemilaminectomy, similar to a surgical "sunroof," out of the bone overlying the spinal cord and removes the problematic disc material, relieving pressure on the spinal cord. Over 90 percent of dogs improve with this surgery, if medical attention is prompt and the degree of neurological impairment is not too severe. Both extrusion and bulge herniations can be treated with decompression surgery.

In lieu of or in addition to surgery, rehabilitation (known as physical therapy in human medicine) can be an essential part of spinal injury treatment. Rehabilitation can involve underwater treadmills and exercises designed to strengthen muscles and neurological function. The University of Illinois Veterinary Teaching Hospital is among the first institutions to implement veterinary rehabilitation.

Unfortunately, disc herniation is an injury that can happen repeatedly, in different vertebrae, especially in breeds that are predisposed. The most common sites for disc herniation are the lower back and neck areas, where the immobile rib cage joins areas of high movement, causing stress on those vertebrae.

Owners of dwarf-breed dogs or other dogs that are predisposed can minimize risk of disc injuries or avoid repeated episodes by keeping their dogs weight down. Excess body weight adds biomechanical load and stress on the discs. A lean, well-muscled, and fit dog is also better able to recover from injuries if they occur, so Dr. Dunning recommends daily moderate exercise.

Also, use a chest harness instead of attaching leashes to buckle collars that can pull suddenly on the neck. If possible, avoid sudden stops and starts that can stress the spine, such as launching off furniture. Training a small dog not to jump off furniture can curb risky habits.

"Most importantly," Dr. Dunning emphasizes, "owners should not feel guilty. Disc injuries are never really anyones fault but rather a function of how the animal is built."

For more information about disc herniation or other spinal injuries, contact your local veterinarian.