PET COLUMN FOR THE WEEK OF NOVEMBER 10, 1997
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2938 Vet. Med. Basic Sciences Bldg.
2001 S. Lincoln Ave.
Urbana, Illinois 61802
By Theresa A. Fuess, Ph.D.
University of Illinois
College of Veterinary Medicine
Dogs, like humans, are susceptible to painful and debilitating back problems. Disk disease is most common among small breeds, such as beagles, pekingese, and dachshunds, according to Dr. Scott Averill, small animal surgical resident at the University of Illinois Veterinary Medicine Teaching Hospital in Urbana.
"The spine is a stack of bones (vertebrae) interspersed with 'cushions' (intervertebral disks) and held together by ligaments," explains Dr. Averill. "Bony extensions of each vertebra form a canal through which runs the spinal cord, an extension of the brain that allows communication throughout the body. The vertebrae support the animal's torso and protect the spinal cord. The intervertebral disks act as shock absorbers and allows the spinal column to be flexible."
Healthy disks are filled with water, collagen, and other substances that provide cushioning and resiliency. In intervertebral disk disease, the disks lose much of this water and may even calcify. This type of degeneration begins when the dog is around 7 months old. By age two years, the disks are fully degenerate. Eventually the disk may rupture into the spinal canal and compresses the spinal cord. The result is severe pain and compromised communication via nerve impulses to the body beyond that point.
Ruptured disks are seen most often in the lower back, beyond the rib cage, but about 15 percent of cases occur in the neck. Ruptured disks in the lower back will cause severe back pain. The rear legs will often be weak, wobbly. Ruptured disks in the neck will cause the dog to hold its head down in a hunched, motionless position. The signs may appear suddenly, with a cry of pain when the dog is running, or may progress gradually. Compression on the spinal cord by disk material will cause pain and cord damage, ultimately resulting in paralysis.
Treatment depends on the severity and frequency of occurrence. "At the first episode, when the dog shows just pain or mild weakness, treatment consists of confining the dog to its crate for 4 to 6 weeks, allowing it outside only to relieve itself," says Dr. Averill. Restriction of activity will prevent further extrusion of the disk material. Dr. Averill does not recommend using anti-inflammatories or steroids, which may make the dog feel too good and encourage activity that worsens the problem. Most dogs that receive crate rest show some improvement within 3 days.
Surgery to decompress the spinal cord is indicated if cage rest is not successful, if the dog suffers more than one incident of pain, or if the dog is very weak or paralyzed. The surgeon makes a "window" in the vertebral bodies and removes all the disk material from the spinal canal. The prognosis for full recovery following this surgery is very good. Three percent of the dogs that have had one disk rupture, will eventually have a second one rupture, but this possibility can be eliminated if the remaining disks are prophylactically removed during the first decompression surgery.
In cases that don't regain full function, permanent nerve damage has occurred. If the dog shows signs of such permanent damage prior to surgery, a procedure called a durotomy can be done to directly view the spinal cord. If the nerve fibers are intact, the dog may recover; if not, its neurological status will worsen, leading to continued loss of motor control and potentially of the ability to breathe.
Caring for a dog with severe disk disease takes a big commitment. During the post-operative period owners will need to catheterize or manually express the bladder three times a day. If the dog cannot defecate, intermittent enemas may be necessary. The dog should be turned every 4 hours and given physical therapy, including making a bicycling motion with the rear legs and walking with the dog's weight supported.
For more information about disk disease in dogs, contact your local veterinarian.
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