February 27, 2008
Symptoms and Treatment of Intervertebral Disc Disease
What is an intervertebral disc?
An intervertebral disc is a shock absorber-like structure located between the vertebral bones to help dissipate the forces placed on the spine. An intervertebral disc is made up of two portions, an outer fibrous portion called the annulus fibrosis and an inner more gelatinous portion called the nucleus pulposis.
Who develops intervertebral disc disease?
Intervertebral disc disease is common in dogs and rare in cats. This disease is one of the most common neurologic disorders seen in dogs. Young to middle-aged dogs are most commonly affected.
Disc degeneration occurs in almost any breed, but small breed dogs are more commonly affected such as the Beagle, Basset Hound, Pekingese, Cocker Spaniel, Poodle, and Dachshund, which appears more predisposed than any other breed. Intervertebral disc disease can occur in any area of the spinal cord, however eighty percent are seen in the thoracolumbar spine (mid back region) compared to twenty percent seen in the cervical spine (neck).
Why does intervertebral disc disease occur?
As the intervertebral discs age, they lose water and become less able to withstand compressive forces placed on the spine. This is a degenerative process that leads to the discs becoming mineralized (calcified). If the amount of stress placed on the degenerative discs exceeds their ability to handle the force then the discs will be squeezed between the vertebral bones of the spine causing them to bulge or rupture. The bulging or rupture usually occurs in an upward direction into the spinal canal where the spinal cord resides. The signs of intervertebral disc disease then develop either due to the bulging disc compressing the spinal cord or due to force of the ruptured disc material hitting the spinal cord and interfering with its blood supply.
What are the signs of intervertebral disc disease?
Signs that your pet may be suffering from a disk problem range from pain alone, loss of coordination, difficulty walking and being unable to move their limbs. The greater the spinal cord damage the more severe the clinical signs. Pets with the most severe spinal cord injury from disc disease lose the ability to move and to feel (conscious sensation) their limbs. If the pet has lost pain sensation in the legs, their chances of walking again are about 50% or less. If the pet still has feeling in the limbs, even if they can't move their legs, there is a 75% chance or greater that the animal can walk again if surgery is performed.
What is the treatment for intervertebral disc disease?
Your veterinarian may suspect that your pet is suffering from disc disease based on clinical signs initially; however, in order to prove that a disk is pressing on the spinal cord an X-ray or a myelogram (a special X-ray study) is often necessary. Treatment for intervertebral disc disease is usually dependent upon the severity of clinical signs. Mildly affected animals (animals with pain alone or mild weakness but ability to walk) may be managed with cage confinement and anti-inflammatory medications. Strict confinement is very important to allow for healing of a partially damaged disc. If a pet is not improving or the clinical signs are worsening (unable to stand and walk) then additional diagnostic work-ups, including spinal x-rays and myelogram, are indicated. A CT or MRI is another diagnostic technique that can be used to identify if a ruptured disc is present. During a myelogram a spinal tap is performed and then a contrast agent (dye) is injected around the spinal cord to outline it. A myelogram usually shows where the spinal cord is compressed, and helps the surgeon to know exactly where the surgery should be performed. The surgery (a hemilaminectomy over the thoracolumbar region or a ventral slot over the cervical region of the spinal column) is performed to remove bulging or extruded disk material, relieve the compression on the spinal cord, and give the patient the best chance at recovering from the spinal cord injury.
Jeffrey Meinen, DVM, DACVS
Wisconsin Veterinary Referral Center (WVRC) is the Midwest’s leader in veterinary specialty and emergency care. Its Waukesha location (one half mile south of I-94, Exit 294) is open 24 hours/7 days a week and is staffed by full-time emergency veterinarians and specialists in Emergency/Critical Care, Surgery, Cardiology, Anesthesia/Pain Management, Medical Imaging, Dermatology, and Internal Medicine. WVRC now also has a Grafton location (one half mile west of I-43, Exit 92) that provides emergency veterinary care weekdays 5pm – 8am and weekends and holidays 24 hours. For more information visit www.wiwvrc.com.
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