Intervertebral Disk Disease
This information is not meant to be a substitute for veterinary care.
Always follow the instructions provided by your veterinarian.
What are Intervertebral Disks?
The intervertebral disks
sit between the vertebrae in the spine. They act like shock-absorbers to help
dissipate the forces placed on the spine. They have two portions, an outside
fibrous covering ( the annulus fibrosis) and an inside, more gelatinous portion,
the nucleus pulposis. In this way they kind of resemble a jelly donut. The
outside of the donut is the annulus, and the jelly on the inside is like the
nucleus pulposis
Related anatomy
When the intervertebral disks become damaged, this is referred to as
intervertebral disk disease ("Disk disease", "Slipped disk"). As disks age,
they lose water content, and become less able to withstand compression. They
become less able to withstand forces placed upon them. If too much force is
placed on them, they can be squeezed and expand or rupture. This rupture
usually occurs in an upward direction, and the disk extrudes into the spinal
canal where the spinal cord is. Signs develop either because of the force of
the disk material hitting the cord, or due to the disk material compressing
the spinal cord.
Intervertebral disk disease can occur in any area of the spinal cord.
Dachshunds appear predisposed, as their disks age or degenerate quicker than
most dogs. Young to middle-aged dogs are most commonly affected. Dogs less
than 1 year of age rarely have intervertebral disc disease. Geriatric dogs
are occasionally affected. Clinical signs of disk disease are rare in cats.
Signs of a disk problem range from being painful to being unable to move. The
more spinal cord damage, the worse the clinical signs. Animals with the worse
spinal cord damage from disk disease lose the ability to move and to feel
(conscious sensation) their limbs. To know if an animal can consciously feel, we
have to pinch the toes and see if the animal vocalizes or tries to bite us.
While this test may seem harsh, it is very important. If an animal has lost the
ability to feel in the legs, its chance of walking again is about 50%. If an
animal can still feel in the legs, even if they can't move, there is a 75%
chance or greater that the animal can walk again if surgery is performed.
The diagnosis of disk disease is based on clinical signs initially. To
prove that a disk is pressing on the spinal cord, a special X-ray study
known as a myelogram is often necessary. To perform a myelogram, first a
spinal tap is done. Next, a dye or contrast agent is injected around the
spinal cord to outline it. This usually shows where the spinal cord is
damaged, and helps the surgeon to know exactly where the surgery should be
performed. For both the myelogram and the spinal tap the animal needs to be
very still, therefore anesthesia is necessary to perform these tests.
CT or MRI are other techniques that can be used to see the ruptured disk.
General guidelines have been established for therapy depending upon
severity of clinical signs. Mildly affected animals (animals with pain alone
or mild weakness but able to walk) may be managed with cage confinement for
at least two weeks. Strict confinement is very important to allow for
healing of a partially damaged disk. If after 2 weeks signs are not
improved, diagnosis and surgery should be considered. If the animal worsens
during this time, surgery should be considered sooner.
If improvement is noted, continuation of cage confinement is indicated for
up to one to two weeks after the animal is clinically normal.
More severely affected animals (those who are unable to stand and walk) are
considered for surgery. The surgery is performed to remove extruded disk
material from around the spinal cord, relieving the compression and giving
the spinal cord the best chance at healing.
This information was made possible by funds from the
Neurology
Endowment
at Washington State University.
Washington State University assumes no liability for injury to you
or your pet incurred by following these descriptions or procedures.
top of page
|
|
Did you find this information useful? Please
consider helping us train the veterinarians of tomorrow by making a
gift to the college.
The Pet Health Topics Web site is a free
service provided by the College of Veterinary Medicine at Washington
State University. Your donation will help support veterinary
education and research.
|
