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.
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Last Edited: Dec 21, 2007 4:48 PM
