Intervertebral Disc Disease (IVDD) in Cats
Although intervertebral disc disease (IVDD) is seen less frequently in cats than dogs, it is still a serious condition. IVDD occurs when the cushioning discs between the vertebrae of the spinal column either bulge or burst (herniate) into the spinal cord space. These discs then press on the nerves running through the spinal cord causing pain, nerve damage, and even paralysis.
Symptoms and Types
Made up of a gelatinous substance surrounded by a thick outer layer, intervertebral discs are basically the shock absorbers of the spine. There are two types of disc herniation seen in cats: Type I and Type II, of which Type II generally has less severe signs and symptoms.
Symptoms of IVDD may include:
- Unwillingness to jump
- Pain and weakness in rear legs (lameness)
- Anxious behavior
- Crying out in pain
- Muscle spasms over back or neck
- Hunched back or neck with tense muscles
- Reduced appetite and activity level
- Loss of bladder and/or bowel control (urinary and fecal incontinence, respectively)
In Type I, more commonly found in the neck region, discs develop a hardening (or calcification) of the outer layer. This damages the disc, allowing it to break down easier. Any forceful impact such as jumping and landing can cause one or more disc(s) to burst, and the inner material to press on the spinal cord. With Type II herniation, the discs become hardened and fibrous over a long period of time and eventually break down, bulge out, and compress the spinal cord.
When the nerves of the spinal cord are compressed, the nerve impulses are not able to transmit their signals to the final destination in the limbs, bladder, etc. If the damage is severe enough, paralysis and loss of bladder and bowel control can occur. Depending on the location of the disc that is bulging, signs occur anywhere in the body from the neck to the rear legs. In cats, the discs more commonly bulge in the neck and upper back.
Examination by your veterinarian will include a complete neurologic exam, which will help identify where in the spinal cord the injury is located. Plain X-rays may show an abnormal area in the spine. However, because the spinal cord does not appear on X-rays, special imaging may be necessary to locate the source of the injury.
Once such procedure, called a myelogram, injects a special dye into the spine, which surrounds the spinal cord and allows it to appear on X-rays. This test requires the animal to be put under anesthesia. In some cases, further testing such as an MRI (magnetic resonance imaging) or CT (computed tomography) scan can also be used to locate where the nerves are being pinched, which is necessary for surgical repair.