Intervertebral Disc Disease (IVDD) - Thoracolumbar Area in Cats
Dr. Nicholas Trout
Thoracolumbar (T-L) disc disease is a condition that occurs when pressure is placed on the spinal cord by disc material that herniates beneath or adjacent to the cord. This condition is commonly referred to as Intervertebral Disc Disease (IVDD) that can occur in the thoracolumbar area of the back. It may be an acute (occurs suddenly) or chronic (slowly develops over time) condition and is uncommon in cats. Back pain
The exact cause of disc degeneration is unknown but in many animals there is a change in the content of the disc from a soft, pliable gel to a stiff mineral. This stiff material can slowly compress the spinal cord or suddenly burst into the spinal canal. When the disc involved is in the mid-portion or thoracolumbar area of the spine, the front legs are not affected. However, the back legs may be affected in varying degrees.
If your cat develops a T-L disc herniation, the symptoms may be mild back pain only or, in severe cases, complete paralysis of the rear legs without the ability to perceive any sensation in the limbs.
T-L disc disease most commonly occurs when animals are between three and seven years of age.
What to Watch For
Reluctance to play
Crying when handled, petted or lifted
Reluctance to climb stairs
Inability to walk or paralysis
Diagnostic tests are needed to recognize T-L disc disease and differentiate it from other diseases that may cause similar signs.
In addition to obtaining a complete medical history and performing a thorough general physical examination, your veterinarian will likely perform the following tests:
Neurological assessment. Because the amount of disc material pressing on the spinal cord can be small or large, and the rate at which the spinal cord is pinched can be fast or slow, the signs your cat shows can be extremely variable.
If your cat can walk normally but has back pain, your veterinarian will palpate the spine by applying gentle pressure to it to try to locate the affected area.
If your cat can walk but is clumsy, your veterinarian will check to see that only the back legs are affected and the front legs and head are normal.
If your cat cannot walk, your veterinarian will pinch the toes of the back legs to assess your cat's awareness of pain. Your cat may pull the leg back as a reflex response (the withdrawal reflex); however, your veterinarian will want to see if your cat cries out or tries to bite, indicating that he feels pain in the affected limbs. Just pulling the leg back does not indicate that your cat can feel his legs.
Radiographs of the spine may be helpful to localize the affected disc space, but definitive diagnosis of spinal cord compression is usually obtained by injecting a dye into the spinal canal, a procedure called a myelogram. When available, a CT scan may prove to be an alternative to myelography.
The type of appropriate treatment will depend on the severity of the clinical signs. Cats with milder forms of the disease may be treated medically, whereas more severe cases may need surgery. Treatment for T-L disc disease may include one or more of the following:
Medical treatment may consist of rest and anti-inflammatory medication, usually in the form of steroids. Muscle relaxants may also be used to alleviate spinal muscle spasm.
Surgical management may be recommended, particularly if the signs are severe or there is no response to medical management. This involves localizing the exact site of the disc extrusion with a myelogram or CT scan. Then a "window" is made in the spinal bone to relieve the pressure on the spinal cord and to allow access to the disc material so that it can be removed.
Strict cage rest will be essential for at least four weeks when opting for medical management. This rest is essential to allow a scar to form over the top of the disc material; early activity may precipitate the herniation of the rest of the disc material and worsening of your cat's condition. Failure to confine a cat with disc herniation is a common reason for early recurrence.
If your cat is unable to urinate on his own, he will need help emptying his bladder. When the bladder overfills, urine dribbles out, but this results in stretching of the bladder and may make your cat unable to urinate even if there is improvement in the condition of the spinal cord. Bladder emptying is usually done three to four times a day. If your cat is released from the hospital while he is still having difficulty urinating be sure that your veterinarian shows you how to empty the bladder (called "expressing" the bladder).
If your cat is unable to walk, physical therapy is important to promote muscle strength. Have your veterinarian or the veterinary staff show you how to do this.
Be prepared for small increments of improvement. Depending on the severity of the disease your veterinarian will estimate how long your cat's recovery may take. Most likely your cat won't walk immediately away after surgery. Just as in people, it takes time to recover from spinal cord injury, so be patient.
Observe your cat closely for any worsening of clinical signs. If you notice any deterioration in your cat's condition, contact your veterinarian immediately. If he is predisposed to back problems be aware of the early signs of disc disease. If he shows any sign that might indicate a neurologic problem, seek veterinary advice as soon as possible.