Intervertebral Disc Disease - Thoracolumbar Area in Dogs

Intervertebral Disc Disease (IVDD) - Thoracolumbar Area in Dogs

By: Dr. Nicholas Trout

Section: Veterinary Care In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations.

Diagnosis In-depth

Diagnostic tests are needed to recognize T-L disease and differentiate it from other diseases that might cause similar signs.

In addition to obtaining a detailed history, your veterinarian will perform a general physical examination, usually taking into consideration your dog's possible back pain. Depending on the findings, other tests that your veterinarian may wish to perform include:

  • A neurological examination. This consists of a series of tests which help define the location of the spinal cord damage.

    The head, neck and front legs are assessed to determine whether the spinal cord in front of the third thoracic vertebrae (T3) is normal or not. With T-L disc disease only the rear limbs should be affected.


    The back legs may be assessed for the ability to move and walk – the presence of motor function and the ability to respond to the brain's command to walk. Your dog may be assessed as normal, clumsy or unable to walk. The tail may be held at the base to assist in this activity. The feet may then be turned over or "knuckled" to assess your dog's ability to recognize the abnormal position of the paw. Loss of the ability to recognize how the feet are placed (proprioception) indicates mild damage to the spinal cord and often precedes the loss of motor function (or the ability to move the legs). Other tests may follow to evaluate the brain's awareness of the position of the feet.

    If your dog cannot walk even with support your veterinarian will pinch the toes of the back legs to assess for deep pain sensation. This is done either with fingers or with an instrument such as a hemostat. Although this may appear barbaric, it is an important test to help define the severity of the spinal cord injury. If your dog feels the stimulus, he or she should cry out or try to turn around and bite. In some dogs, subtle signs such as pupil dilation may indicate that they feel the pinch.

    If your dog does not show any indication of feeling pain from this procedure, typically severe damage to the spinal cord has occurred. It is important to note that pulling the leg away when the toe is pinched does not mean that your dog feels the pain. This is just the "withdrawal reflex," not conscious sensation of pain. Crying or biting suggests that the information from the toe being pinched got past the damaged region and was received by the brain; pulling away does not.

    Other reflexes are tested on the back legs to better define the location of the injury.

    Your veterinarian may feel for your dog's bladder and check the muscle tone in the anal region. These sites could be affected by spinal cord injury.

    Palpation, which is a technique of examining organs or body parts by touching and feeling, along the spine may reveal the most sensitive, affected area.

    At the end of the examination your veterinarian will likely be able to define the location of your dog's injury, determine the severity of the problem, and make recommendations about how it should be treated. Obviously, the more marked the damage to the spinal cord, the more severe the effects on the back legs and the worse the prognosis. Additionally, the longer the damage has been present, the worse the prognosis.

  • Blood tests are usually not specific for this disease.

  • Plain radiographs (X-rays) may be helpful but are not definitive for a disc compressing the spinal cord. A myelogram – an X-ray study in which dye is injected into the spinal canal – is needed to show that the cord is swollen or pinched or buckled. Alternatively, a CT scan may be used. Myleography and CT scans require general anesthesia and are usually performed prior to surgery so that anesthesia is administered only once.

     
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