Intervertebral Disc Disease (IVDD) – Cervical Area
Dr. Nicholas Trout
Diagnosis In-depth A neurological examination will follow. This will consist of a series of tests that aim to define the location of the damage to the spinal cord. The head, and in particular the cranial nerves, which are the nerves that supply the head, will be assessed to make sure that there is no lesion in the brain. Your pet may be neurologically normal and experience only neck pain. Your pet may be able to walk, but appears to be clumsy or drunk. Which side(s) is/are affected and which leg(s) are noted. All four legs are assessed for the ability to move and walk, as well as the presence of motor function. 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 pet's ability to recognize the abnormal position of the paw. This is an early sensation to be lost, and usually precedes loss of motor function. Other tests may follow to evaluate the brain's awareness of the position of the feet.
After taking a detailed history, your veterinarian will perform a general physical examination, which is usually normal aside from cervical pain. Ability to flex and extend the neck is noted together with range of motion to the left or the right.
If your pet cannot walk even with support the toes of all four legs are pinched, either with fingers or often with an instrument called a hemostat to clamp down on the toes. This may look barbaric but is very important to 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. If your dog does not feel the pinch, this is an indication that deep pain sensation has been lost. This is the most severe type of spinal injury.
It is important to note that pulling the leg away when the toe is pinched does not mean that your pet feels the pain. This is just the "withdrawal reflex" and 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.
Your veterinarian will feel for your pet's bladder and check the muscle tone in the anal region. These sites could be affected by spinal cord injury.
Your veterinarian will be trying to define whether the muscle tone and reflexes in the front legs are reduced or exaggerated. Reduced activity may suggest that the neck lesion lies in the region of the brachial plexus or lower cervical area, whereas exaggerated activity would indicate a higher neck injury.
At the end of the examination your veterinarian will be able to define the location of the injury, the severity of the problem and make recommendations about how best it should be treated. Obviously, the more marked the damage to the spinal cord, the more severe the effects on the legs and the worse the prognosis. The longer this damage has been present the worse the prognosis.
Blood tests are not specific for this disease.
Plain 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 or MRI may be used. Myleography, CT scans and MRI require general anesthesia and are usually performed when the pet is going from this procedure to surgery.
The choice of medical versus surgical treatment will depend on the severity of the problem.
For dogs with mild neck pain, or very mild neurological signs such as clumsiness, that still retain the ability to walk, medical management can be an appropriate course of treatment. This involves strict cage rest and the use of medications such as muscle relaxants and steroids. Your dog may be hospitalized and given a course of intravenous steroids, or may receive a course of oral steroids that taper off over a number of weeks when your dog goes home.
The common steroid used is prednisone and this usually results in increased thirst, urination and appetite. Some dogs can also become very excitable. Medical management has been reported to fail in about 33 percent of dogs in one study.
When neck pain is severe, fails to respond to medical options or produces significant neurological problems in the legs, surgery is indicated. A myelogram, CT scan or MRI are performed to locate the exact disc space affected. A small window of bone is drilled in the underside (ventral aspect) of the spinal bones (ventral slot) on either side of the affected disc space. This allows access to the ruptured disc material and its removal from the spinal canal.
Your pet will not be cured instantly by the surgery. The procedure takes the pressure off the cord, allowing it the opportunity to heal but does nothing directly to the cord itself. It has to heal on its own. Fortunately, however, the spinal canal is at its largest through the neck region such that the cord is more tolerant of extruded disk material. Recovery is usually quicker here than for disc disease at the thoracolumbar site, for example.
If your dog was able to walk before surgery, even though the walk was wobbly, the prognosis following surgery is excellent.
If your dog had lost the ability to walk, but had deep pain sensation, the prognosis following surgery is still good to excellent.
If your dog had lost deep pain sensation, the prognosis following surgery becomes guarded.