The first part of almost any diagnostic protocol is a thorough history and a complete physical examination. When spinal injuries are suspected, a complete neurological examination is warranted. In cases of IVDD, the neurological examination will be consistent with a single, focal lesion in the spinal cord and will help the veterinarian localize the site of injury to a particular section of the spine. However, a neurological examination will not confirm whether intervertebral disk disease is the cause of the dog’s injury.
Regular blood work (a complete blood count and a serum biochemistry panel) and a urinalysis are not particularly useful if the sole problem is IVDD; the results of these “initial database tests” will be normal in an otherwise healthy dog. Sampling and assessing the cerebrospinal fluid (CSF) by way of a spinal tap can provide more helpful information, as can an electromylogram (EMG). Typically, CSF analysis is most useful to rule out causes other than IVDD, such as cancer, infection or inflammation from another source. Radiographs (x-rays) of the spine are almost always recommended and typically are performed under anesthesia or heavy sedation. Radiographs can reveal abnormalities in the vertebrae and the spaces between them that can help rule out IVDD, such as bone tumors, fractures, discospondylitis or other potential causes of spinal cord damage. Radiographs can also reveal narrowed intervertebral disk spaces that are consistent with, but not diagnostic of, IVDD.
Another form of medical imaging that is indicated for most dogs suspected of having spinal cord damage is called myelography. This involves injecting a contrast medium directly into the spinal canal, waiting a specific period of time to allow that material to move through the cerebrospinal fluid within that canal, and then taking survey radiographs to look for any pressure points from bulging disk material. Disk herniation and spinal cord compression will usually show up with the contrast between the injected dye and the radiographic outline of the vertebral bones. Other advanced imaging procedures that can be highly useful to diagnose IVDD include computed tomography (CT/CAT scan) and magnetic resonance imaging (MRI). Myelography, CT scan and MRI are all advanced diagnostic procedures that are not routinely available at most general veterinary practices. They are, however, available at specialty veterinary clinics and at veterinary teaching hospitals affiliated with veterinary schools.
While the diagnostic process for dogs with neurological spinal injuries can be quite involved and usually requires the involvement of several different veterinary specialists, it is usually worthwhile. The prognosis for dogs with IVDD is generally quite good if treatment is initiated early in the course of the disease.