Intervertebral Disk Disease
Presented by Veterinary Neurosurgeon, Dr. Peter Brofman, DVM, MS, ACVIM
One of the most common reasons I see pets from the Charleston, SC area in need of a veterinary neurosurgeon is intervertebral disk disease (IVDD). IVDD occurs when the intervertebral disk degenerates resulting in extrusion or protrusion of disk material causing compression of the spinal cord and/or the nerve roots. Clinical presentation is variable and your pet may have mild signs of intermittent pain or severe signs with paralysis of the limbs and loss of any sensation. The intervertebral disk is made of a jelly-like inner nucleus pulposus and a fibrous outer ring called the annulus fibrosus. The disk acts as a cushion between adjacent vertebrae (back or neck bones). Effectiveness as a cushion is dependent upon the water content of the nucleus pulposus and the integrity and flexibility of the outer annulus fibrosus.
There are two main types of disk protrusion that may occur. Type I IVD extrusion most commonly occurs in chondrodystrophic breeds (long and short dogs such as the Dachshund). In chondrosytrophic dogs the disks undergo degeneration between 8 months and 2 years of age (75% of disks are degenerating by 1 year). The degeneration results in loss disk flexibility and calcification and then often ruptures causing a sudden onset of signs. This rupture may be precipitated by an activity but is also often a result from less strenuous, everyday activities.
Type II IVD protrusion is more commonly seen in nonchondrodystrophoid breeds (example; German Shepherd) and usually at a later time in life. These usually present with a more chronic and gradual onset of signs. While the Type I and Type II disk disease are more likely to occur in the respective breeds as stated above, this is not always the case and either may occur in any breed.
There are many diseases that may present with signs similar to IVD herniation, including meningitis, fibrocartilaginous embolism (FCE; a spinal cord stroke), diskospondylitis, and others. Diagnosis of IVD herniation cannot be made from plain x-rays and requires advanced imaging, such as a myelogram, CT scan, or MRI. All imaging modalities require general anesthesia. Myelograms are x-rays taken following the injection of a liquid dye into the subarachnoid space (similar to an epidural injection) so that it outlines the spinal cord. A CT scan and MRI do not require the invasiveness of the subarachnoid injection and give much more detail and information than the myelogram. Their costs are often greater than a myelogram; however, a myelogram carries risks that the MRI and CT scan do not, such as seizures, worsening of neurological signs including complete paralysis, bleeding into the spinal cord or brain, or fatal reactions to the contrast. The pros and cons can be discussed more specifically on case by case basis with each owner.
Based upon the history and signs being exhibited will help determine the best treatment options for IVD herniation. In some cases with mild weakness or short term pain, conservative medical management may be appropriate. In cases of severe or chronic pain, severe weakness, or rapid worsening of signs surgery may be a more appropriate choice. Again, these options will be discussed in more detail on a case by case basis. With surgery the prognosis for recovery is generally quite good with approximately 90% of the patients regaining function of their limbs and being pain free. The chance of recovery is less in patients that have lost sensation in their limbs. As with any surgical procedure, there are risks of anesthesia, bleeding complications, or worsening or no improvement of neurological signs, however, these are uncommon.
Postoperative care at home will vary depending upon the neurological status of your pet. All pets need to be restricted for at least 4-6 weeks. Some pets may require manual expression of their bladder, range of motion exercises of their limbs, and sling support to get them around.