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Intervertebral Disc Disease
The intervertebral discs link the vertebral bodies (or vertebrae) of the spine. Their main function is to stabilize the vertebral bodies, but the also act as shock absorbers when force is applied to the spinal column.
There are two main structures that make up the intervertebral disc:
1) The outer Annulus Fibrosus
2) The inner Nucleus Pulposus
There are three main classifications of Inervertebral Disc Disease (IVDD):
Hansen Type I: This is what we think of as the true “ruptured disc”. It appears acutely (it actually happens over a period of 1-5 days) and it is characterized by an extrusion of the Nucleus Pulposus into the spinal canal resulting in cord compression and nerve root irritation. This type of disc rupture affects young to middle aged small breed, chondrodystrophic dogs (Dachshunds, Lhasa Apsos, Shih Tzus, Pekingese, etc.) The most frequent area of rupture is at the junction of the thoracic and lumbar spine. The onset of symptoms is usually sudden and many of these dogs present with impaired motor function (wobbly gait) or complete loss of voluntary movement in both hind limbs (paraplegia). Surgery is generally viewed as the best option for these patients.
Hansen Type II: This is the protrusion of the Annulus Fibrosus, and is often referred to as a “bulging disc”. This type of disc is more commonly seen in older, large breed dogs such as Labradors , Rottweilers, and Golden Retrievers. However, the small breeds are not immune to these types of discs. The onset of symptoms is typically slow and progressive with a history of difficulty in rising, climbing stairs or jumping. It usually presents with increasing ataxia of the hind limbs. Very often if the disc does not completely rupture, and if the neurological deficits and pain are mild, these dogs may be treated conservatively with much success. Management of these cases may include strict cage confinement for a minimum of 4 weeks and medical pain and anti-inflammatory drug treatment.
Hansen Type III: Although some professionals do not even consider this a classification, I believe it deserves mention . Although fairly rare, it is the most traumatic form of a disc rupture. The disc material literally explodes up into the spinal cord causing severe damage and in the worst cases, ascending death of the cord. This is the type we most typically associate with Myelomalacia or cord death. When it occurs, most often the only humane option for these pets is euthanasia.
Once your pet has had a thorough neurological exam by your Veterinarian, he may refer you to a specialist (in this case, a Board Certified Surgeon) to further work up your pet’s case..
The surgeon is going to do another neurological exam on your pet. This is standard procedure. He may also suggest taking a blood sample and running some routine tests to rule out any other problems your pet may have that would make him or her a higher risk for anesthesia.
Now that the surgeon has confirmed this diagnosis of a ruptured disc, he will recommend one of two things depending on the findings of his exam:
1) Treat conservatively. *Starting with a loading dose of Prednisone or other steroid (commonly an injection given in the clinic), he will most likely send you home with a prescription of oral steroids and possibly some pain medications also. You will be given instructions to strictly confine your pet for a minimum of 4-6 weeks. He will also want updates on your pet during that time to make sure that the neurological signs have not worsened.
2) Surgery. If your pet has no deep pain sensation at his exam or if your pet is on the verge of losing deep pain, surgery is usually the option most surgeons will suggest. In these cases it is most important to act quickly and remove the disc material before any further damage to the cord can be done.
If surgery is the option chosen, then your pet will be placed under anesthesia and a myelogram will be performed. MRIs ( a non-invasive diagnostic method) are being used in some practices now, but a myelogram is still the standard diagnostic tool used by most surgeons today.
Myelogram: Myelograms are performed under general anesthesia. A liquid contrast agent is injected into the subarachnoid space (the space around the spinal cord). This injection is usually made in the lower lumbar region (most commonly at L5-L6, or just slightly in front of where the tail joins the body). When the spinal cord is compressed as with IVDD, the resulting contrast columns will appear deviated or narrowed around the rupture area, making it very evident on radiographs. On the films a disc rupture will appear as a “hump” in the dye column. This diagnostic tool is very efficient in pinpointing the exact area of disc rupture.
* Please note that these are procedures followed at our clinic. Some Specialists may differ slightly on their methods of treatment.
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