Introduction to Intervertebral Disk Disease (IVDD)
Intervertebral disk disease (IVDD) in dogs is a common cause of back pain, rear limb paralysis, and inability to walk or feel the back legs. Other names used to describe intervertebral disk disease include a slipped disk, bulging disk, herniated disk, and ruptured disk. Certain breeds including the Dachshund, Shih Tzu, Pekingese, and Beagle are commonly affected. IVDD can affect any part of the canine spine; however, this article will focus on the thoracolumbar (mid-back) spine.
Intervertebral disks are the structures between the bones of the spinal column (called vertebrae). They act as shock absorbers and give mobility to the spine. They consist of a soft center, called the nucleus pulposus and an outer fibrous part called the annulus fibrosus (see Figure 1 below).
In some breeds, the inner nucleus pulposus loses it’s ‘jelly-like’ properties and becomes dry and brittle. The top of the annulus fibrosus is thinner than the rest of the annulus fibrosus. In dogs that herniate (or ‘slip’) a disk, the nucleus pulposus extrudes dorsally from the annulus fibrosus and may forcibly strike the spinal cord and/or compress the spinal cord (Figure 2).
Figure 1: Normal Canine Spine, Reprinted with permission by the copyright owner, Hill’s Pet Nutrition, Inc.
Figure 2: Canine Spine with IVDD. Reprinted with permission by the copyright owner, Hill’s Pet Nutrition, Inc.
What are the symptoms of intervertebral disk disease in dogs?
Signs of thoracolumbar IVDD include back pain, rear limb weakness and wobbliness, inability to stand, inability to move the rear legs or even inability to feel the back legs. A grading scale is used in dogs:
- Grade 1) Pain Only – These dogs are able to walk normally, but exhibit signs of pain including not wanting to move or jump, shivering, crying, muscle spasms and/or a tense belly.
- Grade 2) Ambulatory Paraparesis – These dogs are able to walk, but are weak and wobbly in the rear legs. They may cross their back legs when walking, splay out, knuckle over or stumble in their back legs.
- Grade 3) Non-Ambulatory Paraparesis – These dogs are still able to move their legs and wag their tails, but are not strong enough to support their own weight and walk.
- Grade 4) Paraplegia – These dogs cannot move the rear legs, but can still feel the rear toes.
- Grade 5) Paraplegia with Absent Nociception (no ‘deep pain’) – In addition to being unable to move the back legs, they are unable to feel their back legs.
How is intervertebral disk disease diagnosed?
There are other diseases that can cause similar clinical signs of spinal cord disease including meningitis/myelitis, spinal tumors, trauma, infection, malformations, vascular problems, and others.
- Neurological Examination – Gives the veterinarian an idea of which of these are more likely than others, but tests are necessary to accurately determine the cause.
- Spinal Radiographs – X-rays are useful for screening for disk infection and bony tumors, but typically are insufficient to diagnose IVDD. Sometimes X-rays can support a diagnosis of IVDD by showing a narrowed disk space or calcification, but typically cannot be used to make a certain diagnosis.
- Myelography – Involves injecting contrast around the spinal cord to visualize it on radiographs. In general, this is an older technique and is not typically performed at Southeast Veterinary Neurology since there are better ways to diagnose IVDD.
- Computed Tomography (CT) Scan – Useful (often combined with a myelogram) and allows the body to be visualized in ‘slices’. Sometimes a CT scan can give a diagnosis of intervertebral disk disease but can miss other causes that may look similar to IVDD.
- Magnetic Resonance Imaging (MRI) – MRI is considered the imaging modality of choice when visualizing the soft tissues of the body, including the nervous system. High-field MRI offers several advantages over low-field MRI, CT and/or myelography. This is typically the BEST test and the one that we use almost exclusively at Southeast Veterinary Neurology (figure 3).
MRI of the thoracolumbar spine showing a herniated intervertebral disk (arrow)
How is Intervertebral Disk Disease in Dogs Treated?
Thoracolumbar intervertebral disk disease can cause severe signs. Symptoms can occur rapidly and can cause irreversible damage. Because of this, dogs showing symptoms of intervertebral disk disease should be evaluated by a neurologist as soon as possible, especially if they are dragging their rear limbs or cannot walk.
Treatment depends on the severity of the signs, but can be divided into two options:
- Non-Surgical – For dogs with the first episode of back pain or mild pelvic limb ataxia, a conservative approach of cage rest and medications may be elected. This involves strict crate confinement for at least four weeks. Dogs that cannot walk often cannot urinate on their own and need to be expressed. The patient can come out of the cage for urination and defecation or for physical therapy, but should otherwise be crate rested. Pain medications are often necessary and depend on the dog and the prescribing veterinarian.
- Surgical – Dogs with more severe signs (grade two through five) or recurrent or persistent back pain that does not respond to rest and medications are best managed with surgery to decompress the spinal cord. The goal of surgery is to remove any disk material that is compressing the spinal cord. The most common surgery to relieve the spinal compression is called a hemilaminectomy, in which a window is made in the side of the backbones to allow removal of the herniated disk material. Additionally, a preventative procedure is often performed to make it less likely that your pet ever experiences intervertebral disk disease again.
What is the likelihood of my dog walking again with intervertebral disk disease?
The prognosis with intervertebral disk disease depends on several factors, including the severity of the symptoms, how quickly the signs came on, how much compression there is, how quickly the signs are addressed by a neurologist and the surgical skill and experience of the neurosurgeon.
- Grade 1-4 – The chances of success are about 95% in the hands of an experienced neurosurgeon. For dogs that are managed non-surgically, the chances of regaining the ability to walk are about 50-60%. However, dogs that are managed without surgery have a much higher risk for recurrence, may take longer to improve, and are at risk for worsening when compared to those that are treated with surgery.
- Grade 5 – Is a surgical emergency. The chances of recovery are significantly lower than those that can still feel their back legs. If surgery is to be successful, it should be performed as soon as reasonably possible and certainly within 48 hours of losing the ability to feel the back legs. Dogs that are paraplegic with absent nociception are at risk for myelomalacia, an extremely serious condition that is typically progressive and fatal.
Why should I bring my dog with suspected intervertebral disk disease to Southeast Veterinary Neurology?
Southeast Veterinary Neurology is South Florida’s most trusted and experienced name in veterinary neurology when it comes to intervertebral disk disease in dogs. We are the only team of board-certified neurologists in South Florida.
Since intervertebral disk disease is often an emergency, our team is available 7 days a week for your pet.
We were the first neurologists in South Florida to use a high-field MRI. Our state-of-the-art hospitals are equipped with the latest technology, most advanced techniques, and a compassionate team of humble experts. Our neurologists have helped over 20,000 patients recover the ability to walk.