Introduction to Intervertebral Disk Disease (IVDD)
IVDD in dogs is a common cause of back pain, rear limb paralysis, and inability to walk or feel the back legs. 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.
Normal Canine Spine, Reprinted with permission by the copyright owner, Hill’s Pet Nutrition, Inc.
Canine Spine with IVDD. Reprinted with permission by the copyright owner, Hill’s Pet Nutrition, Inc.
MRI of the thoracolumbar spine showing a herniated intervertebral disk (arrow)
Symptoms & Signs of IVDD
In some breeds, the inner nucleus pulposus loses it’s ‘jelly-like’ properties and becomes dry and brittle. The dorsal (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.
This leads to signs of IVDD. Signs of thoracolumbar IVDD include back pain, pelvic limb ataxia (walking wobbly), 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 reluctance to move, reluctance to jump, shivering, crying, muscle spasms and/or a tense abdomen.
- 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 have no voluntary movement in the rear legs.
- 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.
Diagnosis of IVDD
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 – are useful for screening for disk infection and bony tumors, but typically are insufficient to diagnose IVDD.
- Myleography – Involves injecting contrast around the spinal cord to visualize it on radiographs.
- Computed Tomography (CT) Scan – Useful (often combined with a myelogram) and allows the body to be visualized in ‘slices’.
- Magnetic Resonance Imaging (MRI) – 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
Treatment of IVDD
Treatment depends on the severity of the signs, but can be divided into two options:
- Non-Surgical – For dogs with a first episode of back pain or mild pelvic limb ataxia, a conservative approach of cage rest and medications may be elected.
- 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.
After examination and MRI, the size, site and side of the disk herniation can be located. A hemilaminectomy (removal of one side of the side of the vertebrae) can be performed to allow the neurosurgeon to remove the herniated disk material and decompress the spinal cord.
Living with IVDD
- 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 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 – Are 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.
IVDD After Surgery