INTERVERTEBRAL DISC DISEASE (IVDD)
WHAT IS AN INTERVERTEBRAL DISC?
The intervertebral discs are located in between each vertebrae of the spinal column. Each disc consists of 2 parts: an outer fibrous ring and an inner soft portion often described as a jelly donut. The spinal column of dogs and cats, just like in people, is made of small bones called vertebral bodies or vertebrae. The center of each vertebrae is hollow and form the spinal canal or the space where the spinal cord is positioned. The spinal cord transmits nerve signals back and forth between the brain and peripheral nerves of the body. The intervertebral discs allow for the spinal column to bend and will protect the spinal cord from excessive forces from this motion.
WHAT IS THE FUNCTION OF THE INTERVERTEBRAL DISCS?
Each intervertebral disc serves as a “shock absorber” and protect the spinal cord from excessive stress. They also allow for flexibility of the spinal column.
WHAT HAPPENS WHEN AN INTERVERTEBRAL DISC RUPTURES OR HERNIATES?
There are two common types of intervertebral disc herniations. A Type I herniated disc occurs when the jelly part of the disc (nucleus pulposus) becomes hard and breaks through the outer covering (annulus fibrosis) and enters the spinal canal. The disc material will often strike the spinal cord at high speed causing damage and inflammation to the spinal cord. A Type II herniated disc occurs when the nucleus pulposus may begin to harden and expand in the central part of the disc. This expansion causes bulging of the entire disc including the outer annulus fibrosis and results in gradual pressure on the spinal cord.
WHICH PETS ARE MOST COMMONLY AFFECTED?
All dogs are at risk of developing a herniated disc, but chondrodystophic bredds, such as Dachshunds and Pekingnese, are at a much higher risk. In these dogs, the average age of onset is between 3-6 years old. Large breed dogs like Labrador Retrievers and German Shepherds can also develop intervertebral disc disease, but are more often affected later in life. Cats can develop interevertebral disc disease as well but is much less frequent compared to dogs.
WHAT IS THE LONG-TERM PROGNOSIS?
Most pets recover fully or have mild residual weakness but are able to live happy, active lives. Activity modification will be necessary. Re-injury or herniation of a new disc are possible, so running, jumping and rough play should always be limited. Maintaining a lean body weight will also be important.
WHAT ARE THE SIGNS OF A HERNIATED DISC?
There is limited space within the spinal cord, so when herniated disc material hits or pushes on the spinal cord it becomes compressed. The signs that result are dependent on the location of the herniation along the spinal column and degree of spinal cord compression. Spinal cord compression in the neck region can lead to weakness or paralysis of all four legs, whereas spinal cord compression in the mid to lower back affects only the rear limbs.
Herniated disc herniation will lead to the following signs:
Pain or restlessness resulting in refusal to walk or eat. Some of these pets will cry when touched or lifted.
A “wobbly” gait with falling, crossing of the limbs or stepping on the tops of the paws.
Inability to move the front and/or rear legs
Inability to urinate
Loss of pain perception
HOW IS INTERVERTEBRAL DISC DISEASE (IVDD) DIAGNOSED?
A strong suspicion of IVDD can typically be formed after a thorough physical and neurologic exam. Radiographs of the spinal column are usually performed first to get an overview of the spine. Advanced imaging (myelogram, CT Scan, or MRI) is necessary to confirm the presence and location of the herniated disc.
WHAT ARE THE TREATMENT OPTIONS?
The treatment recommended for IVDD will depend on the duration and severity of the signs and nerve deficits. If your pet is mildly affected and still has good leg function, cage rest and pain medication may be recommended. LASER therapy, acupuncture and therapeutic exercises to improve core strength may also help relieve pain during this period and assist recovery.
If your pet has severe pain, weakness, or paralysis, surgery to remove the herniated disc material and alleviate compression on the spinal cord will be recommended.