Intervertebral Disc Disease

Dr Peter H. Laverty, BVSc, MACVSc, Dip. ACVS

Dr Simon T. Kudnig, BVSc, MACVSc, Dip. ACVS, FACVSc

Specialist Small Animal Surgeon

What is Intervertebral Disc Disease?

The dog’s spinal column consists of the spinal cord and surrounding vertebrae. The bony vertebrae serve to protect the soft spinal cord. Intervertebral discs are structures that sit between the vertebrae and act as “shock absorbing cushions”. Each disc consists of a tough outer fibrous layer called the annulus fibrosus and a gelatinous inner core called the nucleus pulposus.(as seen in the picture below). This gelatinous inner core has a high water content and functions as a hydraulic shock absorber. “Disc disease” involves a decrease in water content and calcification of the nucleus, which causes a loss of elasticity within the disc. These degenerative processes increase the chance that your dog may suffer a ruptured disc. When this occurs, a breakdown of the annulus allows extrusion or herniation of the nucleus upwards into the bony tunnel (spinal canal) which contains the soft spinal cord.

The herniated disc material injures the spinal cord and results in cord swelling and compression. Subsequently, the nerves traveling within the spinal cord from the brain to the legs and bladder are injured. This in turn results in loss of limb function ranging from weakness to complete paralysis, and in some cases loss of bladder control.

Treatment Options:

In some cases, the damage to the spinal cord is minor and clinical signs are mild. These cases maybe successfully treated with conservative management. This involves the use of anti-inflammatory drugs to reduce the swelling in and around the cord and allow function to return. If anti-inflammatories are used it is IMPERATIVE that your dog be strictly confined for a minimum of 6 weeks to prevent further herniation of disc material. After this time, the disc may have healed and the dog can gradually resume normal exercise.

However, in other cases the amount of spinal cord damage and compression is so great that conservative therapy will NOT be successful. These dogs require surgery to remove an area of bone over the spinal cord (hemilaminectomy), and to remove the herniated disc material in order to relieve the pressure on the cord. Before taking your dog to surgery, radiographs (X-rays) and a myelogram (a special X-ray in which dye is injected around the spinal cord) must be performed to identify the exact location in which the spinal cord is compressed. The prognosis for your dog walking again after surgery, depends largely on the neurological status of your dog before surgery. Unless there has been severe damage to the cord, most dogs (85%) will regain neurologic function and will eventually be able to walk.

Some dogs have such severe damage to the spinal cord that they can no longer feel when their toes are pinched and are said to be “deep pain negative”. This group of dogs has a much poorer prognosis for regaining the ability to walk again. These dogs can still receive decompressive surgery and we then must adopt a wait and see approach. Six months after surgery, if the dog has not regained function it is highly unlikely that the dog will ever walk again.

Home care after surgery:

Following surgery your dog was closely monitored for signs of discomfort, post surgical complications and changes in their neurological status. We are now comfortable discharging your dog to your care. Your dog requires supportive home care as detailed below:

• Confinement – Because your dog is paralyzed or uncoordinated, confinement is necessary to prevent injury. We recommend cage/crate confinement unless under direct supervision.

• Bedding – Soft bedding, at least one inch thick must be provided to prevent the development of bed sores. Furthermore, the bedding MUST be kept clean and dry at all times to prevent urine scald. If your dog does come in contact with urine, rinse the affected area with warm water and pat dry with a towel.

• Bladder management – If your dog is unable to urinate on his/her own we will demonstrate the art of manual bladder expression. By gently squeezing the abdomen it is possible to empty the bladder. It is ESSENTIAL that this be performed at least 3-4 times a day. Failure to empty the bladder can result in urinary tract infections and bladder damage. If you notice that the urine is discolored or foul smelling, please call my office or your regular veterinarian for advice.

• Physical therapy – “PT” is an extremely important part of your dogs post surgical care. While we are waiting for the spinal cord to recover it is important to maintain muscle tone and avoid joint stiffness. This can be achieved by performing passive range of motion exercises. This involves the repeated extending and flexing of all the joints in both of the back legs at least 10 times 3 times a day. In addition you should assist your dog to stand and walk (“towel walking”) such that they are forced to support some of their own weight. Swimming is also an excellent form of “PT” if available. We will demonstrate the various exercises to you at the time of discharge.

• Surgical site – Removal of skin sutures/staples is usually performed in 7 -10 days. Please monitor the surgical site for any sign of infection (discharge, excessive redness or swelling) and if concerned call my office.

• Medications- Antibiotics are sometimes prescribed following surgery. These will help guard against infection. A short course of anti-inflammatories may also be used following this type of surgery. These will help reduce post operative swelling and discomfort. Please give all medications as directed.

• Deterioration- If your dog shows a worsening of neurologic status, such as breathing difficulties, or changes in movement in the front limbs, you should contact the hospital immediately.

• Recheck examinations – These are routinely performed at 3 and 6 weeks after surgery. Please schedule these appointments well in advance.