When an intervertebral disc ruptures completely, the outer ring collapses and the inner jelly-like portion is forced into the spinal canal

Severe pain, forelimb lameness or, in severe cases, paralysis of all four limbs may occur

Surgery is indicated to remove the offending disc material

Our doctors in the surgery and neurology departments have extensive special training required to perform successful spinal surgery

What is it?

• It is the compression of the spinal cord by a diseased intervertebral disc.
• An intervertebral disc becomes diseased either through gradual degeneration or injury.
• The thinner top portion of the outer ring tears, and disc material becomes displaced into the spinal canal located directly above the disc. Press play in the two illustrations (to right and below) for a demonstration of a herniated disc.
• The spinal cord is located in the spinal canal. A bulging or ruptured disc causes irritation, pressure, or damage to the spinal cord. This causes inflammation which results in further irritation, pressure, or damage to the spinal cord.
• The resulting inflammation causes neck pain, and in severe cases weakness, incoordination, and paralysis of all four limbs.
• The damage to the spinal cord impairs the transmission of "messages" down the cables (neurons) in the spinal cord. Thus, loss of use of the limbs and little or no control of the bladder and bowels occur.
• When severe damage to the spinal cord is present, loss of pain sensation to the limbs occurs.

Anatomy

• See the illustrations of spine (side view and cross-sectional view) above and to the right.
• The bones of the spine are called vertebrae. They are held together by ligaments, muscles, and intervertebral discs. The discs act as shock absorbers between the vertebrae.
• An intervertebral disc has a fibrous outer ring (annulus fibrosis) and an inner part (nucleus pulposus) that is soft and jelly-like (sort of like a jelly donut).
• The fibrous outer ring is thinner at the top than the bottom, thus the nucleus pulposus usually herniates out through the top of the disc and compresses the spinal cord.

Clinical signs

• Breeds: both small and large breeds can develop a herniated disc, but small breeds are more commonly affected
  • Beagle
  • Dachshund
  • Lhasa apso
  • Poodle
  • Cocker spaniel
  • Shitzu
  • Dobermans and Rottweilers - usually a chronic disc
• Age: usually mid age, but young dogs are also affected
• Sex: no sex predilection
• Signs
  • Guarding of the neck (i.e. stiff neck - does not want to move the neck and has a difficult time trying to reach the food and water bowl)
  • Episodes of crying out in pain
  • Lameness on one of the fore limbs especially if the herniated disc is pinching one of the nerves of a forelimb
  • Less common signs:
    • Limb weakness
    • Knuckling of the paws
    • Wobbly gait - looks drunk
    • Paralysis of all four limbs

Diagnosis

• A diagnosis of intervertebral disc disease is based on physical signs, neurological tests, and diagnostic imaging tests such as a myelogram, CT scan or MRI.
• Myelogram: dye is injected into the fluid space surrounding the spinal cord, then radiographs (x-rays) are made to see where the spinal cord is being compressed. Take note of the compression of the spinal cord (arrow) on the myelogram (photo right).
• CT-myelogram: dye is injected into the fluid space around the spinal cord and a special type of cross-sectional x-ray is made. This test allows the surgeon to identify the extend of the herniated disc better than a regular myelogram
• MRI: no injections into the spine are required. Cross-sectional and sagittal images are obtained from this scan. An MRI is the ideal test used to identify a nerve sheath tumor that is outside of the spinal canal.

Treatment

• Conservative therapy can be effective in mild cases - this involves 4 to 6 weeks of strict rest (no running, jumping, rough-housing, or stairs, with short leash walks for bathroom duties only), plus an anti-inflammatory medication.
• Surgery is frequently the best treatment and is indicated if
  • your pet is in severe pain that does not respond to conservative therapy
  • if your pet's pain is recurrent
  • if your pet shows signs of weakness at all
  • if your pet cannot walk
• A surgical ventral slot is usually needed to remove ruptured disc material, which is compressing the spinal cord. During the surgery a window is made on the under side of the vertebrae at the site of the offending disc. In some cases the surgeon may need to open the spine from the top or the side in order to remove the disc material.
• Fenestration of intervertebral discs in the area is frequently performed. Fenestration involves making an incision into the bottom of the disc to allow removal of the jelly portion of the disc. This may decrease the risk of recurrent clinical signs due to another disc rupture.

Potential complications

• Anesthetic death is a very uncommon complication under the care of our trained specialists.
• Infection of the spine, although possible, is very uncommon.
• Bladder infection may result from inadequate emptying of the bladder due to neurological dysfunction. Antibiotics are needed to correct this problem.
• Permanent paralysis can occur, but is unusual.
• Unresolving neck pain may be due to prolapsed disc material that is still irritating a nerve root. The clinical signs may ameliorate with time, however, in some cases additional testing and potential surgery may be needed.
• Side effects due to medications may include vomiting, diarrhea and loss of appetite. If any of these clinical signs occur notify the doctor who has performed the surgery on your pet.

Postoperative care

• Medications that you may need to administer to your pet may include:
  • Steroids: help reduce swelling and inflammation
  • Muscle relaxants: help to minimize painful muscle spasms
  • Analgesics: a variety of medications are available for this purpose
• Rest: Your pet should be kept in a crate at all times except for urination and bowel movements for a period of one month.
• Rehabilitation therapy is very important of patients that are weak or paralyzed.
  • Passive rehabilitation: flex and extend the joints of the fore and hindlimbs. These exercises should be done three to four times daily, 20 minutes per session.
  • Active rehabilitation: assist your pet in a standing position. When your pet gets tired and lies down, allow a short period of rest (30 seconds) and then get him/her back into a standing position.
• Bladder care is not needed in most dogs that have had surgery for a cervical spinal cord lesion. If your pet is paralyzed, bladder control also may be lost. You may need to express the bladder so that it does not become too distended.
• Check the incision for signs of infection: redness, swelling, pain or discharge. Do not allow your pet to scratch or rub the incision. If needed the neck may need to be bandaged until the incision has healed.
• A soft padded bed is essential during the recovery phase to prevent the development of bed sores/ulcers. If your pet cannot turn him/herself you will need to turn him/her from side to side every four hours.
• An evaluation of your pet will be made about 2 weeks after surgery at our hospital by a surgeon or neurologist.
• After a disc herniation, it is recommended that a harness be used for leash walking (instead of a neck lead) in order to distribute the strain over a greater area of the body.

Prognosis

• Some dogs will have immediate relief of pain after surgery, yet others may have continued discomfort, which may last a couple of weeks (particularly those breeds, e.g. Beagles, that have a low tolerance for pain).
• If your pet was paralyzed prior to surgery it may take 1 to 3 weeks to be able to walk again.
• If severe damage to the spinal cord has occurred, i.e. there was loss of pain sensation to the limbs, your pet may not recover at all or residual deficits may be present.
• Dogs that have had one disc herniation event are at greater risk than ordinary dogs for a repeat event.