Overview:

The intervertebral discs (the cushion in the space between the bones of the spine) can have conditions and forces that make them swell or rupture over time. This rupture leads to two types of damage to the spinal cord, compression and concussion. The extent of the damage and nerve cells loss is determined by:

  • Type of force.
  • Degree of force applied to the spinal cord.
  • Length of time that the force was applied.

Relatively minor spinal cord damage can lead to loss of coordination and a “drunken sailor” type of walk. Damage that is more significant leads to loss of walking or inability to move the legs voluntarily. Severe damage can lead to a total loss of pain sensation. This can carry a very poor prognosis for recovery depending on the duration that pain perception has been lost.

Breeds such as Dachshund, Pekinese, Beagle, Lhasa Apso, etc. (Chondrodystrophoid breed dogs) account for the vast majority of all disc ruptures, with the Dachshund accounting for 45-70% of all cases. In these dogs, the average onset of clinical signs is between three to six years of age, although x-rays can show the presence of disc calcification by two years of age. Labrador Retrievers, German Shepherd Dogs, etc. (Nonchondrodystrophoid dogs) usually present between five and twelve years of age. Thoracolumbar (back region) discs account for 65% of all disc ruptures, while cervical (neck region) account for up to 18% of presenting cases.

Signs and Symptoms:

Disc rupture presents with different degrees of pain; however, when nerve damage starts to develop and progress, it follows a predictable pattern:

  1. Back or neck pain, possibly refusing to walk around the room.
  2. “Drunken sailor” walk or wobbly in the hind end, hind feet will often cross as the pet steps.
  3. Complete loss of hind limb motor function. Usually, at the same time, the pet loses the ability to urinate and the ability to void (empty) their bladder completely.
  4. Pain perception is lost, which is a sign of severe cord injury that can carry a guarded to poor prognosis.

Classification of disc ruptures is generally grouped into large regions. The following groupings are described:

  • Cervical vertebral 1–5 (C1–C5).
  • Cervical vertebrae 6 through thoracic vertebrae 2 (C6–T2).
  • Thoracic vertebrae 3 to lumbar vertebrae 3 (T3–L3).
  • Lumbar vertebrae 4 through the sacrum (L4–S3).

This grouping is called neurolocalization, which allows an ACVS board-certified surgeon to begin to plan which diagnostic tests and potential surgeries will be offered. Intervertebral disc rupture is generally thought to be a ‘true’ surgical emergency and prognosis varies significantly with the degree of function remaining when the pet is evaluated and surgically treated.

Diagnostics:

Figure 1. A lateral myelogram of a dachshund with a herniated disc.

Most primary care veterinarians may suggest an initial health screening, as well as any of the imaging techniques listed:

  • Blood work: complete blood count (CBC), serum chemistry, and a urinalysis.
  • X-rays of the spine or chest.
  • Myelogram, which is an x-ray series where a needle injects dye around the spinal cord to highlight any compression (Figure 1).
  • CT scan instead of or after the myelogram.
  • Magnetic resonance imaging (MRI) study in addition or instead of a CT scan.
  • Spinal tap at the same time as the imaging.

Treatment:

Figure 2. A surgical photograph of the patient from Figure 1. A portion of the bone over the spinal canal has been removed (‘hemilaminectomy’) in order to expose the spinal cord and remove the herniated disc material.

Conservative treatment with cage rest, confinement, and pain medications are often only offered to patients that have recently begun their first episode, and the neurologic deficits are mild. Further consultation with your veterinarian may result in a referral to a veterinary surgeon to fully explore your options.

Multiple diverse surgical procedures and approaches exist, varying on the veterinary surgeon and the location of the disc. The choice of exactly which procedure to perform is made by the veterinary surgeon based on his or her experience and preferences. Surgical decompression of the spine by removal of the bone over the spinal canal is nearly always recommended (Figure 2).

Surgery

  • A hemilaminectomy is usually needed to remove ruptured disc material, which is compressing the spinal cord. During the surgery, a hole or window is made on the side of the vertebrae at the site of the offending disc. The hemilaminectomy also relieves some pressure off of a swollen spinal cord.
  • If the mid-back is being operated, ‘fenestration’ of intervertebral discs in the area is frequently performed. Fenestration involves making an incision in the side of the disc to allow the jelly portion to leak out. This decreases the risk of a future disc rupture and spinal cord compression in the future.

Prognosis

  • If your pet has sensation in the hind limbs prior to and after surgery, there is a 90% chance that your pet will regain the ability to walk well again. After surgery, some pets will regain function quicker than others.
  • By three to six weeks after surgery, most pets will be able to walk again. Sometimes no improvement in the neurological status is seen in the first month, then a rapid improvement occurs. Healing of the spinal cord will continue for a period of six months after surgery (at most nine months). Therefore, by the time six to nine months have passed, your pet’s neurological status will be as good as it is going to get.
  • Occasionally some pets will still have some residual weakness in the hind limbs but will be able to walk/move about well enough to be a functional pet.
  • Dogs that have no deep pain sensation to the hind limbs may never walk again. If surgery is done within 12 hours after the sensation to the hind limbs is lost, there is about a 50 to 75% chance that the pet will walk again.

In the event that your pet does not regain the ability to walk again, a K-9 cart can be fitted to your pet. This device is similar to a wheelchair for pets. It has a harness, which is strapped around the pet and wheels to allow the pet to ambulate with the front limbs.

Aftercare and Outcome:

Most pets are discharged three to seven days after surgery. They are usually returned for recheck and removal of stitches or staples (if present). Pain can be well controlled with owner-administered medications.

Postoperative recovery following surgery may include:

  • Bladder expression three to four times daily (if necessary).
  • Physical rehabilitation for muscle strength and flexibility.
  • Exercise restriction to “bed rest” for at least four weeks.

Lifestyle changes may include weight loss, switching to a body harness instead of neck lead, and minimizing jumping off furniture.

Postoperative complications can include:

  • Myelogram could precipitate seizures in the first 24 hours after the procedure.
  • Incisional infection.
  • Many patients have another disc herniated later in life.
  • Continued wobbly walk or dragging hind toes when walking.

Prognosis varies significantly with the degree of injury and the location of the injury. Most disc ruptures that present in dogs, still walking, have an excellent chance to return to walking. However, if the pet has lost the ability to sense pain in their legs before surgery is performed, they may never walk again.

If left untreated, disc rupture can lead to permanent loss of the ability to walk. Most dogs that reach this point will also lose control of their urinary bladder and are at risk for chronic urinary tract infections and urine scald. Additionally, without motor function, patients cannot turn themselves and may develop bedsores and wounds.

Intervetebral disc disease in chondrodystrophic dogs: