Intervertebral Disc Disease

Disc Disease is a common cause of back pain, in-coordination and paralysis in pets

Dogs, and rarely cats, can have disc problems that cause a variety of clinical syndromes such as the following:

• Back Pain- manifested by an arched back or stiff neck, reluctance to jump, get up or do stairs, stiffness in rising, crying with certain movements, etc.
• In-coordination – in rear legs only or all 4 legs. Your pet can look “drunk” and waddle around or zig-zag from side to side.
• Weakness/paralysis – in one leg, both rear legs or all 4 legs. The signs can vary from losing balance and falling while turning, sinking down frequently during a walk to total inability to stand or move the legs.

These symptoms can come on very suddenly or slowly progress over a day or a few days. As soon as these signs appear you should consult your veterinarian as soon as possible. If back pain is persistent or there is loss of coordination or weakness your pet may be a surgical candidate and a consult with a surgical specialist is advised at the earliest opportunity. If your veterinarian is not available our hospital is staffed 24 hours with our emergency service (613 731 9911).

Understanding Disc Disease

In order to understand disc disease you need to understand some anatomy of your pet’s spine. The spine is composed of a series of vertebrae. The spinal cord is protected within a bony spinal canal formed by overlapping vertebrae. Intervertebral discs are located between each vertebra from the head to the tail. They allow for flexibility of the spine. A normal intervertebral disc has two distinct components - a fibrous outer casing (annulus fibrosus), and an inner gelatinous center (nucleus pulposus). The nucleus pulposus consists of water and elasticated cartilage and acts like a shock absorber in the spine.

Mechanics of Disc Prolapse:

During normal motion the nucleus pulposus changes shape as the spine bends and straightens and absorbs a lot of the energy of motion. Certain breeds are predisposed to disc problems because their nucleus degenerates from an early age and loses its elastic properties. This makes the disc less able to absorb the energy of motion and tends to be forced up through the annulus fibrosus into the spinal canal. Once the nucleus prolapses into the spinal canal it puts pressure on the spinal cord resulting in neurologic symptoms ranging from pain to paralysis.

Depending on how much and how fast this process happens the clinical signs will vary. If a small amount of disc is pushed up rapidly and forcefully, damage to spinal cord will be sudden and severe and result in acute paralysis. If a large amount of nucleus oozes up slowly, the paralysis may proceed more slowly over a 24 –72 hour period, progressing from signs of back pain to in-coordination to paralysis.

Breeds affected:

Disc problems occur most commonly in small breed dogs such as the daschund, beagle, lhasa apso, shih tzu, cocker spaniel, basset, Pekingese, poodle, etc. However, it is also being seen more often in certain large breed dogs such as golden retrievers and others. The middle of the back (the thoraco-lumbar area) is most commonly affected followed by the neck. Most dogs are affected from 3-8 years of age.

Recognizing Disc Prolapse According to Area Affected:

1. Neck (cervical) Disc: The hallmark of cervical disc disease is neck pain. The muscles in the neck are tense or quivering, the nose is often pointed toward the ground, muscle tremors may be palpated in the neck and shoulder areas, the back may be arched, and there is reluctance to move the head from side to side or to lift the chin and look up. Weakness or paralysis of all four limbs or weakness just on one side may occur. A nerve root running to one front leg may become "pinched" leading to lameness or reluctance to place weight on a front leg. Due to the pain, a dog is usually less active - reluctant to jump, play, or go on walks. Dogs with cervical disc extrusions will often be quite vocal in demonstrating pain, especially when picked up.

2. Middle of the Back – thoraco-lumbar: Thoraco-lumbar disc extrusions are the most common and often the most urgent. Symptoms often start with pain and reluctance to walk, jump, and/or play. The back may be arched. Weakness or ataxia (in-coordination) may be present in the hind legs, but the front legs are normal. One leg may be more severely affected than the other. If your pet is unable to stand or walk then they are usually unable to pass stool or urine and must be attended to quickly.

3. Lower Back – lumbo-sacral: The clinical signs reflect varying degrees of involvement of the hind legs, urinary bladder, anal sphincter, and tail. Pain may be the only symptom present. Affected dogs usually have decreased activity and are reluctant to jump. Many have difficulty rising and some have difficulty posturing to defecate. Pain is often present over the lumbo-sacral (lower back) area. Hind limb lameness may be present and one leg may be involved more than the other. Pain may be present when the tail is lifted. Bowel and/or bladder dysfunction (partial or complete incontinence) may be present. A dog is typically able to walk, but the gait may be abnormal and progressively worsen.

Treatment options – what are they?

Treatment options for inter-vertebral disc disease are either medical or surgical.

Medical Treatment:

Medical therapy may be used if low-grade pain or minor in-coordination are present. Anti-inflammatory drugs and muscle relaxants are typically used. It is mandatory to restrict activity for 6-8 weeks even if the pain or in-coordination resolve. Avoid jumping, stairs, playing with other dogs, and running during this time. Premature resumption of normal activity can lead to extrusion of more disc material which may in turn lead to worsening of clinical signs or even paralysis.

While it is uncommon, the medications used in medical therapy can have some potentially serious side effects. Steroids and other anti-inflammatory medications can cause severe gastrointestinal ulceration. Clinical signs include loss of appetite, decreased activity, lethargy, vomiting (with or without blood), and a dark, sometimes tar-like stool. If you see any of these symptoms please stop the medication and call your doctor.

Surgical Treatment

The indications to proceed to a surgical treatment include the following:

• Persistent or recurrent back pain.
• Back pain continuing despite medical therapy.
• Weakness or in-coordination.
• Complete paralysis.

Surgical treatment involves surgically removing the prolapsed disc but is not undertaken until a specific diagnosis is made and the exact location of the disc prolapse identified.

How is the diagnosis made?

Once a disc prolapse is suspected its exact location must be determined. Routine x-rays and a myelogram are performed to pinpoint the location of the prolapsed disc. Plain x-rays show the bone very well but do not show the condition of the spinal cord, which is a soft tissue, and does not show up on a plain x-ray. A myelogram is a series of x-rays that are taken after a special dye is injected into the area around the spinal cord. This dye outlines the spinal cord and shows where the disc prolapse has occurred (see below). The contrast material is displaced around the protruded disc. Once the general location of the disc prolapse is known, often a CT scan (a 3- dimensional, computerized x-ray) is taken to determine which side of the spinal cord the disc is mostly located. This helps the surgeon to more accurately determine which side to approach the spinal canal which allows removal of the disc with least amount of trauma to the spinal cord.

Surgical Disc Removal:

If the diagnosis of a prolapsed disc is made, your pet will usually go immediately from x-rays to surgery under the same anesthesia. Surgery requires special instrumentation and meticulous technique. Surgery is performed to remove extruded disc material and relieve excessive pressure on the spinal cord. A high-speed burr is used to remove vertebral bone at the site over the prolapsed disc. The prolapsed disc material is removed, thus relieving compression of the spinal cord and/or nerve root.

Surgical Disc Removal:

Yes. The incidence of complications is very low, but the risks exist, just as they would for surgery on people. Complications from myelography, surgery, and anesthesia can never be totally eliminated. Our experienced staff (anesthesia and nursing staff) and surgeons deal with neurological cases on a regular basis and will do everything they can to optimize your pet’s recovery. Early recognition and intervention are important to a successful outcome

Will my pet be able to run and play again?

To answer that question the most important indicators are how badly paralysed your pet is before surgery and for how long. Overall, most (approximately 90%) pets will recover with surgery provided that they have pain sensation in their toes prior to surgery. If the pain sensation to the toes is lost before surgery the prognosis decreases and only 50-60% of those pets will recover their function.

The length of time for recovery is also very variable. Most animals that still have pain sensation before surgery are walking at suture removal (10-14 days after surgery). Others may need help for several weeks. Coordination is always the last thing to come back and may not be fully recovered for several months. As long as your pet can walk and urinate properly you can afford to give him/her the time to recover full function with minimal nursing care. There are some helpful physical therapies that can be tried to improve the recovery of coordination.

Pets that can not feel their toes before surgery may or may not recover and the time to recovery is going to be a lot slower. In one study, 85% of dogs that did recover their pain sensation did so within the first 4 weeks after surgery. The longer it goes after surgery with no recovery of pain sensation the poorer the chance for recovery becomes.

It takes a special owner to undertake the care of a paraplegic pet, but some people do it. There are custom made carts available so that the pet can pull him/herself around in it and there is daily nursing care needed to make sure that the bladder is emptied appropriately.

Aftercare – what will I need to do?

The amount of nursing care needed is directly proportional to how severely paralyzed your pet is before and after surgery. The speed of recovery is very variable and sometimes you will need to be very patient for recovery to take place. It can take from a few days to a few months. Your pet will usually be kept in hospital until you are able to manage him/her at home. Most commonly the hospitalization time is 2-5 days but in some cases it can be 2 weeks.

Bladder management:

One of the main issues in aftercare is management of the bladder. When your pet loses control of the hind legs the ability to urinate is also lost. Urination is a highly coordinated function and will usually return as the voluntary motion of the hind legs comes back. Until it comes back the bladder must be emptied 3-4 times daily, either with a urinary catheter or by manual expression. This is often the main reason for keeping your pet in the hospital postoperatively. Depending on owner interest and comfort level, patient cooperation and other circumstances pets can sometime be discharged early and bladder management performed at home. Passing stool is usually not a problem, although your pet may not always know when he/she is passing stool at first.

Physical therapy and exercise:

While the function is coming back to the nerve supply, physical therapy can be very helpful to maintain muscle tone, move joints and help to prevent bed sores. In addition, paralyzed dogs need to be moved often and kept on soft, dry bedding in order to prevent bed sores. This can be quite a strain physically for the one nursing the pet, especially with large breed dogs.

Could this happen again?

Yes, but unlikely. The incidence of a second intervertebral disc extrusion that would also require surgery for resolution of the problem is less than 1% in the cervical area and less than 3% in the thoracolumbar area. These statistics apply primarily to dachshunds and the incidence of more than one disc extrusion is considerably less in other breeds. The main thing to know is that yes it could occur again, but the probability is low. Lifestyle modifications such as avoidance of unnecessary jumping and weight gains help reduce the risk.