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Dogs and cats have a vertebral column and intervertebral discs very similar to humans. However, the disease processes that affect the discs have some important differences. Disc disease in the dog and cat can be a very serious and urgent problem. Why? Two main reasons: 1) their spinal cord ends low in the back rather than in the center of the back like ours. A dog's spinal cord travels almost the entire length of the spine. 2) Due to our upright posture versus the dog's horizontal posture, we most commonly have problems with discs low in our back - lower than the termination of the spinal cord. However, dogs and cats most commonly have disc problems in the middle of their back or in their neck, and ruptured discs impinge directly on the spinal cord and nerve roots. People with extruded discs often have signs of shooting pain. In contrast, dogs often have pain plus acute and even complete paralysis within a matter of hours. Because of these facts, early recognition of a disc problem is extremely important, and early intervention often means the difference between a very good prognosis and paralysis for life.

 

WHAT IS NORMAL?

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 fibrosis), and an inner gelatinous center (nucleus pulposus). The nucleus pulposus is normally 80% water, and has shock absorbing properties.
 

WHAT HAPPENS?

It is very important to realize that some dogs (primarily small breeds) are predisposed to degenerative disc disease. This is a slow process that begins as a biochemical change when dogs are less than one year of age. The nucleus pulposus of the disc slowly degenerates during the first few years of life. It loses a high percentage of its water and may become partially calcified. As this occurs, the outer casing of the disc (annulus fibrosis) becomes more susceptible to cracks and fissures.  Normal activity or minor trauma to the discs such as jumping, falling while playing, or running can initiate disc extrusion. Approximately 85% of the disc problems occur in the thoracolumbar area (back) and 15% occur in the cervical area (neck). When the disc extrudes, the nuclear content extrudes upward into the spinal canal. This results in pressure and compression on the spinal cord and/or spinal nerve roots. The compression collapses blood vessels and decreases circulation leading to deprivation of oxygen and glucose to the nervoustissue of the spinal cord. Dysfunction follows in direct proportion to circulation disruption. If the extrusion occurs during activities the disc material may extrude with significant force - enough to cause impact injury in conjunction with the compression that follows. Different terminology is used to describe similar problems that occur. Disc extrusion and disc protrusion most accurately describe the condition. Other common descriptions of disc disease include ruptured, herniated, slipped, or prolapsed disc. Although disc extrusion is most common, a disc protrusion can occur - especially in large dogs. A protrusion implies that the disc nuclear material has not escaped into the spinal canal but it is bulging into the fibrous portion of the disc.Sometimes it is not possible to distinguish between an extrusion and a protrusion preoperatively. The prognosis is not necessarily better with one versus the other. Clinical signs of disc disease usually do not develop until a protrusion or extrusion occurs.
 

WHAT BREEDS ARE AFFECTED AND AT WHAT AGE?

Any breed of dog or cat can have intervertebral disc problems. However, some breeds have more problems than others. These breeds include Dachshunds, Beagles, Pekinese, Basset Hounds, Welsh Corgis, Spaniels, Lhasa Apsos, Shih Tzus, Poodles, and Bulldogs. The risk of disc disease for Dachshunds is about ten times greater than all other breeds combined. About 85% of the dogs that extrude a disc are between three and eight years of age. 

THINGS TO CONSIDER

The importance of establishing an accurate history can not be overemphasized. The answers to the following questions are very helpful: When was your pet last normal? Did the problem begin acutely, on a specific day, or did it have an insidious onset? Was one side worse than the other? What medicine or treatment was prescribed and did it help? Is your pet getting better, worse, or about the same?Most of all, do not wait until is is too late We recommend a prompt physical and neurological examination if your pet is exhibiting any clinical signs associated with disc disease. Medical and surgical options can be discussed in detail during your initial consultation.

WHAT ARE THE SYMPTOMS AND CLINICAL SIGNS?

Disc disease always has the potential to lead to lifelong neurological deficits or paralysis. Therefore, patient assessment and treatment should not be delayed. The onset of disc disease may be abrupt (minutes), sudden (hours), or gradual (several days or weeks). The signs may be rapidly progressive, slowly progressive, or static. Recovery may occur only to have recurrence later. Recurrent attacks are typically more severe than those of the initial episode. Recurrent attacks are usually the result of progressive extrusion at the same disc. More than one disc can extrude in a lifetime, but is uncommon. Multiple disc extrusions at the same time are rare. Classical symptoms vary with the location of the disc extrusion, the rate of disc extrusion, the amount of disc extruded, and the direction of the extrusion. Dogs that extrude a large amount of nuclear material at a high velocity directly beneath the spinal cord can have complete paralysis within a matter of hours. Dogs that extrude a small amount of disc material may only show signs of pain, without lameness or neurological deficits. In most instances, a comprehensive history and neurological examination can determine the severity and localize the problem. The spine is categorized into four anatomical areas. The four locations are cervical (neck), thoracolumbar (back), lumbosacral (lower back), and a combination (multifocal syndrome).
 

CERVICALThe 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.Pain is elicited when the head is moved or the muscles in the neck are palpated. Posturing with the nose held close to the ground may result in arching of the back. Weakness or paralysis of all four limbs or lateralization to one side may be present, but often is not. A nerve root running to one front leg may become "pinched" leading to lameness or reluctance to place weight on the leg. The pain can be persistent and unrelenting or it may be intermittent. Due to the pain, a dog is usually less active - reluctant to jump, play, or go on walks. Many dogs are content to lay and sleep most of the day and may hide. Sometimes a dog will have a diminished appetite or may back away from the food bowl while attempting to eat. Dogs with cervical disc extrusions will often be quite vocal in demonstrating pain, especially when picked up. At times, seemingly unprovoked, they may cry out unexpectedly.

THORACOLUMBAR

Thoracolumbar disc extrusions are the most common and often the most urgent. Symptoms can progress extremely rapidly in a matter of hours and occasionally even minutes. Symptoms often start with pain and reluctance to walk, jump, and/or play. The back may be arched. Weakness or ataxia (incoordination) may be present in the hind legs, but the front legs are normal. Owners often observe hind leg weakness, ataxia, or difficulty standing. This can progress to paralysis. One leg may be more severely affected than the other. Digital pressure at the level of the disc extrusion usually elicits pain. The abdomen may be tense Animals usually have fecal and urinary incontinence if they are unable to stand and walk.

LUMBOSACRAL (Low Back)

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 lumbosacral area when digitally palpated or when the hind legs are extended. 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.

MULTIFOCAL

This syndrome occurs infrequently but can have catastrophic effects. It is often the result of a massive disc extrusion accompanied by hemorrhage in the spinal canal and/or within the spinal cord. The neurological signs frequently reflect ascending and descending spinal cord damage initiated at the site of the disc extrusion and resulting in flaccidity with loss of reflexes in the hind legs. If the lesion continues to ascend cranially, the front legs and diaphragm may become involved, leading to respiratory paralysis and death. No reliable medical or surgical therapy is currently available for animals that manifest signs of progressive ascending and descending spinal cord destruction. Early surgical intervention may help prevent onset of this syndrome.

TREATMENT OPTIONS WHAT ARE THEY?

Treatment for intervertebral disc disease is managed by one of two options - medical or surgical. Medical therapy may be used if low grade pain and minor or no neurological deficits are present. Anti-inflammatory drugs and muscle relaxants are typically used.It is mandatory to strictly restrict activity since pain relief may result in premature resumption of normal activity. Normal activity can then lead to extrusion of more disc material which may in turn lead to worsening of clinical signs or even paralysis. Once again, strict confinement is mandatory since recurrence of clinical signs following medical treatment is common. Medications that inhibit blood coagulation such as non-steroidal anti-inflammatory drugs, (e.g., aspirin, phenylbutanzone, banamine, and Adequan) should be avoided if future surgical intervention is contemplated.Surgical treatment should be considered whenever there is persistent or recurring pain, difficulty standing or walking, recurrent episodes, rapidly progressing symptoms, or symptoms which have an incomplete response to medical treatment.

TIME IS OF THE ESSENCE - WHY?

Early detection and diagnosis followed by immediate appropriate treatment results in the best possible prognosis. There are three basic neurological functions: proprioception (joint sense or knowing where the extremities are without looking), motor movement (movement of extremities voluntarily with nerve and muscle function intact), and sensory perception (ability to feel noxious stimuli). In addition to pain, proprioception deficits (knuckling on feet, ataxia, staggering) are usually seen first in animals suffering from a extruded disc. Motor deficits (weakness, paresis or paralysis) generally occur simultaneously or follow proprioception loss. If motor function is decreased or lost, the problem is urgent! Loss of sensory perception signifies severe spinal cord injury and is associated with a decreased chance of recovery following treatment. Intervention should be carried out as early as possible following onset of neurological deficits.

HOW IS THE DIAGNOSIS MADE?

Routine radiographs and a myelogram are produced to pinpoint the location of the extruded disc. During a myelogram, a spinal tap is performed, contrast material is injected, and radiographs are taken. If an extruded disc is present, the contrast material is displaced. Magnetic resonance imaging (MRI) may be necessary to make a diagnosis. Cerebrospinal fluid is saved for analysis if necessary.
 

WHAT DOES SURGERY ENTAIL?

If the diagnosis of an extruded disc is made, animals usually go immediately from radiology to surgery while under 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 extruded disc. The extruded disc material is removed, thus relieving compression of the spinal cord and/or nerve root. Since the fibrocartilaginous portion of the disc is intact and functional, it remains in placed and fusion of the disc space is rarely necessary.

AFTERCARE - IS IT DIFFICULT? WHAT WILL I NEED TO DO?

The amount of nursing care needed postoperatively is directly proportional to the severity and rate of onset of the neurological deficits present preoperatively. Activity should be restricted for about four weeks. If your animal can not walk, you will need to provide physical therapy and assistance to help speed recovery. Special exercises that are easy to perform are demonstrated at the time of discharge.Nerve supply and muscles in the urinary bladder are necessary for normal urination. The bladder can be affected just as the muscles to the hind legs can be affected. If necessary₅ owners will be instructed how to perform bladder expression at home in order to assist urination until normal bladder function returns. Most clients learn this exercise quickly with a little practice. Animals can typically defecate without assistance.

WHAT ARE THE RISKS OF MEDICAL TREATMENT?

Medical treatment of an extruded disc usually involves one or more of the following medications: steroids, non-steroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, or tranquilizers. All of these medications can have potentially serious side effects. Steroids and NSAJD's used for treatment of neurological problems have been associated with causing severe gastrointestinal ulceration. Clinical signs include loss of appetite, decreased activity, lethargy, vomiting (with or without blood), and a dark, sometimes tar-like stool. The ulceration and bleeding can be life threatening. In addition, aspirin and NSAIDs inhibit blood coagulation which can complicate surgery. The medications may cause a sense of euphoria or dramatically reduce the level of pain. This may lead to excessive activity which is likely to worsen the condition due to progressive extrusion in the face of medical treatment. Prompt surgical therapy is recommended if neurological function is deteriorating, especially if clinical signs appeared suddenly, if your animal is in pain, or if ability to walk is affected.

WHAT IS THE LONG TERM OUTCOME? WILL MY DOG WALK, RUN, JUMP, AND PLAY AGAIN?

The length of time for rehabilitation is variable. As you might expect, the rehabilitation time and long term prognosis is directly proportional to the severity and duration of the neurological problems. Most animals (>80%) are walking (often normally) at suture removal (10-14 days after surgery) providing good sensory perception and motor movement was present pre-operatively. Others may need help for several weeks. Animals that have no deep pain perception at the time of surgery may or may not recover - most do not.Our goal is for your animal to resume normal activity; however, it is important for you to understand that nerve cells and pathways do not regenerate like other tissues such as skin, muscle, and bone. Therefore, it is possible that deficits could persist and in severe cases, your animal may not walk again or may walk with some handicap. An anticipated prognosis can be determined at the time of neurological examination during your initial visit. Estimations of anticipated success of surgery, time until recovery, and extent of recovery can be given. The prognosis is greatly improved when treatment is instituted early and aggressively in the course of the disease.

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.

ARE THERE ANY SURGICAL RISKS?

Yes. The incidence of complications is very low, but the risks exist, just as they would for surgery on people. Complications from infection, surgery, and anesthesia can never be totally eliminated. Complications are minimized by utilizing the newest and safest anesthetic agents and monitoring devices available. Surgical complications can be greatly reduced if performed with specially designed high-speed instruments rather than with hand instruments such as rongeurs. An extremely high spinal surgery caseload has resulted in a very proficient staff, minimal anesthesia time, and low complication rate.We are confident that we can deal with your dog's neurological disorder appropriately. However, it is important for clients to understand that the spinal cord is very unforgiving. Early recognition and intervention are the keys to a successful outcome.

THE PARALYSIS AND PAIN -WHAT ELSE COULD BE CAUSING THE PROBLEM?

The most likely cause of your dog's problem is intervertebral disc disease. However, other problems including vertebral infection or instability, vascular problems, inflammatory disease, cancer, injury and/or fracture, or a congenital malformation could be present. The definitive diagnosis will be made by evaluation of radiographs, the myelogram films, and the cerebrospinal fluid. If one of these unexpected diagnoses is made, the problem will be discussed with you before proceeding. It is also possible that the treatment option may be changed from surgery to medical or vice versa.

HOW DO WE GET STARTED?

Time is critical with neurological problems. Once the initial examination is completed, diagnostics are performed. When the onset of symptoms is sudden or if the symptoms are severe, it is usually important that we receive permission to proceed from the myelogram to surgery. This saves valuable time, eliminates the need for a second anesthesia, is most cost effective for the owners, and in most cases, improves the prognosis.

HOW LONG IS THE HOSPITAL STAY?

We would like to discuss your animals progress each day during hospitalization. The length of stay usually ranges from one to four days. We will want to answer all of your questions concerning aftercare at the time of release from the hospital.

Reference: Braund, Kyle G. intervertebral Disc Disease. In Bajrab: Disease Mechanisms in Small Animal Surgery. p.960-969 Lea & Febiger, 2nd. Edition 1993.

 

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