Overview of Canine Intervertebral Disc Disease in the Thoracolumbar Area

Thoracolumbar (T-L) disc disease is a condition that occurs when pressure is placed on the spinal cord by disc material that herniates beneath or adjacent to the cord. This condition is commonly referred to as Intervertebral Disc Disease (IVDD) that can occur in the thoracolumbar area of the back. The condition may be an acute (occurs suddenly) or chronic (slowly develops over time) condition in dogs.

The exact cause of disc degeneration is unknown but in many animals there is a change in the content of the disc from a soft, pliable gel to stiff mineral. This stiff material can slowly compress the spinal cord or suddenly burst into the spinal canal. When the disc involved is in the mid-portion or thoracolumbar area of the spine (the T-L region) the front legs are not affected; they remain normal. However, the back legs may be affected to varying degrees.

If your dog develops a T-L disc herniation the signs that he shows may be mild back pain only or, in severe cases, complete paralysis of the rear legs without the ability to perceive any sensation in the limbs.

Chondrodystrophic breeds – breeds that are prone to disorders of cartilege formation such as the dachshund, Lhasa apso and Pekingese – are among the breeds more commonly affected. T-L disc disease most commonly occurs when animals are between three and seven years of age.

What to Watch For

Signs of IVDD in dogs may include: 

Back pain

Reluctance to play

Yelping when handled, petted or lifted

Reluctance to climb stairs

Clumsiness

Walking drunk

Inability to walk or paralysis

 

Diagnosis of IVDD in Dogs

Diagnostic tests are needed to recognize T-L disc disease and differentiate it from other diseases that may cause similar signs.

In addition to obtaining a complete medical history and performing a thorough general physical examination, your veterinarian will likely perform the following tests:

Neurological assessment. Because the amount of disc material pressing on the spinal cord can be small or large, and the rate at which the spinal cord is pinched can be fast or slow, the signs your dog shows can be extremely variable.

If your dog can walk normally but has back pain, your veterinarian will palpate the spine (apply gentle pressure to it) to try to localize the pain.

If your dog can walk but is clumsy, your veterinarian will check to see that only the back legs are affected and the front legs and head are normal.

If your dog cannot walk, your veterinarian will pinch the toes of the back legs to assess your dog’s awareness of pain. Your dog may pull the leg back as a reflex response (the withdrawal reflex); however, your veterinarian will want to see if your dog cries out or tries to bite, indicating that he/she feels pain in the affected limbs. Just pulling the leg back does not indicate that your dog can feel his legs.

Radiographs of the spine may be helpful to localize the affected disc space, but definitive diagnosis of spinal cord compression is usually obtained by injecting a dye into the spinal canal, a procedure called a myelogram. When available, a CT scan may prove to be an alternative to myelography.

Treatment of IVDD in Dogs

The type of appropriate treatment will depend on the severity of the clinical signs. Dogs with milder forms of the disease may be treated medically, whereas more severe cases may need surgery. Treatment for T-L disc disease may include one or more of the following:

Medical treatment may consist of rest and anti-inflammatory medication, usually in the form of steroids. Muscle relaxants may also be used to alleviate spinal muscle spasm.

Surgical management may be recommended, particularly if the signs are severe or there is no response to medical management. This involves localizing the exact site of the disc extrusion with a myelogram or CT scan. Then a “window” is made in the spinal bone to relieve the pressure on the spinal cord and to allow access to the disc material so that it can be removed.

Home Care

Strict cage rest will be essential for at least four weeks when opting for medical management. This rest is essential to allow a “scar” to form over the top of the disc material; early activity may precipitate the herniation of the rest of the disc material and worsening of your dog’s condition. You should carry your dog outside several times a day to allow him to urinate and defecate, but do not allow him to run around the yard. Failure to confine a dog with disc herniation is a common reason for early recurrence.

If your dog is unable to urinate on his own, he will need help emptying his bladder. When the bladder overfills, urine dribbles out, but this results in stretching of the bladder and may make your dog unable to urinate even if there is improvement in the condition of the spinal cord. Bladder emptying is usually done three to four times a day. If your dog is released from the hospital while he is still having difficulty urinating be sure that your veterinarian shows you how to empty the bladder (called “expressing” the bladder).

If your dog is unable to walk, physical therapy is important to promote muscle strength. Have your veterinarian or the veterinary staff show you how to do this.

Be prepared for small increments of improvement. Depending on the severity of the disease your veterinarian will estimate how long your dog’s recovery may take. Most likely your dog won’t walk immediately away after surgery. Just as in people, it takes time to recover from spinal cord injury, so be patient.

Observe your dog closely for any worsening of clinical signs. If you notice any deterioration in your dog’s condition, contact your veterinarian immediately. If he is predisposed to back problems be aware of the early signs of disc disease. If he shows any sign that might indicate a neurologic problem, seek veterinary advice as soon as possible.

Don’t let your dog become overweight. Obesity increases stress to the mid-portion of the spine of these “long dogs.”

Information In-Depth in Canine Intervertebral Disc Disease (IVDD)

T-L disc disease is the most common spinal disorder that occurs in dogs. It is particularly common in three- to seven-year-old chondrodystrophoid breeds. Your dog’s breed, combined with the history of clinical signs and initial examination findings, will alert your veterinarian to the possibility of a spinal problem.

Other conditions that might cause similar clinical signs include:

Fracture or dislocation of the spine. This is nearly always associated with severe trauma such as falling from a high place or being hit by a car. The symptoms depend on the severity of the fracture and its location. Severe disruption of the cord results in total paralysis; however, some fractures can be repaired so that there is gradual return to normal.

Congenital abnormalities of the spine. Young dogs can develop hind leg neurological abnormalities due to congenital deformities of the spine. Such deformities are typically visible on radiographs (X-rays). The severity of the signs depends on the abnormality and its location.

Spinal infections. Infections within the disc space or of the spinal bones can produce back pain and weakness or paralysis. These infections occur more commonly in young, growing dogs and usually produce changes that can be seen on X-rays.

Tumors of the spinal bone or cord. Tumors that compress the spinal cord tend to occur in very young animals or old animals. These tumors may or may not be visible on a radiograph. Myelography or a CT scan may be needed to define the lesion, particularly if the tumor is within the spinal cord or canal and not arising from the vertebral bone.

Fibrocartilaginous emboli. Dogs can have a “stroke-like” disorder of the spinal cord called a fibrocartilaginous emboli or FCE. A small piece of disc material is thought to block the blood vessels supplying an area of the cord. This may result in cord damage and problems like weakness or paralysis in the back legs. This disorder is normally not progressive and is not painful. Additionally, one leg may be more severely affected than the other depending on which blood vessels are damaged.

Orthopedic conditions. Some orthopedic disorders of the back legs such as simultaneous rupture of the cruciate ligaments in both limbs can produce signs similar to a T-L spinal cord disorder because the animal may not be able to walk.

Toxicity. During the history and general physical examination your dog will likely be evaluated to ensure that no poison or other toxic substance has been ingested that could be causing a “drunken” hind leg gait.

Veterinary Care In-Depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations.

In-depth Information on Diagnosis 

Diagnostic tests are needed to recognize T-L disease and differentiate it from other diseases that might cause similar signs.

In addition to obtaining a detailed history, your veterinarian will perform a general physical examination, usually taking into consideration your dog’s possible back pain. Depending on the findings, other tests that your veterinarian may wish to perform include:

A neurological examination. This consists of a series of tests which help define the location of the spinal cord damage.

The head, neck and front legs are assessed to determine whether the spinal cord in front of the third thoracic vertebrae (T3) is normal or not. With T-L disc disease only the rear limbs should be affected.

The back legs may be assessed for the ability to move and walk – the presence of motor function and the ability to respond to the brain’s command to walk. Your dog may be assessed as normal, clumsy or unable to walk. The tail may be held at the base to assist in this activity. The feet may then be turned over or “knuckled” to assess your dog’s ability to recognize the abnormal position of the paw. Loss of the ability to recognize how the feet are placed (proprioception) indicates mild damage to the spinal cord and often precedes the loss of motor function (or the ability to move the legs). Other tests may follow to evaluate the brain’s awareness of the position of the feet.

If your dog cannot walk even with support your veterinarian will pinch the toes of the back legs to assess for deep pain sensation. This is done either with fingers or with an instrument such as a hemostat. Although this may appear barbaric, it is an important test to help define the severity of the spinal cord injury. If your dog feels the stimulus, he or she should cry out or try to turn around and bite. In some dogs, subtle signs such as pupil dilation may indicate that they feel the pinch.

If your dog does not show any indication of feeling pain from this procedure, typically severe damage to the spinal cord has occurred. It is important to note that pulling the leg away when the toe is pinched does not mean that your dog feels the pain. This is just the “withdrawal reflex,” not conscious sensation of pain. Crying or biting suggests that the information from the toe being pinched got past the damaged region and was received by the brain; pulling away does not.

Other reflexes are tested on the back legs to better define the location of the injury.

Your veterinarian may feel for your dog’s bladder and check the muscle tone in the anal region. These sites could be affected by spinal cord injury.

Palpation, which is a technique of examining organs or body parts by touching and feeling, along the spine may reveal the most sensitive, affected area.

At the end of the examination your veterinarian will likely be able to define the location of your dog’s injury, determine the severity of the problem, and make recommendations about how it should be treated. Obviously, the more marked the damage to the spinal cord, the more severe the effects on the back legs and the worse the prognosis. Additionally, the longer the damage has been present, the worse the prognosis.

Blood tests are usually not specific for this disease.

Plain radiographs (X-rays) may be helpful but are not definitive for a disc compressing the spinal cord. A myelogram – an X-ray study in which dye is injected into the spinal canal – is needed to show that the cord is swollen or pinched or buckled. Alternatively, a CT scan may be used. Myleography and CT scans require general anesthesia and are usually performed prior to surgery so that anesthesia is administered only once.

In-depth Information on Treatment

The choice of medical versus surgical treatment depends on the severity of the problem.

Medical treatment

For dogs that can walk but that have back pain or are clumsy, medical treatment may be appropriate. This involves strict cage rest and the use of medications such as muscle relaxants and steroids. Your dog may be hospitalized and given a course of intravenous steroids or a course of oral steroids that taper off over a number of weeks when your dog goes home.

The common steroid used is prednisone. Administration of prednisone will likely result in your dog having an increased thirst, urinating more often, and having an increased appetite.

Surgical treatment

When the dog is unable to walk normally, is paralyzed or has no deep pain sensation, surgery may be recommended. A myelogram or CT scan may be performed to locate the exact disc space affected. The disc may have erupted on the right or left side or from directly below the spinal cord and this will affect the type of surgery performed. Usually a small window of bone is drilled in the spinal bone (laminectomy) to allow decompression of the spinal cord and access to the ruptured disc material.

Your dog will not be cured instantly by surgery. The procedure takes the pressure off the cord, allowing it the opportunity to heal. The surgery does not do anything directly to the cord itself, which must heal on its own. The chance that this can occur varies with the severity and duration of the injury.

Prognosis of Intervertebral Disc Disease (IVDD) in Dogs

Medical management is successful in about 80 to 90 percent of dogs with just back pain.

If your dog could still walk before surgery, but was wobbly, the prognosis following surgery is excellent.

If your dog had lost the ability to walk, but still had deep pain sensation, the prognosis following surgery is good.

If your dog had lost deep pain sensation, the prognosis following surgery becomes guarded. If this had been the case for greater than 48 hours, then the outlook for walking again is grave, whether surgery is performed or not.

Follow-up Care for Dogs with Intervertebral Disc Disease

Following surgery, dogs are usually hospitalized for several days to assess their early improvement and to determine the level of bladder function.

Many dogs need help emptying their bladders for awhile after surgery. Generally expressing the bladder is done three to four times a day until control over the bladder returns, and your veterinarian will show you how to perform the procedure. Medication may be used to help with bladder function.

Check the incision daily for swelling, redness or discharge. Stitches or staples are usually removed in two weeks.

Most dogs have control of their bowel movements but are unable to stand to defecate, and therefore have a tendency to soil themselves. If you can, support your dog to encourage a more normal bowel movement, and make sure the hind limbs and rump area stay clean.

After the stitches have been removed swimming in the bath can be an excellent form of physiotherapy. Passive range of motion should be encouraged in all dogs. This involves hip and knee flexion and extension exercises. This promotes good muscle tone and joint mobility in order to offset muscle wasting.

For dogs that are unable to walk, soft padded bedding will be very important. Turning your dog from side to side often, at least four times a day can help prevent the development of pressure sores.

Following spinal surgery all dogs need rest and confinement for a period of four to six weeks, even if they appear to be moving well. This allows the tissue around the surgical site to heal.

Recovery time is extremely variable. Some dogs that have been completely paralyzed may walk within a few days, and others may take several months. Some dogs may return to normal completely, while others may have residual neurological deficits. These deficits may be mild and not affect the quality of your dog’s life, while others may be so significant that an owner may be forced to consider using a paraparetic cart to restore some type of mobility. Others may be forced to opt for euthanasia, when they realize that an acceptable quality of life for their dog cannot be restored.

An early diagnosis of disc disease is very important to optimize your dog’s outcome. Have your dog evaluated for suspected disc disease in an emergency because progression from weakness to paralysis can occur within hours. Your veterinarian may refer you to a surgical or neurological specialist for treatment.

Avoid excessive weight gain in chondrodystrophic breeds of dogs that will result in excessive load across the thoracolumbar region of the spine.

It is uncommon for a dog that has had spinal surgery to have a recurrence at the same or another site at a later date, but if you suspect that this has happened see your veterinarian as soon as possible.