The disc is composed of two parts. The outer covering is much like a thick shell; it is comprised of tough fibres that protect and contain the central part. The disc is thinnest at the top, this area is located just below the spinal cord. The central part of the disc is much softer than the outer part and has the consistency of thick toothpaste.
When the outer shell degenerates, it allows the central part of the disc to escape. This is called a disc rupture or a slipped disc. Since the disc is thinnest near the spinal cord, disc material that escapes through the tear usually goes upward, putting pressure on the spinal cord. Because the spinal cord is encased within its bony canal, it cannot move away from the pressure and it becomes pinched.
Degenerative disc disease causes spontaneous degeneration of the outer part of the disc, resulting in disc rupture. It may not be related to injury, although trauma is a common cause. It is also not related to age. Most dogs with degenerative disc disease are 3-7 years old. It is a sudden event most likely due to genetic factors. Certain breeds, especially the Dachshund, Poodle, Pekinese, Lhaso Apso, German Shepherd, Doberman and Cocker Spaniel have a high incidence of disc disease.
The spinal cord is like a telephone cable carrying thousands of tiny wires. When it is crushed, transmission of information through the wires is slowed or stopped. When the disc degenerates and ruptures, a similar event in the spinal cord occurs. The central part is forced upward, putting pressure on the spinal cord and the nerves that leave the spinal cord over the discs (i.e. spinal nerves). Pressure on the spinal nerves results in pain. Pressure on the spinal cord results in pain and/or loss of information transmission causing partial or complete paralysis.
Most disc ruptures occur in the middle to lower part of the back. However, they may also occur in the neck. Back injuries often cause paralysis without severe pain while neck injuries usually cause severe pain without paralysis. If paralysis affects all four legs, the disc rupture must be in the neck. Due to the way nerve tracts are arranged in the spinal cord, disc ruptures in the neck may affect the rear legs first and may not involve the front limbs.
Disc degeneration usually occurs relatively slowly, usually over several days or weeks. The dog often experiences pain and becomes reluctant to move. It may lie around for a few days allowing the body to try to heal the injury, often without the owner being aware that a problem existed. However, discs may also rupture very acutely. Some dogs will go from normal walking to total paralysis in less than an hour.
A presumptive diagnosis of disc disease is made based on the dog's history of neck or back pain, uncoordinated walking, or paralysis when there is no history of trauma. The physical examination will indicate that the problem originates from the spinal cord, giving further evidence to disc disease. Another important factor is the breed. If the dog is one of the high incidence breeds, the diagnosis is even more likely.
Treatment is based on the stage of the disease. Stage I disc disease produces mild pain and is usually self-correcting in a few days. Stage II disc disease causes moderate to severe pain in the neck or lumbar (lower back) area. Stage III disc disease causes partial paralysis (paresis) and results in the dog walking in staggering or uncoordinated movements. Stage IV disc disease causes paralysis but the ability to feel is present. Stage V disc disease causes paralysis and loss of feeling. These stages tend to overlap in some dogs, and dogs may move from one stage to another over a period of hours to days.
Dogs with Stage II and III disease are usually treated with anti-inflammatory drugs, pain relievers, and restriction from exercise. Surgery may be considered if the pain or lack of coordinated movements persists after 4-7 days of treatment or if the neurological status declines from one day to the next. The time of confinement will vary based on each patient’s condition.
Dogs with Stage IV disease should have surgery, although a small percentage will recover without it. Dogs with Stage V disease should have surgery immediately. The sooner that surgery is done, the better the prognosis. Ideally, these dogs should be operated on within the first 24 hours of the onset of paralysis.
The goal of surgery is to remove pressure from the spinal cord. If the disc rupture occurs in the lower back, a window is made in the side of the vertebral bone to expose the spinal cord. This window allows removal of disc material and relieves pressure from the cord. If the disc rupture occurs in the neck, a window is made in the bone exposing the spinal cord. This may be done either from the top or the bottom, depending on the situation and the veterinarian’s preference.
If paralysis was present before surgery, your dog may not be able to walk when it is discharged from the hospital. You will be given detailed instructions on the procedures that should be performed. Recovery is dependent on four factors: whether or not permanent damage was done before surgery, if the surgery relieved the pressure quickly enough, physical therapy performed at home, and the motivation of your dog.
Dogs with CDRM do get frustrated when they find that they cannot jump up (eg into the back of a car) or perform normal daily activities (such as getting up stairs), but they do not exhibit signs of pain or discomfort. The diagnosis is made based upon clinical signs and the absence of another cause. The rate of progression varies greatly from one dog to another. The definitive diagnosis is confirmed by post mortem histological examination of the spinal cord.
Breeds affected: - Dobermans and Great Danes primarily - young Danes are more commonly affected - symptoms usually manifest themselves from 10 months to 18 months. Dobermans - young and old, can grow through the problem as youngsters, more commonly seen in middle aged to older Dobermans (3 to 9 years of age).
The cause of Wobblers Syndrome is unknown, although a link to fast growth and genetics is suspected. Some breeders say that there has been a marked decrease in the incidence of not only Wobblers Syndrome, but other diseases that occur during the early, fast growth stages of Great Danes, when weight is kept down and growth rate has been slowed nutritionally.
Symptoms usually appear first in the rear legs as a mild ataxia in gait (lack of coordination) and can escalate to involvement of the forelegs as well. The severely affected dog moves like a drunk and the ataxia shows up most when the dog is walked and then moved sharply into a turn.
A veterinarian will do a neurological work up on the dog and this often includes not only cervical spine x-rays, but a mylogram x-ray. The owner should thoroughly investigate the advisability of this procedure, especially since if it is Wobblers Syndrome, surgery may not be the best option. Treatment of Wobblers Syndrome can include the use of corticosteroids, a neck brace and surgery. The surgery fuses the 2 unstable vertebrae which relieves the pressure on the spinal cord. Unfortunately this also puts further stress on adjoining vertebrae which can cause instability to recur in them. Many Wobblers can live a long and pain free life with little or no treatment. Others can deteriorate quickly and euthanasia then becomes the only kind choice.
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