What is degenerative disc disease in dogs, and what are signs and symptoms of the condition? How is it diagnosed and treated? Our Lexington vets will answer these questions in today's post.
What is a Disc and What is Its Purpose?
The spinal cord runs through a bony canal within the spine and is surrounded by protective bone everywhere except the junction of the vertebrae. Rubber-like junctions called intervertebral discs fill these junctions. Individual vertebrae and intervertebral discs enable the back to move flexibly - up and down and sideways - without the bones of the spinal column coming into contact. This extreme protection of the spinal cord reflects the fact that it's one of the body's most critical and sensitive organ systems.
If the spinal cord is damaged, nerve cells will not regenerate. Instead, they're replaced with scar or fibrous tissue. Spinal cord injuries typically lead to permanent, irreversible damage.
What Happens When a Disc Ruptures?
An intervertebral disc has two components, and its structure is similar to a jelly donut. Its fibrous ring is the outer covering and acts much like a thick shell. Made of tough fibers, it protects and contains the pulpy nucleus (central part) of the disc, which is softer and has the consistency of thick toothpaste.
With degenerative disc disease, spontaneous degeneration of the outer part of the sick occurs, leading to sudden rupture or herniation of the disc. The disc is thinnest near the spinal cord, so the disc material usually goes upward when a tear happens, putting pressure on the spinal cord. Because the spinal cord is contained within its bony canal, it's unable to shift away from the pressure and becomes pinched.
An injury may or may not cause disc rupture. In many circumstances, the disc rupture happens after a fall or a relatively small jump. While these are often blamed on a disc rupture, the injury actually occurred due to chronic disc degeneration, which often occurs in adult dogs between the ages of three and seven years old. While dogs of any age and breed can suffer from the condition, Basset Hounds, Corgis, Lhasa Apsos, Pekingese, Cocker Spaniels, Dachshunds and Shih Tzus are all at increased risk for degenerative disc disease.
How Does a Ruptured Disc Impact the Spinal Cord?
Think of the spinal cord like a telephone cable that's carrying thousands of tiny wires. When crushed, information is no longer transmitted through the wires. A similar event happens when the disc degenerates and ruptures. Its central component is forced upward, putting pressure on the spinal cord and/or the spinal nerves.
This pressure on the spinal cord and/or spinal nerves causes pain and/or loss of information transmission, resulting in partial or full paralysis.
While most disc ruptures happen in the lower back, they may also occur in the neck. While the former often causes paralysis without severe pain, the second often causes severe pain without paralysis. If all four legs are paralyzed, the disc rupture must be in the neck. The nerve tracts are arranged in a certain way within the spinal cord, which means disc ruptures in the neck can affect the rear legs first or even exclusively.
Symptoms of a Slipped Disc in a Dog
Common signs that your dog has slipped a disc include:
- Loss of coordination
- Sudden back pain
- Loss of sensation in the legs
- Weakness of lameness in limbs
- Inability to use back legs or hind leg paralysis
- Dogs unable to walk may also have problems peeing on their own
Symptoms of a herniated disc can also mirror other spinal conditions. If your pet is showing any signs of degenerative disc disease, depending on whether you see a sudden onset of symptoms you may bring them to Bluegrass Veterinary Specialists + Animal Emergency for emergency care and advanced diagnostics before they are referred to a veterinary neurologist near Lexington and tested to eliminate other possibilities such as a spinal fracture, infection or tumor.
How is Degenerative Disc Disease Diagnosed?
A presumptive diagnosis of disc disease can be made based on a dog's history of neck or back pain, incoordination when walking, or paralysis when there is no history of trauma. A physical exam will indicate that a problem starts in the spinal cord, which may further support a diagnosis of disc disease. Breed is another important factor - if your dog is one of the breeds mentioned above that are most at risk for degenerative disc disease, diagnosis is even more likely.
In some cases, X-rays (radiographs) can be used to diagnose the disease. They may also be normal since neither the disc nor the spinal cord are visible. A myelogram may also be done if the diagnosis has not been confirmed or if surgery is required. This procedure involves a special dye that's injected around the spinal cord while a dog is under anesthetic. When radiographs are taken, the dye will outline the spinal cord. A break in the dye column indicates pressure on the spinal cord.
How are Disc Ruptures Treated?
Treatment falls under the area of veterinary neurology and is often performed by a pet neurologist. It is based on the stage of the disease, and may or may not include surgery.
- Stage 1 results in mild pain and is usually self-correcting in a few days.
- Stage 2 causes moderate to severe pain in the neck or lumbar (lower back) area.
- Stage 3 causes partial paralysis (paresis) and leads to staggering and/or uncoordinated movements when walking.
- Stage 4 causes paralysis, but sensations are still present.
- Stage 5 causes paralysis and loss of feeling. In some dogs, these stages tend to overlap, and dogs may move from one stage to another over a period of hours or days.
Inflammatory drugs, pain relievers and exercise restriction are usually used to treat dogs with Stage 2 and 3 degenerative disc disease. If pain and incoordination persists after 4 to 7 days of treatment or if there is neurological decline from one day to the next, it's important that pain medication not be administered unless total crate or cage confinement is enforced.
If the pain sensation is taken away, the dog is more likely to suffer a total disc rupture. The sensation of pain is important for limiting motion. Length of confinement will vary depending on the dog.
While dogs with Stage 4 will likely need surgery, a small percentage can recover without it. The sooner that surgery is performed for dogs with Stage 5 degenerative disc disease, the better the prognosis. If possible, these dogs should be operated on within the first 24 hours of onset of paralysis.
What is the Purpose of Surgery?
The main goal of performing surgery is to remove pressure from the spinal cord. If the disc rupture has occurred in the lower back, a window is created in the side of the vertebral bone to expose the spinal cord. This window allows disc material to be removed, relieving pressure on the spinal cord. This can be done from either the top or the bottom of your dog's spinal cord, depending on the situation and training of the vet neurologist.
It may take several days or weeks for your dog to walk again, so whether the surgery is successful cannot be immediately determined.
After surgery, your dog will be hospitalized for 3 to 7 days. When a dog is paralyzed, they will often lose control of their bladder and bowel, so it's best to wait for these functions to return before your dog goes home.
Motivation will be an important part of the recovery process, as well exercise. You'll be given detailed instructions on procedures and any post-op recovery care that should be performed at home.
What is the Prognosis of Surgery?
Dogs that have surgery on the lower back are generally no worse following surgery unless spinal cord damage has advanced due to rupture of the disc. However, if your dog has had surgery on their neck, they may experience lameness in one or both front legs. This is a setback due to manipulation around the spinal cord normally associated with surgery.
Lameness may persist for a few days but should be temporary. Improvement should progress until your dog's legs return to normal.
Surgery either greatly helps most dogs so they return to normal or near normal. There's also the possibility that they do not improve at all. If walking is not regained, most dogs will not regain control of their bowels or bladder. This means that stool and urine incontinence will come along with paralysis.
It's possible for a dog to rupture a disc again. However, more than 95% of degenerated discs will heal without surgery. The chance of your dog requiring surgery a second time is less than 5%.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.