The intervertebral discs are structures located between the bodies of the vertebrae and act as shock absorbers. They are composed of a rim of tough, fibrous connective tissue covering surrounding a gel-like center. A Hansen Type I rupture occurs when the fibrous capsule breaks, allowing the inner nucleus to push out through the opening and impinge on the spinal cord or a nerve root.
A Hansen Type II occurs when the entire disc, surrounded by an unbroken capsule, impinges on nerve tissue.
Hansen Type I ruptures usually occur in small breeds such as dachshunds, beagles, cocker spaniels, Pekingese and small mixed breeds. Ruptured discs are more common in dachshunds than in all other breeds combined. The capsule can start to degenerate when the dog is only two to nine months of age. Nearly 80 percent of Type 1 ruptured discs occur in the lower back between the last thoracic and the first two lumbar vertebrae. The history often includes jumping off a sofa or stairs, but any abrupt movement can be sufficient to cause a Type 1 rupture. It is also possible for more than one disc to rupture.
The symptoms of a Type I rupture usually progress gradually but can appear suddenly. The dog holds her/his back stiffly and may vocalize with pain or snap at the hand palpating in or around the injured area. The dog will usually refuse to walk up stairs or jump into a car. Neurological signs include weakness, lameness, and a wobbly gait. A dog experiencing severe back pain resulting from an acute rupture usually assumes a hunched-up position with a tight abdomen and may pant and tremble. Sudden ruptures can result in complete hindlimb paralysis.
Dogs with a Hansen Type I rupture in the neck usually carry their head low and stiff and are in extreme pain. The dog will often cry out when patted on the head and refuse to lower her head to eat or drink. There may be weakness and/or lameness of the front legs. Complete paralysis of all four limbs can occur but is rare.
Hansen Type II disc ruptures occur most in German shepherds, labrador retrievers and other larger breeds. With this condition the entire disc, surrounded by its capsule, gradually impinges on the spinal canal. Symptoms usually appear gradually and progress slowly in dogs five to 12 years of age.
Your veterinarian can diagnose a ruptured disc by doing a neurological examination and prove it with imaging studies including spine X-rays, a myelogram, and possibly a CT scan or MRI.
Dogs still able to walk but with pain and mild weakness can be treated by confining them to a cage for a minimum of two weeks with appropriate anti-inflammatory drugs and drugs for pain control. If there is no improvement, or the dog’s condition worsens during this time, surgery is necessary. Surgery for disc disease involves surgical decompression of the spine by removal of bone over the spinal cord a laminectomy or partial bone removal (hemilaminectomy) and removal of the extruded disk material impinging on the spinal cord thus relieving the compression of the cord. Obviously, a very well trained and experienced veterinary surgeon is necessary for these procedures.
The prognosis for these cases depends upon the degree of injury and the location. Most patients that retain motor function have a good chance for recovery. If motor function is compromised the prognosis is more guarded and if deep pain perception is absent, a return to normal is less likely. We have all seen those photos of paralyzed dogs suspended in a two-wheeled cart who suffered this condition and still function as loved pets.
D. R. Gross graduated from Colorado State University’s veterinary school in 1960 and was in private practice for ten years. He enrolled in graduate school at Ohio State University earning a M.Sc. degree in 1972 and a Ph.D. degree in 1974. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is a Fellow of the Cardiovascular Section of the American Physiological Society. During his academic career, he published over 90 papers in refereed scientific journals and over 100 abstracts in proceedings of scientific meetings.
Dr. Gross is the author of “Animals Don’t Blush,” which describes the unique patients and even more unique clients of a veterinary practice in Sidney, Montana in the early 1960s.