Healthy Dogs

Ruptured Discs in Dogs

A disc is a cushion of cartilage that sits between the vertebrae and acts as a shock absorber. It is composed of a rim of tough, fibrous connective tissue that surrounds a gel-like center called the nucleus. When a disc ruptures, one of two things may happen. The first is that the fibrous capsule breaks, allowing the inner nucleus to push out through the opening and impinge on the spinal cord or a nerve root. This type of rupture is called a Hansen Type 1. The second is that the entire disc, surrounded by an unbroken capsule, can bulge outward. This is called a Hansen Type 2.

The diagnosis of ruptured disc is made by neurological examination and imaging studies including spine X-rays, a myelogram, and possibly a CT scan or MRI.

Ruptured discs in the back of the Hansen Type 1 occur in small breeds such as the Dachshund, Beagle, Cocker Spaniel, Pekingese, and small mixed breeds. In fact, ruptured discs are more frequent in Dachshunds than in all other breeds combined.

The capsule begins to degenerate at about 2 to 9 months of age, and signs of impingement on the spinal cord appear at 3 to 6 years of age. About 80 percent of Type 1 ruptured discs occur in the lower back between the last thoracic and the first two lumbar vertebrae. Most of the remainder occur in the neck. There is often a history of mild trauma, such as jumping off a sofa, but normal movements are sufficient to cause a Type 1 rupture. Occasionally, more than one disc becomes ruptured.

The symptoms of a Type 1 rupture usually come on gradually but can appear with sudden explosiveness. The main sign is pain. The dog holds her back stiffly and may cry or whine when patted or handled in the injured area. She usually refuses to walk up stairs or jump into a car. Neurological signs include weakness, lameness, and a wobbly gait. A dog experiencing the severe back pain of an acute rupture will have a hunched-up position and a tight abdomen. The dog may pant and tremble. Sudden disc ruptures can produce complete hindquarter paralysis.

Hansen Type 2 discs ruptures occur in the larger breeds, including German Shepherd Dogs and Labrador Retrievers. The entire disc, surrounded by its capsule, gradually impinges on the spinal canal. Symptoms appear in dogs 5 to 12 years of age. Because the process is gradual, symptoms progress slowly.

Ruptured discs in the neck of the Hansen Type 1 cause a dog to carry her head low and rigidly, making the neck look shorter. This type of injury is extremely painful. A dog will often cry out when patted on the head and refuse to lower her head to eat and drink. Weakness and lameness involve the front legs. Complete paralysis of all four legs does occur but is rare.