Intervertebral disc disease (IVD) can occur in all breeds of dogs, but it is most commonly seen in the chondrodystrophic breeds (these are the short leg, long back breeds, such as dachshunds, shih tzus, Lhasa apsos, beagles, and basset hounds). These breeds of dogs are susceptible to degeneration of their intervertebral discs at a young age. This degeneration weakens the disc, making it more susceptible to rupture. Clinical signs are related to the ruptured disc putting pressure on the spinal cord.

The back of a dog is made of a series of bones (the vertebrae). The intervertebral disc lies between each vertebrae. The spinal cord is located directly above the discs. The cord is surrounded on each side and on its top by bone. The normal disc is composed of a tough outer layer (the annulus fibrosus) and a gelatinous inner layer (the nucleus pulposus). The normal disc provides a cushioning function and imparts flexibility to the back.

The disc degeneration associated with IVD can start within the first year of life. The degeneration causes the nucleus pulposus to dehydrate (lose its water content) and to lose proteins. This together causes the disc to become less elastic and, in a sense, more brittle. The diseased disc is less able to withstand the forces put on the back during normal activity (such as running and jumping). If a force is placed on the diseased disc greater than that disc can withstand, the disc can rupture. When a disc ruptures, the top part of the annulus fibrosus (the part closest to the spinal cord) will tear and the nucleus pulposus is forced upwards. The rupturing disc hits the spinal cord, causing swelling and a disruption of the normal blood flow to the cord. This disrupts the function of the nerves traveling through the spinal cord. Clinical signs are related to how many nerves are affected. Clinical signs range from mild back pain only to complete paralysis of the hind legs. Surgery is the treatment of choice in dogs whose ruptured disc causes paralysis.

Surgical treatment for IVD disease is a step-wise process. Normally, neither the disc nor the spinal cord can be seen on regular x-rays. To determine if a disc has ruptured, and to identify which disc has ruptured, a myelogram must be performed. A myelogram involves the injection of a dye (which can be seen on an x-ray) into the space immediately surrounding the spinal cord. If a disc has ruptured, it will disrupt the normal filling of the dye in the area where the disc came out. Surgery is directed at the site of disc rupture.

Surgery for IVD is ideally performed within 24 to 48 hours after the onset of paralysis. The goals of surgery are to decompress the spinal cord (relieve the pressure off of the spinal cord) and, if possible, to remove the ruptured disc material from the spinal canal. The specific surgery done for ruptured discs in the back is called a laminectomy. This involves the removal of the bony roof that lies over the spinal cord. This will help to remove the pressure off of the cord. It also gives access to the spinal canal so that the ruptured disc material can be removed. This is very delicate surgery since the work involves the tissues immediately surrounding the spinal cord, but, if done early, it usually carries a good prognosis.

The prognosis for improvement after surgery varies from dog to dog and depends upon the severity of clinical signs. For dogs who have hind leg paralysis but who still have sensation in their legs, surgery done within 24 to 48 hours after onset carries about a 90 percent success rate. The length of time after treatment required to see the start of improvement varies from several days to four or five months. Most dogs will show some signs of improvement within several weeks after surgery. During this period - before the dog starts to regain function of its legs - it remains paralyzed and requires special home care.

Treatment for paralyzed dogs is usually straightforward, but can require some effort. It is much, much more difficult to maintain a paralyzed large breed dog (such as the typical 90 pound Doberman) than it is a dachshund. The dog will need to be confined to a small area, such as a playpen for small dogs, to keep it from dragging itself around with its front legs. The confined area should be well padded to help prevent pressure sores. The dog might also need to be turned from side to side several times daily to help prevent sores. A fairly large number of paralyzed dogs will lose bladder function in addition to losing hind leg function. Most of these dogs are unable to urinate. If this is the case, we have to express and empty their bladders for them (this is usually easily done by putting pressure on their bladder through their abdomen). Ideally, this is done several times per day. Return of bladder function varies widely also, but generally tends to improve at the same time that hind leg function improves. Finally, it is helpful to do some physical therapy on the paralyzed legs. The legs are flexed and extended to stimulate the muscles to keep them from getting too weak during the period of paralysis. Although there appears to be a lot of work to do to maintain a paralyzed dog, most people find that, once a routine is established, it is very manageable. It is also very rewarding in that the majority of dogs will regain use of their legs after surgery.

The preceding was written by Dr. Bud Siemering and Dr. Dan Brehm, the surgeons at SouthPaws. Drs. Siemering and Brehm can be reached at SouthPaws at (703) 451-0909.

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