------------------------------------------------------------ THE "SLIPPED" DISC ------------------------------------------------------------ It seems frightening and sinister. A "slipped disc" sounds like what could be causing the nagging pain in your back. Somewhere you've heard that a friend needed extensive back surgery or manipulation to restore or reposition a slipped disc into proper position. A tidy explanation. However, as with most matters of a medical nature, a little science, history and anatomy often reveal a more accurate mixture of facts. In 1764 a malady named sciatica was described in the medical literature of the time. It referred to a sharp pain radiating downwards into the legs, frequently originating from the region of the lower back. By 1864 the terms sciatica and lumbago were associated in medical journals. The intervertebral disc was described in detail by the German pathologist Virchow in about 1855 who noted briefly a specimen which displayed a "tumor" or "swelling" he had observed protruding into the spinal canal from one of the intervertebral discs. Later the German physician Ribbert demonstrated that these protrusions were not tumors but were extrusions of the intervertebral disc tissue itself. By 1861 the French physician Sicard proposed a theory that sciatica might be due to pressure upon the nerve roots in the region now named the sciatic nerve. The Italian doctor Putti advanced the theory further by suggesting that the pressure or irritation might be due to intervertebral disc abnormalities or malformations. The chain of cause and effect was almost complete, but it was not until 1933 that a single cause was attributed directly to the afflictions of sciatica and lumbago. Doctors Mixter and Barr, American physicians practicing at Massachusetts General Hospital, finally drew the threads of information into a single coherent strand by linking the protrusion of intervertebral disc tissue with pressure on the sciatic nerve as the cause of the intense pain of sciatica. A word of caution. Not every manifestation of sciatica is caused by protruding or damaged disc tissue. However this is the most common source of severe back pain which radiates or "shoots" into the legs. Let's turn back a few pages and glance at the anatomy of the disc. The intervertebral disc is actually constructed of several tissues. Roughly oval in shape, it is composed of 1) top and bottom plates of gristle-like cartilage which are joined to the bony vertebrae, 2) the sides of the disc which are rounded and quite elastic. These layers of tissue are present in a radial layered arrangement like the belts of a tire. This makes them extremely tough. These layers comprise the annulus fibrous. Inside this disc "containment wall" is 3) the inner core of the disc, the nucleus pulposus, which is a white flexible gel-like tissue. Its function is to act as a shock absorber and force distribution mechanism. Technically only this pulpy core is the disc. If you hear that a disc has been removed during surgery, it is normally the inner nucleus pulposus which is extracted. As an aside, about 22% of the average height or length of the spinal column is due to the discs which provide both support and lateral side-to-side movement. Their design allows a fair degree of movement, but remember that the disc can only stretch so far before it ruptures. The outer walls of the disc are bonded directly to the vertebra and restrict their movement beyond certain limits. To understand the nature of a disc rupture you need to understand that the pulpy inner core of a disc acts like all hydraulic fluids. It can move, change shape and absorb shock but it CANNOT be compressed to occupy a smaller volume (at least at pressures normally present in the human body.) If the pressure becomes too great, the fluid will bulge outwards at a point opposite the compression. If a weak spot has been created in the outer containment of the disc, a rupture can take place. Sometimes the wall of the annulus merely bulges without actual escape of the nucleus pulposis. Other times the nucleus can also rupture. Once this happens the disc loses its value as a shock absorber because the pulpy core is no longer contained. It is important to note that the shock absorbing nature of the discs sometimes causes the bones of the vertebra to fracture first in cases of severe impact! Surprisingly some victims of car accidents or falls have fractured vertebra and scarcely damaged their discs - a testament to their excellent design and load bearing characteristics! A slipped disc, then, is not slipped at all but actually a rupture of the inner pulp of the disc either outwards away from the spinal canal or inwards into the spinal canal. In most cases the deterioration of the protective capsule of the disc is a gradual process which frequently begins at the rear portion of the disc. This is due to the fact that the wall of the disc is thinner there than the front of the capsule. A gradual softening or wearing down takes place in this outer disc wall. Then perhaps a sudden twist of the spine, a load improperly lifted or a fall causes a rupture to take place. This can produce the classic protruded disc. Frequently the bulge enlarges through the posterior longitudinal ligament of the spine and begins to press on either the spinal cord or the nerve roots which descend from it. Usually the protrusion will be slightly to the left or right side of the midline of the spinal canal which causes painful symptoms on only one side of the body. This single-sidedness of the pain is sometimes a diagnostic clue in cases of disc damage. Two separate types of pain are frequently reported by patients suffering from disc damage. If sensory nerves of the skin are irritated by the pressure of the ruptured or protruding disc, then the patient may report burning or tingling of the skin. If motor nerves supplying muscles are pressed by the protruding disc, muscles of the leg or back may go into uncontrollable painful spasm - classic sciatica. It is important to note that for all practical purposes the disc does not "slip" back into place and only rarely heals itself. The damage is permanent and does not heal completely. Eventually tissue scarring will begin to take place in the area of the protrusion which may further inflame nerve roots. If the pressure of the protruding disc becomes too great, nerves of the bladder and bowel may also be affected which almost always indicates surgical intervention. Lumbago is a different type of pain in which the back "suddenly seizes up." The muscles of the lumbar region go into rigid spasm and refuse to relax. The spasm may fade in a few hours or days. By lying perfectly still, the pain may be minimized and finally disappear as quickly as it began. Disc related pain may also produce another manifestation. Lack of activity of a disc-damaged back may cause recurring stiffness unless the back is kept supple with motion and exercise. The pain seems to be worse with inactivity and will diminish when the person moves around a bit. This may also reflect both true arthritis as well as a form of arthritis caused directly by long term disc degeneration. Treatment for mild disc protrusion is relatively specific. Initially some physicians may prescribe bed rest, since standing increases the pressure on the damaged disc. Pelvic traction may be initiated while a patient lies in bed. The function of the traction is not to pull or stretch the spine, but to tilt the pelvis and reduce the curve of the spine which relieves some pressure and produces comfort. Pain medications and some muscle relaxants might be prescribed by a physician. X rays would be taken along with some blood tests. After one or more weeks of bed rest or traction some standing might be permitted with no sitting allowed. Back strengthening exercises would gradually be added to build muscle tone. This course assumes surgical intervention is not attempted. In more severe cases, a myelogram or NMR scan would be done to confirm substantial disc protrusion and probable need for surgery to remove the inner core of the disc. After surgery the space within the disc gradually fills with scar tissue. In time, and with some patients, the space between the two vertebrae may gradually grow together in a type of spontaneous bone to bone fusion which lessons mobility and further damage at that area of the spine. After disc surgery, rehabilitative exercises are prescribed to build up the muscles of the back so that proper support is maintained. The topic of surgical fusion, the deliberate joining of two or more vertebrae after disc surgery, is controversial. Some physicians routinely fuse vertebrae after a disc operation, others fuse on a more selective basis. Usually small pieces of bone from the hip or other area of the body are grafted directly between vertebral bodies to limit their motion and provide support. This technique is generally the most severe course of action and is usually reserved for the extreme cases of disc degeneration. It also performed for other diseases such as spinal bifida, a birth defect. So far we have discussed problems usually seen in the lower lumbar region of the back. However, the cervical discs of the neck region can occasionally be affected. Arthritis is a common culprit here. Symptoms can involve radiating pain into the shoulders, arms and hands. In severe cases of cervical disc rupture or degeneration weakness of the arm and hand muscles will be seen and "tingling" or even complete loss of sensation in the skin of the hands and arms. Again this is caused by pressure on sensory or motor nerves in the area of the cervical region of the spine. Cervical disc problems are more frequently seen in older people since these complains are more commonly arthritic in origin. Cervical disc protrusion can be more serious than lumbar disc problems since a large section (more nerves) of the spinal cord is present at this level of the spine. Bed rest, traction and neck braces or cervical collars are usually attempted in milder forms of this disc problem. The bottom line, however, in dealing with disc disease is that a weak back is unstable and prone to disc disease and injury. Proper exercise and posture can go a long way to preventing disc disease in the first place and minimizing its impacts. This tutorial is merely a starting point! For further information on back care and back pain, be sure to register this software ($25.00) which brings by prompt postal delivery a printed, illustrated guide to back pain written by a physician plus two software disks. From the main menu select "Print Registration Form." Or from the DOS prompt type the command ORDER. Mail to Seattle Scientific Photography (Dept. BRN), PO Box 1506, Mercer Island, WA 98040. If you cannot print the order form, send $25.00 to the above address and a short letter requesting these materials. End of chapter.