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                              THE "SLIPPED" DISC 
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       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. 

