Guillain-Barré syndrome is a disorder in which the body's immune system attacks part of the peripheral nervous system. The first symptoms of this disorder include varying degrees of weakness or tingling sensations in the legs. In many instances, the weakness and abnormal sensations spread to the arms and upper body. These symptoms can increase in intensity until the muscles cannot be used at all and the patient is almost totally paralyzed. In these cases, the disorder is life-threatening and is considered a medical emergency. The patient is often put on a respirator to assist with breathing. Most patients, however, recover from even the most severe cases of Guillain-Barré syndrome, although some continue to have some degree of weakness. Guillain-Barré syndrome is rare. Usually Guillain-Barré occurs a few days or weeks after the patient has had symptoms of a respiratory or gastrointestinal viral infection. Occasionally, surgery or vaccinations will trigger the syndrome. The disorder can develop over the course of hours or days, or it may take up to 3 to 4 weeks. No one yet knows why Guillain-Barré strikes some people and not others or what sets the disease in motion. What scientists do know is that the body's immune system begins to attack the body itself, causing what is known as an autoimmune disease. Guillain-Barré is called a syndrome rather than a disease because it is not clear that a specific disease-causing agent is involved. Reflexes such as knee jerks are usually lost. Because the signals traveling along the nerve are slower, a nerve conduction velocity (NCV) test can give a doctor clues to aid the diagnosis. The cerebrospinal fluid that bathes the spinal cord and brain contains more protein than usual, so a physician may decide to perform a spinal tap. Is there any treatment? There is no known cure for Guillain-Barre syndrome, but therapies can lessen the severity of the illness and accelerate the recovery in most patients. There are also a number of ways to treat the complications of the disease. Currently, plasmapheresis and high-dose immunoglobulin therapy are used. Plasmapheresis seems to reduce the severity and duration of the Guillain-Barré episode. In high-dose immunoglobulin therapy, doctors give intravenous injections of the proteins that in small quantities, the immune system uses naturally to attack invading organism. Investigators have found that giving high doses of these immunoglobulins, derived from a pool of thousands of normal donors, to Guillain-Barré patients can lessen the immune attack on the nervous system. The most critical part of the treatment for this syndrome consists of keeping the patient's body functioning during recovery of the nervous system. This can sometimes require placing the patient on a respirator, a heart monitor, or other machines that assist body function. What is the prognosis? Guillain-Barré syndrome can be a devastating disorder because of its sudden and unexpected onset. Most people reach the stage of greatest weakness within the first 2 weeks after symptoms appear, and by the third week of the illness 90 percent of all patients are at their weakest. The recovery period may be as little as a few weeks or as long as a few years. About 30 percent of those with Guillain-Barré still have a residual weakness after 3 years. About 3 percent may suffer a relapse of muscle weakness and tingling sensations many years after the initial attack.