Disease of the month: Guillain-Barré syndrome

It is rare, but with its sudden and unexpected onset, GBS can be devastating. Fergus Bescoby explains

Guillain-Barré syndrome (pronounced Ghee-lan Bar-ray) is a rare but serious condition in which the body’s immune system attacks part of the peripheral nervous system. It currently affects about 1,500 people every year in the UK and is slightly more common in men than women. It can affect people of any age, including children.

Although rare, the condition has received recent publicity due to its possible link with the flu vaccination, which has been thought to trigger the syndrome. However, this has not been proven and from all accounts there is no cause for concern.

Guillain-Barré syndrome (GBS) is called a syndrome rather than a disease because it is not clear that a specific disease-causing agent is involved.

Diagnosis

Because the signals travelling along the nerves are slower, a nerve conduction velocity (NCV) test can give doctor’s clues to aid the diagnosis. Reflexes such as knee jerks are usually lost. 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 as another means of possible diagnosis.

Symptoms

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. GBS is rare and has an incidence of 1 person per 100,000, usually occurring a few days or weeks after a respiratory or gastrointestinal viral infection. The disorder can develop over the course of hours or days, or it may take up to 3 to 4 weeks. It is one of the leading causes of (acute) non-trauma-induced paralysis in the world.

Some patients have a similar but longer-lasting illness called chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), once known as chronic Guillain-Barré but now usually regarded as a related condition

Cause

To date, no-one knows why GBS - which is not contagious - affects some people and not others. Similarly it is still not known exactly 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. Usually the cells of the immune system attack only foreign material and invading organisms. In GBS however, the immune system starts to destroy the myelin sheath that surrounds the axons of many peripheral nerves, or even the axons themselves.

In diseases in which the peripheral nerves’ myelin sheaths are injured or degraded, the nerves cannot transmit signals efficiently. That is why the muscles begin to lose their ability to respond to the brain’s commands, commands that must be carried through the nerve network. The brain also receives fewer sensory signals from the rest of the body, resulting in an inability to feel textures, heat, pain, and other sensations. Alternately, the brain may receive inappropriate signals that result in tingling, “crawling-skin,” or painful sensations.

Because the signals to and from the arms and legs must travel the longest distances they are most vulnerable to interruption. Therefore, muscle weakness and tingling sensations usually first appear in the hands and feet and progress upwards.

When GBS is preceded by a viral or bacterial infection, it is possible that the virus has changed the nature of cells in the nervous system so that the immune system treats them as foreign cells. It is also possible that the virus makes the immune system itself less discriminating about what cells it recognizes as its own, allowing some of the immune cells, such as certain kinds of lymphocytes and macrophages, to attack the myelin.

Scientists are investigating these and other possibilities to find why the immune system is so affected by GBS and other autoimmune diseases. The cause and course of GBS is an active area of neurological investigation, incorporating the cooperative efforts of neurological scientists, immunologists, and virologists.

Treatment

There is no known cure for GBS. However, there are therapies that 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, plasma exchange (sometimes called plasmapheresis) and high-dose immunoglobulin therapy are used. Both of them are equally effective, but immunoglobulin is easier to administer.

Plasma exchange is a method by which whole blood is removed from the body and processed so that the red and white blood cells are separated from the plasma, or liquid portion of the blood. The blood cells are then returned to the patient without the plasma, which the body quickly replaces. Scientists still don’t know exactly why plasma exchange works, but the technique seems to reduce the severity and duration of the GBS episode. This may be because the plasma portion of the blood contains elements of the immune system that may be toxic to the myelin.

In high-dose immunoglobulin therapy, doctors give intravenous injections of the proteins that, in small quantities, the immune system uses naturally to attack invading organisms. It has been found that by giving high doses of these immunoglobulins, derived from a pool of thousands of normal donors, to GBS patients can lessen the immune attack on the nervous system.

The use of steroid hormones has also been tried as a way to reduce the severity of GBS, but controlled clinical trials have demonstrated that this treatment is not effective and may even have a detrimental effect on the disease.

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. The need for this sophisticated machinery is one reason why GBS patients are usually treated in hospitals, often in an intensive care ward. In the hospital, doctors can also look for and treat the many problems that can afflict any paralyzed patient - complications such as pneumonia or bed sores.

Prognosis

GBS 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 GBS 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.

Most patients, however, recover from even the most severe cases of GBS, although some continue to have some degree of weakness.

Fergus Bescoby is underwriting development manager at PruProtect