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Guillain-Barré syndrome - Paralysis after a cold |
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Written by Lev Prasov
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Apr 29, 2006 at 10:33 AM |
Guillain-Barré syndrome is an autoimmune disease in which antibodies target the myelin sheath around peripheral nerve cells. It frequently occurs after an infection and passes after several weeks.
All of us have had upper respiratory tract infections, such as colds. After a few days, we are usually back to normal health. A very small percentage of people may not be so lucky. Two to four weeks after a viral infection or a bacterial one, some people may have trouble walking and eventually develop lasting muscle weakness or even paralysis. This very peculiar disease is known as Guillain-Barré syndrome, and it is the topic for this week's DOTW.
 Figure I: Structure of a neuron. Guillain-Barré syndrome causes the loss of the myelin sheath of neurons outside of the central nervous system, leading primarily to muscle weakness. ( Image courtesy of the National Cancer Institute)
Guillain-Barré syndrome (GBS) is an autoimmune disease that targets the myelin sheath of nerve fibers in the peripheral nervous system (the nerves that travel out from the brain and spinal cord to the rest of the body). The myelin sheath is a multilayered membrane that surrounds and insulates nerve fibers, allowing for faster conduction of signals. The sheath is composed of a number of lipids, including sphingomyelin and gangliosides. In GBS, the gangliosides, in particular, are targeted by antibodies. The binding of antibodies activates the immune system, leading to the ultimate destruction of the myelin. Losing this myelin has the same result as stripping the insulation off of a wire: short-circuiting of the conduction system occurs and impulses tend to travel slower.
Why are normal components of the myelin sheath suddenly targeted by the immune system? While the exact culprit is unknown, infection with viruses and bacteria can lead to this antibody response. It is thought that these bugs have liposaccharides that resemble human gangliosides. For example, Campylobacter jejuni, a common pathogen that causes bloody diarrhea, contains a membrane protein that mimics ganglioside GM1. Other viruses and bacteria may target different components of the myelin, and yet cause the same general symptoms.
GBS can be a very devastating disease. It occurs very suddenly and can progress very quickly. The decrease in myelination of nerves leads to muscle weakness and loss of sensation. Patients generally first feel these symptoms in the legs. Later, the weakness and tingling can spread to the rest of the body. A major problem of this disease is that it is progressive. The more myelin that is lost, the worse the symptoms. As a result, patients may eventually become paralyzed in the upper and lower extremities. Paralysis can be particularly debilitating and life-threatening if it targets the muscle of respiration. Fortunately, patients recover most of the function in their muscles after a few weeks, though some people may have long-lasting muscle weakness.
Unfortunately, there are is no cure for Guillain-Barré syndrome and treatments come with their own risk of side-effects. Supportive therapy (monitoring vital signs and putting a patient on a ventilator if necessary) is generally effective for getting a patient through this disease, as it will recede in several weeks. Additionally, treatments that target the antibodies against myelin components can reduce the complications of the disease. intravenous immunoglobulin can be given to bind up all of these antibodies and prevent them from reaching the target cells. Plasmaphoresis can also be used to physically get rid of these excess antibodies. Additionally, immunosuppressive drugs, such as corticosteroids, can be given. However, these drugs can increase the risk of infection by other pathogens. Overall, after a few weeks, a large percentage of patients (80%) recover from this disease without any long-term complications. A small percentage, however, have long-term muscle weakness or even paralysis and 2-3% of people can die from respiratory failure or other severe complications.
For more information on Guillain-Barré syndrome, check out the following resources:
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