What is Guillain-Barré syndrome?
Guillain-Barre syndrome, or GBS, is a disorder in which the body’s immune system attacks the peripheral nervous system.
Guillain-Barré (ghee-yan bah-ray) syndrome, or GBS, is a disorder in which the body’s immune system attacks part of the peripheral nervous system. The peripheral nervous system includes the cranial nerves (except the optic [eye] nerve), the spinal nerves, and the autonomic nervous system that governs involuntary actions. The central nervous system, which is composed of the spinal cord and brain, is not directly involved by Guillain-Barré syndrome, as opposed to certain other immune-mediated neurologic diseases such as multiple sclerosis.
Guillain-Barré syndrome includes several variants, the most common of which is a multifocal demyelinating disorder of the peripheral nerves referred to as an acute inflammatory demyelinating polyneuropathy (AIDP). Some cases of Guillain-Barré syndrome are associated with a primarily motor axonal process (acute motor axonal neuropathy; AMAN) with axonal degeneration (axons are long, thin extensions of the nerve cells and carry nerve signals) and sparing of the myelin (the myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons and is not spared by AIDP). Other cases appear to involve both sensory and motor axons and such cases are termed acute motor and sensory axonal neuropathy (AMSAN).
More than 90 percent of patients with Guillain-Barré syndrome in Europe and North America have AIDP. AMAN occurs in less than 10 percent of persons with Guillain-Barré syndrome in the western hemisphere but in more than 40 percent of those affected in China and Japan. The incidence of AMSAN is very low (less than 10 percent of that of AMAN).
Miller Fisher syndrome (MFS) is another Guillain-Barré syndrome variant that occurs in about 5 percent of people affected by Guillain-Barré syndrome. It is characterized by ophthalmoplegia (eye muscle weakness), areflexia (absence of reflexes), ataxia (the inability to coordinate voluntary muscular movements such as walking), and, in some cases, facial and bulbar palsy (affecting vital functions regulated by the brain stem, like breathing, and swallowing or speech).
Guillain-Barré syndrome can strike at any age but there are peaks in young adults and the elderly; men may be more likely to develop Guillain-Barré syndrome than women. Seasonality has not been reported in developed countries like the United States .
Although this syndrome is rare (affecting about one to two persons in 100,000), it is the most common cause of acute neuromuscular paralysis in the world.
Where does Guillain-Barré syndrome come from?
Guillain-Barré syndrome often occurs a few days or weeks after a person has had symptoms of a respiratory or gastrointestinal viral or bacterial infection; in fact, two-thirds of affected individuals have had a preceding infection. Campylobacter jejuni, a common bacterial cause of gastrointestinal infection, is the most common infection associated with Guillain-Barré syndrome and may precede over 25 percent of Guillain-Barré syndrome cases. Less commonly, other infections such as cytomegalovirus, Epstein-Barr virus, and Mycoplasma pneumonia may precede this syndrome. Rarely, surgery, trauma, bone marrow transplantation, certain systemic illnesses, and the use of some medications or vaccinations (e.g. influenza vaccination) will trigger Guillain-Barré syndrome.
Despite the observation that a large percentage of Guillain-Barré syndrome cases follow infection, Guillain-Barré syndrome itself is not contagious.
No one yet knows why Guillain-Barré syndrome strikes some people and not others. Nor does anyone know 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 but in the case of Guillain-Barré syndrome, the body’s response to foreign material and infection results in an immune response that cross-reacts with components of the host’s own peripheral nervous system. This is thought to occur because the host’s peripheral nervous system may share certain similarities with the foreign material or invading organisms at the molecular level. This is known as molecular mimicry.
In Guillain-Barré syndrome, the immune system starts to destroy the myelin sheath that surrounds the axons of many peripheral nerves, or even the axons themselves. The myelin sheath surrounding the axon speeds up the transmission of nerve signals and allows the transmission of signals over long distances. In diseases in which these 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 commands from the brain 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 known as paresthesias. 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.