Guillain–Barré syndrome

Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain often in the back along with muscle weakness, beginning in the feet and hands, often spreading to the arms and upper body. The symptoms may develop over hours to a few weeks. During the acute phase, the disorder can be life-threatening, with about 15% of people developing respiratory muscle weakness requiring mechanical ventilation. Some are affected by changes in the function of the autonomic nervous system, which can lead to dangerous abnormalities in heart rate and blood pressure. Although the cause is unknown, the underlying mechanism involves an autoimmune disorder in which the body's immune system mistakenly attacks the peripheral nerves and damages their myelin insulation. Sometimes this immune dysfunction is triggered by a viral infection or, less commonly, by surgery or by vaccination. The diagnosis is usually based on the signs and symptoms through the exclusion of alternative causes and supported by tests such as nerve conduction studies and examination of the cerebrospinal fluid. There are several subtypes based on the areas of weakness, results of nerve conduction studies, and the presence of certain antibodies. It is classified as an acute polyneuropathy. In those with severe weakness, prompt treatment with intravenous immunoglobulins or plasmapheresis, together with supportive care, leads to good recovery in the majority of cases. Recovery may take weeks to years, with about a third having some permanent weakness. Globally, death occurs in approximately 7.5% of patients. Guillain–Barré syndrome is rare, at 1 or 2 cases per 100,000 people every year. The syndrome is named after the French neurologists Georges Guillain and Jean Alexandre Barré, who, together with French physician André Strohl, described the condition in 1916.

Signs and symptoms The first symptoms of Guillain–Barré syndrome are numbness, tingling, and pain, alone or in combination. This is followed by weakness of the legs and arms that affects both sides equally and worsens over time. The weakness can take half a day to over two weeks to reach maximum severity, and then becomes steady. In one in five people, the weakness continues to progress for as long as four weeks. The muscles of the neck may also be affected, and about half experience involvement of the cranial nerves that supply the head and face; this may lead to weakness of the muscles of the face, swallowing difficulties and sometimes weakness of the eye muscles. In 8%, the weakness affects only the legs (paraplegia or paraparesis). Involvement of the muscles that control the bladder and anus is unusual. In total, about a third of people with Guillain–Barré syndrome continue to be able to walk. Once the weakness has stopped progressing, it persists at a stable level ("plateau phase") before improvement occurs. The plateau phase can take between two days and six months, but the most common duration is a week. Pain-related symptoms affect more than half, and include back pain, paraesthesia, muscle pain, and pain in the head and neck relating to irritation of the lining of the brain. Many people with Guillain–Barré syndrome have experienced the signs and symptoms of an infection in the 3–6 weeks before the onset of the neurological symptoms. The infection typically affects the upper respiratory tract (rhinitis, sore throat, cough) or gastrointestinal tract (diarrhea, abdominal pain, bloating).

In children, particularly those younger than six years old, the diagnosis can be difficult, and the condition is often initially mistaken (sometimes for up to two weeks) for other causes of pain and difficulty walking, such as viral infections, or bone and joint problems. On neurological examination, characteristic features are the reduced strength of muscles and reduced or absent tendon reflexes (hypo- or areflexia, respectively). However, a small proportion have normal reflexes in affected limbs before developing areflexia, and some may have exaggerated reflexes. In the Miller Fisher variant of Guillain–Barré syndrome, a triad of weakness of the eye muscles, abnormalities in coordination, as well as absent reflexes can be found. The level of consciousness is normally unaffected in Guillain–Barré syndrome, but the Bickerstaff brainstem encephalitis subtype may feature drowsiness, sleepiness, or coma.

Respiratory failure A quarter of all people with Guillain–Barré syndrome develop weakness of the breathing muscles leading to respiratory failure, the inability to breathe adequately to maintain healthy levels of oxygen, and/or carbon dioxide in the blood. This life-threatening scenario is complicated by other medical problems such as pneumonia, severe infections, blood clots in the lungs, and bleeding in the digestive tract in 60% of those who require artificial ventilation.

Autonomic dysfunction The autonomic or involuntary nervous system, which is involved in the control of body functions such as heart rate and blood pressure, is affected in two-thirds of people with Guillain–Barré syndrome, but the impact is variable. Twenty percent may experience severe blood-pressure fluctuations and irregularities in the heart beat, sometimes to the point that the heart beat stops and requires pacemaker-based treatment. Other associated problems are abnormalities in perspiration and changes in the reactivity of the pupils. Autonomic nervous system involvement can affect even those who do not have severe muscle weakness.

Causes

Infection onset

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