Guillain-Barre syndrome (GBS) is a rare neurological disorder in which the immune system mistakenly attacks part of the peripheral nervous system, which is the network of nerves outside the brain and spinal cord. The exact cause of GBS is not fully understood, but most cases follow an infection with a virus or bacteria, such as Campylobacter jejuni, which causes gastroenteritis. Occasionally, surgery or vaccinations can trigger GBS, but the chance of this occurring is very low.

GBS can cause muscle weakness, tingling, and numbness in the hands and feet, which can quickly spread and eventually paralyze the whole body. In its most severe form, GBS is a medical emergency that can interfere with breathing, blood pressure, or heart rate. GBS has several forms, including acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and Miller Fisher syndrome (MFS) .

Diagnosis of GBS is based on symptoms and findings on neurological examination, including diminished or loss of deep-tendon reflexes. A lumbar puncture or electromyography (EMG) may be done for supportive information, though should not delay treatment. Other tests, such as blood tests, to identify the underlying trigger are not required to make the diagnosis of GBS and should not delay treatment.

Common treatments for GBS include plasma exchange and intravenous immunoglobulin therapy. Most people with GBS recover, even those with severe cases, and 85% of people with GBS make a full recovery within 6 to 12 months. Once a person recovers, the chance of GBS returning is very small.