Definition and Overview
Guillain-Barré syndrome (GBS) is an acute inflammatory polyneuropathy that occurs in peripheral nerves. It is characterized by progressive ascending paralysis and loss of reflexes due to damage to the myelin or axon of peripheral nerves due to an autoimmune reaction after infection.
The global annual incidence is approximately 1 to 2 per 100,000 people, and the incidence increases with age. It occurs at any age, but is more common in adults, and the incidence rate is approximately 1.5 times higher in men than in women. It is the most common cause of acute flaccid paralysis since the eradication of poliomyelitis.
Type classification
Classical acute inflammatory demyelinating polyneuropathy (AIDP) accounts for approximately 85-90% of all cases, and myelin damage is the main form. Acute motor axonal neuropathy (AMAN) and acute motor sensory axonal neuropathy (AMSAN) are forms in which axons are mainly damaged instead of myelin, and are relatively common in East Asia. Miller Fisher syndrome is a unique variant that shows three symptoms: eye muscle paralysis (ophthalmoplegia), gait ataxia, and loss of deep tendon reflexes, accounting for approximately 5% of all cases.
Causes and Pathogenesis
Approximately two-thirds of all patients are preceded by infection, and the disease usually develops within 1 to 4 weeks after an upper respiratory or gastrointestinal infection. The most common cause of preceding infection is Campylobacter jejuni, but cytomegalovirus (CMV), Epstein-Barr virus, influenza, and COVID-19 have also been implicated.
Molecular mimicry is the key mechanism. Because the antigen structure of the infectious agent is similar to nerve components (particularly gangliosides), antibodies in response to infection also attack peripheral nerves. Antibodies to GM1 and GD1a gangliosides are associated with AMAN type, and GQ1b antibodies are associated with Miller Fisher syndrome.
Autonomic nervous system invasion
Autonomic instability occurs in approximately 65-75% of Guillain-Barré syndrome patients and causes serious complications and death.
Cardiovascular autonomic abnormalities include rapid fluctuations in blood pressure (alternating between high and low blood pressure), tachycardia, bradycardia, and arrhythmia. Severe bradycardia and cardiac arrest can occur, so electrocardiogram monitoring is essential. Abnormal sweating, bladder dysfunction (ileus), and paralytic ileus may also be present.
In severe cases of autonomic instability, intensive care in an intensive care unit is required to control blood pressure and heart rate. Autonomic dysfunction usually improves after the acute phase.
clinical course
Symptoms progress over several days to up to four weeks, and if they progress for more than four weeks, chronic inflammatory demyelinating polyneuropathy (CIDP) is considered.
The typical presentation is progressive symmetrical muscle weakness starting in the lower extremities. It affects both the proximal and distal regions and ascends to the upper extremities, face, and respiratory muscles. Reduction or loss of deep tendon reflexes is a characteristic finding. Sensory symptoms (numbness, abnormal sensations, pain) often appear before muscle weakness. Approximately 25-30% of patients require ventilator treatment due to respiratory muscle involvement.
diagnosis
Nerve conduction study (NCS) is a key diagnostic test, and in AIDP, electrophysiological evidence of demyelination appears, including decreased conduction velocity, prolonged distal latency, potential dispersion, and conduction block. AMAN shows a pattern of axonal damage.
In cerebrospinal fluid examination, protein-cell dissociation (albuminocytologic dissociation) is characteristic. Protein is increased (>0.45 g/L), but cell count is normal (≤10 cells/μL). This finding may be normal in the first week of illness.
Ganglioside antibodies (anti-GQ1b, anti-GM1, anti-GD1a) are useful for diagnosing specific variants.
treatment
The standard treatment for intravenous immunoglobulin (IVIG) is 0.4 g/kg/day for 5 days. Plasmapheresis is performed 4 to 6 times every other day. Both treatments are equally effective and there is no additional benefit when used together. Steroids are not effective for Guillain-Barré syndrome and are not recommended for single administration.
Supportive care includes monitoring of respiratory function (consider tracheal intubation for vital capacity <20 mL/kg), intensive monitoring for autonomic instability, deep vein thrombosis prevention, pain management, and rehabilitation.
prognosis
Approximately 80% of patients are able to walk independently within 6 months, and approximately 60% fully recover. However, permanent disability remains in about 20% of cases, and the mortality rate is about 3-5%. Poor prognosis factors include advanced age, rapid progression, prior Campylobacter infection, AMAN variant, need for ventilator treatment, and electromyography findings of axonal damage.
Long-term aftereffects may include fatigue, pain, anxiety/depression, and decreased social functioning. Rehabilitation therapy and psychological support play an important role in recovery.