Guillain-Barré Syndrome (GBS)

• Guillain-Barré syndrome (GBS) is a group of acute, monophasic immune-mediated peripheral neuropathies.
• GBS initially only included the acute inflammatory demyelinating polyneuropathy (AIDP) form.
• Now, variant forms such as Miller Fisher syndrome (MFS), pharyngeal–cervical–brachial syndrome, acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN) are also included.
• Axonal variants of GBS are more common in some populations, linked to higher rates of infectious disease in lower-income countries.
• GBS awareness increased after a cluster of cases followed mass swine influenza vaccinations in 1976.
• Recent studies show a small increased risk of one to two additional GBS cases per million population within 6 weeks of vaccination.
• The risk of GBS from vaccination is insignificant compared to the risks of influenza infection.

Symptoms and Prognosis

• GBS patients usually develop weakness over days to weeks.
• Respiratory weakness and/or autonomic instability can cause critical illness.
• Mortality rate for GBS patients is 5% to 12% despite ICU care.
• About 20% of patients have residual weakness a year later.
• Patients with axonal GBS forms typically have limited and protracted recovery.
• GBS incidence is between 1 and 2 per 100,000, usually without relapse.

Pathophysiology and Causes

• GBS often follows an upper respiratory or gastrointestinal infection by 1 to 4 weeks in two-thirds of cases.
• Common viruses include cytomegalovirus (CMV) and Epstein-Barr virus.
• Common bacteria include Campylobacter jejuni (23% to 45%), Mycoplasma pneumoniae (5%), and Haemophilus influenzae.
• Zika virus infection has also been linked to postinfection GBS.
• SARS-CoV-2 infection has been associated with GBS-like symptoms, but the cause is unclear.
• Any febrile illness or immunization can potentially trigger GBS.
• Molecular mimicry, where the immune system attacks peripheral nerve components, is believed to cause GBS.
• Axonal forms are associated with antibodies to the GM1 and GD1a components of the peripheral nerve.
• Ophthalmoplegia in MFS patients is almost exclusively linked to anti-GQ1b antibodies.
• Cervical–pharyngeal–brachial syndrome is associated with GT1a antibodies.
• Serum autoantibodies against moesin on Schwann cells have been found in AIDP patients after CMV infection.
• Antibodies cause an influx of T lymphocytes and macrophages, activating membrane attack complex and damaging the nerve myelin or axon.

Clinical Presentation

• Patients develop symmetrical paresthesias and/or weakness, usually starting in the lower extremities.
• A history of antecedent infection is common.
• Back pain is frequent, but bowel or bladder dysfunction is rare early on.
• Weakness can spread to the upper extremities, respiratory muscles, and potentially complete paralysis.
• Weakness typically peaks in about 3 weeks, with 25% of patients developing respiratory insufficiency and two-thirds unable to walk independently.
• GBS should always be considered in cases of acute nontraumatic weakness.
• AMAN patients may have preserved reflexes and less pain compared to AIDP.
• MFS patients will have ophthalmoplegia (diplopia), ataxia, and areflexia, along with possible distal paresthesias.
• MFS peaks in 1 week, with patients tending to recover more quickly and completely.
• Subjective presentation commonly presents with sensory symptoms but objective sensory findings are often mild.
• Progressive weakness from the legs to the arms with loss of deep tendon reflexes, is typical of GBS.

Symptoms Continued

• Respiratory muscle weakness causes decreased breath sounds, weakened cough, reduced vital capacity, and neck muscle weakness.
• Autonomic instability can cause fluctuations in pulse rate and blood pressure, urinary retention, and bowel dysmotility.

Diagnostics

• Screening for systemic infection or organ dysfunction uses the history and abnormalities from the physical examination, CBC, and complete metabolic profile.
• Erythrocyte sedimentation rates and liver transaminases are often elevated due to the antecedent infection.
• Serum sodium abnormalities can arise from SIADH or central diabetes insipidus.
• Urine and stool cultures may help identify a preceding infectious cause.
• Lumbar puncture is important if GBS is suspected.

Lumbar Puncture

• Classic finding is albuminocytologic dissociation which means elevated CSF protein with minimal increase in mononuclear CSF white blood cells.

Guillain-Barré syndrome (GBS) is a group of acute, monophasic immune-mediated peripheral neuropathies. GBS includes AIDP, Miller Fisher syndrome (MFS), and axonal variants AMAN and AMSAN. The risk of GBS from vaccination is insignificant compared to the risks of influenza infection.