Residency · Residency · Neurology

Guillain-Barre Syndrome and Acute Inflammatory Neuropathies

Overview

Guillain-Barre syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy and the most common cause of acute flaccid paralysis worldwide, with an incidence of 1-2 per 100,000 per year. It is typically monophasic and preceded by infection in 60-70% of cases. The neurological nadir is reached within 4 weeks (usually 2-3 weeks); if progression continues beyond 8 weeks, CIDP should be considered instead.

Antecedent Infections and Triggers

Campylobacter jejuni is the most common antecedent infection (30-40%), associated with axonal variants and anti-GM1/GD1a antibodies, and carrying a worse prognosis. Cytomegalovirus is associated with severe sensory involvement and anti-GM2 antibodies. Other triggers include Epstein-Barr virus, Mycoplasma pneumoniae, Haemophilus influenzae, and Zika virus (which demonstrated a strong association during outbreaks). COVID-19 has been reported in association with GBS, though causality remains debated. Vaccination carries an exceedingly rare association (1-2 additional cases per million doses), with the 1976 swine flu vaccine having the strongest historical link. The typical latency between infection and neurological symptom onset is 1-4 weeks.

Subtypes

AIDP (Acute Inflammatory Demyelinating Polyneuropathy)

AIDP is the most common form in North America and Europe, accounting for approximately 90% of cases. It involves macrophage-mediated segmental demyelination of peripheral nerves. NCS findings include prolonged distal latencies, slowed conduction velocities, conduction block, temporal dispersion, and prolonged F-waves. Secondary axonal degeneration may occur in severe cases.

AMAN (Acute Motor Axonal Neuropathy)

AMAN is more common in Asia and Central/South America. It is associated with anti-GM1 and anti-GD1a antibodies, typically following C. jejuni infection. NCS show reduced CMAP amplitudes with normal or near-normal conduction velocities and normal SNAPs. The pathology involves antibody-mediated attack on the axolemma at nodes of Ranvier. "Reversible conduction failure" (RCF) may occur, representing transient conduction block at nodes that resolves rapidly and can mimic demyelination.

AMSAN (Acute Motor and Sensory Axonal Neuropathy)

AMSAN is a severe variant with both motor and sensory axonal damage. It carries the worst prognosis for recovery and often requires prolonged ventilatory support.

Miller Fisher Syndrome (MFS)

MFS presents with the classic triad of ophthalmoplegia, ataxia, and areflexia. Anti-GQ1b antibodies are positive in more than 90% of cases (GQ1b is enriched at oculomotor nerve paranodes). Overlap syndromes include Bickerstaff brainstem encephalitis (MFS plus encephalopathy and/or pyramidal signs, also anti-GQ1b positive). The prognosis is generally good, with most cases recovering spontaneously.

Other Variants

The pharyngeal-cervical-brachial (PCB) variant produces oropharyngeal and cervical/upper limb weakness with anti-GT1a antibodies. The paraparetic variant confines weakness to the legs. Pure sensory GBS, though rare, presents with acute sensory loss and areflexia without weakness. Autonomic GBS manifests as acute pandysautonomia.

<image>Diagram showing the different GBS subtypes with their associated antibodies, electrodiagnostic patterns, and geographical distribution</image>

Clinical Features

Motor

Weakness is ascending and symmetric, affecting the legs before the arms. Areflexia or hyporeflexia is an early finding. Both proximal and distal weakness occur (unlike most neuropathies). Facial weakness occurs in approximately 50% of patients, and bilateral facial palsy is highly suggestive of GBS. Bulbar weakness produces dysphagia and dysarthria. Respiratory failure requiring mechanical ventilation occurs in 20-30% of patients.

Sensory

Paresthesias and numbness are usually mild compared to the motor deficit. Pain is common (55-89%) and may be severe, manifesting as back pain, radicular limb pain, or myalgia. Pain is often the presenting symptom before weakness develops.

Autonomic

Autonomic dysfunction includes tachycardia, bradycardia, and labile blood pressure. Urinary retention may be transient, but prominent urinary symptoms should prompt reconsideration of the diagnosis and urgent evaluation for a cord lesion. Ileus can occur. The risk of fatal cardiac arrhythmia, while rare, mandates continuous telemetry monitoring.

Diagnosis

CSF Analysis

Albuminocytologic dissociation, defined as elevated protein with a normal cell count (fewer than 10 cells per microliter), is the characteristic CSF finding. CSF protein may be normal in the first week and should be repeated at 1-2 weeks if initially normal. A cell count above 50 per microliter should prompt consideration of alternative diagnoses including HIV polyradiculopathy, CMV infection, leptomeningeal disease, and sarcoidosis.

Electrodiagnostic Studies

NCS may be normal or show only absent F-waves in the first 3-5 days. Repeat studies at 2-3 weeks are more informative. Serial studies help distinguish AIDP from axonal variants and predict prognosis. Reduced CMAP amplitude at nadir is the strongest predictor of poor motor recovery.

MRI

Gadolinium enhancement of nerve roots, especially the cauda equina, supports the diagnosis in equivocal cases. MRI is not required for diagnosis but is important for excluding compressive myelopathy.

Anti-Ganglioside Antibodies

Anti-GM1 and anti-GD1a antibodies are associated with AMAN. Anti-GQ1b antibodies are associated with Miller Fisher syndrome. Anti-GT1a antibodies are associated with the PCB variant. These are not required for diagnosis but are helpful in atypical presentations.

<image>Spinal MRI with gadolinium showing enhancement of the cauda equina nerve roots in a patient with AIDP</image>

Respiratory Monitoring

Bedside respiratory assessment is critical; pulse oximetry alone should not be relied upon as it is a late indicator of respiratory compromise. Forced vital capacity (FVC) should be monitored every 4-6 hours in progressive disease. Negative inspiratory force (NIF) should be measured regularly. The "20/30/40 rule" for intubation states that intubation should be considered when FVC falls below 20 mL/kg, NIF is less negative than -30 cmH2O, or FVC has declined by more than 40% from baseline. A single-breath count below 20 correlates with FVC less than 1 liter. Other indications for intubation include bulbar dysfunction with aspiration risk, rapid progression, and autonomic instability.

Treatment

Intravenous Immunoglobulin (IVIG)

The standard dose is 0.4 g/kg/day for 5 days (total 2 g/kg). IVIG has equivalent efficacy to plasmapheresis and is preferred in many centers due to ease of administration and wider availability. It should be started as early as possible, being most effective within the first 2 weeks of symptom onset. Side effects include headache, anaphylaxis in IgA deficiency (IgA level should be checked), aseptic meningitis, thromboembolic events, hemolytic anemia, and renal failure.

Plasmapheresis (Plasma Exchange, PLEX)

Five exchanges are typically performed over 1-2 weeks. Plasmapheresis has equivalent efficacy to IVIG and is more effective if started within 7 days of onset. It is preferred in some settings where IVIG is unavailable or contraindicated. It requires central venous access, and hemodynamic instability can complicate administration.

What Does NOT Work

Corticosteroids are not effective in GBS; multiple randomized controlled trials show no benefit and they may even slow recovery. Combined IVIG plus PLEX is not superior to either alone. IV methylprednisolone added to IVIG provides no proven benefit.

Second Course of IVIG

Treatment-related fluctuations (TRFs) occur in approximately 10% of patients, manifesting as improvement followed by secondary worsening within 8 weeks. A second IVIG course may be considered for TRFs. If progressive worsening continues beyond 8 weeks, the diagnosis should be reclassified as acute-onset CIDP.

Prognostic Indicators

Poor Prognostic Factors

These include older age (above 60 years), preceding C. jejuni infection, rapid progression to nadir, need for mechanical ventilation, low CMAP amplitudes at nadir (the strongest electrodiagnostic predictor), axonal variant (AMAN, AMSAN), and elevated serum neurofilament light chain (NfL).

GBS Disability Scale

The scale ranges from 0 (healthy) through 1 (minor signs, able to run), 2 (able to walk 10 meters without assistance), 3 (able to walk 10 meters with assistance), 4 (bed or wheelchair bound), 5 (requiring assisted ventilation), to 6 (dead).

Recovery Timeline

Most recovery occurs within 6-12 months but can continue up to 2-3 years. Approximately 80% of patients walk independently at 6 months. About 20% have significant residual disability. Mortality is 3-7%, usually from respiratory failure, autonomic dysfunction, pulmonary embolism, or sepsis.

<image>Graph showing typical GBS clinical course including the progressive phase, plateau, and recovery phase with timeline for treatment windows</image>

Clinical Pearls

GBS is a clinical diagnosis; treatment should not be delayed while waiting for CSF or NCS results if the clinical picture is classic. Normal CSF protein in the first week does not exclude GBS; sensitivity of elevated protein increases after the first week. Bladder dysfunction is uncommon in GBS, and prominent urinary retention should prompt urgent evaluation for spinal cord compression with MRI. Back pain and radicular pain are frequently the presenting symptoms, leading to initial misdiagnosis as a musculoskeletal or disc problem. Corticosteroids are not effective for GBS, a common mistake especially when GBS is confused with CIDP. Vigilance for autonomic complications is essential: sudden bradycardia or asystole can occur, particularly during suctioning or Valsalva-like maneuvers. If a patient who initially improved develops secondary deterioration within 8 weeks, a treatment-related fluctuation should be considered and second IVIG given; if deterioration occurs after 8 weeks or there are more than 2 fluctuations, the diagnosis should be reclassified as acute-onset CIDP. Anti-GQ1b positivity with ophthalmoplegia and ataxia but without limb weakness supports Miller Fisher syndrome, which usually resolves without treatment, though IVIG is often given in practice.

References

• Shahrizaila N, Lehmann HC, Kuwabara S. Guillain-Barre syndrome. Lancet. 2021;397(10280):1214-1228.
• Hughes RA, Swan AV, van Doorn PA. Intravenous immunoglobulin for Guillain-Barre syndrome. Cochrane Database Syst Rev. 2014;(9):CD002063.
• Fokke C, van den Berg B, Drenthen J, et al. Diagnosis of Guillain-Barre syndrome and validation of Brighton criteria. Brain. 2014;137(Pt 1):33-43.
• Uncini A, Kuwabara S. The electrodiagnosis of Guillain-Barre syndrome subtypes: where do we stand? Clin Neurophysiol. 2018;129(12):2586-2593.
• Walgaard C, Lingsma HF, Ruts L, et al. Prediction of respiratory insufficiency in Guillain-Barre syndrome. Ann Neurol. 2010;67(6):781-787.

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