Neurology · PANCE / PANRE

Guillain-Barré Syndrome

Acute immune-mediated ascending demyelinating polyneuropathy; can cause respiratory failure.

Also known as: GBS, Guillain-Barré, acute inflammatory demyelinating polyneuropathy, AIDP, Miller Fisher syndrome

Overview

Acute, immune-mediated, predominantly demyelinating polyradiculoneuropathy causing rapidly progressive symmetric weakness, areflexia, and variable sensory and autonomic involvement. Most common subtype in Western countries is acute inflammatory demyelinating polyneuropathy (AIDP); axonal subtypes (AMAN, AMSAN) more common in Asia. Miller Fisher syndrome variant: ophthalmoplegia + ataxia + areflexia, associated with anti-GQ1b antibodies.

Epidemiology

Incidence ~1-2 per 100,000 per year. Affects all ages; slight male predominance. Most common cause of acute generalized weakness in developed countries.

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Risk factors

Antecedent infection (~2/3 of cases, 1-4 weeks before onset):
Campylobacter jejuni (most common; associated with AMAN axonal variant and anti-GM1 antibodies)
Cytomegalovirus
Epstein-Barr virus
Mycoplasma pneumoniae
Influenza
Zika virus
SARS-CoV-2 (associations reported)
Vaccinations (rare; modest signal historically with swine flu 1976; small risk with some vaccines)
Surgery, malignancy (rare)

Pathophysiology

Molecular mimicry: antibodies generated against pathogen surface antigens cross-react with epitopes on peripheral nerve myelin (gangliosides — GM1, GD1a, GQ1b). Complement activation and macrophage-mediated demyelination produce conduction block. Axonal subtypes target the nodes of Ranvier and axolemma directly. Resolves over weeks-months as nerve remyelinates.

Clinical presentation

Symptoms

Symmetric ascending weakness beginning in the legs, progressing over hours to days (peak by 2-4 weeks)
Distal paresthesias and pain (often missed by clinicians but very common — back pain especially)
Areflexia or hyporeflexia (key feature)
Cranial nerve involvement in ~50% — bilateral facial weakness, dysphagia, dysarthria
Respiratory muscle weakness — 25% require mechanical ventilation
Autonomic dysfunction: tachy/bradyarrhythmias, BP swings, ileus, urinary retention
Miller Fisher variant: ophthalmoplegia, ataxia, areflexia (anti-GQ1b)

Signs / physical exam

Symmetric weakness, often distal>proximal initially, progressing to flaccid paralysis
Decreased or absent deep tendon reflexes
Mild distal sensory loss; rarely sensory level
Bilateral facial weakness (peripheral CN VII pattern)
Respiratory: tachypnea, paradoxical breathing, decreased forced vital capacity (NIF/MIP)
Autonomic instability

Classic findings

Acute ascending symmetric weakness + areflexia + antecedent infection + albuminocytologic dissociation in CSF (elevated protein with normal cell count).

Differential diagnosis

Spinal cord compression / transverse myelitis — Sensory level, bowel/bladder early, upper motor neuron signs — MRI spine mandatory
Myasthenia gravis — Fatigability, ocular/bulbar predominance, normal reflexes, AChR antibodies; not ascending
Botulism — Descending paralysis, dilated pupils, dry mucous membranes (anticholinergic effect on autonomic nerves), recent home-canned food or honey (infants)
Tick paralysis — Tick attached; rapid recovery after removal
Lyme disease (Bannwarth syndrome) — Painful radiculopathy, facial palsy, erythema migrans history
Acute intermittent porphyria — Abdominal pain, neuropsychiatric symptoms, dark urine, low motor function
Critical illness polyneuropathy/myopathy — Develops in ICU patients with sepsis/multiorgan failure
Heavy metal toxicity (lead, thallium, arsenic) — Subacute course, sensory >> motor, exposure history
Toxic neuropathies / drug-induced — Vincristine, isoniazid, statins; medication history

Diagnostic workup

Diagnostic criteria

Clinical: progressive symmetric weakness + areflexia, peak by 4 weeks, exclusion of alternative causes. Supportive: CSF albuminocytologic dissociation, electrodiagnostic features of demyelination.

Labs

CBC, BMP, LFTs, ESR, CRP, HIV, HBV, HCV
Antiganglioside antibodies (anti-GM1, anti-GD1a, anti-GQ1b — Miller Fisher)
Stool for Campylobacter (low yield, usually cleared by presentation)
Heavy metal screen if exposure history
Pulmonary function: bedside NIF (negative inspiratory force) and FVC every 4-8 h; intubate if FVC <20 mL/kg, NIF less negative than -30 cm H2O, or MEP <40 cm H2O ('20/30/40 rule')

Imaging

MRI spine with gadolinium — exclude compressive lesion; nerve root enhancement (especially cauda equina) supports GBS
Nerve conduction studies / EMG: slowed conduction velocities, prolonged distal latencies, conduction block, F-wave abnormalities (early), low amplitudes (axonal variants)
Lumbar puncture: albuminocytologic dissociation (elevated protein, normal WBC <5 cells/μL) — may be normal in first week; cell count >50 suggests alternate diagnosis (HIV, sarcoid, lymphomatous infiltration)

Diagnostic algorithm

Feature	GBS	Myasthenia Gravis	Botulism
Pattern	Ascending symmetric	Fatigable, ocular/bulbar	Descending
Reflexes	Decreased/absent (early)	Normal	Decreased
Pupils	Normal (autonomic instability)	Normal	Dilated, sluggish
Antecedent	Infection 1-4 wk prior	Insidious	Canned food, honey (infants)
CSF	↑ protein, normal cells	Normal	Normal
EMG	Demyelinating, conduction block	Decremental on repetitive stim	Incremental on rapid repetitive stim
Treatment	IVIG or PLEX (not steroids)	Pyridostigmine, immunosuppression	Antitoxin, supportive

Distinguishing GBS from other acute neuromuscular weakness.

Treatment

First-line

ICU admission for any patient with autonomic instability, bulbar weakness, or rapidly progressive disease
Frequent pulmonary monitoring (FVC, NIF q4-8h); intubate at 20/30/40 thresholds — do not wait for hypoxia
IVIG 0.4 g/kg/day × 5 days (total 2 g/kg) — first-line, equivalent efficacy to PLEX, easier to administer
Plasma exchange (plasmapheresis) — 5 exchanges over 1-2 weeks; alternative first-line
Combining IVIG and PLEX provides NO additional benefit
Corticosteroids are NOT effective and may be harmful — do not use
Supportive: DVT prophylaxis, pain control (gabapentin, opioids — neuropathic pain common), bowel/bladder care, pressure ulcer prevention, PT/OT

Second-line / adjunct

Treat autonomic dysfunction: cautious BP management (avoid sudden drops), pacemaker pads available for bradyarrhythmias
Nutrition: NG/PEG if dysphagia
Psychological support (locked-in syndrome possible during peak)
Long inpatient rehab often required
Most patients improve over weeks-months; ~80% walk independently by 6 months

Complications

Respiratory failure requiring mechanical ventilation (~25%)
Autonomic dysfunction with fatal arrhythmias
DVT/PE from immobility
Pneumonia (aspiration, ventilator-associated)
Decubitus ulcers
Chronic pain (persistent in some patients)
Residual weakness in ~20% at one year
Mortality 3-5%, mostly from respiratory or autonomic complications
Recurrence rare (~3%); persistent worsening >8 weeks → consider CIDP

PANCE pearls

Loss of reflexes early is a defining feature — preserved reflexes argues against GBS.
Albuminocytologic dissociation: elevated CSF protein with normal cell count. Pleocytosis (>5-10 WBC) should make you reconsider GBS — think HIV, Lyme, sarcoid, lymphomatous meningitis.
20/30/40 rule for intubation: FVC <20 mL/kg, NIF less negative than -30, or MEP <40 cm H2O.
Steroids do NOT work in GBS — use IVIG or PLEX.
Miller Fisher variant: ophthalmoplegia + ataxia + areflexia + anti-GQ1b antibodies. Usually self-limited.
Persistent or progressive weakness >8 weeks moves the diagnosis to CIDP — which DOES respond to steroids.

References

AAN 2003 / 2012 update — Practice Parameter: Immunotherapy for Guillain-Barré Syndrome (Hughes et al., Neurology 2003; reaffirmed)
GBS Consensus — Diagnosis and Management of Guillain-Barré Syndrome — International Consensus Guideline (Leonhard et al., Nat Rev Neurol 2019)
Cochrane IVIG — Intravenous Immunoglobulin for Guillain-Barré Syndrome (Hughes et al., Cochrane Database 2014)
Brighton Criteria — Guillain-Barré Syndrome and Variants — Brighton Collaboration Case Definitions (Sejvar et al., Vaccine 2011)

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