Key Facts

GBS is a medical emergency. Rapid identification, monitoring of respiratory function, and early treatment with IVIg or plasma exchange are essential. Most patients recover well but ~5% die and ~20% have significant residual disability.

Epidemiology

Incidence ~1-2 per 100,000/year. All ages (slight peak in young adults and elderly). M:F 1.5:1. Commonest cause of acute flaccid paralysis in developed countries.

Aetiology

Post-infectious molecular mimicry: microbial antigens share epitopes with gangliosides on peripheral nerves → immune cross-reactivity. Campylobacter jejuni lipooligosaccharides are structurally similar to GM1/GD1a gangliosides → anti-ganglioside antibodies → nerve damage.

Pathophysiology

• AIDP (~90% in UK): macrophage-mediated segmental demyelination of peripheral nerves and nerve roots; cell-mediated + humoral immunity; complement activation
• AMAN (acute motor axonal neuropathy): anti-GM1/GD1a antibodies target motor axons; more common in Asia, associated with Campylobacter; axonal degeneration
• AMSAN (acute motor and sensory axonal neuropathy): axonal variant affecting motor + sensory axons; worst prognosis
• Miller Fisher syndrome: anti-GQ1b antibodies; triad of ophthalmoplegia, ataxia, areflexia

Classic Presentation (AIDP)

• Preceding infection 1-4 weeks before (diarrhoea — Campylobacter; URTI — CMV, EBV)
• Ascending symmetrical weakness: starts in legs, progresses to arms, then bulbar/respiratory muscles
• Areflexia or hyporeflexia: early and universal
• Sensory symptoms: paraesthesiae, numbness (distal); pain in back/limbs is common (~70%)
• Progression to nadir within 4 weeks (usually 2 weeks)
• Autonomic dysfunction: tachycardia, bradycardia, labile BP, urinary retention, ileus

Miller Fisher Syndrome (~5%)

• Triad: ophthalmoplegia + ataxia + areflexia
• Anti-GQ1b antibodies (~95% positive)
• Usually good recovery

Red Flags

• Rapidly declining FVC → imminent respiratory failure
• Inability to lift head off pillow → severe weakness
• Bulbar weakness → aspiration risk
• Autonomic instability → cardiac arrhythmia risk
• Bladder involvement early → consider spinal cord pathology instead

Bedside

• FVC (forced vital capacity): serial monitoring Q4-6 hourly; intubate if <20 mL/kg, declining >30% from baseline, unable to cough effectively, or bulbar weakness with aspiration
• Observations: HR, BP (autonomic monitoring), SpO₂

CSF (Lumbar Puncture)

• Albuminocytological dissociation: raised protein (often >0.4 g/L) with normal white cell count (<10/μL)
• May be normal in first week — repeat if initially normal and clinical suspicion high
• Cell count >50/μL → consider alternative diagnosis (HIV, Lyme, sarcoid)

Neurophysiology

• NCS/EMG: AIDP — prolonged distal motor latencies, reduced conduction velocities, conduction block, prolonged/absent F-waves, temporal dispersion
• AMAN — reduced CMAP amplitudes with preserved conduction velocities, no conduction block
• May be normal in first few days

Bloods

• Anti-ganglioside antibodies: anti-GM1 (AMAN), anti-GQ1b (Miller Fisher); not always positive and results may take time
• Campylobacter serology/stool culture: preceding infection
• HIV test: HIV seroconversion can cause GBS-like picture
• U&Es, LFTs: baseline

Imaging

• MRI spine with gadolinium: enhance nerve roots (may show enhancement); exclude compressive myelopathy

Acute Treatment

• IVIg 0.4 g/kg/day × 5 days: first-line in UK; equally effective to plasma exchange; easier to administer
• Plasma exchange: 5 exchanges over 10-14 days; equally effective; preferred if IVIg contraindicated
• Steroids are NOT effective in GBS (unlike CIDP) — do NOT give
• Combination IVIg + PE is NOT more effective than either alone

Monitoring

• ITU/HDU admission for: bulbar dysfunction, FVC <20 mL/kg or declining, autonomic instability
• Serial FVC Q4-6h (even more frequently if declining)
• Continuous cardiac monitoring (autonomic dysfunction — arrhythmias)
• VTE prophylaxis: LMWH (enoxaparin 40 mg OD SC) + compression stockings

Supportive

• Respiratory: intubation and ventilation if FVC <15-20 mL/kg; ~25% require mechanical ventilation
• Pain management: paracetamol, gabapentin 300-3600 mg/day, opioids if severe
• DVT prophylaxis: LMWH
• Physiotherapy: early rehabilitation; passive exercises to prevent contractures
• Nutrition: nasogastric feeding if bulbar weakness
• Psychological support: anxiety, depression common in prolonged illness

Referral Criteria

• All suspected GBS: emergency neurology admission
• Declining FVC: ITU involvement immediately

~80% make a good or complete recovery (may take months to years). ~5% mortality (respiratory failure, autonomic dysfunction, PE). ~20% have significant residual disability at 1 year. ~5-10% develop CIDP (relapsing course >8 weeks). Predictors of poor outcome: older age, rapid onset, axonal variant (AMAN/AMSAN), preceding Campylobacter infection, need for ventilation. Erasmus GBS Outcome Score (EGOS) predicts ability to walk at 6 months.

GBS Subtypes

Indicators for Intubation