Guillain–Barré syndrome
Weakness climbing up from the legs with absent reflexes after an infection. Measure vital capacity, because SpO₂ stays normal until it's too late.
A 28-year-old man had diarrhoea 2 weeks ago. Over 4 days his legs have become weak and now his arms too. He can no longer climb stairs. Knee and ankle reflexes are absent. He has tingling in his feet and back pain. He feels breathless lying flat. SpO₂ 97% on air. Single breath count 12. FVC 1.6 L (he weighs 70 kg).
What is happening to his breathing, what do you measure and how often, and when do you call ICU?
- Measure breathing strengthFVC (with a facemask if the face is weak) or single breath count, plus neck flexion, cough and swallow.
- Call ICU earlyFVC below 20 mL/kg, falling by 30%, weak cough, bulbar weakness, or rapid progression.
- Exclude mimicsCord compression (sensory level, early bladder), low potassium, krait bite, myasthenia, botulism.
- Bloods, LP and nerve conductionCSF protein high with normal cells (may be normal in week 1).
- IVIG or plasma exchangeWithin 2 weeks in patients unable to walk 10 metres unaided or worsening.
- Autonomic monitoringCardiac monitor, frequent BP, watch for retention and ileus.
- Supportive careVTE prophylaxis, pain relief, swallow assessment, pressure care, physio, bladder and bowel care.
- FVC below 20 mL/kg or falling quickly
- Weak cough, choking, nasal voice, can't lift head
- BP swinging or arrhythmias
- Sensory level or early bladder problems (think cord)
- Weakness getting worse within hours
- Neuromuscular breathing failure
- Autonomic instability and arrhythmia
- Spinal cord compression
- Low potassium
- Myasthenic crisis
- Krait bite
- Polio or acute flaccid myelitis in children
- Botulism
| FVC monitoring | Every 4–6 hours, more often if falling |
| 20/30/40 rule for ICU | FVC below 20 mL/kg, max inspiratory pressure weaker than −30 cmH₂O, max expiratory pressure below 40 cmH₂O |
| Single breath count | Below about 15 suggests poor breathing reserve |
| IVIG | 0.4 g/kg daily for 5 days (2 g/kg total) |
| Steroids | Not effective |
| Enoxaparin | 40 mg subcutaneously daily while immobile |
Check every dose against a current drug reference and your hospital protocol.
On this page
What is GBS?
An immune attack on the peripheral nerves, usually 1–4 weeks after diarrhoea (often Campylobacter) or a respiratory infection. Antibodies against the infection cross-react with nerve components (molecular mimicry), damaging myelin or axons. It causes rapidly progressive, fairly symmetrical weakness with loss of reflexes, reaching its worst within 4 weeks. About a quarter of patients need ventilation. Most recover over weeks to months.
Presentation
- Weakness starting in the legs and climbing up over days to 4 weeks.
- Tingling in the hands and feet, back or limb pain (pain can be severe).
- Reduced or absent reflexes.
- Facial weakness, difficulty swallowing, breathing muscle weakness.
- Autonomic problems: BP swings, fast or slow heart rate, arrhythmias, urinary retention, ileus.
- Miller Fisher variant: eye movement weakness, unsteadiness, absent reflexes.
History
- Recent diarrhoea or chest infection, vaccination.
- How fast is it progressing? Can they walk? Stairs? Lift their arms?
- Breathless lying flat, weak cough, choking, voice change.
- Early bladder or bowel problems suggest a cord lesion instead.
- Snake bite, sleeping on the floor (krait); diarrhoea, diuretics or vomiting (low potassium); home-canned food (botulism).
Examination
- BreathingRR, use of accessory muscles, paradoxical breathing, single breath count, FVC.
- Bulbar and neckCough, swallow, voice, neck flexion (parallels breathing muscle strength).
- LimbsPower in all groups, tone, reflexes (reduced or absent).
- SensationUsually mild; look for a sensory level (cord).
- Cranial nervesFacial weakness, eye movements (Miller Fisher).
- AutonomicPulse, BP lying and standing, bladder.
Why breathing is the danger
SpO₂ stays normal until the patient is close to respiratory arrest. Measure FVC or the single breath count regularly and act on the trend. Look at neck flexion, cough and swallow. Don't wait for the blood gas.
The 20/30/40 rule: any of these means ICU review for possible elective intubation:
- FVC below 20 mL/kg.
- Maximum inspiratory pressure weaker than −30 cmH₂O.
- Maximum expiratory pressure below 40 cmH₂O.
- Also: FVC falling by more than 30%, bulbar weakness, weak cough, rapid progression.
GBS or a mimic?
- Spinal cord compression or transverse myelitis
- Urgent MRI spine
- Hypokalaemic paralysis
- Replace potassium
- Krait bite
- ASV, ventilation
- Myasthenic crisis
- Neurology
- Botulism
- Antitoxin
- Polio or acute flaccid myelitis
- Report AFP, stool samples
Investigations
| Test | Findings or why |
|---|---|
| FVC (or single breath count) | Below 20 mL/kg = high risk of respiratory failure |
| Electrolytes, CK, glucose | Exclude low potassium and myositis |
| Lumbar puncture | High protein with normal cell count (may be normal in the first week); high cells suggest another cause |
| Nerve conduction studies | Demyelination or axonal loss |
| MRI spine | If cord compression is possible |
| ECG and cardiac monitor | Arrhythmias |
| Stool for Campylobacter, viral studies | Trigger |
| Stool samples (children under 15) | Polio surveillance (acute flaccid paralysis) |
Treatment
- Breathing planFVC 4–6-hourly, ICU review if criteria met.
- IVIG or plasma exchangeFor patients unable to walk 10 metres unaided, or worsening, ideally within 2 weeks of onset.
- SwallowAssessment; NG tube if unsafe.
- AutonomicCardiac monitor, treat BP swings cautiously (they can reverse quickly), watch for retention and ileus.
- SupportiveEnoxaparin, pressure care, physio, bladder and bowel care, nutrition.
- Pain and moodNeuropathic pain treatment; explain and support.
Steroids are not effective in GBS and are not given.
Children
- Every case of acute flaccid paralysis in a child under 15 must be reported to the district EPI or polio programme, and two stool samples sent, even if GBS seems likely.
- Children may present with pain and refusal to walk.
Common mistakes
- Relying on SpO₂ or a blood gas to judge breathing.
- Not measuring FVC regularly.
- Missing a cord lesion (sensory level, early bladder).
- Forgetting to check potassium.
- Giving steroids.
- Not reporting acute flaccid paralysis in a child.
Follow-up
- Most improve over weeks to months; recovery is fastest in the first year.
- Some are left with weakness, pain or fatigue.
- Rehabilitation and physiotherapy are essential.
- Recurrence is uncommon.
Frequently asked questions
What FVC means a GBS patient needs ICU?
An FVC below 20 mL/kg, or one falling by more than 30%, along with bulbar weakness or a weak cough.
What is the IVIG dose for Guillain–Barré syndrome?
2 g/kg in total, usually given as 0.4 g/kg a day for 5 days.
Do steroids help Guillain–Barré syndrome?
No. Steroids are not effective in GBS.
What is the first sign of breathing failure in GBS?
A falling FVC or single breath count, weak cough and weak neck flexion come before oxygen saturation falls.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A man with ascending weakness after diarrhoea has absent reflexes. Which measurement best warns of respiratory failure?
Answer: Forced vital capacity. FVC (or single breath count) falls before oxygen saturation. FVC below 20 mL/kg needs ICU.
- Chest X-ray: Not useful.
- Respiratory rate alone: Less reliable.
- Peak flow: Not the standard measure.
- SpO₂: Falls late.
2. Which treatment is effective in Guillain–Barré syndrome?
Answer: IV immunoglobulin. IVIG (0.4 g/kg daily for 5 days) or plasma exchange speeds recovery.
- IV methylprednisolone: Steroids are not effective.
- Pyridostigmine: For myasthenia.
- Antibiotics: Not effective.
- Oral prednisolone: Not effective.
3. A patient with leg weakness has a sensory level at T10 and early urinary retention. What is more likely than Guillain–Barré syndrome?
Answer: Spinal cord compression. A sensory level and early bladder involvement suggest a cord lesion: urgent MRI.
- Hypokalaemia: No sensory level.
- Myasthenia gravis: No sensory level.
- Botulism: Descending, no sensory level.
- Polymyositis: No sensory level.
4. Two weeks after a diarrhoeal illness, a 30-year-old has ascending symmetrical leg weakness, areflexia and tingling. Forced vital capacity is falling. What is the treatment?
Answer: IV immunoglobulin. GBS (acute inflammatory demyelinating polyneuropathy) often follows Campylobacter jejuni, CMV or EBV. Features: ascending flaccid weakness, areflexia, mild sensory symptoms, autonomic instability. CSF: high protein, normal cells (albuminocytological dissociation). Nerve conduction confirms. Monitor FVC (intubate if < 15–20 mL/kg). Treat with IVIG or plasma exchange within 2 weeks; steroids don’t help. Miller Fisher variant: ophthalmoplegia, ataxia, areflexia (anti-GQ1b).
- Oral prednisolone: Steroids are ineffective in GBS.
- IV methylprednisolone: IV methylprednisolone is ineffective in GBS.
- Pyridostigmine: Pyridostigmine is for myasthenia.
5. A woman in preterm labour at 34 weeks has a previous baby who had early-onset GBS sepsis. What is recommended during labour?
Answer: Intrapartum IV penicillin. Intrapartum antibiotic prophylaxis (IV benzylpenicillin; clindamycin if allergic) reduces early-onset neonatal GBS sepsis. Indications: previous baby with GBS disease, GBS bacteriuria in current pregnancy, positive GBS swab (where screening is used), preterm labour, intrapartum fever. Antenatal oral antibiotics do not eradicate carriage. Give ≥ 4 hours before delivery for best effect.
- Antibiotics only if fever: A previous affected baby is an indication regardless of fever.
- Oral amoxicillin in third trimester: Oral antibiotics antenatally do not prevent transmission.
- Antibiotics to baby only: The mother needs intrapartum antibiotics.
6. Bloody diarrhoea follows eating undercooked chicken; weeks later the patient develops ascending paralysis. Which organism was responsible?
Answer: Campylobacter jejuni. Campylobacter jejuni (curved Gram-negative, grows at 42 °C, microaerophilic) is a commonest cause of bacterial gastroenteritis from poultry and unpasteurised milk. Complications: Guillain–Barré syndrome (molecular mimicry of gangliosides) and reactive arthritis (HLA-B27). Shigella causes dysentery with a very low infectious dose; Salmonella from eggs and poultry; Vibrio parahaemolyticus from seafood.
- Salmonella Enteritidis: Possible cause of diarrhoea, but GBS link is Campylobacter.
- Shigella dysenteriae: Dysentery, HUS.
- Vibrio parahaemolyticus: Seafood.
- Clostridium perfringens: Food poisoning, cramps.
7. Which mechanism explains autoimmune disease after an infection, such as rheumatic fever after streptococcal pharyngitis?
Answer: Molecular mimicry. Molecular mimicry: antibodies or T cells against streptococcal M protein cross-react with cardiac myosin and valve tissue (rheumatic fever); Campylobacter lipooligosaccharide mimics peripheral nerve gangliosides (Guillain–Barré); Coxsackie B and islet antigens (proposed in type 1 diabetes). Normal tolerance mechanisms (deletion, anergy, Tregs) prevent autoimmunity.
- Clonal deletion: Prevents autoimmunity.
- T-cell anergy: Prevents autoimmunity.
- Regulatory T-cell expansion: Prevents autoimmunity.
- Central thymic tolerance: Prevents autoimmunity.
References and dose sources
- EAN/PNS — Guillain–Barré syndrome guideline (2023)
- Association of British Neurologists
- Enoxaparin dosing: Drugs.com: Enoxaparin dosage (see also our enoxaparin dose page)
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Pregabalin dosing: Drugs.com: Pregabalin dosage (see also our pregabalin dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.