Updated October 2025

Neuromuscular Emergencies

Guillain–Barré Syndrome (GBS) and Other Acute Demyelinating Neuropathies

GBS is the most common cause of acute flaccid paralysis worldwide. Early recognition of ascending weakness, areflexia, and autonomic risk, followed by timely IVIg or plasma exchange, improves outcomes. Miller Fisher syndrome (MFS) is often mild and self-limited, while axonal variants carry worse prognosis. Prompt respiratory and autonomic monitoring are essential to prevent morbidity.

Clinical question

How should clinicians recognize, risk-stratify, and treat Guillain–Barré syndrome and related acute demyelinating neuropathies to optimize short- and long-term outcomes?

GBSAIDPAMAN/AXONALMFSCIDPIVIgPlasma exchangeNeuromuscular respiratory failure

Key points

Recognize the phenotype

Rapidly progressive, symmetrical weakness with areflexia; back/neuropathic pain, facial diplegia, dysautonomia, and sensory symptoms are common. Consider variants: AIDP, AMAN/axonal forms, and MFS (ophthalmoplegia-ataxia-areflexia) ^[1], ^[5], ^[7].

Monitor for respiratory failure

Serial FVC, NIF, and bulbar assessment; early ICU transfer when FVC <20 mL/kg, rapid decline, or bulbar/autonomic involvement. Early treatment improves outcomes ^[7], ^[8].

Initiate disease-modifying therapy

IVIg or plasma exchange are the only proven effective therapies; start as early as possible when nonambulant or rapidly progressive ^[8], ^[9], ^[11].

Confirm and classify

CSF albuminocytologic dissociation (often after day 7), and electrodiagnostics to distinguish demyelinating vs axonal variants and to inform prognosis ^[5], ^[7].

Set expectations

Most recover substantially, but residual deficits and fatigue are frequent. Persistent or relapsing weakness beyond 8 weeks suggests CIDP spectrum and requires re-evaluation ^[1], ^[7], ^[11].

Evidence highlights

0.6–1.9 per 100,000/year ^[2]

Incidence (NA/EU)

≈20% despite therapy ^[11]

Unable to walk at 6 months

≈2–10% in modern series ^[11]

Mortality

Near-complete recovery ≤6 months, often without treatment ^[1]

Prognosis in pure MFS

Frontline Approach

Diagnosis, Risk Stratification, and Initial Management

Early diagnosis and treatment mitigate respiratory failure, dysautonomia, and long-term disability.

Recognize core features and exclude mimics

Look for rapidly progressive, relatively symmetric limb weakness with areflexia over hours to 4 weeks, often following infection. Red flags for alternative diagnoses include marked asymmetry, hyperreflexia with spasticity, sensory level, or sphincter disturbance. MFS presents with ophthalmoplegia, ataxia, and areflexia, typically with anti-GQ1b positivity and a benign course ^[1], ^[7].

Baseline tests and monitoring

Obtain CSF (protein elevation with ≤10 cells/µL after first week) and electrodiagnostics (reduced CMAPs, demyelinating conduction slowing/block in AIDP; low CMAP without slowing in axonal variants). Monitor FVC, NIF, bulbar function, and autonomic signs every 4–6 hours if moderate–severe ^[5], ^[7].

When to treat

Initiate therapy in nonambulant patients, those with rapid progression, bulbar or autonomic involvement, or declining respiratory metrics. Earlier IVIg is associated with better outcomes; timing is a modifiable prognostic factor (earlier is better) ^[8].

Choose therapy

Either IVIg (2 g/kg total over 2–5 days) or plasma exchange (4–5 exchanges over ~7–14 days) are effective; do not combine routinely. Corticosteroids are not effective in classic GBS. Refractory cases may need retreatment or trial enrollment; novel immunomodulatory approaches are under investigation ^[9], ^[11].

Supportive care to prevent complications

DVT prophylaxis, pain control (neuropathic agents), bowel/bladder care, pressure-sore prevention, and early PT/OT are critical. Vigilantly manage dysautonomia (arrhythmias, BP lability). Consider early intubation for rapid decline or bulbar dysfunction ^[7], ^[11].

Decision Support

Phenotypes, Prognosis, and Treatment Pearls

Use this grid to differentiate variants, anticipate course, and fine-tune therapy.

GBS Variants and Typical Course

AIDP (Europe/NA predominant): demyelinating features; sensory symptoms frequent; recovery usually favorable with therapy ^[5], ^[7].

AMAN/axonal: faster progression, more severe weakness; worse short-term prognosis, lower CMAPs; recovery may be prolonged ^[5], ^[7].

MFS: ophthalmoplegia–ataxia–areflexia; anti-GQ1b common; generally mild with near-complete recovery ≤6 months, often without treatment ^[1].

Epidemiology and Outcomes

Incidence 0.6–1.9 per 100,000/year in NA/EU; male predominance ^[2].

Despite treatment: mortality ≈2–10%; ≈20% unable to walk at 6 months; many with residual fatigue/neuropathic pain ^[11].

Most severe cases recover substantially over months; counseling on realistic timelines is essential ^[12].

Diagnostics That Shift Management

CSF: albuminocytologic dissociation typically after day 7; pleocytosis >50 suggests alternative/infectious etiologies ^[7].

Electrodiagnostics: classify demyelinating vs axonal; absent H-reflexes early support radiculopathy; reduced SNAPs/CMAPs support peripheral neuropathy ^[7].

Serologies: consider anti-GQ1b in MFS; infectious work-up guided by history ^[7].

Timing and Choice of Immune Therapy

Start treatment promptly when criteria met; earlier IVIg initiation is linked to improved outcomes (functional recovery) ^[8].

IVIg and plasma exchange are the only proven effective immune treatments over the last 30 years ^[9], ^[11].

Routine combination or steroids in classic GBS are not recommended; consider retreatment in selected nonresponders ^[11].

Red Flags and Pitfalls

Do not delay treatment while waiting for CSF/EMG if clinically clear and progressing.

Watch for dysautonomia: malignant hypertension/hypotension and arrhythmias can be fatal; continuous monitoring in moderate–severe disease ^[7], ^[11].

Differentiate acute-onset CIDP if deterioration continues beyond 8 weeks or with relapses; management shifts to CIDP regimens ^[3], ^[4], ^[6].

Long-term Care and Transition

Rehabilitation, fatigue management, neuropathic pain therapy, and mental health support.

Assess for treatment-related fluctuations; consider CIDP workup if relapse or progression beyond expected GBS window ^[3], ^[4], ^[6].

Patient-reported outcome measures can track disability, pain, fatigue, and quality of life through recovery ^[6].

References

Source material

Primary literature that informs this article.