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GBS

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GBS (Guillain-Barre Syndrome) is an acute immune-mediated polyneuropathy that typically follows an infection and causes ascending weakness, areflexia, and occasionally respiratory failure. It is one of the most common causes of acute flaccid paralysis worldwide.
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"Guillain-Barre syndrome"[MeSH Terms]

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Here is a thorough overview of Guillain-Barre Syndrome (GBS):

Guillain-Barre Syndrome (GBS)

Definition

GBS refers to a group of acquired, acute-onset inflammatory polyradiculoneuropathies characterized by:
  • Progressive limb weakness
  • Areflexia or hyporeflexia
  • Elevated CSF protein with low cell count (albuminocytological dissociation / cytoalbuminologic dissociation)
  • Monophasic course
It is the leading cause of acute flaccid paralysis in Western countries following the eradication of poliomyelitis.
  • Goldman-Cecil Medicine, p. 4080; Bradley and Daroff's Neurology in Clinical Practice, p. 2663

Epidemiology

  • Annual incidence: 1-2 per 100,000
  • Male : Female ratio = 1.4-1.5 : 1
  • Affects all ages; incidence rises with age (0.8 per 100,000 in <18 years to 3.2 per 100,000 in >60 years)
  • 60% of cases are preceded by a respiratory or GI infection
  • Campylobacter jejuni diarrhea is the most common identified preceding infection, especially in axonal variants
  • Zika virus is significantly associated with GBS
  • SARS-CoV-2 infection or vaccination does not appear substantially associated with GBS, except a slight increase (0.6/100,000 doses) with the ChADOx1 (AstraZeneca) vaccine

Subtypes & Variants (Classification)

SubtypeKey Features
AIDP (Acute Inflammatory Demyelinating Polyneuropathy)Most common in Europe/North America (97%); demyelinating pattern on NCS
AMAN (Acute Motor Axonal Neuropathy)Pure motor; first described in northern China; summer epidemics in children
AMSAN (Acute Motor-Sensory Axonal Neuropathy)Both motor and sensory axons; more severe; poor recovery
Miller-Fisher Syndrome (MFS)Triad: ophthalmoplegia + ataxia + areflexia; GQ1b antibodies >85%; normal NCS
Pharyngeal-cervical-brachial variantBulbar/arm weakness
Acute pandysautonomiaPredominant autonomic involvement
Facial diplegia with paresthesiasBilateral facial weakness + sensory symptoms

Pathophysiology

All forms likely result from postinfectious molecular mimicry: the immune system attacks peripheral nerve antigens that resemble microbial antigens (particularly C. jejuni). In AIDP:
  • Endoneurial perivascular mononuclear cell infiltration
  • Multifocal demyelination of spinal roots and peripheral nerves (most at ventral roots, proximal spinal nerves, lower cranial nerves)
  • Macrophages strip myelin lamellae from axons
  • Infiltrate: class II-positive monocytes/macrophages and T lymphocytes
In axonal forms (AMAN/AMSAN), antibodies (anti-GM1, anti-GD1a) directly attack axonal membranes at nodes of Ranvier.

Clinical Features

Cardinal features:
  • Symmetrical ascending weakness starting in the legs, progressing to arms and cranial muscles
  • Areflexia / hyporeflexia (invariable; may be absent early)
  • Mild sensory loss (vibration sense distally); sensory loss is NOT a prominent feature
  • Weakness may range from mild (can walk) to near-total quadriplegia
Cranial nerve involvement: 45-75% of cases
  • Bilateral facial paresis in ~50%
  • Extraocular and lower cranial nerve involvement less common
Autonomic dysfunction: ~65% of hospitalized patients
  • Orthostatic hypotension, hypertension, sinus tachycardia, urinary retention, ileus
  • Most significant in first 2-4 weeks
Respiratory failure: 9-30% require mechanical ventilation (increases with age)
Pain: Moderate to severe in ~70% during acute phase (extremities, back, interscapular area); may persist for a year in 1/3 of patients

Diagnosis

Required features (Asbury & Cornblath criteria):
  1. Progressive weakness of both legs and arms
  2. Areflexia or hyporeflexia
Supportive clinical features:
  • Progression over days to 4 weeks
  • Relative symmetry
  • Mild sensory symptoms
  • Bifacial palsies
  • Autonomic dysfunction
  • Absence of fever at onset
  • Recovery beginning 2-4 weeks after progression ceases
Laboratory:
  • CSF: Elevated protein with <10 cells/uL (cytoalbuminologic dissociation). Note: CSF may be normal in first 7-10 days and in up to 10% overall
  • Nerve conduction studies (NCS): Slowing/block in AIDP; reduced CMAP amplitudes in axonal forms
  • EMG: Helps exclude myopathy
  • Anti-GQ1b antibodies: >85% of Miller-Fisher syndrome

Differential Diagnosis

Warning signs suggesting an alternative diagnosis:
Warning SignConsider
Sensory-predominantSensory neuronopathy
Prominent bowel/bladder symptomsMyelopathy
Spinal sensory levelMyelopathy
Persistently asymmetric weaknessEnteroviral myelitis, vasculitis, diabetic amyotrophy
Distal-predominant patternToxic neuropathy (arsenic)
Slow progression (>4 weeks)CIDP
CSF >50 WBCs/uLHIV seroconversion, Lyme, CMV
Other key differentials: myasthenic crisis, botulism (unreactive pupils, no sensory symptoms), tick paralysis, transverse myelitis, critical illness polyneuropathy (normal CSF, axonal NCS pattern).

Treatment

Supportive Care (ICU monitoring is essential)

  • Respiratory monitoring: Intubate if vital capacity <1 L or NIF <-25 cmH2O (-70 cmH2O by some thresholds)
  • Monitor autonomic function and swallowing
  • DVT prophylaxis: subcutaneous heparin + compression devices
  • Prevent pressure ulcers, keratitis (facial diplegia), nosocomial infections
  • Nutritional support, physical therapy from early on

Disease-Modifying Therapy

Both options are equally effective; combination does not provide additional benefit:
1. IVIG (preferred in practice)
  • Dose: 2 g/kg divided over 2-5 days (adjust for cardiac/fluid status)
  • Should be started within 2 weeks of onset
  • Higher completion rate than PE, hence generally preferred
  • A second course of IVIG does NOT improve outcomes and should not be given
  • Mechanism: anti-idiotypic antibodies neutralize pathogenic autoantibodies
2. Plasma Exchange (PE)
  • 4-5 exchanges (40-50 mL/kg each), alternate days
  • Using saline + albumin as replacement
  • Most beneficial within 2 weeks of onset; some benefit up to 30 days
  • 4 exchanges optimal for moderate/severe cases; 6 exchanges show no additional benefit
  • Contraindications: active bleeding, severe cardiovascular instability, septicemia
Corticosteroids: NOT recommended as sole therapy; methylprednisolone + IVIG shows only slight initial advantage with no long-term benefit.

Prognosis

  • 50% reach maximum disability within 2 weeks, 75% within 3 weeks, >90% within 4 weeks
  • Mortality: ~1-5% (modern era with ventilatory support; previously ~33%)
  • Most patients recover completely or with minor sequelae
  • ~20% have persistent disability
  • Poor prognostic factors:
    • Older age
    • Preceding diarrheal illness (C. jejuni)
    • Axonal variants (AMAN/AMSAN)
    • Low CMAP amplitudes in upper extremities
    • Greater severity of weakness at nadir
Sources: Bradley and Daroff's Neurology in Clinical Practice (Box 106.10-11, pp. 2663-2666); Goldman-Cecil Medicine (pp. 4080-4081)
Recent evidence note: A 2026 systematic review (PMID 41038424) examined exercise programs in GBS and CIDP for fatigue and functional capacity, consistent with current rehabilitation recommendations.
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