Guillain-Barré Syndrome (GBS)

Definition

GBS is an acute, immune-mediated polyradiculoneuropathy characterized by progressive weakness, areflexia, and albuminocytological dissociation in the CSF. It is the leading cause of acute paralytic disease in Western countries following the eradication of polio, with a mean annual incidence of 1.8 per 100,000 population.

Pathophysiology

About two-thirds of cases are preceded by an infection that triggers microbe-specific T cells and antibodies that cross-react with peripheral nerve antigens (molecular mimicry). Both T cell-mediated and antibody-mediated mechanisms operate, though T cells are thought to play the dominant role. Injury is most extensive at the nerve roots and proximal nerve segments and is associated with mononuclear cell infiltrates rich in macrophages.

Key triggering pathogens:

Campylobacter jejuni (most common bacterial trigger)
Epstein-Barr virus
Cytomegalovirus (CMV)
HIV
Zika virus
SARS-CoV-2

Subtypes and Variants

Subtype	Notes
AIDP (Acute Inflammatory Demyelinating Polyradiculoneuropathy)	Most common in Europe/North America; demyelinating
AMAN (Acute Motor Axonal Neuropathy)	Pure motor axonal; summer epidemics in China in children/young adults
AMSAN (Acute Motor-Sensory Axonal Neuropathy)	Motor + sensory axons; more severe, poor recovery
Miller-Fisher Syndrome (MFS)	Ophthalmoplegia, ataxia, areflexia; 6% in West, up to 18% in Taiwan
Pharyngeal-cervical-brachial variant	Descending pattern; bulbar + upper limb predominance
Acute pandysautonomia	Rare; predominant autonomic involvement
Facial diplegia with paresthesias	Rare cranial nerve-dominant variant

Clinical Features

Demographics: Males > females (1.5:1); all ages; incidence rises sharply with age (0.8/100,000 under 18 vs. 3.2/100,000 over 60).

Classic presentation:

Ascending weakness - starts in lower limbs, ascends over hours to days to involve arms, face, oropharynx, and potentially respiratory muscles
Areflexia/hyporeflexia - invariable (may be absent early)
Sensory symptoms - paresthesias (often in hands/fingers); sensory loss is usually mild; vibration sense most affected distally
Pain - moderate to severe in 70% of patients; may persist for a year in one-third
Cranial nerve involvement - occurs in 45-75%; facial paresis (bilateral) in at least 50%
Respiratory failure - 9-30% require assisted ventilation

Autonomic dysfunction (65% of hospitalized patients):

Orthostatic hypotension, urinary retention, GI atony
Episodic hypertension, sinus tachycardia, tachyarrhythmias
Bradycardia, heart block, asystole ("vagal spells" - can be triggered by suctioning)
ECG changes: T-wave abnormalities, ST depression, QRS widening, QT prolongation, heart block

Diagnostic Criteria (Asbury & Cornblath 1990)

Required:

Progressive weakness of both legs and arms
Areflexia or hyporeflexia

Supportive (Clinical):

Progression over days to 4 weeks
Relative symmetry
Mild sensory symptoms/signs
Bifacial palsies
Autonomic dysfunction
Absence of fever at onset
Recovery beginning 2-4 weeks after progression ceases

Supportive (Laboratory):

CSF: Elevated protein with <10 cells/µL (albuminocytological dissociation)
Electrodiagnostics: Nerve conduction slowing or block (demyelination pattern in AIDP)

Treatment

IVIg (intravenous immunoglobulin) - suppresses immune response; given as 0.4 g/kg/day for 5 days
Plasmapheresis (plasma exchange) - removes offending antibodies; equivalent efficacy to IVIg
Supportive care: Ventilatory support (critical - mortality dropped from 33% to 1-5% with positive-pressure ventilation), DVT prophylaxis, pain management, autonomic monitoring
Corticosteroids: NOT effective (do not improve outcomes in GBS)
Combination IVIg + plasmapheresis: Not superior to either alone

Monitoring for respiratory failure: Serial FVC measurements; intubate when FVC <15-20 mL/kg ("20-30-40 rule").

Prognosis

Plateau reached in most patients by 4 weeks
Recovery usually begins 2-4 weeks after plateau
Majority recover functionally with time
~20% have significant residual disability at 6 months
Mortality approximately 1-5% in the modern era (was 33% before ventilator support)

GBS vs. CIDP (Key Distinction)

Feature	GBS	CIDP
Time course	Acute, peaks ≤4 weeks	Progressive ≥2 months
Course	Monophasic	Relapsing-remitting or progressive
Response to steroids	No benefit	Good response
Associations	Post-infectious	Paraproteinemias, lymphoma, HIV

Sources:

Bradley and Daroff's Neurology in Clinical Practice, Box 106.10-106.11
Robbins & Kumar Basic Pathology, p. 808-809

Recent evidence (2026): A systematic review (PMID 41038424) confirms that physical exercise programs improve fatigue and functional capacity in GBS and CIDP - rehabilitation is a meaningful part of long-term management.

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