Guillain-Barré Syndrome

Introduction & Epidemiology

Guillain-Barré Syndrome (GBS) represents an acute, severe, fulminant polyradiculoneuropathy of autoimmune origin.

• Acquired, post-infectious demyelinating disease involving peripheral nervous system.
• Primarily affects motor nerves; sensory and autonomic nerves frequently involved.
• Incidence: 10–20 cases per million annually.
• Demographics: Males affected slightly more than females.
• Age Distribution: Adults more frequently affected than children in Western countries.

Antecedent Events and Etiology

Infection precedes onset in ~70% of cases by 1–3 weeks.

Infectious Triggers

• Gastrointestinal/Respiratory: Most common prior illnesses.
• Campylobacter jejuni: Most frequent bacterial trigger. Accounts for 20–30% of cases globally. Documented in ~27% of AIIMS cohorts. Strongly associated with axonal subtypes (AMAN, AMSAN).
• Human Herpes Viruses: Cytomegalovirus (CMV), Epstein-Barr virus (EBV).
• Other Viruses: HIV, Hepatitis E, Zika virus, SARS-CoV-2 (COVID-19).
• Atypical Bacteria: Mycoplasma pneumoniae.

Non-Infectious Triggers

• Vaccinations: Historically linked to 1976 swine influenza vaccine. Modern influenza vaccines pose minimal risk (<1 per million). Recent data indicates slightly increased risk with adenovirus-vector SARS-CoV-2 vaccines; mRNA vaccines confer no risk.
• Immunosuppressed States: Increased incidence in lymphoma (Hodgkin’s disease), HIV-seropositivity, Systemic Lupus Erythematosus (SLE).
• Medications: Immune checkpoint inhibitors (cancer immunotherapies).

Immunopathogenesis

• Molecular Mimicry: Core pathogenic mechanism. Immune responses generated against non-self antigens (infectious agents) misdirect to host neural tissue.
• Neural Targets: Glycoconjugates, specifically gangliosides (GM1, GD1a, GQ1b, GT1a).
• Ganglioside Localization: Complex glycosphingolipids exposed on plasma membranes, rendering susceptibility to antibody-mediated attack. Highly concentrated at Nodes of Ranvier.
• Pathogen Interaction: C. jejuni surface glycolipids antigenically cross-react with human gangliosides. Pathogenic C. jejuni sialic acid residues trigger Toll-like receptor 4 (TLR4) on dendritic cells, driving B-cell differentiation and amplifying humoral autoimmunity.
• Complement Activation: Autoantibody binding initiates complement cascade, forming Membrane-Attack Complex (MAC).

Pathophysiology by Subtype

Demyelinating Forms (AIDP)

• Target: Schwann cell surface.
• Mechanism: Widespread myelin damage, macrophage activation, lymphocytic infiltration.
• Result: Conduction block causing flaccid paralysis and sensory disturbance.
• Recovery: Axonal connections intact. Rapid recovery enabled by remyelination. Residual disability dictated by extent of secondary axonal damage.

Axonal Forms (AMAN/AMSAN)

• Target: Nodes of Ranvier (axolemma).
• Mechanism: IgG anti-GM1/GD1a autoantibodies bind nodal axolemma. MAC formation leads to disappearance of voltage-gated sodium (Nav) channel clusters and detachment of paranodal myelin.
• Result: Early reversible conduction block progressing to primary axonal degeneration.
• Progression: Macrophages invade periaxonal space, scavenging injured axons. Recovery slow and incomplete if extensive degeneration occurs.

Clinical Features

Motor Manifestations

• Paralysis: Rapidly evolving, flaccid, symmetrical, ascending weakness.
• Progression: Maximum weakness reached within 2 weeks (50-75% of cases) up to 4 weeks (90-98%).
• Topography: Lower limbs affected first, ascending to trunk, followed by upper limbs.
• Reflexes: Deep tendon reflexes (DTRs) attenuate or disappear within the first few days of onset.
• Cranial Nerves: Bilateral cranial nerve involvement frequent. Facial diparesis present in 50%. Facial nerve (VII) most commonly affected.
• Bulbar Weakness: Lower cranial nerve involvement causes difficulty handling secretions, dysphagia, maintaining airway (seen in ~50%).
• Respiratory Insufficiency: Thoracic muscle weakness necessitates mechanical ventilatory assistance in ~30% of patients.

Sensory Manifestations

• Paresthesia: Distal tingling dysesthesias frequent in extremities.
• Sensory Deficits: Cutaneous sensory deficits (pain/temperature) typically mild. Large sensory fiber functions (proprioception, vibration) more severely affected.
• Pain: Back, neck, shoulder, or diffuse spinal pain present early in ~50% of cases. Deep aching pain in weakened muscles resembles severe overexertion. Dysesthesia extremity pain prominent.

Autonomic Manifestations

• Incidence: Common, even in clinically mild motor disease.
• Cardiovascular: Loss of vasomotor control. Wide blood pressure fluctuations, postural hypotension, lethal cardiac dysrhythmias (tachycardia).
• Gastrointestinal/Genitourinary: Constipation, transient urinary retention, incontinence.

Clinical Subtypes of GBS

Subtype	Clinical Features	Electrophysiology/Pathology	Associated Antibodies
AIDP (Acute Inflammatory Demyelinating Polyneuropathy)	Adults > children. 90% of Western cases. Rapid recovery.	Demyelinating. Macrophage activation. Secondary axonal damage.	Anti-GM1 (<50%).
AMAN (Acute Motor Axonal Neuropathy)	Children/young adults. Preceded by C. jejuni. Motor weakness only.	Axonal. Primary axonal damage. Node of Ranvier conduction block.	Anti-GM1, Anti-GD1a.
AMSAN (Acute Motor-Sensory Axonal Neuropathy)	Adults > children. Severe. Delayed/incomplete recovery.	Axonal. Primary sensory and motor axonal degeneration.	Anti-GM1, Anti-GD1a.
MFS (Miller Fisher Syndrome)	Ataxia, areflexia, ophthalmoplegia.	Axonal or demyelinating.	Anti-GQ1b (90%), Anti-GT1a.
Regional Variants	Pure sensory, acute pandysautonomia, pharyngeal-cervical-brachial weakness.	Variable based on variant.	Anti-GT1a, Anti-GQ1b (bulbar variants).

Differential Diagnosis

Clinical Distinction Table

Feature	GBS	Poliomyelitis / Acute Flaccid Myelitis	Transverse Myelitis
Progression	Hours to 10–28 days.	24–48 hours to full paralysis.	Hours to 4 days.
Fever at Onset	Absent (fever casts doubt on Dx).	High, present at onset.	Rarely present.
Flaccidity Pattern	Acute, symmetrical, ascending (distal to proximal).	Acute, asymmetrical, proximal.	Acute, lower limbs, symmetrical.
Sensation	Tingling, hypoesthesia palms/soles, muscle pain.	Severe myalgia, backache. No sensory loss.	Anesthesia of lower limbs with defined sensory level.
CSF Profile	Albumino-cytological dissociation. WBC <50/cumm.	Pleocytosis. WBC high.	Protein high/normal. WBC high (<10).

Additional Mimics

• Spinal Cord Disease: Acute myelopathy. Strongly consider if early bowel/bladder dysfunction or distinct sensory level exists.
• Neuromuscular Junction Disorders: Myasthenia gravis, Botulism (pupillary reactivity lost early).
• Infectious Polyradiculitis: Lyme disease, CMV (in immunocompromised), HIV.
• Toxic/Metabolic: Porphyria (abdominal pain, psychosis), organophosphates, thallium, arsenic, severe hypophosphatemia.
• Vasculitic Neuropathy: Check erythrocyte sedimentation rate.

Diagnostic Evaluation

1. Cerebrospinal Fluid (CSF) Analysis

• Classic Finding: Albumino-cytological dissociation.
• Protein: Elevated >80 mg/dL (1–10 g/L). Often normal ≤48 hours post-onset; rises reliably by end of first week.
• Cells: Normal WBC count <10/cumm. Total WBC <50 cells/μL required for diagnostic certainty.
• Red Flags: Sustained pleocytosis (>50 cells/cumm) provides strong evidence against typical GBS. Mandates investigation for HIV, Lyme, CMV, neurosarcoidosis, or lymphomatous infiltration.

2. Electrodiagnostic Studies (EDx: NCS/EMG)

• Timing: Findings minimal early in course. Lags behind clinical evolution. Best performed 2-3 weeks post-onset.
• AIDP Features: Prolonged F-wave latencies, prolonged distal latencies, reduced compound muscle action potential (CMAP) amplitudes. Progression shows conduction slowing, conduction block, temporal dispersion.
• Axonal Features (AMAN/AMSAN): Reduced CMAP amplitudes (and SNAPs in AMSAN) without demyelinating features (no conduction slowing/prolonged distal latencies). Reflects conduction block or primary axonal degeneration.

3. Laboratory and Serologic Testing

• Autoantibodies: Antiganglioside antibodies (GQ1b strongly diagnostic for MFS).
• Pathogen Screening: Serology for Campylobacter jejuni. HIV, Hepatitis B/C, CMV, EBV screening indicated to exclude mimics, especially if CSF pleocytosis or atypical features exist.
• Metabolic: Screen for porphyria if abdominal pain, psychiatric illness, or profound dysautonomia present.

4. Brighton Collaboration Case Definitions (Validation Criteria)

• Level 1 (Highest Certainty):
  • Bilateral flaccid weakness of limbs.
  • Decreased/absent DTRs in weak limbs.
  • Monophasic illness pattern (onset to nadir 12h–28 days) followed by plateau.
  • EDx findings consistent with GBS.
  • Cytoalbuminologic dissociation (elevated protein + WBC <50 cells/μL).
  • Absence of alternative diagnosis.
• Level 2 & 3: Variations allowing diagnosis without full CSF or EDx confirmation if clinical criteria strictly met.

Management and Treatment

1. Specific Immunotherapy

• Timing: Initiate immediately upon diagnosis. Efficacy proven within 2–4 weeks of motor symptom onset. If patient reached plateau, treatment may lack benefit unless severe weakness persists.
• Intravenous Immunoglobulin (IVIg):
  • Status: Preferred initial therapy due to ease of administration and high safety profile.
  • Dose: 2.0 g/kg divided over 5 days (e.g., 0.4 g/kg/day).
  • Mechanism: Neutralizes pathogenic autoantibodies via anti-idiotypic interactions.
• Plasmapheresis (PLEX):
  • Status: Equally effective to IVIg.
  • Dose: 40–50 mL/kg plasma exchange, 4–5 times over 7–10 days.
  • Mechanism: Mechanical removal of circulating pathogenic autoantibodies.
• Efficacy: IVIg and PLEX reduce need for mechanical ventilation (from 27% to 14%) and increase likelihood of full recovery at 1 year (from 55% to 68%). Combination therapy (IVIg + PLEX) yields no additional benefit.
• Corticosteroids: Not recommended. Lack efficacy and may be detrimental to recovery.

2. Intensive Supportive Care

• Critical Care Monitoring: Mandatory during worsening phase.
• Respiratory Support: Continuous vital capacity monitoring. Intubation/mechanical ventilation required for progressive respiratory insufficiency. Early tracheotomy consideration (>2 weeks intubation). Chest physiotherapy crucial.
• Cardiovascular Support: Intensive monitoring of cardiac rhythm and blood pressure for dysautonomia.
• Prophylaxis: Deep-vein thrombosis (DVT) prophylaxis, nutrition management, frequent turning, meticulous skin care.
• Musculoskeletal: Daily range-of-motion exercises to prevent joint contractures.
• Pain Control: Dysesthetic and muscular pain managed with standard analgesics.

Prognosis and Complications

Recovery Timeline and Morbidity

• Functional Recovery: ~85% achieve full functional recovery within months to 1 year. Minor residual findings (areflexia, fatigue) may persist chronically.
• Mortality: <5% in optimal critical care settings. Death usually secondary to severe pulmonary complications, sepsis, or dysautonomia.

Poor Prognostic Factors

• Advanced age.
• Rapid fulminant attack progression.
• Delay in treatment initiation.
• Requirement for mechanical ventilation.
• Severe proximal motor and sensory axonal damage (primary or secondary) precluding successful regeneration.

Long-term Complications

• Relapses: 5–10% of patients with typical GBS experience late relapses.
• Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Diagnosis reconsidered if clinical deterioration continues >9 weeks post-onset, or if patient experiences ≥3 relapses. Shares demyelinating features but requires long-term immunosuppression (corticosteroids, IVIg, PLEX).