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

Differential Diagnosis

Clinical Distinction Table

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).