Guillain-Barré Syndrome

Guillain‑Barré Syndrome (GBS) – High‑Yield Study Guide for Medical Students

Definition

Guillain‑Barré Syndrome (GBS) is an acute, immune-mediated polyradiculoneuropathy characterized by rapidly progressive, typically symmetric weakness with diminished or absent deep tendon reflexes. It usually follows an infectious trigger and can lead to life-threatening respiratory failure and autonomic instability.

Epidemiology

GBS is the most common cause of acute flaccid paralysis in many developed countries.

• Incidence: approximately 1–2 cases per 100,000 persons per year.
• Can occur at any age; incidence increases with age.
• Slight male predominance.
• Often preceded by an infection 1–4 weeks prior, most commonly Campylobacter jejuni gastroenteritis, respiratory viral infections, CMV, EBV, HIV, and others.
• Seasonal variation may be seen in some regions, often correlating with infectious triggers.

Pathophysiology

GBS is driven by an aberrant immune response, most often triggered by an antecedent infection or, rarely, vaccination or surgery. The predominant mechanism is immune-mediated demyelination or axonal injury of peripheral nerves and nerve roots.

• Molecular mimicry: Antibodies generated against microbial antigens cross-react with gangliosides or other components on peripheral nerves (e.g., GM1, GD1a, GQ1b).
• Inflammation: Complement activation and inflammatory cell infiltration (macrophages, T cells) result in segmental demyelination, conduction block, and in some variants, primary axonal degeneration.
• Subtypes:
  • AIDP (Acute Inflammatory Demyelinating Polyradiculoneuropathy): The classic and most common form in Europe and North America; primary demyelinating process.
  • AMAN (Acute Motor Axonal Neuropathy): Predominantly motor axonal damage; more common in East Asia and Latin America; strongly associated with C. jejuni.
  • AMSAN (Acute Motor and Sensory Axonal Neuropathy): Axonal involvement of both motor and sensory fibers; usually more severe with slower recovery.
  • Miller Fisher syndrome (MFS): Variant characterized by ophthalmoplegia, ataxia, and areflexia; associated with anti-GQ1b antibodies.

Clinical Presentation

Classically, GBS presents as acute to subacute, ascending symmetric weakness with areflexia, often following an infection by 1–4 weeks.

Typical Symptoms and Signs

• Motor:
  • Progressive, relatively symmetric limb weakness, typically starting in the legs and ascending proximally.
  • Difficulty climbing stairs, rising from a chair, or walking; may progress to quadriparesis or quadriplegia.
  • Decreased or absent deep tendon reflexes (areflexia or hyporeflexia) early and prominent.
• Sensory:
  • Distal paresthesias (tingling, numbness) in hands and feet.
  • Subjective sensory symptoms often exceed objective deficits.
  • Mild sensory loss to vibration or pinprick; severe sensory loss is less typical but can occur, especially with axonal forms.
• Cranial nerve involvement:
  • Facial weakness (often bilateral facial palsy) is common.
  • Dysphagia, dysarthria due to bulbar muscle involvement.
  • Ophthalmoplegia in Miller Fisher syndrome.
• Autonomic dysfunction:
  • Fluctuating blood pressure (hypertension or hypotension).
  • Cardiac arrhythmias (bradycardia, tachyarrhythmias, heart block).
  • Urinary retention, ileus, constipation, abnormal sweating.
• Pain:
  • Deep aching pain in back or limbs, radicular pain, or neuropathic pain is frequent and may precede weakness.

Time Course

• GBS is typically monophasic.
• Symptoms usually progress over days to 4 weeks, with most patients reaching maximal weakness by 2–3 weeks.
• A plateau phase follows, then gradual recovery over weeks to months (sometimes longer than a year, particularly in axonal forms).

Red Flags and Severity Indicators

• Rapid progression of weakness (inability to walk independently).
• Bulbar involvement (dysphagia, weak cough, pooling of secretions).
• Respiratory muscle weakness (dyspnea, orthopnea, reduced vital capacity).
• Marked autonomic instability (labile blood pressure, arrhythmias).

Diagnosis

Diagnosis of GBS is primarily clinical, supported by electrophysiological studies and cerebrospinal fluid (CSF) analysis, and by excluding important mimics.

Diagnostic Approach

• Clinical criteria:
  • Progressive weakness in more than one limb.
  • Areflexia or hyporeflexia in affected limbs.
  • Monophasic course with a time to nadir of 4 weeks or less.
• Cerebrospinal fluid (CSF):
  • Typical finding: albuminocytologic dissociation – elevated CSF protein with normal or only mildly elevated WBC count.
  • CSF protein may be normal in the first week and elevated thereafter; repeat lumbar puncture can be helpful if early.
  • Marked pleocytosis should prompt evaluation for alternative diagnoses (e.g., infectious polyradiculitis, HIV, malignancy).
• Nerve conduction studies (NCS) and electromyography (EMG):
  • Demonstrate features of demyelination in AIDP: prolonged distal motor latencies, slowed conduction velocities, conduction block, temporal dispersion, prolonged or absent F-waves.
  • Axonal variants show reduced CMAP amplitudes with relatively preserved conduction velocities early.
  • Studies may be normal in the very early phase; repeat testing can be diagnostically valuable.
• Laboratory tests:
  • Routine blood tests to rule out metabolic or systemic causes of weakness (e.g., electrolytes, CK, thyroid studies, B12).
  • Serologic testing for recent infections (e.g., C. jejuni, CMV, HIV) may be considered but is not required for diagnosis.
  • Ganglioside antibodies (e.g., anti-GM1, anti-GQ1b) can support diagnosis in specific variants such as Miller Fisher syndrome.
• Imaging:
  • Spinal MRI may show nerve root enhancement but is primarily used to exclude other causes (e.g., cord compression, transverse myelitis).

Differential Diagnosis

• Acute transverse myelitis.
• Spinal cord compression (epidural abscess, hematoma, tumor).
• Myasthenia gravis or myasthenic crisis.
• Botulism.
• Diphtheritic neuropathy.
• Tick paralysis.
• Acute myopathy (e.g., polymyositis, critical illness myopathy, rhabdomyolysis).
• Periodic paralysis due to electrolyte disturbances.

Management

Management focuses on immunotherapy, meticulous supportive care (especially respiratory and autonomic), and rehabilitation. Early recognition and treatment improve outcomes.

Initial Assessment and Monitoring

• Assess degree of weakness, cranial nerve involvement, and functional status (e.g., ability to walk independently, swallow, cough).
• Monitor respiratory function: serial measurement of vital capacity, negative inspiratory force (NIF), and signs of impending respiratory failure (tachypnea, use of accessory muscles, paradoxical breathing).
• Continuous cardiac and blood pressure monitoring in patients with significant weakness or autonomic involvement.

Specific Immunotherapy

• Intravenous immunoglobulin (IVIG):
  • Standard regimen: 0.4 g/kg/day for 5 days.
  • Mechanisms include neutralization of pathogenic antibodies, modulation of Fc receptors, and suppression of complement-mediated damage.
  • As effective as plasma exchange when started within 2 weeks of onset of weakness in most patients.
  • Adverse effects: headache, aseptic meningitis, thromboembolic events, renal dysfunction (especially with sucrose-containing preparations).
• Plasma exchange (plasmapheresis):
  • Typically 4–6 exchanges over 1–2 weeks.
  • Removes circulating antibodies and complement components.
  • Most beneficial when started within 4 weeks of onset, especially in non-ambulatory patients.
  • Requires central venous access and experienced staff; may cause hypotension, sepsis, bleeding, or electrolyte disturbances.
• Corticosteroids:
  • Systemic steroids alone have not shown clear benefit in classic GBS and are not recommended as monotherapy.
• Combination therapy:
  • Combining IVIG and plasma exchange sequentially has not consistently shown additional benefit over either treatment alone and is not routinely recommended.

Supportive Care

• Respiratory support:
  • Frequent monitoring of vital capacity and NIF to anticipate need for ventilatory support.
  • Early involvement of critical care and respiratory therapy in patients with rapidly progressive weakness, bulbar symptoms, or reduced vital capacity.
• Autonomic dysfunction:
  • Monitor for arrhythmias and blood pressure instability.
  • Use short-acting agents for blood pressure control; avoid drugs that cause excessive hypotension or bradycardia.
• Pain management:
  • Neuropathic pain can be treated with agents such as gabapentin, pregabalin, or low-dose tricyclics, with attention to side-effect profiles.
  • Use opioids judiciously if needed.
• Prevention of complications:
  • Deep vein thrombosis prophylaxis with pharmacologic anticoagulation and mechanical methods in non-ambulatory patients.
  • Pressure ulcer prevention with frequent repositioning and appropriate mattresses.
  • Bladder and bowel care, including intermittent catheterization if urinary retention is present.
  • Nutrition support, including enteral feeding if bulbar dysfunction limits oral intake.
• Rehabilitation:
  • Early involvement of physical and occupational therapy to maintain joint range of motion and prevent contractures.
  • Progressive strengthening and functional training during recovery phase.

Prognosis

• Most patients survive and recover the ability to walk independently within 6–12 months.
• Mortality is generally low with modern intensive care but remains significant in severe cases, often due to respiratory or autonomic complications.
• Residual deficits (fatigue, distal weakness, neuropathic pain) are common, especially in axonal variants or in patients with severe initial disease.

Key Clinical Pearls (High‑Yield for Exams)

• Classic triad: rapidly progressive ascending weakness, areflexia, and recent infection (often diarrheal from Campylobacter jejuni).
• Red flag: any signs of respiratory compromise or bulbar involvement require close monitoring and potential airway support.
• CSF hallmark: albuminocytologic dissociation – high protein with normal or mildly elevated WBC count; may be absent in the first week.
• NCS/EMG: demyelinating features (slowed conduction, conduction block, prolonged F waves) support AIDP; low CMAP amplitudes suggest axonal variants.
• Immunotherapy: IVIG or plasmapheresis shortens time to recovery; steroids alone are not effective.
• GBS vs. myasthenia gravis: GBS has areflexia and sensory symptoms; MG has normal reflexes and no sensory involvement, with fluctuating weakness and fatiguability.
• Miller Fisher syndrome: triad of ophthalmoplegia, ataxia, and areflexia; associated with anti-GQ1b antibodies and considered a GBS variant.
• Course: monophasic; time to nadir usually <4 weeks; beware of alternative diagnoses in relapsing or chronic progression (e.g., CIDP).
• Exam tip: “Acute flaccid paralysis with areflexia and albuminocytologic dissociation” is almost always pointing to GBS in board-style questions.

Summary for Medical Students

Guillain‑Barré Syndrome is a monophasic, immune-mediated polyradiculoneuropathy that presents with acute to subacute, ascending weakness, areflexia, and frequent sensory symptoms following an infectious trigger. Early recognition, prompt initiation of IVIG or plasmapheresis, and careful monitoring for respiratory and autonomic complications are crucial. Understanding the classic clinical pattern, CSF and NCS findings, and key variants like Miller Fisher syndrome is high-yield for exams and clinical practice.