What are the symptoms and diagnostic methods of Guillain-Barré Syndrome (GBS)?

Guillain-Barré Syndrome: Symptoms and Diagnostic Methods

Guillain-Barré syndrome (GBS) is characterized by rapidly progressive bilateral weakness of the limbs, typically starting in the legs and ascending to the arms and cranial muscles, accompanied by decreased or absent reflexes and often preceded by an infection. 1

Clinical Presentation

Typical Symptoms

• Rapidly progressive bilateral weakness of legs and/or arms, typically ascending from legs to arms and cranial muscles 1
• Decreased or absent reflexes in affected limbs 1
• Distal paresthesias or sensory loss preceding or accompanying weakness 1
• Pain (muscular, radicular, or neuropathic) is frequently reported 1
• Dysautonomia, including blood pressure or heart rate instability, pupillary dysfunction, and bowel or bladder dysfunction 1
• Acute or subacute onset with maximum disability typically reached within 2 weeks 1

Atypical Presentations

• Asymmetrical weakness (though always bilateral) 1
• Predominantly proximal or distal weakness 1
• Weakness starting in arms, legs, or simultaneously in all limbs 1
• Severe diffuse pain or isolated cranial nerve dysfunction preceding weakness 1
• In young children (<6 years): poorly localized pain, refusal to bear weight, irritability, meningism, unsteady gait 1
• Normal or exaggerated reflexes in some patients with pure motor variant and AMAN subtype 1

Clinical Variants

• Pure motor variant: weakness without sensory signs 1
• Miller Fisher syndrome (MFS): ophthalmoplegia, areflexia, and ataxia 1
• Pharyngeal-cervical-brachial weakness: weakness limited to upper limbs 1
• Paraparetic variant: weakness limited to lower limbs 1
• Bilateral facial palsy with paresthesias: weakness limited to cranial nerves 1

Diagnostic Methods

Clinical Evaluation

• History of recent infection (about two-thirds of patients report symptoms of infection in the 6 weeks preceding GBS) 1
• Neurological examination showing progressive bilateral weakness and reduced/absent reflexes 1
• Monitoring disease progression (maximum disability within 2 weeks is typical; if <24h or >4 weeks, consider alternative diagnoses) 1

Cerebrospinal Fluid (CSF) Analysis

• Classic finding: albumino-cytological dissociation (elevated protein level with normal cell count) 1
• Important caveat: protein levels may be normal in 30-50% of patients in the first week and 10-30% in the second week 1
• Marked pleocytosis (>50 cells/μl) suggests alternative diagnoses 1
• Mild pleocytosis (10-50 cells/μl) is compatible with GBS but should prompt consideration of alternative diagnoses 1

Electrodiagnostic Studies

• Not required for diagnosis but helpful in supporting it, especially in atypical presentations 1
• Typically reveals sensorimotor polyradiculoneuropathy or polyneuropathy 1
• Findings include: reduced conduction velocities, reduced sensory and motor evoked amplitudes, abnormal temporal dispersion, and/or partial motor conduction blocks 1
• "Sural sparing pattern" is characteristic (normal sural sensory nerve action potential with abnormal median and ulnar sensory nerve action potentials) 1
• May be normal early in disease course (within 1 week of onset) or in mild cases 1
• Can distinguish between subtypes: AIDP (acute inflammatory demyelinating polyradiculoneuropathy), AMAN (acute motor axonal neuropathy), and AMSAN (acute motor sensory axonal neuropathy) 1
• Consider repeat testing after 2-3 weeks if initial results are normal but clinical suspicion remains high 1

Imaging

• MRI is not part of routine evaluation but can help exclude differential diagnoses 1
• Nerve root enhancement on gadolinium-enhanced MRI can support GBS diagnosis, especially in young children 1
• Ultrasound imaging may show enlarged cervical nerve roots early in disease course 1

Antibody Testing

• Anti-ganglioside antibodies may be present in a subgroup of patients 1, 2
• Anti-GQ1b antibodies are particularly associated with Miller Fisher syndrome 2

Diagnostic Pitfalls and Caveats

• Normal CSF protein does not rule out GBS, especially early in the disease course 1
• Normal electrophysiological findings early in disease course do not exclude the diagnosis 1
• Features that cast doubt on diagnosis include: marked CSF pleocytosis, persistent asymmetry of weakness, bladder/bowel dysfunction at onset, sharp sensory level, hyperreflexia, extensor plantar responses, fever at onset, and continued progression for >4 weeks 1
• Consider alternative diagnoses if maximum disability is reached within 24 hours or after 4 weeks from onset 1
• About 5% of patients initially diagnosed with GBS may develop chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with acute onset 2, 3
• Treatment-related fluctuations (TRFs) occur in 6-10% of patients within 2 months following initial improvement 1