What is the diagnostic approach to Guillain-Barré Syndrome (GBS)?

Diagnostic Approach to Guillain-Barré Syndrome

The diagnosis of Guillain-Barré Syndrome (GBS) should be based primarily on clinical features including rapidly progressive bilateral weakness, decreased or absent reflexes, and preceding infection history, supported by cerebrospinal fluid analysis and electrodiagnostic studies. 1, 2

Clinical Presentation

• GBS typically presents with rapidly progressive bilateral weakness of the legs and/or arms, often in an ascending pattern, reaching maximum disability within 2 weeks 1, 3
• Decreased or absent reflexes in affected limbs are seen in most patients at presentation and almost all patients at nadir 1
• Distal paresthesias or sensory loss frequently precede or accompany weakness 2, 3
• Pain (muscular, radicular, or neuropathic) is a common symptom reported by patients 2
• Dysautonomia may occur, including blood pressure or heart rate instability, pupillary dysfunction, and bowel or bladder dysfunction 1, 3
• Cranial nerve involvement, especially bilateral facial weakness, is common 2
• History of recent infection (within 6 weeks) is present in approximately two-thirds of patients 3

Atypical Presentations

• Weakness and sensory signs, though always bilateral, can be asymmetrical or predominantly proximal or distal 1
• Some patients may present with normal or even exaggerated reflexes, particularly those with pure motor variants and acute motor axonal neuropathy (AMAN) 1, 4
• Young children (<6 years) often present with nonspecific features such as poorly localized pain, refusal to bear weight, irritability, or unsteady gait 1
• Clinical variants include pure motor variant, bilateral facial palsy with paresthesias, pharyngeal-cervical-brachial weakness, paraparetic variant, and Miller Fisher syndrome (ophthalmoplegia, areflexia, and ataxia) 1

Diagnostic Algorithm

Step 1: Clinical Assessment

• Document pattern and progression of weakness 2
• Assess tendon reflexes (typically decreased or absent) 1
• Evaluate for sensory symptoms 2
• Check for cranial nerve involvement 3
• Look for signs of autonomic dysfunction 1
• Inquire about preceding infections within 6 weeks 3

Step 2: Laboratory Testing

• Complete blood count, glucose, electrolytes, kidney function, and liver enzymes to exclude other causes 2
• Cerebrospinal fluid (CSF) examination:
  • Look for albumino-cytological dissociation (elevated protein with normal cell count) 1, 3
  • Important caveat: Normal CSF protein does not rule out GBS, especially early in the disease course 1, 2
• Anti-ganglioside antibody testing:
  • Limited value in typical GBS but helpful in uncertain diagnoses 2
  • Consider anti-GQ1b antibody testing when Miller Fisher syndrome is suspected 3
  • Test for nodal-paranodal antibodies when autoimmune nodopathy is suspected 5

Step 3: Electrodiagnostic Studies

• Nerve conduction studies and electromyography to:
  • Support the diagnosis of GBS, especially in atypical presentations 2, 3
  • Distinguish between subtypes: acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and acute motor sensory axonal neuropathy (AMSAN) 1
  • Important caveat: Normal initial electrodiagnostic studies do not rule out GBS 2

Step 4: Imaging (in select cases)

• MRI or ultrasound imaging should be considered in atypical cases 5
• Nerve root enhancement on gadolinium-enhanced MRI can support diagnosis, especially in young children 3

Important Diagnostic Considerations

• The progressive phase of GBS typically lasts from days to 4 weeks, usually less than 2 weeks 1, 2
• If maximum disability is reached within 24 hours or after 4 weeks, consider alternative diagnoses 1
• Consider changing the diagnosis to acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP) if progression continues after 8 weeks from onset (occurs in approximately 5% of patients initially diagnosed with GBS) 5
• GBS is a monophasic illness, though treatment-related fluctuations can occur 1
• Relapses of GBS occur in 2-5% of patients 1, 2

Common Pitfalls to Avoid

• Relying solely on CSF protein levels or waiting for antibody test results before initiating treatment 2
• Dismissing the diagnosis due to normal initial electrodiagnostic studies 2
• Failing to recognize atypical presentations, especially in young children 1, 2
• Missing the diagnosis in patients with preserved or hyperactive reflexes 4
• Delaying diagnosis and treatment due to incomplete clinical presentation early in the disease course 6
• Failure to monitor respiratory function, as respiratory failure can occur without symptoms of dyspnea 1

Prognostic Assessment

• Calculate modified Erasmus GBS outcome score (mEGOS) on admission to assess outcome 1, 5
• Use modified Erasmus GBS Respiratory Insufficiency Score (mEGRIS) to assess the risk of requiring artificial ventilation 5
• Recovery can continue for more than 3 years after onset 1