What are the diagnostic criteria for Guillain-Barré Syndrome?

Diagnostic Criteria for Guillain-Barré Syndrome

The diagnosis of Guillain-Barré syndrome requires progressive bilateral weakness of the limbs with absent or decreased tendon reflexes, supported by cerebrospinal fluid analysis showing elevated protein with normal cell count and electrodiagnostic studies demonstrating peripheral nerve dysfunction. 1

Required Features for Diagnosis

The two essential criteria that must be present are: 1

• Progressive bilateral weakness of arms and legs (initially only legs may be involved)
• Absent or decreased tendon reflexes in affected limbs at some point during the clinical course

Features That Strongly Support the Diagnosis

These findings significantly increase diagnostic certainty when present alongside the required features: 1

• Progressive phase lasting days to 4 weeks (usually <2 weeks) 1
• Relative symmetry of symptoms and signs 1
• Mild sensory symptoms and signs (absent in pure motor variant) 1
• Cranial nerve involvement, especially bilateral facial palsy 1
• Autonomic dysfunction including blood pressure/heart rate instability 1, 2
• Muscular or radicular back or limb pain 1, 2
• Increased CSF protein with normal cell count (albumino-cytological dissociation) - though normal protein levels do not rule out diagnosis, particularly in the first week when 30-50% may have normal CSF 1, 3, 2
• Electrodiagnostic features of motor or sensorimotor neuropathy - normal electrophysiology early in disease does not exclude GBS 1, 3

Features That Cast Doubt on the Diagnosis

These findings should prompt consideration of alternative diagnoses: 1

• Elevated CSF cell count (>50 × 10⁶/L mononuclear or polymorphonuclear cells) 1
• Marked, persistent asymmetry of weakness 1
• Bladder or bowel dysfunction at onset or persistent during disease course 1
• Severe respiratory dysfunction with limited limb weakness at onset 1
• Sensory signs with limited weakness at onset 1
• Fever at onset 1
• Nadir reached in <24 hours 1
• Sharp sensory level indicating spinal cord injury 1
• Hyper-reflexia, clonus, or extensor plantar responses 1
• Continued progression >4 weeks after symptom onset 1
• Altered consciousness (except in Bickerstaff brainstem encephalitis variant) 1

Diagnostic Approach Algorithm

Step 1: Clinical History - Look for antecedent infection (diarrhea or respiratory illness) within 1-4 weeks before symptom onset 2, 4

Step 2: Neurological Examination - Document ascending bilateral symmetric weakness pattern (legs → arms → cranial nerves), assess reflexes in all limbs, test for sensory deficits, examine cranial nerves particularly for bilateral facial weakness, and check for autonomic signs 1, 2

Step 3: CSF Analysis - Perform lumbar puncture to demonstrate albumino-cytological dissociation (elevated protein with normal cell count <50 × 10⁶/L), though this may be absent in the first week 1, 3, 4

Step 4: Electrodiagnostic Studies - Conduct nerve conduction studies to demonstrate peripheral nerve dysfunction and classify subtypes (AIDP, AMAN, AMSAN), recognizing that studies may be normal early in disease and should be repeated 3-8 weeks after onset if initially equivocal 1, 3, 4

Step 5: Respiratory Assessment - Measure vital capacity and negative inspiratory force as respiratory failure can occur rapidly without obvious dyspnea in 20% of patients 2, 4

Important Clinical Variants

The diagnosis must account for several recognized variants that may not meet all typical criteria: 1

• Pure motor variant (5-70% of cases) - motor weakness without sensory signs 1
• Miller Fisher syndrome (5-25% of cases) - ophthalmoplegia, ataxia, and areflexia 1, 2
• Paraparetic variant (5-10% of cases) - weakness restricted to legs 1
• Pharyngeal-cervical-brachial variant (<5% of cases) - weakness of pharyngeal, cervical and brachial muscles without lower limb involvement 1

Critical Diagnostic Pitfalls

Timing of investigations matters: CSF protein may be normal in 30-50% of patients during the first week, and electrodiagnostic studies can be normal early in the disease course 3, 4. Do not exclude GBS based on normal early investigations.

Reflexes can be preserved initially: Approximately 10% of patients have normal or brisk deep tendon reflexes at presentation, though almost all develop areflexia at nadir 2. Early preserved reflexes do not exclude the diagnosis.

Children present atypically: Pediatric patients may present with pain, refusal to walk, or abnormal gait rather than classic ascending weakness, and GBS is correctly diagnosed at admission in only one-third of preschool-aged children 1.

Consider A-CIDP: If progression continues beyond 8 weeks from onset, change the diagnosis to acute-onset chronic inflammatory demyelinating polyradiculoneuropathy, which occurs in approximately 5% of patients initially diagnosed with GBS 4.