What are the diagnostic criteria for Guillain‑Barré syndrome?

Diagnostic Criteria for Guillain-Barré Syndrome

Guillain-Barré syndrome is diagnosed primarily on clinical grounds when a patient presents with rapidly progressive bilateral weakness, diminished or absent reflexes, and a monophasic disease course reaching maximum disability within 2–4 weeks. 1, 2

Core Clinical Features Required for Diagnosis

Essential Criteria

• Bilateral ascending weakness starting in the legs and progressing to the arms and cranial muscles is the hallmark feature, though weakness can occasionally start in the arms or occur simultaneously in all limbs 1, 3
• Decreased or absent deep-tendon reflexes in affected limbs are present in 91% of patients initially and in 100% during follow-up; however, normal or even exaggerated reflexes can persist in a minority of AMAN variant cases 1, 4, 5
• Acute or subacute onset with progression to maximum disability typically within 2 weeks (80% of patients) and almost always within 4 weeks (97% of patients) 1, 4
• Monophasic disease course occurs in 95% of patients, though treatment-related fluctuations occur in 6–10% 1, 4

Typical Associated Features

• Distal paresthesias or sensory loss often precede or accompany the weakness 1, 3
• Recent infection history within 6 weeks before symptom onset is reported in approximately two-thirds of patients and serves as an important diagnostic clue 1, 3
• Pain (muscular, radicular, or neuropathic) is frequently reported and affects approximately two-thirds of patients, often as an early symptom 1, 3
• Dysautonomia including blood pressure or heart rate instability, pupillary dysfunction, and bowel or bladder dysfunction is common 1, 3

Supportive Laboratory and Electrodiagnostic Findings

Cerebrospinal Fluid Analysis

• Albumino-cytological dissociation (elevated protein with normal cell count) is the classic CSF finding, but is present in only 64% of patients overall and is highly timing-dependent 2, 4
• CSF protein is elevated in only 49% of patients on day 1, increasing to 88% after 2 weeks—do not exclude GBS based on normal CSF protein in the first week 2, 4
• Mild pleocytosis (5–50 cells/μL) is found in 15% of patients; marked CSF pleocytosis (>50 cells/μL) should prompt reconsideration toward infectious or inflammatory myelitis 4, 2

Electrodiagnostic Studies

• Nerve conduction studies and EMG are compatible with neuropathy in 99% of patients but only 59% fulfill criteria for a distinct electrophysiological subtype at initial testing 4
• "Sural sparing pattern" (normal sural sensory nerve action potential with abnormal median/ulnar responses) is a typical and specific electrodiagnostic feature 2
• Electrodiagnostic studies may be normal in the first week; repeat testing after 2–3 weeks if initial studies are nondiagnostic and clinical suspicion remains high 2, 6
• The sensitivity of electrophysiological criteria (85–87.5%) is lower than clinical criteria, particularly in early stages 6

Clinical Variants to Recognize

Common Variants

• Classic sensorimotor GBS (30–85% of cases): bilateral ascending weakness with sensory signs and areflexia 2
• Pure motor variant (5–70% of cases): motor weakness without sensory symptoms; reflexes may be normal or exaggerated in AMAN subtype 2, 5
• Miller Fisher syndrome (5–25% of cases): characterized by ophthalmoplegia, ataxia, and areflexia; anti-GQ1b antibodies present in up to 90% 2

Regional Variants

• Bilateral facial palsy with paresthesias: weakness limited to cranial nerves 2
• Pharyngeal-cervical-brachial weakness: involvement of upper limbs and bulbar muscles 2
• Paraparetic variant: weakness limited to lower limbs 2

Features That Should Prompt Reconsideration of Diagnosis

• Marked persistent asymmetry of weakness 2
• Bladder dysfunction at onset 2
• Marked CSF pleocytosis (>50 cells/μL) 2, 4
• Progression beyond 4 weeks without plateau should raise consideration of alternative diagnoses 1
• Progression continuing after 8 weeks or three or more treatment-related fluctuations suggests acute-onset CIDP rather than GBS (occurs in ~5% of initial GBS diagnoses) 2

Practical Diagnostic Algorithm

1. Establish clinical diagnosis based on bilateral progressive weakness, areflexia, and acute/subacute onset 1, 3
2. Obtain immediate neurology consultation for every suspected case 2
3. Perform lumbar puncture to look for albumino-cytological dissociation and exclude alternative diagnoses (meningitis, malignancy) 2
4. Order nerve conduction studies and EMG to support diagnosis and classify subtype, but do not delay treatment awaiting results 2
5. Do not wait for antiganglioside antibody results before initiating immunotherapy if clinical suspicion is high 2
6. Obtain MRI of spine with contrast to exclude compressive lesions and assess for nerve root enhancement 2

Common Diagnostic Pitfalls

• Dismissing GBS due to normal CSF protein in the first week—protein elevation is timing-dependent and may not appear until week 2 2, 4
• Requiring absent reflexes in all cases—the AMAN variant can present with normal or exaggerated reflexes 5
• Waiting for electrodiagnostic confirmation—clinical criteria are more sensitive than electrophysiological criteria, especially early in the disease course 6
• Missing atypical presentations in young children (<6 years old) who may present with poorly localized pain, refusal to bear weight, irritability, or unsteady gait rather than obvious weakness 1
• Bilateral simultaneous facial weakness is extremely rare in Bell's palsy and should immediately raise suspicion for GBS 2

Brighton Collaboration Diagnostic Certainty Levels

When complete data are available, patients can be classified into Brighton levels of diagnostic certainty (Level 1 = highest certainty to Level 4 = lowest certainty), though patients across all levels show similar clinical characteristics and outcomes 4. In the validation study, 61% met Level 1 criteria, 33% Level 2, and 6% Level 4 4.