What are the diagnostic criteria for Guillain‑Barré syndrome?

Diagnostic Criteria for Guillain-Barré Syndrome

The diagnosis of GBS rests on two required clinical features: progressive bilateral weakness of arms and legs (initially only legs may be involved) and absent or decreased tendon reflexes in affected limbs at some point during the clinical course. 1

Required Features for Diagnosis

The following two features must be present to diagnose GBS:

• Progressive bilateral weakness of arms and legs, though initially only the legs may be involved 1, 2
• Absent or decreased tendon reflexes in affected limbs, which must occur at some point in the clinical course (91% at presentation, 100% during follow-up) 1, 3

Features That Strongly Support the Diagnosis

Once the required features are present, the following characteristics strengthen diagnostic confidence:

• Progressive phase lasting days to 4 weeks (usually <2 weeks), with 80% reaching nadir within 2 weeks and 97% within 4 weeks 1, 3
• Relative symmetry of symptoms and signs 1
• Relatively mild sensory symptoms and signs (absent in pure motor variant) 1, 2
• Cranial nerve involvement, especially bilateral facial palsy 1, 2
• Autonomic dysfunction 1, 2
• Muscular or radicular back or limb pain 1, 2
• Increased CSF protein level (albumino-cytological dissociation), though normal protein levels do not rule out diagnosis—only 49% have elevated protein on day 1, increasing to 88% after 2 weeks 1, 2, 3
• Electrodiagnostic features of motor or sensorimotor neuropathy, including reduced conduction velocities, reduced amplitudes, temporal dispersion, or conduction blocks; normal electrophysiology early does not rule out diagnosis 1, 2
• "Sural sparing pattern" on nerve conduction studies (normal sural sensory nerve action potential with abnormal median/ulnar responses) 1, 2, 4

Features That Cast Doubt on the Diagnosis

The presence of these features should prompt reconsideration of GBS and evaluation for alternative diagnoses:

• Marked CSF pleocytosis (>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 <24 hours 1
• Sharp sensory level indicating spinal cord injury 1
• Hyper-reflexia or clonus 1
• Extensor plantar responses 1
• Continued progression for >4 weeks after start of symptoms 1
• Alteration of consciousness (except in Bickerstaff brainstem encephalitis) 1

Essential Diagnostic Testing

Cerebrospinal Fluid Analysis

• Perform lumbar puncture to identify albumino-cytological dissociation (elevated protein with normal cell count) 1, 2, 4
• Do not exclude GBS based on normal CSF protein in the first week—only 49% have elevated protein on day 1,64% overall, and 88% after 2 weeks 1, 3
• Mild pleocytosis (10-50 cells/μl) is compatible with GBS but should prompt consideration of alternative diagnoses; marked pleocytosis (>50 cells/μl) suggests other pathologies 1

Electrodiagnostic Studies

• Not required for diagnosis but strongly recommended to support clinical suspicion, especially in atypical presentations 1, 2
• Typical findings include sensorimotor polyradiculoneuropathy with reduced conduction velocities, reduced amplitudes, abnormal temporal dispersion, and/or partial motor conduction blocks 1, 2
• Repeat studies in 2-3 weeks if initial studies are normal but clinical suspicion remains high, as electrophysiology may be normal within the first week 1, 2
• Only 59% of patients fulfill criteria for a distinct electrophysiological subtype (AIDP, AMAN, or AMSAN) 3

Laboratory Testing

• Complete blood count, glucose, electrolytes, kidney function, and liver enzymes to exclude metabolic or electrolyte causes of weakness 1, 2
• Anti-ganglioside antibody testing has limited diagnostic value in classical GBS; a positive result is helpful when diagnosis is uncertain, but a negative result does not rule out GBS 1, 2
• Anti-GQ1b antibodies are found in up to 90% of patients with Miller Fisher syndrome and have greater diagnostic value in this variant 1, 2

Imaging

• MRI is not part of routine diagnostic evaluation but can help exclude differential diagnoses such as brainstem infection, spinal cord inflammation, or leptomeningeal malignancy 1
• Nerve root enhancement on gadolinium-enhanced MRI is a sensitive but nonspecific finding that can support the diagnosis 1

Clinical Variants to Recognize

• Classic sensorimotor GBS (30-85% of cases): rapidly progressive symmetrical weakness and sensory signs with absent or reduced reflexes 2, 4
• Pure motor variant (5-70% of cases): motor weakness without sensory signs 2
• Miller Fisher syndrome (5-25% of cases): ophthalmoplegia, ataxia, and areflexia with anti-GQ1b antibodies in up to 90% 1, 2, 4

Practical Diagnostic Algorithm

1. Identify bilateral progressive weakness with reduced or absent reflexes 2
2. Evaluate supporting characteristics: progression <4 weeks, relative symmetry, mild sensory symptoms, cranial nerve involvement 1, 2
3. Perform lumbar puncture to look for albumino-cytological dissociation, but do not exclude GBS if protein is normal in the first week 1, 2
4. Perform electrodiagnostic studies to confirm and classify the subtype, repeating in 2-3 weeks if initially normal 1, 2
5. Exclude alternative diagnoses using laboratory tests and, if necessary, imaging studies 1, 2
6. Consider clinical variants if the presentation is atypical 2

Common Pitfalls to Avoid

• Do not dismiss GBS based on normal CSF protein in the first week—protein elevation lags clinical onset 1, 3
• Do not wait for antibody test results before starting treatment if clinical suspicion is high 1
• Do not exclude GBS based on normal electrophysiology in the first week—repeat testing after 2-3 weeks 1, 2
• Recognize that clinical criteria are more sensitive than electrophysiological criteria, especially in early stages—clinical diagnosis alone may be sufficient when nerve conduction studies are unavailable 5
• Bilateral simultaneous facial weakness is extremely rare in Bell's palsy and should immediately raise suspicion for GBS 1