What are the diagnostic criteria for Guillain‑Barré syndrome?

Diagnostic Criteria for Guillain-Barré Syndrome

GBS diagnosis requires progressive bilateral limb weakness plus decreased or absent reflexes in affected limbs, supported by specific clinical, laboratory, and electrophysiological features that distinguish it from mimics. 1

Core Required Features

The diagnosis of GBS fundamentally depends on two mandatory clinical findings 1:

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

These features alone are insufficient for diagnosis but form the essential foundation upon which additional supportive criteria build diagnostic confidence.

Strongly Supportive Features

The following features significantly increase diagnostic certainty when present 1:

Temporal Pattern

• Progressive phase lasting days to 4 weeks (typically <2 weeks)
• Patients reaching maximum disability within 24 hours or after 4 weeks should prompt consideration of alternative diagnoses
• Monophasic clinical course (though treatment-related fluctuations occur in ~10% and relapses in a minority)

Clinical Characteristics

• Relative symmetry of symptoms and signs (though bilateral weakness can be asymmetrical)
• Weakness typically starts distally in legs, ascending to arms and cranial muscles
• Relatively mild sensory symptoms (distal paresthesias or sensory loss; absent in pure motor variant)
• Bilateral facial palsy or other cranial nerve involvement
• Autonomic dysfunction (blood pressure/heart rate instability, pupillary dysfunction, bowel/bladder dysfunction)
• Pain (muscular, radicular, or neuropathic) - frequently reported

Laboratory Findings

• Elevated CSF protein with normal cell count (albuminocytological dissociation)
  • Critical caveat: Protein is normal in 30-50% of patients in the first week and 10-30% in the second week
  • Normal CSF protein does NOT rule out GBS 1
  • Marked pleocytosis (>50 cells/μl) suggests alternative diagnoses
  • Mild pleocytosis (10-50 cells/μl) is compatible with GBS but warrants consideration of infectious polyradiculitis

Electrophysiological Features

• Sensorimotor polyradiculoneuropathy or polyneuropathy pattern
• Reduced conduction velocities, reduced amplitudes, abnormal temporal dispersion, or partial motor conduction blocks
• "Sural sparing pattern" (normal sural sensory nerve action potential with abnormal median/ulnar potentials) is typical
• Important limitation: Electrophysiology may be normal within 1 week of onset, in proximal weakness, mild disease, or certain variants
• Repeat testing at 2-3 weeks can be helpful if initial studies are normal 1

Preceding Events

• Antecedent infection in preceding 6 weeks (~67% of patients) 1
• Six pathogens with established temporal association: Campylobacter jejuni, cytomegalovirus, hepatitis E virus, Mycoplasma pneumoniae, Epstein-Barr virus, Zika virus
• Absence of antecedent illness does NOT exclude GBS (infections can be subclinical)

Red Flags That Cast Doubt on Diagnosis

These features should prompt reconsideration of the diagnosis 1:

• Marked CSF pleocytosis (>50 cells/μl)
• Marked, persistent asymmetry of weakness
• Bladder or bowel dysfunction at onset or persistent during disease course
• Severe respiratory dysfunction with limited limb weakness at onset
• Sensory signs with limited weakness at onset
• Fever at onset
• Nadir reached in <24 hours
• Sharp sensory level (suggests spinal cord injury)
• Hyper-reflexia, clonus, or extensor plantar responses
• Continued progression >4 weeks after symptom onset (consider acute-onset CIDP in ~5% of cases) 2
• Altered consciousness (except in Bickerstaff brainstem encephalitis)

Recognized Clinical Variants

Several distinct variants exist that may not fulfill classic criteria but are part of the GBS spectrum 1:

• Pure motor variant (weakness without sensory signs; may have normal or exaggerated reflexes in AMAN subtype)
• Miller Fisher syndrome (ophthalmoplegia, areflexia, ataxia; anti-GQ1b antibodies)
• Pharyngeal-cervical-brachial weakness (upper limb predominant)
• Paraparetic variant (lower limb predominant)
• Bilateral facial palsy with paresthesias

Special Diagnostic Considerations

Pediatric Presentations

Children <6 years may present atypically with 1:

• Poorly localized pain
• Refusal to bear weight
• Irritability
• Meningism
• Unsteady gait

Failure to recognize these as early GBS can delay diagnosis.

Diagnostic Utility of Testing

• Anti-ganglioside antibody testing: Limited value in typical motor-sensory GBS 2
• Anti-GQ1b antibody testing: Should be considered when Miller Fisher syndrome is suspected 2
• Nodal-paranodal antibodies: Test when autoimmune nodopathy is suspected 2
• MRI or ultrasound imaging: Consider in atypical cases 2

Practical Diagnostic Approach

The 2023 EAN/PNS guidelines emphasize that GBS diagnosis is primarily clinical 2. While supportive testing (CSF, electrophysiology) strengthens diagnostic confidence, these tests are not required for diagnosis and should not delay treatment in typical presentations. The sensitivity of clinical criteria exceeds that of electrophysiological criteria, particularly in early stages 3.

In resource-limited settings where nerve conduction studies are unavailable, clinical criteria alone may be sufficient for diagnosis and treatment initiation 3. However, electrodiagnostic studies should be performed wherever possible to support the diagnosis, particularly in atypical presentations 1.