What are the diagnostic criteria for Guillain Barre (Guillain-Barré) syndrome?

Diagnosis of Guillain-Barré Syndrome

Guillain-Barré syndrome is diagnosed primarily through clinical recognition of bilateral progressive weakness with reduced or absent reflexes, supported by cerebrospinal fluid analysis showing albumino-cytological dissociation and electrophysiological studies demonstrating peripheral nerve dysfunction. 1

Core Clinical Diagnostic Features

The diagnosis rests fundamentally on pattern recognition from the patient history and neurological examination 2, 1:

• Bilateral progressive weakness starting in the legs and ascending to arms and cranial muscles, with patients typically reaching maximum disability within 2 weeks 2, 3
• Absent or reduced tendon reflexes in affected limbs, present in most patients at presentation and almost all at nadir 1, 3
• Progressive phase lasting days to 4 weeks (generally <2 weeks) with relative symmetry of symptoms 1
• Recent infection history within 6 weeks, present in approximately two-thirds of patients 4
• Distal paresthesias or sensory loss often preceding or accompanying weakness, though sensory symptoms are relatively mild 4, 1

Essential Diagnostic Testing

Cerebrospinal Fluid Analysis

Perform lumbar puncture to identify albumino-cytological dissociation—elevated protein with normal cell count—which is the classic CSF finding in GBS 4, 1:

• Protein levels are normal in 30-50% of patients in the first week and 10-30% in the second week, so do not dismiss GBS based on normal CSF protein early in disease course 4, 1
• Marked pleocytosis (>50 cells/μL) suggests alternative diagnoses 1
• Also analyze CSF for cell count and differential, cytology, glucose, and cultures to exclude other conditions 4

Electrodiagnostic Studies

Nerve conduction studies and EMG should be performed to support diagnosis and classify the neuropathy pattern 4:

• Look for sensorimotor polyradiculoneuropathy with reduced conduction velocities, reduced amplitudes, temporal dispersion, or conduction blocks 4
• "Sural sparing pattern" (normal sural sensory nerve action potential with abnormal median/ulnar responses) is typical for GBS 4
• Electrodiagnostic measurements may be normal when performed early (within 1 week), so repeat testing in 2-3 weeks if clinical suspicion remains high 4
• Approximately one-third of patients cannot be classified initially and are labeled "equivocal" or "inexcitable" 3

Initial Laboratory Workup

Obtain these tests to exclude metabolic or alternative causes 4:

• Complete blood count, glucose, electrolytes, kidney function, liver enzymes 4
• Serum creatine kinase (CK)—elevation suggests muscle involvement 4
• HbA1c, vitamin B12, TSH, vitamin B6, folate to screen for reversible neuropathy causes 4

Antibody Testing

• Anti-ganglioside antibody testing has limited diagnostic value in classical GBS and should not delay treatment 4, 1
• Anti-GQ1b antibodies are found in up to 90% of patients with Miller Fisher syndrome (ophthalmoplegia, ataxia, areflexia) and should be tested when this variant is suspected 4, 1

Imaging Studies

• MRI is not part of routine diagnostic evaluation but may be useful to exclude differential diagnoses such as compressive lesions 1
• Nerve root enhancement on MRI with gadolinium is sensitive but non-specific 1
• Peripheral nerve ultrasound may show enlarged cervical nerve roots at disease onset 1

Critical Assessment for Life-Threatening Complications

Immediately assess respiratory function and autonomic stability, as these determine mortality risk and need for ICU-level care 4:

• Measure vital capacity, negative inspiratory force (NIF), and maximum inspiratory/expiratory pressures at presentation and serially 4
• Apply the "20/30/40 rule": patient is at risk of respiratory failure if vital capacity <20 mL/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 4
• Single breath count ≤19 predicts need for mechanical ventilation 4
• Perform electrocardiography and continuously monitor heart rate and blood pressure for arrhythmias and autonomic instability 4

Key Clinical Variants to Recognize

• Classic sensorimotor GBS (30-85% of cases): rapidly progressive symmetrical weakness and sensory signs with absent or reduced reflexes 4
• Pure motor variant (5-70% of cases): motor weakness without sensory signs 4, 3
• Miller Fisher syndrome (5-25% of cases): ophthalmoplegia, ataxia, and areflexia 4, 1
• Bilateral facial palsy can be the presenting feature before limb weakness develops—bilateral simultaneous facial weakness is extremely rare in Bell's palsy and should immediately raise suspicion for GBS 4

Important Diagnostic Pitfalls

• Do not wait for antibody test results before starting treatment if GBS is suspected 4
• Marked persistent asymmetry, bladder dysfunction at onset, or marked CSF pleocytosis should prompt reconsideration of the diagnosis 4
• Consider changing diagnosis to acute-onset CIDP if progression continues after 8 weeks from onset or if patient has three or more treatment-related fluctuations, which occurs in approximately 5% of patients initially diagnosed with GBS 4, 5
• Descending flaccid paralysis (cranial nerves → trunk → extremities) indicates botulism until proven otherwise, not GBS 3
• Normal or preserved reflexes with flaccid paralysis suggests botulism or myasthenia gravis rather than GBS 3

Electrophysiological Subtypes

GBS is classified into three main subtypes based on nerve conduction studies 3:

• AIDP (acute inflammatory demyelinating polyneuropathy): demyelinating features
• AMAN (acute motor axonal neuropathy): motor axonal damage
• AMSAN (acute motor and sensory axonal neuropathy): both motor and sensory axonal damage

However, the traditional demyelinating versus axonal dichotomy is increasingly challenged, and treatment approach does not differ based on electrophysiological subtype—both IVIg and plasma exchange are first-line regardless of subtype 3, 5, 6.