What are the diagnostic criteria and treatment options for Guillain-Barré Syndrome (GBS)?

Diagnosis of Guillain-Barré Syndrome

GBS diagnosis is primarily clinical, requiring progressive bilateral limb weakness with reduced or absent reflexes, supported by CSF albumino-cytological dissociation and electrodiagnostic findings of polyradiculoneuropathy. 1, 2

Required Clinical Features for Diagnosis

The diagnosis rests on two essential criteria that must both be present 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

Strongly Supporting Clinical Features

These features substantially increase diagnostic confidence 1:

• Progression timeline: Maximum disability reached within days to 4 weeks, typically less than 2 weeks 1, 2
• Relative symmetry of weakness and sensory signs 1
• Mild sensory symptoms: Distal paresthesias or sensory loss (absent in pure motor variant) 1
• Cranial nerve involvement: Especially bilateral facial palsy, occurring in a significant proportion of patients 1, 2
• Dysautonomia: Blood pressure/heart rate instability, pupillary dysfunction, bowel/bladder dysfunction 1
• Pain: Muscular, radicular, or neuropathic pain frequently reported 1, 2
• Preceding infection: Approximately two-thirds report infectious symptoms in the 6 weeks before onset 1

Cerebrospinal Fluid Analysis

CSF examination should be performed during initial evaluation primarily to exclude alternative diagnoses. 1

• Classic finding: Albumino-cytological dissociation (elevated protein with normal cell count) 1, 2
• Critical caveat: Protein levels are normal in 30-50% of patients in the first week and 10-30% in the second week, so normal CSF protein does not exclude GBS 1
• Red flag: Marked pleocytosis (>50 cells/μl) suggests alternative pathology such as leptomeningeal malignancy or infectious/inflammatory polyradiculitis 1
• Mild pleocytosis (10-50 cells/μl) is compatible with GBS but should prompt consideration of infectious causes 1

Electrodiagnostic Studies

Electrophysiological testing is not required for diagnosis but is strongly recommended to support the diagnosis, especially in atypical presentations. 1, 2

• Typical findings: Sensorimotor polyradiculoneuropathy with reduced conduction velocities, reduced sensory and motor evoked amplitudes, abnormal temporal dispersion, and/or partial motor conduction blocks 1, 2
• Sural sparing pattern: Normal sural sensory nerve action potential while median and ulnar sensory potentials are abnormal or absent 1
• Important limitation: Studies may be normal when performed within 1 week of symptom onset, in patients with proximal weakness, mild disease, or certain clinical variants 1
• Repeat testing: Consider repeating electrodiagnostic studies 2-3 weeks later if initial studies are normal but clinical suspicion remains high 1

Laboratory Investigations

Routine laboratory testing serves primarily to exclude alternative diagnoses. 1

• Basic workup: Complete blood count, glucose, electrolytes, kidney function, liver enzymes in all suspected cases 1, 2
• Anti-ganglioside antibodies: Limited diagnostic value in classic GBS; positive results can help when diagnosis is uncertain, but negative results do not exclude GBS 1
• Anti-GQ1b antibodies: Found in up to 90% of Miller Fisher syndrome cases, making them valuable in suspected MFS 1, 2
• Do not delay treatment: Never wait for antibody test results before initiating therapy 1

Clinical Variants Recognition

GBS presents in multiple distinct variants that may not progress to the classic pattern 1:

• Classic sensorimotor (30-85%): Rapidly progressive symmetrical weakness with sensory signs 1
• Pure motor (5-70%): Motor weakness without sensory signs, may have normal or exaggerated reflexes in AMAN subtype 1
• Miller Fisher syndrome (5-25%): Ophthalmoplegia, ataxia, and areflexia 1
• Paraparetic variant: Weakness limited to lower limbs 1
• Pharyngeal-cervical-brachial (<5%): Upper body and cranial weakness without lower limb involvement 1
• Bilateral facial palsy (<5%): Facial weakness with paresthesias and reduced reflexes 1

Features That Cast Doubt on the Diagnosis

These findings should prompt reconsideration of alternative diagnoses 1:

• Marked persistent asymmetry of weakness
• Bladder or bowel dysfunction at onset (though mild dysfunction can occur later)
• Progression continuing beyond 4 weeks from onset
• Marked pleocytosis in CSF (>50 cells/μl)
• Maximum disability reached within 24 hours or after 4 weeks 1

Diagnostic Algorithm

1. Identify core features: Bilateral progressive weakness with reduced/absent reflexes 1, 2
2. Assess timeline: Progression over days to 4 weeks (typically <2 weeks) 1, 2
3. Perform lumbar puncture: Look for albumino-cytological dissociation, but remember normal protein doesn't exclude diagnosis in first 1-2 weeks 1, 2
4. Obtain electrodiagnostic studies: Confirm polyradiculoneuropathy pattern, repeat if initially normal and clinical suspicion high 1, 2
5. Exclude mimics: Use laboratory tests (CBC, metabolic panel, electrolytes) to rule out alternative causes 1, 2
6. Consider imaging: MRI or ultrasound in atypical cases to exclude differential diagnoses 2, 3
7. Classify variant: Determine if presentation fits classic sensorimotor or specific variant pattern 1, 2
8. Monitor for A-CIDP: If progression continues beyond 8 weeks, consider changing diagnosis to acute-onset CIDP, which occurs in approximately 5% of cases initially diagnosed as GBS 3

Common Pitfalls to Avoid

• Don't wait for CSF protein elevation: Normal protein in first 1-2 weeks is common 1
• Don't rely on reflexes alone: Pure motor AMAN variant may have normal or exaggerated reflexes 1
• Don't dismiss atypical presentations in young children: May present with nonspecific features like refusal to bear weight, irritability, or unsteady gait 1
• Don't delay treatment for antibody results: Clinical diagnosis is sufficient to initiate therapy 1
• Don't overlook pain as presenting feature: Severe diffuse pain or isolated cranial nerve dysfunction can precede weakness 1