How to diagnose Guillain-Barré Syndrome in the ICU?

Diagnosing Guillain-Barré Syndrome in the ICU

Diagnosis of GBS in the ICU setting relies on clinical recognition of progressive ascending weakness with reduced reflexes, supported by CSF analysis showing albuminocytologic dissociation (elevated protein with normal cell count) and electrodiagnostic studies demonstrating peripheral nerve dysfunction, while simultaneously excluding critical mimics through targeted imaging and laboratory testing. 1

Clinical Diagnostic Criteria

Core clinical features that establish GBS diagnosis include: 1

• Progressive motor weakness affecting more than one limb, typically ascending and symmetric 1, 2
• Areflexia or hyporeflexia in affected limbs (reduced or absent deep tendon reflexes) 1, 3
• Progression over days to 4 weeks maximum - if progression continues beyond 8 weeks, consider acute-onset CIDP instead 2, 4
• Preceding infection within 2-4 weeks (particularly Campylobacter jejuni, cytomegalovirus, Epstein-Barr virus) 1, 5

Additional supportive clinical features: 1, 3

• Sensory symptoms (paresthesias, neuropathic pain) often starting in lower back and thighs 3
• Cranial nerve involvement (facial weakness, bulbar dysfunction, ophthalmoplegia) 3, 2
• Autonomic dysfunction (blood pressure lability, arrhythmias, bowel/bladder dysfunction) 1, 3

Essential Diagnostic Testing in ICU

Cerebrospinal Fluid Analysis

Lumbar puncture typically reveals: 2, 6

• Elevated protein (often >0.55 g/L) with normal or mildly elevated white blood cell count (<10 cells/μL) - termed albuminocytologic dissociation 3, 2
• Critical caveat: CSF may be normal early in disease course (first week), so normal results do not exclude GBS 1, 2

Electrodiagnostic Studies

Nerve conduction studies and EMG demonstrate: 1

• Evidence of peripheral nerve dysfunction (slowed conduction velocities, prolonged distal latencies, conduction block, temporal dispersion) 2, 6
• Can differentiate between AIDP (demyelinating), AMAN (axonal motor), and AMSAN (axonal motor-sensory) subtypes 1
• Important limitation: Approximately one-third of patients have equivocal or unexcitable findings initially 1
• Consider repeating studies at 3-8 weeks if initial results are inconclusive, though this practice is controversial 1

Imaging Studies

MRI is not routine but valuable for excluding mimics: 1

• Gadolinium-enhanced MRI may show nerve root enhancement (sensitive but nonspecific for GBS) 1
• Essential for ruling out: brainstem stroke, spinal cord compression, transverse myelitis, leptomeningeal malignancy 1
• Particularly useful in children where clinical and electrophysiological assessment is challenging 1
• Critical for distinguishing acute flaccid myelitis from GBS in pediatric cases 1

Emerging Diagnostic Tools

Nerve ultrasound shows enlarged cervical nerve roots early in disease, potentially aiding early diagnosis, though further validation is needed 1

Critical Differential Diagnoses to Exclude in ICU

CNS causes: 1

• Brainstem stroke, brainstem/spinal cord inflammation (sarcoidosis, Sjögren syndrome, neuromyelitis optica), spinal cord compression, leptomeningeal metastases 1

Neuromuscular junction/muscle causes: 1

• Myasthenia gravis, botulism, acute rhabdomyolysis, inflammatory myositis, drug-induced toxic myopathy (statins, colchicine, chloroquine) 1

Metabolic/electrolyte disorders: 1

• Hypokalemia, thyrotoxic periodic paralysis, hypomagnesemia, hypophosphatemia 1

Other critical mimics: 1

• Acute transverse myelitis, acute flaccid myelitis (especially in children), vitamin deficiencies (B1, B12), conversion disorder 1

Immediate ICU-Specific Assessments

Respiratory Function Monitoring

Assess for imminent respiratory failure using: 1, 7

• Vital capacity <15-20 mL/kg or <1 L 1
• Single breath count ≤15 (inability to count to 15 in one breath) 1, 7
• Use of accessory respiratory muscles 1
• Clinical signs: breathlessness at rest or during talking, increased respiratory or heart rate 1
• Maximum inspiratory pressure <30 cmH₂O or maximum expiratory pressure <40 cmH₂O (the "20/30/40 rule") 7, 3
• Arterial blood gas abnormalities or pulse oximetry changes 1

Apply the Erasmus GBS Respiratory Insufficiency Score (EGRIS) to calculate probability (1-90%) of requiring mechanical ventilation within 1 week 1, 7

Autonomic Function Assessment

Monitor for life-threatening autonomic dysfunction: 1

• Continuous ECG monitoring for arrhythmias 7, 3
• Frequent blood pressure monitoring for marked lability 1
• Assessment of bowel/bladder function 7, 3

Bulbar Function Evaluation

Assess swallowing and cough reflex to prevent aspiration pneumonia 1, 7

Common Diagnostic Pitfalls in ICU

Early presentation challenges: 1, 2

• CSF protein may be normal in first week - do not exclude GBS based on normal early CSF 1, 2
• Electrodiagnostic studies may be equivocal or unexcitable initially in one-third of patients 1

Respiratory failure can develop rapidly without obvious dyspnea - serial vital capacity measurements are mandatory, not optional 1, 7

Pain may precede weakness and confuse the diagnosis - consider GBS even when pain is the predominant early symptom 3, 4

Avoid medications that worsen neuromuscular function: β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, macrolides 7, 8

Antibody Testing Considerations

Anti-ganglioside antibody testing has limited clinical value in typical motor-sensory GBS 2

Anti-GQ1b antibody testing should be performed when Miller Fisher syndrome is suspected (ophthalmoplegia, ataxia, areflexia) 2

Nodal-paranodal antibodies should be tested when autoimmune nodopathy is suspected 2