What is the approach to assessing a patient with Guillain-Barre Syndrome (GBS)?

Assessment of Guillain-Barré Syndrome

Immediately assess respiratory function and autonomic stability upon presentation, as these determine mortality risk and ICU admission need, then proceed with systematic clinical, laboratory, and electrodiagnostic evaluation to confirm the diagnosis. 1

Immediate Life-Threatening Assessment

Respiratory Function Monitoring

• Measure vital capacity, negative inspiratory force (NIF), and maximum inspiratory/expiratory pressures at presentation and serially throughout hospitalization 1
• Apply the "20/30/40 rule": patient is at high risk of respiratory failure if:
  • Vital capacity <20 ml/kg, OR
  • Maximum inspiratory pressure <30 cmH₂O, OR
  • Maximum expiratory pressure <40 cmH₂O 1
• Single breath count ≤19 predicts need for mechanical ventilation 1
• Look for clinical signs of respiratory distress: breathlessness at rest or during talking, inability to count to 15 in a single breath, use of accessory respiratory muscles, increased respiratory or heart rate 2

Autonomic Dysfunction Assessment

• Perform electrocardiography and continuously monitor heart rate and blood pressure for arrhythmias and blood pressure instability 1
• Assess for pupillary dysfunction, bowel or bladder dysfunction 3, 4
• Autonomic cardiovascular dysfunction (arrhythmias or marked blood pressure variation) warrants ICU admission 2

Bulbar Function

• Test swallowing and coughing ability to identify aspiration risk 1
• Severe swallowing dysfunction or diminished cough reflex requires ICU-level care 2
• Check corneal reflex in patients with facial palsy to prevent corneal ulceration 1

Clinical History and Examination

Key Historical Features

• Document pattern and progression of weakness: rapidly progressive bilateral weakness typically reaching maximum disability within 2 weeks is characteristic 3, 4
• Inquire about preceding events: approximately two-thirds of patients report infection within 6 weeks before symptom onset (respiratory infection or diarrhea) 3, 5
• Assess pain: back and limb pain (muscular, radicular, or neuropathic) affects approximately two-thirds of patients and is often an early symptom 3, 1

Neurological Examination Specifics

• Grade muscle strength using Medical Research Council scale in neck, arms, and legs 1
• Assess tendon reflexes: decreased or absent reflexes in affected limbs are a common finding, typically beginning in lower limbs 3, 4
• Document sensory symptoms: distal paresthesias or sensory loss preceding or accompanying weakness are typical 3, 4
• Assess for cranial nerve involvement: bilateral facial palsy is particularly common; also check for ophthalmoplegia 3, 1
• Assess functional disability using GBS disability scale 1
• Note relative symmetry of symptoms, though asymmetry can occur in some cases 3

Critical Pitfall

Marked persistent asymmetry, bladder dysfunction at onset, or marked CSF pleocytosis should prompt reconsideration of the diagnosis 1

Laboratory Investigations

Initial Blood Tests

• Complete blood count, glucose, electrolytes, kidney function, liver enzymes to exclude metabolic or electrolyte dysfunction as causes of weakness 1
• Serum creatine kinase (CK): elevation suggests muscle involvement and helps differentiate from myopathy 1

Cerebrospinal Fluid Examination

• Perform lumbar puncture to look for albumino-cytological dissociation (elevated protein with normal cell count), which is characteristic but not always present 3, 1, 5
• Do not dismiss GBS based on normal CSF protein in the first week, as protein levels may be normal early in the disease course 4, 1
• CSF examination also helps rule out alternative diagnoses 1

Antibody Testing

• Anti-ganglioside antibody testing has limited value in typical motor-sensory GBS 3, 5
• Anti-GQ1b antibody testing should be considered when Miller Fisher syndrome is suspected (ophthalmoplegia, ataxia, areflexia) 5
• Do not wait for antibody test results before starting treatment if GBS is suspected 1

Electrodiagnostic Studies

Nerve Conduction Studies and EMG

• Perform electrodiagnostic studies to support diagnosis and classify the neuropathy pattern, especially in atypical presentations 3, 1
• Look for sensorimotor polyradiculoneuropathy with reduced conduction velocities, reduced amplitudes, temporal dispersion, or conduction blocks 1
• "Sural sparing pattern" (normal sural sensory nerve action potential with abnormal median/ulnar responses) is typical for GBS 1
• Do not dismiss GBS based on normal initial electrodiagnostic studies: approximately one-third of patients do not meet specific criteria initially and are labeled "equivocal" or "inexcitable" 2
• Repeating studies 3-8 weeks after disease onset may aid classification 2

Imaging Studies

MRI Indications

• MRI is not part of routine diagnostic evaluation but can help exclude differential diagnoses 2, 4, 5
• Consider MRI to exclude: brainstem infection or stroke, spinal cord or anterior horn cell inflammation, nerve root compression, leptomeningeal malignancy 2, 4
• Nerve root enhancement on gadolinium-enhanced MRI is a sensitive but nonspecific feature that can support GBS diagnosis, especially in young children where clinical and electrophysiological assessment is challenging 2, 4
• MRI is particularly useful to distinguish GBS from acute flaccid myelitis in children, though nerve root enhancement can occur in a minority of acute flaccid myelitis cases 2, 4

Ultrasound

• Ultrasound imaging of peripheral nerves may reveal enlarged cervical nerve roots early in disease course, though further validation is required 2

Differential Diagnosis Assessment

CNS Causes to Exclude

• Brainstem or spinal cord inflammation/infection (sarcoidosis, Sjögren syndrome, neuromyelitis optica, acute transverse myelitis) 2
• Malignancy (leptomeningeal metastases, neurolymphomatosis) 2
• Brainstem or spinal cord compression 2
• Brainstem stroke 2
• Vitamin deficiency (Wernicke encephalopathy, subacute combined degeneration) 2

Muscle Disorders to Exclude

• Metabolic or electrolyte disorders (hypokalemia, thyrotoxic hypokalemic periodic paralysis, hypomagnesemia, hypophosphatemia) 2
• Inflammatory myositis, acute rhabdomyolysis 2
• Drug-induced toxic myopathy (colchicine, chloroquine, statins) 2

Other Considerations

• Conversion or functional disorder 2

Timing Considerations for Diagnosis

Disease Progression Timeline

• Progressive phase typically lasts from days to 4 weeks, usually less than 2 weeks 3
• Reaching maximum disability within 24 hours or progression continuing after 4 weeks may indicate alternative diagnoses 3
• Consider changing diagnosis to acute-onset CIDP if progression continues after 8 weeks from onset, which occurs in approximately 5% of patients initially diagnosed with GBS 5

Psychological Assessment

Mental Status and Communication

• Recognize that patients with GBS, even those with complete paralysis, usually have intact consciousness, vision, and hearing 1
• Screen for anxiety, depression, and hallucinations, which are frequent complications 1
• Be mindful of bedside conversations and explain procedures to reduce anxiety 1