Diagnostic Investigations for Guillain-Barré Syndrome

Initial Clinical Assessment

Evaluate for progressive, typically symmetrical muscle weakness with absent or reduced deep tendon reflexes, often starting with sensory symptoms in the lower back and thighs, according to the American Academy of Neurology 1
Assess for involvement of facial, respiratory, bulbar, and oculomotor nerves, as recommended by the American College of Physicians 2
Monitor for signs of autonomic dysfunction (blood pressure fluctuations, arrhythmias), as suggested by the American Academy of Neurology 1

Perform lumbar puncture during initial evaluation to look for albumino-cytological dissociation (elevated protein with normal cell count), as recommended by the American Academy of Neurology 3, 4
Note that protein levels may be normal in 30-50% of patients in the first week and 10-30% in the second week, according to the American Academy of Neurology 4
Marked pleocytosis (>50 cells/μl) suggests alternative diagnoses, as stated by the American Academy of Neurology 4

Conduct nerve conduction studies (NCS) and electromyography (EMG) to support diagnosis and differentiate GBS subtypes, as recommended by the American Academy of Neurology 3, 4
Look for characteristic findings: reduced conduction velocities, reduced sensory and motor evoked amplitudes, abnormal temporal dispersion, and/or partial motor conduction blocks, according to the American Academy of Neurology 4
Consider repeat studies 2-3 weeks later if initial results are normal or inconclusive, as suggested by the American Academy of Neurology 4

Complete blood counts, glucose, electrolytes, kidney function, and liver enzymes to exclude other causes of acute flaccid paralysis, as recommended by the American Academy of Neurology 4
Consider testing for anti-ganglioside antibodies, especially anti-GQ1b antibodies when Miller Fisher variant is suspected, according to the American Academy of Neurology 3, 4
Screen for reversible neuropathy causes: HbA1c, vitamin B12, folate, TSH, HIV, as recommended by the American College of Physicians 6, 7

MRI of spine with and without contrast to rule out compressive lesions and evaluate for nerve root enhancement/thickening, as recommended by the American College of Radiology 2, 5, 6
Consider MRI brain if cranial nerve involvement is present, according to the American College of Radiology 8
Ultrasound imaging of peripheral nerves may reveal enlarged cervical nerve roots early in disease course, as suggested by the American Institute of Ultrasound in Medicine 1

Perform pulmonary function testing (negative inspiratory force/vital capacity), as recommended by the American Thoracic Society 2, 5
Monitor for signs of respiratory distress: breathlessness at rest or during talking, inability to count to 15 in a single breath, use of accessory respiratory muscles, according to the American Thoracic Society 1
Implement frequent neurological checks to assess for progression, as recommended by the American Academy of Neurology 2, 5

Diagnosis is primarily clinical but supported by ancillary investigations, as stated by the American Academy of Neurology 4
Normal CSF protein does not rule out GBS, especially in the first week, according to the American Academy of Neurology 4
Consider GBS variants (Miller Fisher syndrome, pharyngeal-cervical-brachial, paraparetic) which may present atypically, as recommended by the American Academy of Neurology 9