Table 1.

Causes of GBS + CNS in the presence of an initial “correct” GBS diagnosis.

Condition	Clinical Clues	Additional Investigations
1. Initial Diagnosis Correct
Intrinsic feature of GBS illness	−week 1‐2‐hypnagogic/hypnopompic dreaming/misperceptions −hallucinations + delusions	MRI Brain normal EMG/NCS may be suggestive CSF albuminocytologic dissociation
Intrinsic feature of GBS variant
Anti‐Gq1b disease	−Ataxia −Areflexia −Ophthalmoplegia −+/‐ GBS‐like weakness	Serum anti‐Gq1b antibody positivity Brain MRI usually normal
Complications of disease
Metabolic derangement
Hyponatremia (SIADH)	−Non‐specific: ‐Headache ‐Nausea ‐Vomiting ‐Weakness ‐Confusion ‐Seizures	Serum sodium, Serum Osmolality, Urine Osmolality.
Hypercarbia (respiratory muscle weakness)	−Flushing −Bounding pulses −Drowsiness/confusion	Arterial blood gas ‐ CO2 levels
Infections	Signs of pulmonary, urinary or skin infection especially	Elevated WCC, CRP; Abnormal CXR or urinalysis
Autonomic instability
Posterior reversible encephalopathy syndrome (PRES)	−Headache −Seizure −Visual disturbance −Focal neurologic signs	T2 and FLAIR hyperintensities predominantly in posterior brain regions
Complication of treatment
IVIG‐relatesd
Hypercoagulability(also rarely encountered with plasmapheresis)	Focal neurological deficits(arterial/venous)+/‐seizures, headache, papilloedema(venous)	MRI Brain: Diffusion restriction; vascular imaging help define cause and extent of thrombosis
PRES	as above	as above
Aseptic meningitis	−Headache ‐‐Fever ‐Meningism	Culture‐negative CSF pleocytosis
Medications −Opioids −Gabapentin/Pregabalin −Tricyclic antidepressants −Anaesthetic/sedative drugs	−Opioid: pinpoint pupils, depressed respiratory rate	Medication administration review

CNS, Central Nervous System; CRP, c‐reactive protein; CO2, carbon dioxide; CSF, cerebrospinal fluid; CXR, chest X‐ray; EMG, Electromyography; FLAIR, fluid‐attenuated inversion recovery; GBS, Guillain‐Barré Syndrome; IVIG, intravenous immunoglobulin; MRI, magnetic resonance imaging; NCS, nerve conduction studies; PRES, posterior reversible encephalopathy syndrome; SIADH, syndrome of inappropriate ADH secretion; WCC, white cell count