Guillain-Barré Syndrome Complicated by Posterior Reversible Encephalopathy Syndrome and Reversible Cerebral Vasoconstriction Syndrome.

Introduction: Guillain-Barré syndrome is an immune-mediated inflammatory polyneuritis characterised by rapidly progressive flaccid paralysis. Guillain-Barré syndrome may present with posterior reversible encephalopathy syndrome or reversible cerebral vasoconstriction syndrome in rare cases. Case description: A woman in her 60s with a history of follicular lymphoma presented with a one-week history of difficulty walking and thunderclap headaches. The patient was diagnosed with Guillain-Barré syndrome based on neurological examination, cerebrospinal fluid analysis and nerve conduction findings. Further diagnosis of posterior reversible encephalopathy and reversible cerebral vasoconstriction syndromes was based on imaging findings and headache history. The patient was treated with intravenous immunoglobulin and amlodipine, and symptoms improved. Discussion: We reviewed the literature on Guillain-Barré syndrome associated with posterior reversible encephalopathy and/or reversible cerebral vasoconstriction syndrome. The underlying pathophysiology may involve dysautonomia resulting in unstable blood pressure, and hyponatraemia causing endothelial dysfunction. The SNOOP mnemonic highlights the 'red flags'. This SNOOP mnemonic suggests the possibility of secondary headaches that require imaging studies. In this case, the patient exhibited three SNOOP symptoms: S (history of malignancy: follicular lymphoma), O (sudden-onset headache) and O (over 50 years old). Conclusion: This case highlights the importance of considering coexisting central neurological disorders in patients with Guillain-Barré syndrome. LEARNING POINTS: Guillain-Barré syndrome (GBS) alone rarely causes headaches; therefore, when GBS patients complain of severe headaches, especially when the headache is associated with 'red flags', other complications and differential diagnosis should be considered.Posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS) can be triggered by GBS.Hyponatraemia, age over 50 years and female gender may be risk factors for developing PRES and RCVS in GBS patients.