Reversible Cerebral Vasoconstriction Syndrome Induced by Pseudoephedrine

Background: Thunderclap headache and focal neurologic deficits are major diagnostic challenges to the neurologists. Besides subarachnoid hemorrhage and stroke, reversible cerebral vasoconstriction syndrome (RCVS) should be given high priority in the differential diagnosis. Case Report: A 46-year-old woman visited our hospital with thunderclap headache and left hemiparesis. Computed tomography (CT) angiography showed multifocal narrowing of the basilar artery. Headache, resistant to conventional medication, had a waxing and waning course during hospitalization. After a review of the medication history, administration of pseudoephedrine for allergic rhinitis was noted 3 days before hospital admission. History of a prior episode of severe headache after taking the same medication was also revealed. Under suspicion of secondary RCVS related to sympathomimetics, she was treated with nimodipine, and then, the headache improved gradually. Follow-up CT angiography showed normalization of the previously narrowed cerebral vessels. Conclusion: The problem of underdiagnosis of RCVS cannot be overcome without a high level of vigilance. Thunderclap headache with normal brain parenchyma on MRI but multifocal narrowing of brain vessels highly suggests the need for scrutiny of potential triggers of RCVS.