Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by segmental vasoconstriction and dilatation of intracranial arteries, typically affecting bilateral medium-sized intracranial arteries and their branches. The diagnosis usually relies both on clinical presentations and cerebral vascular imaging such as magnetic resonance angiography or conventional angiography. Dual energy computed tomography angiography (CTA) could provide high-quality imaging and is usually immediately

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... lable for the diagnosis at the emergency department. A 37-year-old previously healthy woman was admitted to the neurology ward for recurrent episodes of headaches within 3 days. She was diagnosed as having RCVS presenting with thunderclap headaches. Dual energy CTA provided high-quality imaging and almost immediately available for diagnosis at the emergency department (ER). CT perfusion showed adequate brain perfusion. Transcranial Doppler disclosed increased arterial velocities at bilateral middle cerebral arteries. We treated the patient with oral diclofenac and nimodipine. After a few days, she had great improvement of headaches. The follow-up CTA 3 months after her initial presentation disclosed complete resolution of the constrictions of these intracranial arteries. Brain magnetic resonance imaging (MRI) with magnetic resonance angiography (MRA) and MR venography is the choice for initial investigation; however, CTA is an alternative diagnostic tool when MRI is not readily available. Dual energy CTA has the great advantage in providing high-resolution imaging, high speed scanning with a lower radiation dose.