Hyperdense Vessel Sign in Brain Computed Tomography as an Early Indication of Reversible Cerebral Vasoconstriction Syndrome

We herein report a case of reversible cerebral vasoconstriction syndrome (RCVS) with an unusual presentation of hyperdense blood vessels. A 53-year-old woman developed thunderclap headache. Brain computed tomography (CT) showed hyperdensity of the anterior cerebral artery. Brain magnetic resonance imaging revealed cerebral infarctions in the left anterior cerebral artery (ACA) territory and cerebellum. The left ACA presented with a hyperintense vessel sign, although magnetic resonance angiography (MRA) appeared normal. One week later, stenotic changes were confirmed using MRA. The vasoconstriction disappeared on day 20, and the patient was diagnosed with RCVS. CT-defined hyperdense vessel signs can be observed at an early stage of RCVS, leading to ischemic events.