Licorice consumption-associated thunderclap headache: posterior reversible encephalopathy syndrome or subarachnoid hemorrhage?

admitted to hospital for thunderclap headache, blurred vision and hypertension. Based on clinical manifestations, diagnostic work-up and follow-up, the authors diagnosed the case as posterior reversible encephalopathy syndrome (PRES) [1]. We agree that PRES should be considered in this case, while diff erential diagnosis such as subarachnoid hemorrhage (SAH) requires further investigation and exclusion. PRES represents a clinicoradiological disease entity arising from failure of cerebrovascular autoregulation and ensuing disruption of the blood–brain barrier upon acuteonset hypertension [2]. Th e underlying patho genesis of PRES is vasogenic edema, which requires apparent diff usion coeffi cient mapping by magnetic reso nance imaging for confi rmation [3]. In this reported case, the brain computed tomography (CT) showed hemorrhage in the left Sylvian fi ssure, which was highly suggestive of SAH. Th e condition of SAH may also present as thunderclap headache, hypertension and reversible cerebral vasoconstriction, appearing as bilateral hypointensity in CT images. Lumbar puncture is needed to identify SAH in suspected cases [4]. As another diff erential diagnosis, reversible cerebral vasoconstriction may also be associated with licorice [5] and ought to be excluded after performing cerebral angiography. In summary, PRES and SAH share some clinical similarities. Th e case reported by van Beers and colleagues merits further investigation, especially to diff erentiate between PRES and SAH