Reversible cerebral vasoconstriction syndrome: a thunderclap headache-associated condition.

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by a sudden, severe headache at onset, vascular narrowing involving the circle of Willis and its immediate branches, and angiographic evidence of vasoconstriction reversibility within minutes to weeks of onset. RCVS is underrecognized and often misdiagnosed; it can defy clinical detection because it can mimic common conditions such as migraine and ischemic stroke. A lack of shared nosology has hampered awareness and understanding of the syndrome. Clinicians must consider primary angiitis of the central nervous system because of its high rates of morbidity and mortality if left untreated. RCVS has a number of primary and secondary associations (cerebral hemorrhage, vasoactive substances, the peripartum period, bathing, and physical exertion) but also occurs in isolation. RCVS can present in conjunction with hypertensive encephalopathy, preeclampsia, and reversible posterior leukoencephalopathy. This review provides an up-to-date account of RCVS.