Contributor:  Aaron Lessen, MD Educational Pearls: When evaluating a thunderclap headache, don’t forget RCVS! RCVS: reversible cerebral vasoconstriction syndrome Due to reversible spasms of cerebral blood vessels Can sometimes be seen on CTA or MRA, but often the imaging is normal and formal angiograms only occasionally show it It can be caused by medications, intense physical activity, orgasm, and postpartum conditions, but the exact etiology is unknown Typically seen in females in their 40s Can result in bleeding, strokes, and seizures  There is no good treatment, but stopping the suspected offending agent may help References Sattar A, Manousakis G, Jensen MB. Systematic review of reversible cerebral vasoconstriction syndrome. Expert Rev Cardiovasc Ther. 2010;8(10):1417-1421. doi:10.1586/erc.10.124 Summarized by John Spartz, MS3 | Edited by Erik Verzemnieks, MD