A warning leak is a curious phenomenon attributed to cerebral aneurysms. Once the leak occurs, it has been postulated it could lead to a more catastrophic rebleeding. The designation "warning leak" trickled into neurosurgery vocabulary as early as the 1950s. The phenomenon has been poorly understood and characterized, but its presence spurs emergency physicians and neurointensivists to take action to secure the aneurysm. Rapid treatment of a recently discovered aneurysm is now commonplace, but it has not always been so. Antifibrinolytic agents spawned particular interest in the late 1970s, when many neurosurgeons postponed surgery after a recent hemorrhage. This historical vignette reviews the early views on aneurysmal rupture, rerupture, and the role of fibrinolysis.
Keywords: Antifibrinolytic agents; Cerebral aneurysm; Fibrinolysis; Warning leak.