Spontaneous and early thrombosis of a ruptured aneurysm dependent on a perforating branch of P1

Spontaneous thrombosis of intracranial aneurysms (IA) is a rare event with a poorly understood mechanism. Several factors may induce a thrombogenic state inside the aneurysmal sac, such as vasospasm, hypotension, hemodynamic alterations, IA geometrical configuration, or local vessel wall damage. Thrombosis is more frequent in ruptured aneurysms than in non-ruptured aneurysms, often occurring as a delayed event, suggesting that subarachnoid hemorrhage may play a role. Here, we describe a patient who presented with early thrombosis of a ruptured IA in the P1 segment of the posterior cerebral artery.