“Double Trouble”: Ultra-Early Formation and Rupture of a De Novo Terminal Basilar Artery Aneurysm After Aneurysmal Subarachnoid Hemorrhage

Introduction: The formation of de novo intracranial aneurysms (DNIAs) often occurs months or years after the initial identification of an intracranial aneurysm. Consensus on surveillance after surgery remains elusive. Case Presentation: A 53-year-old woman presented with a recurrent subarachnoid hemorrhage (SAH) caused by a rapidly expanding de novo basilar tip aneurysm, which developed and ruptured within 6 days of a previous SAH due to the rupture of a posterior communicating artery aneurysm. Both SAH incidents were successfully treated with microsurgical clipping. A computed tomography angiography at a 1-year follow-up did not detect any DNIAs. Conclusion: DNIAs can form within days after primary surgery. Therefore, conducting early postoperative angiography is crucial to detect and manage DNIAs and prevent SAH, especially in high-risk cases. In addition, since DNIAs are more prone to rupture, early clinical intervention is recommended.