Coexistence of Intracranial Aneurysm and Pituitary Adenoma: A Case Report and Literature Review.

Unrecognized intracranial aneurysms pose a rare but catastrophic risk during transsphenoidal surgery. Pituitary adenomas are among the brain tumors most frequently reported to coexist with intracranial aneurysms, yet routine preoperative aneurysm screening is not universally recommended. We report a 73-year-old woman who underwent elective transsphenoidal resection for recurrent pituitary adenoma and developed sudden hemodynamic instability and massive epistaxis intraoperatively, followed by an abrupt reduction in electroencephalographic activity with increased suppression on processed EEG monitoring despite unchanged anesthetic targets. Computed tomography angiography demonstrated a ruptured pseudoaneurysm involving the anterior communicating artery complex with extensive subarachnoid and intraventricular hemorrhage and hydrocephalus. Despite intensive surgical and critical care, the hemorrhage progressed with secondary cerebral injury. After discussion with the family, life-sustaining measures were withdrawn, and the patient died. This case underscores that the rupture of an unrecognized aneurysm during elective transsphenoidal surgery, although uncommon, can be rapidly fatal and difficult to control intraoperatively, and supports careful preoperative cerebrovascular assessment, particularly in patients with recurrent or anatomically complex sellar disease.