SERPINA1 and Dilatation of the cerebral artery: <h4>Background</h4>Alpha 1-antitrypsin (A1AT) helps maintain vascular-wall integrity, but its role in the formation and rupture of intracranial aneurysms is unclear.<h4>Objective</h4>To compare A1AT levels between patients with ruptured and unruptured intracranial aneurysms and assess the associations with vasospasm and functional outcomes.<h4>Methods</h4>We retrospectively analyzed the medical records of patients who had serum A1AT levels measured between 2018 and 2022 during routine outpatient evaluations.