Decompressive Craniectomy After Aneurysmal Subarachnoid Hemorrhage (DECIDE-SAH)

DECIDE-SAH is an international, multicenter, retrospective, observational, non-interventional secondary-use cohort study of adults with aneurysmal subarachnoid hemorrhage (aSAH). The study combines pre-existing routine-care patient-level data from consecutive retrospective aSAH cohorts. Its primary objective is to evaluate the association between decompressive craniectomy (DC) strategies and unfavorable functional outcome approximately 6 months after aSAH, with particular emphasis on exact or best-available ictus-to-DC timing, the neurological context at the treatment decision, the indication for decompression, and technical characteristics of DC. The primary endpoint is modified Rankin Scale (mRS) 4-6 approximately 6 months after ictus. No prospective patient recruitment, study-specific treatment, additional diagnostic procedure, treatment allocation, or patient contact is planned.

Inclusion Criteria: * Age 18 years or older at ictus or hospital admission. * Confirmed aneurysmal subarachnoid hemorrhage caused by rupture of a qualifying intracranial aneurysm. * Eligible qualifying aneurysm morphologies include saccular, blister-like, dissecting, fusiform, and other non-excluded aneurysmal morphologies. * Treatment or clinical management at a participating center during its documented consecutive retrospective cohort period. * Availability of the Minimum Required Dataset (MRD) for scientific cohort contribution. The MRD requires a technical center-specific study identifier without direct identifiers, an index time period for the qualifying aSAH episode, age, sex, initial clinical severity represented by an accepted grading scale or valid Good Grade/Poor Grade classification, aneurysm-treatment status and modality, decompressive-craniectomy status, and at least one interpretable discharge clinical outcome. * Complete Standard Dataset or Extension Module information is not required for cohort eligibility. Six-month mRS is not required for participation in analyses that do not use the registered primary endpoint. Exclusion Criteria: * Age below 18 years. * Non-aneurysmal subarachnoid hemorrhage, including subarachnoid hemorrhage caused primarily by another vascular lesion without a qualifying ruptured intracranial aneurysm. * Traumatic subarachnoid hemorrhage. * Rupture of an infectious/mycotic intracranial aneurysm. * Rupture of a traumatic pseudoaneurysm. * Rupture of an iatrogenic pseudoaneurysm. * Rupture of an AVM-/AVF-associated flow-related aneurysm. * Source information insufficient to establish the qualifying aSAH diagnosis or to meet the Minimum Required Dataset threshold. Pregnancy, acute lack of decision-making capacity during the original aSAH episode, and non-German language are not exclusion criteria for this retrospective secondary use of pre-existing routine-care data.