BACKGROUND: Decompressive craniectomy (DC) is a last-tier treatment for managing refractory intracranial hypertension in patients with aneurysmal subarachnoid hemorrhage (aSAH), though concerns persist about whether it primarily prolongs survival in a state of severe disability. This study investigated patient characteristics, surgical indications, complications, and outcomes following DC in aSAH. METHODS: In this Swedish, retrospective multi-center study, 123 aSAH patients treated with DC between 2008-2022 were included. Data collection included demographic details, aSAH characteristics, injury severity, DC indication, complications, and outcome at roughly six months post-DC (modified Rankin scale [mRS]) dichotomized as survival vs. mortality (0-5 vs. 6) and favorable vs. unfavorable (0-3 vs. 4-6). RESULTS: The median age was 53 years and 66% were females. Two thirds presented with a WFNS grade 4-5 and 83% with a Fisher grade 4 hemorrhage. Most aneurysms were located at the middle cerebral artery (65%) and treated with clip ligation (59%). DC significantly reduced midline shift from 9 to 2 mm and obliteration rates of basal cisterns from 95 to 22% (p <
0.05). Reoperation for hematomas or extension of the DC were rare (<
5%). At follow-up, 20% were deceased, while 33% had recovered favorably. In univariate logistic regressions, younger age was associated with favorable outcome and reduced mortality. Other patient demographics, injury severity, and factors related to the DC surgery lacked association with outcome. CONCLUSIONS: aSAH patients treated with DC presented with severe primary brain injuries and signs of intracranial hypertension. DC resulted in radiological improvements regarding mass effect and a low rate of postoperative complications. Although the results were based on a selected population of aSAH patients, an encouraging rate of favorable outcome was found, particularly among younger patients. However, the absence of additional outcome predictors underscores the ongoing challenges in improving patient selection for DC in aSAH.