Outcome of Aneurysmal Subarachnoid Hemorrhage in a Population-Based Cohort: Retrospective Registry Study

BACKGROUND: Studies of aneurysmal subarachnoid hemorrhage report an association between higher patient volumes and better outcomes. In regions with dispersed settlement, this must be balanced against the advantages with shorter prehospital transport times and timely access. The aim of this study is to report outcome for unselected aneurysmal subarachnoid hemorrhage cases from a well-defined rural population treated in a low-volume neurosurgical center. METHODS: This is a retrospective, population-based, observational cohort study from northern Norway (population 486 450). The University Hospital of North Norway provides the only neurosurgical service. We retrieved data for all aneurysmal subarachnoid hemorrhage cases (n=332) admitted during 2007 through 2019 from an institution-specific register. The outcome measures were mortality rates and functional status assessed with the modified Rankin scale. RESULTS: The mean annual number of cases was 26 (range, 16-38) and the mean crude incidence rate 5.4 per 100 000 personyears. Two hundred seventy-nine of 332 (84%) cases underwent aneurysm repair, 158 (47.5%) with endovascular techniques and 121 (36.4%) with microsurgical clipping, while 53 (15.9%) did not. The overall mortality rate was 16.0% at discharge and 23.8% at 12 months. The proportion with a favorable outcome (modified Rankin scale scores 0-2) was 36.1% at discharge and 51.5% at 12 months. In subgroup analysis of cases who underwent aneurysm repair, the mortality rate was 4.7% at discharge and 11.8% at 12 months, and the proportion with a favorable outcome 42.3% at discharge and 59.9% at 12 months. CONCLUSIONS: We report satisfactory outcomes after treatment of aneurysmal subarachnoid hemorrhage in a low-volume neurosurgical department serving a rural population. This indicates a reasonable balance between timely access to treatment and hospital case volume