Incidence, risk factors, clinical and cognitive impact of secondary hemorrhage after spontaneous aneurysmal subarachnoid hemorrhage.

Introduction: Evidence on secondary hemorrhage (SH) in patients with spontaneous aneurysmal subarachnoid hemorrhage (aSAH) is limited. Most studies focus external ventricular drain (EVD)-related bleeding, while data on hemorrhage types, particularly under peri-interventional antiplatelet therapy (PIAT), are scarce. Research question: To investigate the incidence, risk factors, and clinical impact of SH after aSAH, including the role of PIAT. Material and methods: In this registry-based two-centre study we retrospectively analyzed 170 patients with aSAH treated between September 2021 and June 2025. EVD placement was performed in 128 patients; 120 underwent endovascular treatment, and 78 received PIAT. SH was classified as intracranial or peripheral. Functional and cognitive outcome were assessed using the modified Rankin Scale and the Montreal Cognitive Assessment, respectively, at admission, discharge, and three months. Results: SH occurred in 39% of patients. Intracranial hemorrhages predominated, with drain-associated (29%), aneurysm rebleeding (27%), and access-related hemorrhages (21%) being most frequent. EVD placement was independently associated with SH (OR 5.07, p = 0.002). No significant association between PIAT and SH was observed. SH was associated with worse functional and cognitive outcomes, however, age and WFNS grade were the main independent predictors. Discussion and conclusion: SH after aSAH is common and reflects a heterogeneous spectrum of bleeding events. The association with EVD likely reflects disease severity rather than causality. No association between PIAT and SH was found, although analyses were limited. SH appears to be a marker of disease severity associated with worse early outcomes, emphasizing careful procedural management and individualized risk assessment.