The Impact of Multiple Intracranial Aneurysms on Outcome Following Acute Aneurysmal Subarachnoid Hemorrhage

Aims: To compare patient, aneurysm, and outcome characteristics of individuals with multiple intracranial aneurysms (MIA) compared with patients with single intracranial aneurysms (SIA) in a large-scale unselected population of patients with acute aneurysmal subarachnoid hemorrhage (aSAH).

Methods: The SwissSOS dataset was used to study the relationship between patient variables, aneurysm characteristics, and clinical outcome at discharge and at 1 year with descriptive and multivariate regression analysis.

Results: 1787 consecutive patients with aSAH including 474 with MIA (26.5%) were analyzed. The mean age was 55.9yrs (SD/−12yrs) for patients with MIA, and 55.9years (SD/−13.8yrs) for those with SIA. Males were less likely to have MIA than females (OR 0.76 [95% CI 0.56 – 0.96] p = .024). Patients with a ruptured [r] MCA or BA aneurysm were more prone to having MIA than patients with a ruptured AcommA aneurysm (MCA OR 1.96 [1.45–2.65] p = <.0001; BA OR 2.34 [1.47–3.70] p = .0003). The mean diameter was significantly larger for rMIA than for rSIA (mean 7.7mm, SD/−4.8mm versus mean 7.1mm, SD/−4.5mm; p = .005). Similarly, aneurysms were more likely larger in males and in patients with MIA than in females or patients with SIA (Male OR 1.07 [1.01–1.13] p = .03 per mm; rMIA OR 1.07 [1.01–1.14] p = .026 per mm). Also, the rMIA was likely larger than any bystanding nrMIA (OR 0.72 [0.66–0.79] p < .0001 per mm). The modality of aneurysm treatment, treatment- or vasospasm-related infarction, and the overall survival at both discharge and at one year did not differ between patients with MIA except for MCA-location, were surgery was performed with a higher proportion in MIA- than in SIA patients (69% versus 76%). Patients with MIA were more prone for having a thick clot on admission CT (OR 1.47 [1.01–2.14] p = 0.042), had a higher chance for developing a new FND during hospitalization (OR 1.49 [1.15 – 1.93] p = .003), and hence more likely suffered from a FND at discharge (OR 1.74 [1.25 – 2.42] p = .001).

Interpretation: About one quarter of patients with acute aSAH has MIA, with females and patients with a ruptured MCA or BA aneurysm being particularly prone to having MIA. While the modality of aneurysm treatment and the overall survival at both discharge and at one year do not differ in patients with MIA compared with patients with SIA, MIA patients are associated with a higher morbidity including more new FND, potentially due to a higher amount of surgically treated ruptured MCA-aneurysms.