# The rupture of smaller counterpart aneurysms in patients with multiple intracranial aneurysms

## TL;DR

This study shows that smaller aneurysms, not the largest ones, can rupture in patients with multiple brain aneurysms, and identifies risk factors beyond size for predicting rupture.

## Contribution

The study identifies new risk factors for rupture of smaller aneurysms in patients with multiple intracranial aneurysms, challenging the reliance on size alone.

## Key findings

- The total number of aneurysms and use of multiple antihypertensive drugs were significant risk factors for smaller aneurysm rupture.
- Smoking, radiographic features, and hypertension were not significantly associated with smaller aneurysm rupture.
- The study suggests that some patients with multiple aneurysms may benefit from treating more than one aneurysm at once.

## Abstract

In case of multiple (unruptured) intracranial aneurysms (M[U]IA), deciding which intracranial aneurysms (IA) should be treated and which at first can be challenging. The most accepted risk factor in making these decisions is IA size. However, a smaller intracranial counterpart aneurysm (SICA) and not the largest IA in patients with MIA might cause subarachnoid hemorrhage (aSAH). By falsely assessing a SICA as benign and withholding treatment, these patients are put at risk for SICA rupture before treatment. Therefore, there is a paramount need to improve the identification of more rupture-prone SICA, especially regarding the improved accessibility to intracranial imaging leading to increasing incidences of patients with (M)IA. From our institutional observational cohort, containing data of all patients with IA treated between 01/2003 and 06/2016, 285 patients with MIA who were hospitalized for acute aSAH were identified. In 261 patients, the largest of their IA ruptured, and in 24 patients, a SICA ruptured (defined by a size difference of ≥ 2 mm). Different demographic, clinical, laboratory, and radiographic characteristics of patients and IA were collected. Univariate and multivariate binary regression analyses (UVA, MVA) were performed to identify putative risk factors for the rupture of SICA. In the final MVA, the total number of IA (p = 0.043; aOR = 1.61) and the intake of multiple antihypertensive drugs (p < 0.001; aOR = 3.96) showed a statistically significant association with the ruptured status of SICA. In contrast, smoking (p = 0.825), radiographic risk factors (i.e., daughter sack p = 0.736, IA irregularities p = 0.286, location p = 0.665), arterial hypertension (p = 0.869), and blood examinations did not show a statistically significant regression with the rupture of SICA. This study found statistically significant putative risk factors to identify IA rupture factors that might overweight IA size in certain situations. Thereby, a subgroup of MIA patients could be identified who require treatment with ≥ 2 antihypertensive agents or have a high number of IA that might benefit from a simultaneous treatment of more than one UIA in a single session. Further studies are needed to verify these results and improve the identification of more rupture-prone SICA in MUIA patients.

The online version contains supplementary material available at 10.1038/s41598-025-21914-6.