Genetic risk load according to the site of intracranial aneurysms

Objective: We investigated whether risk alleles of single nucleotide polymorphisms associated with intracranial aneurysm (IA) are enriched in patients with familial IA, IA located at the middle cerebral artery (MCA), or IA rupture at a younger age.

Methods: In this case-only study, we calculated genetic risk scores (GRS) for 973 Dutch and 718 Finnish patients with IA by summing effect size–weighted risk allele counts of 7 single nucleotide polymorphisms associated with IAs previously identified through genome-wide association studies. We tested the GRS for association with presence of familial IA or IA at the MCA using logistic regression, and with age at time of IA rupture using linear regression. We also calculated odds ratios with 95% confidence intervals for the proportion of patients with each characteristic in the highest compared with the lowest GRS tertile.

Results: GRS were higher in IA at the MCA in the Dutch (p = 2.5 × 10⁻⁴), Finnish (p = 0.039), and combined cohort (p = 4.9 × 10⁻⁵). GRS were not associated with familial IA in the Dutch (p = 0.34), Finnish (p = 0.45), and combined cohort (p = 0.98), or with age at time of IA rupture in the Dutch (p = 0.28), Finnish (p = 0.86), and combined cohort (p = 0.45). In the combined cohort, odds ratios were 0.89 (0.67–1.20) for familial IA, 1.03 (0.79–1.34) for lower age, and 1.54 (1.20–1.98) for MCA aneurysms.

Conclusions: Our findings suggest that genetic risk factors have a larger role in the development of IA at the MCA than at other sites, and that genetic heterogeneity should be considered in future genetic studies.