Background and purpose: Hematoma volume is the most potent predictor of outcome in spontaneous intracerebral hemorrhage (ICH), and hematoma expansion after hospital presentation occurs in up to 40% of individuals. Among patients with lobar ICH, the apolipoprotein E (APOE) ε2 allele predicts larger hematoma volumes at presentation. We investigated whether the ε2 allele also identifies individuals at increased risk of hematoma expansion.
Methods: We analyzed 510 patients with primary ICH and genetic data available from an ongoing prospective cohort study. Baseline and follow-up CT scans were assessed for ICH location and volume using computer-assisted volumetric methods.
Results: Individuals with lobar ICH who possessed APOE ε2 were at increased risk for hematoma expansion (OR, 2.72; 95% CI, 1.19-6.23; P=0.009). The highest odds of expansion were in patients who qualified for the diagnosis of cerebral amyloid angiopathy-related ICH and carried the APOE ε2 allele (OR, 6.02; 95% CI, 1.60-22.58; P=0.008). There was no effect of ε2 on hematoma expansion in deep ICH and APOE ε4 had no effect on hematoma expansion in lobar or deep ICH.
Conclusions: Possession of APOE ε2 predisposes individuals with lobar ICH to hematoma expansion. This effect is even more pronounced in patients with amyloid angiopathy-related ICH, consistent with the ε2 allele's role in vascular amyloid deposition and vessel fragility.