Lower admission eosinophil levels were independently associated with higher risks of malignant brain edema and poor 3-month functional outcome after mechanical thrombectomy, and malignant brain edema statistically accounted for only 12.05% (95% CI: 2.92-26%) of the eosinophil-outcome association.
Malignant brain edema developed in about one in five acute ischemic stroke patients treated with mechanical thrombectomy in this cohort.
Higher admission eosinophil count (continuous, standardized) was independently associated with a lower risk of malignant brain edema after full adjustment.
Dichotomizing eosinophils at the median produced a consistent association with lower risk of malignant brain edema.
Higher standardized eosinophil count was independently associated with reduced risk of poor 3-month functional outcome after thrombectomy.
Mediation analysis showed that malignant brain edema accounted for a small portion of the eosinophil-outcome association.
The authors conclude that lower admission eosinophil levels are associated with higher risks of MBE and poor outcome, and that findings are hypothesis-generating and need external validation.
This study looked at 442 stroke patients who had a clot-removal procedure (mechanical thrombectomy) and asked whether the number of eosinophils, a type of white blood cell, measured at hospital admission was linked to dangerous brain swelling and to how well patients recovered after three months. Brain swelling severe enough to be called malignant developed in about 22% of patients. Patients with lower eosinophil counts at admission were more likely to develop malignant brain swelling and more likely to have a poor functional outcome at three months, even after accounting for other factors. A statistical mediation analysis suggested that brain swelling explained only about 12% of the link between eosinophils and outcome, so most of the association appears to run through other pathways not identified here. This research suggests eosinophil count might be a useful marker related to risk after thrombectomy, but it does not show that eosinophils cause these outcomes. The data came from a single group of patients, and the authors describe the findings as hypothesis-generating that need confirmation in larger multicenter studies.
Lu H, Guo Z, Yu S, Yang J, Xiao G. (2026). Eosinophils, malignant brain edema, and functional outcome after mechanical thrombectomy: a mediation analysis.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1939369