Association Between Hematoma Expansion Severity and Outcome and Its Interaction With Baseline Intracerebral Hemorrhage Volume

Background and objective: Hematoma expansion (HE) is a major determinant of neurological deterioration and poor outcome in intracerebral hemorrhage (ICH) and represents an appealing therapeutic target. We analyzed the prognostic effect of different degrees of HE. Methods: retrospective analysis of ICH patients admitted at eight academic institutions in Italy, Germany, Canada, China and United States. All patients underwent baseline and follow-up imaging for HE assessment. Relative HE (rHE) was classified as follows: (none < 0%), mild (0-33%), moderate (33.1-66%) and severe (> 66%). Absolute HE (aHE) was classified as none (< 0 mL), mild (0-6.0 mL), moderate (6.1-12.5 mL) and severe (> 12.5 mL). Predictors of poor functional outcome (90 days modified Rankin Scale 4-6) were explored with logistic regression. Results: We included 2163 subjects, of whom 1211 (56.7%) had poor outcome. The occurrence of severe aHE or rHE was more common in patients with unfavorable outcome (13.9% vs 6.5%, p<0.001 and 18.3% vs 7.2 %, p<0.001 respectively). This association was confirmed in logistic regression (rHE OR 1.98, 95% CI 1.38-2.82, p<0.001; aHE odds ratio (OR)1.73,95% confidence interval (CI) 1.23-2.45, p=0.002) while there was no association between mild or moderate HE and poor outcome. The association between severe HE and poor outcome was significant only in patients with baseline ICH volume below 30 mL. Discussion: The strongest association between HE and outcome was observed in patients with smaller initial volume experiencing severe HE. These findings may inform clinical trial design and guide clinicians in selecting patients for anti-expansion therapies.==========.