Hematoma Hounsfield units and expansion of intracerebral hemorrhage: A potential marker of hemostatic clot contraction.

Abstract

Clot contraction reinforces hemostasis by providing an impermeable barrier and contractile force. Since computed tomography attenuation of intracerebral hemorrhage is largely determined by the density of red blood cells, clot contraction can be reflected in an increase of Hounsfield unit (HU) of hematoma. We hypothesized that hematoma expansion is inversely associated with mean HU of intracerebral hemorrhage at presentation. Eighty-nine consecutive spontaneous intracerebral hemorrhage patients with onset to first computed tomography within 24 h were included. Hematomas were segmented using semiautomated planimetry to measure the volume and mean HU. Hematoma expansion was defined as an increase in hematoma volume by over 33% or 6 mL. Multivariable logistic regression was performed for hematoma expansion. The discrimination power of mean HU for hematoma expansion was assessed using C-statistic. The computed tomography attenuation of hematoma at presentation was 57.5 ± 3.3 HU and the volume was 16.9 ± 23.2 mL. Hematoma expansion occurred in 37.1% of patients. The computed tomography attenuation of hematoma was lower in patients with hematoma expansion than with no expansion (55.7 ± 2.9 HU vs. 58.6 ± 3.1 HU, p-value < 0.01). Multivariable logistic regression revealed that the mean HU of hematoma was inversely associated with hematoma expansion (adjusted odds ratio, 0.64; 95% confidence interval, 0.51-0.80). The C-statistic of the model with four known predictors increased from 0.66 to 0.84 after incorporating mean HU (p-value < 0.01). Intracerebral hemorrhage with lower mean HU of hematoma at presentation is more likely to undergo hematoma expansion. This finding suggests the potential presence of clot contraction process that reinforces hemostasis in intracerebral hemorrhage.