Hematoma expansion and hemostasis in traumatic brain injury

When a traumatic brain injury (TBI) causes an intracranial hematoma, follow-up scans often reveal hematoma expansion - a common secondary injury believed to worsen outcomes. This thesis explores the measurement, impact, and underlying mechanisms of hematoma expansion in TBI.

In Study I, we compared the ABC/2 method, which estimates hematoma volume based on ellipsoid geometry, with computer-assisted volumetric analysis. We found that ABC/2 consistently overestimated hematoma volume, particularly for irregularly shaped lesions. Volumetric analysis offered more precise measurements and is recommended for studies where volume accuracy is critical.

Study II focused on identifying the best method for measuring hematoma expansion. We found that absolute expansion (measured in milliliters) was a better predictor of outcomes than relative expansion (measured as a percentage), suggesting that absolute expansion should be the standard in future studies.

In Study III, we mapped the time course of hematoma expansion after injury, finding that the majority of expansion occurs within the first six hours, underscoring this as a critical window for intervention. Contusions also expanded more and over a longer period of time compared to extra-axial hematomas. Additionally, hematoma expansion was identified as an independent predictor of outcomes, supporting its potential as a therapeutic target.

Finally, Study IV examined how post-admission disruptions in coagulation and fibrinolysis contribute to contusion expansion. We observed early changes in fibrinogen levels, activated partial thromboplastin time, prothrombin time, and platelet count. However, these alterations were relatively modest and did not correlate with contusion volume, raising questions about the necessity of targeting these hemostatic changes, and that alternative markers may be needed to measure the body's hemostatic response to TBI.

Together, these studies shed light on the clinical significance of hematoma expansion in TBI and provide guidance for its measurement and potential treatment.

List of scientific papers

I. Fletcher-Sandersjöö A, Lewén A, Hånell A, Nelson DW, Maegele M, Svensson M, Bellander BM, Enblad P, Thelin EP, Svedung Wettervik T. Volumetric assessment of traumatic intracranial hematomas: is ABC/2 reliable? Journal of Neurotrauma. 2024 online ahead of print. https://doi.org/10.1089/neu.2024.0248

II. Fletcher-Sandersjöö A*, Svedung Wettervik T*, Tatter C, Tjerkaski J, Nelson DW, Maegele M, Svensson M, Lewén A, Enblad P, Bellander BM, Thelin EP. Absolute Contusion Expansion Is Superior to Relative Expansion in Predicting Traumatic Brain Injury Outcomes: A Multi- Center Observational Cohort Study. Journal of Neurotrauma. 2024 Mar;41(5-6):705-713. https://doi.org/10.1089/neu.2023.0274

III. Fletcher-Sandersjöö A, Tatter C, Tjerkaski J, Bartek J Jr, Maegele M, Nelson DW, Svensson M, Thelin EP, Bellander BM. Time Course and Clinical Significance of Hematoma Expansion in Moderate-to- Severe Traumatic Brain Injury: An Observational Cohort Study. Neurocritical Care. 2023 Feb;38(1):60-70. https://doi.org/10.1007/s12028-022-01609-w

IV. Fletcher-Sandersjoo A*, Hammarlund E*, Lindblad C, Froese L, Maegele M, Svensson M, Bellander BM, Nelson DW, Thelin EP. Relationship between post-traumatic hemostatic alterations and contusion volume in isolated traumatic brain injury: an observational cohort study. [Manuscript]

* shared first authorship