Temporal patterns of neutrophil recruitment and microthrombus formation in fatal traumatic brain injury: a forensic histopathological study

Estimation of post-traumatic survival time represents a critical issue in forensic neuropathology. While secondary inflammatory and vascular responses after traumatic brain injury (TBI) are known to evolve over time, their intravascular compartmentalization and forensic applicability remain incompletely characterized. We conducted a retrospective histopathological and immunohistochemical study on brain tissue from 51 fatal TBI cases with documented post-traumatic survival times ranging from minutes to approximately two months, and 15 non-traumatic control cases. Neutrophil recruitment was assessed in meningeal and parenchymal cerebral vessels using CD15 immunohistochemistry. Parenchymal vessels were further stratified by caliber. The presence and characteristics of neutrophil-rich microthrombi were systematically evaluated and correlated with survival time. Minimal intravascular neutrophil presence was observed in cases of immediate death and in controls. Early post-traumatic survival was characterized by progressive neutrophil accumulation within meningeal vessels. With increasing survival time, neutrophil recruitment became more prominent in parenchymal vessels, particularly in larger-caliber vessels, and was associated with the appearance of neutrophil-rich microthrombi, which peaked during the subacute phase. In cases with prolonged survival, intravascular neutrophil counts and microthrombi progressively declined. Vascular-associated neutrophil recruitment and neutrophil-rich microthrombus formation follow consistent temporal patterns after fatal TBI. These findings support the forensic relevance of intravascular inflammatory changes as complementary histopathological markers for survival time estimation in fatal TBI. Clinical trial number: not applicable.