Epidemiology studies of traumatic brain injury (TBI) show individuals with a prior history of TBI experience an increased risk of future TBI with a significantly more detrimental outcome. But the mechanisms through which prior head injuries may affect risks of injury during future head insults have not been identified. In this work, we show that prior brain tissue injury in the form of mechanically induced axonal injury and glial scar formation can facilitate future mechanically induced tissue injury. To achieve this, we use finite element computational models of brain tissue and a history-dependent pathophysiology-based mechanically-induced axonal injury threshold to determine the evolution of axonal injury and scar tissue formation and their effects on future brain tissue stretching. We find that due to the reduced stiffness of injured tissue and glial scars, the existence of prior injury can increase the risk of future injury in the vicinity of prior injury during future brain tissue stretching. The softer brain scar tissue is shown to increase the strain and strain rate in its vicinity by as much as 40% in its vicinity during dynamic stretching that reduces the global strain required to induce injury by 20% when deformed at 15 s strain rate. The results of this work highlight the need to account for patient history when determining the risk of brain injury.

中文翻译：

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脑组织拉伸过程中先前轴突损伤对后续损伤的影响——一种中尺度计算方法

创伤性脑损伤 (TBI) 的流行病学研究表明，有 TBI 既往病史的个体未来发生 TBI 的风险会增加，并产生明显更严重的不良后果。但之前的头部受伤可能影响未来头部损伤的受伤风险的机制尚未确定。在这项工作中，我们表明，机械诱导的轴突损伤和神经胶质疤痕形成形式的先前脑组织损伤可以促进未来机械诱导的组织损伤。为了实现这一目标，我们使用脑组织的有限元计算模型和基于历史的病理生理学机械诱导的轴突损伤阈值来确定轴突损伤和疤痕组织形成的演变及其对未来脑组织拉伸的影响。我们发现，由于受伤组织和神经胶质疤痕的硬度降低，先前损伤的存在会增加未来脑组织拉伸过程中先前损伤附近未来受伤的风险。研究表明，较软的脑疤痕组织在动态拉伸过程中，其附近的应变和应变率增加了 40%，当以 15 秒应变率变形时，导致损伤所需的整体应变减少了 20%。这项工作的结果强调了在确定脑损伤风险时需要考虑患者病史。