Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
Injury. 2021 Jun;52(6):1271-1276. doi: 10.1016/j.injury.2020.10.055. Epub 2020 Oct 12.
Brainstem, which connects the distal part of the brain and the spinal cord, contains main motor and sensory nerves and facilitates communication between the cerebrum, cerebellum, and spinal cord. Due to the complicated anatomy and neurostructure of brainstem, surgical interventions to resect brainstem tumors are particularly challenging, and new approaches to reduce the risk of surgical brain injury are of utmost importance. Although previous studies have investigated the structural anisotropy of brain white matter, the effect of axonal fibers on the mechanical properties of white matter has not yet been fully understood. The current study aims to compare the effect of axonal orientation on changes in material properties of brainstem under large deformations and failure through a novel approach. Using diffusion tensor imaging (DTI) on ex-vivo bovine brains, we determined the orientation of axons in brainstem. We extracted brainstem samples in two orthogonal directions, parallel and perpendicular to the axons, and subjected to uniaxial tension to reach the failure at loading rates of 50 mm/min and 150 mm/min. The results showed that the tearing energy and failure strain of samples with axons parallel to the force direction were approximately 1.5 times higher than the samples with axons perpendicular to the force direction. The results also revealed that as the sample's initial length increases, its failure strain decreases. These results emphasize the importance of the axon orientation in the mechanical properties of brainstem, and suggest that considering the directional-dependent behavior for this tissue could help to propose new surgical interventions for reducing the risk of injury during tumor resection.
脑干连接大脑的远端部分和脊髓，包含主要的运动和感觉神经，促进大脑、小脑和脊髓之间的通信。由于脑干的解剖结构和神经结构复杂，对脑干肿瘤进行切除的手术干预极具挑战性，因此，寻找降低手术脑损伤风险的新方法至关重要。尽管先前的研究已经调查了脑白质的结构各向异性，但轴突纤维对脑白质力学性能的影响尚未被充分理解。本研究旨在通过一种新方法比较轴突取向对大变形和失效下脑干物质属性变化的影响。通过对牛脑进行离体扩散张量成像（DTI），我们确定了脑干中轴突的取向。我们分别沿平行和垂直于轴突的两个正交方向提取脑干样本，并在加载速率为 50mm/min 和 150mm/min 时对其进行单轴拉伸，直至失效。结果表明，与垂直于力方向的样本相比，平行于力方向的样本的撕裂能和失效应变大约高出 1.5 倍。结果还表明，随着样本初始长度的增加，其失效应变减小。这些结果强调了轴突取向对脑干力学性能的重要性，并表明考虑该组织的方向依赖性行为有助于提出新的手术干预措施，以降低肿瘤切除过程中损伤的风险。
