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轻度创伤性脑损伤

ID: ANH12059chis
医疗动画文字记录:大脑是人体最复杂的部分。这个3磅重的器官是智力的中心、记忆的数据库、感觉的解释者和所有动作的指挥者。大脑位于颅骨内,被保护液冲洗,大脑也是身体中最脆弱的器官,它的质地和密度与明胶一样。大脑中有超过1000亿个神经细胞,称为神经元,它们向身体发送电信号和化学信号。每个神经元都有一个细胞体,一个长长的神经纤维叫做轴突,细胞体的突起叫做树突。树突从细胞体延伸出来,接收来自其他神经细胞的信息。大脑中的轴突将神经元彼此连接起来,反过来又提供了与其他大脑区域的广泛互联。因为大脑和它的神经细胞是如此脆弱,头部的突然快速运动可能会造成对它的伤害。在一种被称为“对冲伤”或“加速度-减速度”的损伤中,大脑会来回撞击颅骨的骨性内壁。在高速对冲伤中,撞击的强度可能会导致脑组织肿胀和擦伤,这被称为挫伤。然而,在涉及低速对冲伤的情况下,造成的损害可能是肉眼无法看到的。当大脑在颅骨内来回移动时,大脑中不同密度的区域以不同的速度滑动。穿过这些连接的轴突会受到巨大的剪切力,导致它们从细胞体中被拉伸和撕裂。这种现象被称为轴突剪切或弥漫性轴突损伤。脑损伤可在最初损伤后持续数小时或数天。轴突的损伤会导致大脑神经元之间的交流中断。被撕裂的轴突会迅速退化,向细胞外空间释放有毒的化学物质——神经递质。接着,周围的许多神经元在接下来的24~48小时内开始死亡,加剧了损伤的最初影响。轻度至中度弥漫性轴突损伤(DAI)可导致短暂意识丧失、长期记忆受损、解决问题的能力降低、社交抑制能力降低以及注意力和感知问题等症状。严重的弥漫性轴突损伤可能导致昏迷或持续性植物人状态。在美国,每年有超过100万例的轻度创伤性脑损伤患者,包括弥漫性轴突损伤。其中,超过30万名患者受到损害的长期影响。计算机断层扫描(CT)和磁共振成像(MRI)可以检查轻微创伤性脑损伤。但这些检查的结果通常显示正常的指标。因此,医生必须依靠病史和临床检查来诊断轻度创伤性脑损伤。

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