UK Dementia Research Institute, Care Research & Technology Centre, Imperial College London, London, UK.
Department of Brain Sciences, Hammersmith Hospital, Imperial College London, London, UK.
Brain. 2023 Jul 3;146(7):3063-3078. doi: 10.1093/brain/awac485.
Sports related head injuries can cause transient neurological events including loss of consciousness and dystonic posturing. However, it is unknown why head impacts that appear similar produce distinct neurological effects. The biomechanical effect of impacts can be estimated using computational models of strain within the brain. Here, we investigate the strain and strain rates produced by professional American football impacts that led to loss of consciousness, posturing or no neurological signs. We reviewed 1280 National Football League American football games and selected cases where the team's medical personnel made a diagnosis of concussion. Videos were then analysed for signs of neurological events. We identified 20 head impacts that showed clear video signs of loss of consciousness and 21 showing clear abnormal posturing. Forty-one control impacts were selected where there was no observable evidence of neurological signs, resulting in 82 videos of impacts for analysis. Video analysis was used to guide physical reconstructions of these impacts, allowing us to estimate the impact kinematics. These were then used as input to a detailed 3D high-fidelity finite element model of brain injury biomechanics to estimate strain and strain rate within the brain. We tested the hypotheses that impacts producing loss of consciousness would be associated with the highest biomechanical forces, that loss of consciousness would be associated with high forces in brainstem nuclei involved in arousal and that dystonic posturing would be associated with high forces in motor regions. Impacts leading to loss of consciousness compared to controls produced higher head acceleration (linear acceleration; 81.5 g ± 39.8 versus 47.9 ± 21.4; P = 0.004, rotational acceleration; 5.9 krad/s2 ± 2.4 versus 3.5 ± 1.6; P < 0.001) and in voxel-wise analysis produced larger brain deformation in many brain regions, including parts of the brainstem and cerebellum. Dystonic posturing was also associated with higher deformation compared to controls, with brain deformation observed in cortical regions that included the motor cortex. Loss of consciousness was specifically associated with higher strain rates in brainstem regions implicated in maintenance of consciousness, including following correction for the overall severity of impact. These included brainstem nuclei including the locus coeruleus, dorsal raphé and parabrachial complex. The results show that in head impacts producing loss of consciousness, brain deformation is disproportionately seen in brainstem regions containing nuclei involved in arousal, suggesting that head impacts produce loss of consciousness through a biomechanical effect on key brainstem nuclei involved in the maintenance of consciousness.
运动相关的头部损伤可导致短暂的神经事件，包括意识丧失和扭曲姿势。然而，为什么看似相似的头部冲击会产生不同的神经效应尚不清楚。大脑内应变的生物力学效应可以通过大脑应变的计算模型来估计。在这里，我们研究了导致意识丧失、姿势异常或无神经体征的职业美式足球冲击所产生的应变和应变速率。我们回顾了 1280 场美国国家橄榄球联盟美式足球比赛，并选择了球队医务人员诊断为脑震荡的病例。然后，对视频进行分析以寻找神经事件的迹象。我们确定了 20 个头部冲击，这些冲击在视频中清楚地显示出意识丧失的迹象，21 个冲击清楚地显示出异常姿势。选择了 41 个对照冲击，其中没有观察到神经体征的证据，从而得到 82 个冲击的视频进行分析。视频分析用于指导这些冲击的物理重建，使我们能够估计冲击的运动学。然后将这些用作大脑损伤生物力学的详细 3D 高保真有限元模型的输入，以估计大脑内的应变和应变速率。我们检验了以下假设：导致意识丧失的冲击与最高生物力学力有关，意识丧失与参与觉醒的脑干核中的高力有关，扭曲姿势与运动区的高力有关。与对照组相比，导致意识丧失的冲击产生了更高的头部加速度（线性加速度；81.5 g ± 39.8 与 47.9 ± 21.4；P = 0.004，旋转加速度；5.9 krad/s2 ± 2.4 与 3.5 ± 1.6；P < 0.001），并且在体素分析中，大脑的变形在许多大脑区域都更大，包括脑干和小脑的一部分。与对照组相比，扭曲姿势也与更高的变形有关，在包括运动皮层在内的皮质区域观察到大脑变形。意识丧失与参与意识维持的脑干区域的更高应变速率有关，包括在纠正冲击的总体严重程度后。这些区域包括蓝斑核、背缝核和臂旁复合体等脑干核。结果表明，在导致意识丧失的头部冲击中，大脑变形主要出现在包含参与觉醒的核的脑干区域，这表明头部冲击通过对参与意识维持的关键脑干核的生物力学作用导致意识丧失。
