Andreasen Sara H, Andersen Kasper W, Conde Virginia, Dyrby Tim B, Puonti Oula, Kammersgaard Lars P, Madsen Camilla G, Madsen Kristoffer H, Poulsen Ingrid, Siebner Hartwig R
Danish Research Centre for Magnetic Resonance (DRCMR), Centre for Functional and Diagnostic Imaging Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.
Research Unit on Brain Injury Rehabilitation Copenhagen (RUBRIC), Department of Neurorehabilitation, Traumatic Brain Injury, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
Front Neurol. 2020 Sep 4;11:800. doi: 10.3389/fneur.2020.00800. eCollection 2020.
Diffuse traumatic axonal injury (TAI) is one of the key mechanisms leading to impaired consciousness after severe traumatic brain injury (TBI). In addition, preferential regional expression of TAI in the brain may also influence clinical outcome. We addressed the question whether the regional expression of microstructural changes as revealed by whole-brain diffusion tensor imaging (DTI) in the subacute stage after severe TBI may predict the duration of post-traumatic amnesia (PTA). Fourteen patients underwent whole-brain DTI in the subacute stage after severe TBI. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for five bilateral brain regions: fronto-temporal, parieto-occipital, and midsagittal hemispheric white matter, as well as brainstem and basal ganglia. Region-specific calculation of mean FA and MD only considered voxels that showed no tissue damage, using an exclusive mask with all voxels that belonged to local brain lesions or microbleeds. Mean FA or MD of the five brain regions were entered in separate partial least squares (PLS) regression analyses to identify patterns of regional microstructural changes that account for inter-individual variations in PTA. For FA, PLS analysis revealed two spatial patterns that significantly correlated with individual PTA. The lower the mean FA values in all five brain regions, the longer that PTA lasted. A pattern characterized by lower FA values in the deeper brain regions relative to the FA values in the hemispheric regions also correlated with longer PTA. Similar trends were found for MD, but opposite in sign. The spatial FA changes as revealed by PLS components predicted the duration of PTA. Individual PTA duration, as predicted by a leave-one-out cross-validation analysis, correlated with true PTA values (Spearman = 0.68, = 0.008). Two coarse spatial patterns of microstructural damage, indexed as reduction in FA, were relevant to recovery of consciousness after TBI. One pattern expressed was consistent with diffuse microstructural damage across the entire brain. A second pattern was indicative of a preferential damage of deep midline brain structures.
弥漫性创伤性轴索损伤（TAI）是导致重度创伤性脑损伤（TBI）后意识障碍的关键机制之一。此外，TAI在脑内的区域特异性表达也可能影响临床预后。我们探讨了在重度TBI亚急性期，全脑扩散张量成像（DTI）所显示的微观结构变化的区域表达是否可预测创伤后遗忘（PTA）的持续时间。14例患者在重度TBI亚急性期接受了全脑DTI检查。计算了五个双侧脑区的平均各向异性分数（FA）和平均扩散率（MD）：额颞叶、顶枕叶和大脑半球矢状面白质，以及脑干和基底节。仅使用属于局部脑损伤或微出血的所有体素的排他性掩码，对平均FA和MD进行区域特异性计算，仅考虑未显示组织损伤的体素。将五个脑区的平均FA或MD输入单独的偏最小二乘（PLS）回归分析中，以识别解释个体PTA差异的区域微观结构变化模式。对于FA，PLS分析揭示了两种与个体PTA显著相关的空间模式。所有五个脑区的平均FA值越低，PTA持续的时间越长。相对于半球区域的FA值，深部脑区FA值较低的模式也与较长的PTA相关。MD也发现了类似趋势，但符号相反。PLS成分所显示的空间FA变化可预测PTA的持续时间。通过留一法交叉验证分析预测的个体PTA持续时间与真实PTA值相关（Spearman相关系数 = 0.68，P = 0.008）。两种以FA降低为指标的微观结构损伤的粗略空间模式与TBI后的意识恢复相关。所表达的一种模式与全脑弥漫性微观结构损伤一致。第二种模式表明深部中线脑结构存在优先损伤。
