Muñoz Maniega Susana, Meijboom Rozanna, Chappell Francesca M, Valdés Hernández Maria Del C, Starr John M, Bastin Mark E, Deary Ian J, Wardlaw Joanna M
Neuroimaging Sciences, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom.
UK Dementia Research Institute at the University of Edinburgh, Edinburgh, United Kingdom.
Front Neurol. 2019 Jul 25;10:784. doi: 10.3389/fneur.2019.00784. eCollection 2019.
White matter hyperintensities (WMH) are commonly seen on structural MRI of older adults and are a manifestation of underlying and adjacent tissue damage. WMH may contribute to cortical disconnection and cognitive dysfunction, but it is unclear how WMH affect intersecting or nearby white matter tract integrity. This study investigated the effects of WMH on tract microstructure by determining the spatial distribution of water diffusion characteristics in white matter tract areas adjacent to both intersecting and nearby WMH. We used diffusion and structural MRI data from 52 representative participants from the Lothian Birth Cohort 1936 (72.2 ± 0.7 years) including a range of WMH burden. We segmented WMH, reconstructed 18 main white mater tracts using automated quantitative tractography and identified intersections between tracts and WMH. We measured mean diffusivity (MD) and fractional anisotropy (FA) in tract tissue at 2 mm incremental distances from tract-intersecting and non-intersecting (nearby) WMH. We observed a spatial gradient of FA and MD abnormalities for most white matter tracts which diminished with a similar distance pattern for tract-intersecting and nearby WMH. Overall, FA was higher, while MD was lower around nearby WMH compared with tract-intersecting WMH. However, for some tracts, FA was lower in areas immediately surrounding nearby WMH, although with faster normalization than in FA values surrounding tract-intersecting WMH. WMH have similar effects on tract infrastructure, whether they be intersecting or nearby. However, the observed differences in tract water diffusion properties around WMH suggest that degenerative processes in small vessel disease may propagate further along the tract for intersecting WMH, while in some areas of the brain there is a larger and more localized accumulation of axonal damage in tract tissue nearby a non-connected WMH. Longitudinal studies should address differential effects of intersecting vs. nearby WMH progression and how they contribute to cognitive aging.
白质高信号（WMH）在老年人的结构磁共振成像（MRI）中很常见，是潜在和相邻组织损伤的一种表现。WMH可能导致皮质连接中断和认知功能障碍，但尚不清楚WMH如何影响交叉或附近的白质束完整性。本研究通过确定与交叉和附近WMH相邻的白质束区域中水扩散特征的空间分布，研究了WMH对束微观结构的影响。我们使用了来自1936年洛锡安出生队列的52名代表性参与者（72.2±0.7岁）的扩散和结构MRI数据，这些参与者具有一系列的WMH负担。我们对白质高信号进行了分割，使用自动定量纤维束成像重建了18条主要白质束，并确定了束与白质高信号之间的交叉点。我们在距束交叉和非交叉（附近）白质高信号2毫米递增距离处测量了束组织中的平均扩散率（MD）和分数各向异性（FA）。我们观察到大多数白质束的FA和MD异常存在空间梯度，对于交叉和附近的白质高信号，这种梯度以类似的距离模式减小。总体而言，与交叉白质高信号相比，附近白质高信号周围的FA较高，而MD较低。然而，对于一些束，在紧邻附近白质高信号的区域FA较低，尽管其归一化速度比交叉白质高信号周围的FA值更快。无论白质高信号是交叉的还是附近的，它们对束结构的影响相似。然而，在白质高信号周围观察到的束水扩散特性差异表明，小血管疾病中的退行性过程可能在交叉白质高信号处沿束进一步传播，而在大脑的某些区域，在未连接的白质高信号附近的束组织中存在更大且更局部的轴突损伤积累。纵向研究应探讨交叉与附近白质高信号进展的差异效应以及它们如何导致认知衰老。
