Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada; Psychology, University of Toronto, Toronto, Ontario, Canada; Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.
Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada; Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada; Autism Research Centre, Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, Toronto, ON, Canada; Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
Neuroimage Clin. 2021;32:102843. doi: 10.1016/j.nicl.2021.102843. Epub 2021 Sep 28.
Very low birth weight (VLBW) infants are at risk for disrupted white matter maturation, yet little is known about the contributing factors, particularly at preschool-age when cognitive difficulties begin to emerge. We examined white matter microstructure in five-year-old VLBW and full-term (FT) children, and its association with cognitive outcomes and birth weight.
Multi-shell diffusion and MR images were obtained for 41 VLBW (mean birth weight: 1028.6 ± 256.8 g) and 26 FT (3295.4 ± 493.9 g) children. Fractional anisotropy (FA), radial diffusivity (RD), neurite orientation dispersion index (ODI) and density index (NDI) were estimated using diffusion tensor and neurite orientation dispersion and density imaging models. Between-group analyses used a general linear model with group and sex as explanatory variables. Within-group associations between white matter microstructure, cognitive outcomes and birth weight were also investigated.
VLBW compared to FT children showed lower FA and NDI across widespread white matter regions. Smaller clusters of atypical ODI were also found in VLBW children. Within-group analyses in FT children revealed that lower RD and higher NDI were associated with vocabulary acquisition and working memory. In VLBW children, higher FA and NDI, and lower RD and ODI, were associated with improved processing speed. In both groups, FA was positively associated with birth weight.
Our findings demonstrate white matter alterations in young VLBW children, including widespread reductions in axon density that may reflect sustained myelination disruptions. The associations with cognitive outcomes may also highlight which of the VLBW children are at higher risk for later cognitive difficulties.
极低出生体重（VLBW）婴儿的脑白质成熟过程易受到干扰，但对于导致这一现象的因素知之甚少，尤其是在认知问题开始显现的学龄前阶段。我们检测了五岁 VLBW 婴儿和足月（FT）婴儿的脑白质微观结构，并研究了其与认知结果和出生体重的相关性。
为 41 名 VLBW（平均出生体重：1028.6±256.8 克）婴儿和 26 名 FT（3295.4±493.9 克）婴儿采集了多壳层扩散加权成像和磁共振成像。采用弥散张量成像和神经丝取向弥散和密度成像模型，估计各向异性分数（FA）、径向弥散度（RD）、神经丝取向离散指数（ODI）和密度指数（NDI）。采用一般线性模型，以组和性别为解释变量进行组间分析。还研究了脑白质微观结构、认知结果和出生体重之间的组内相关性。
与 FT 婴儿相比，VLBW 婴儿的广泛脑白质区域的 FA 和 NDI 均较低。VLBW 婴儿的 ODI 也存在较小的异常簇。FT 婴儿的组内分析显示，RD 越低、NDI 越高与词汇获取和工作记忆相关。VLBW 婴儿的 FA 和 NDI 越高、RD 和 ODI 越低，与处理速度的提高相关。在两组中，FA 与出生体重呈正相关。
本研究结果表明，VLBW 婴儿存在脑白质改变，包括广泛的轴突密度降低，这可能反映了持续的髓鞘破坏。与认知结果的相关性也可能突出了哪些 VLBW 婴儿存在更高的认知障碍风险。
