Background

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.

Methods

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.

Results

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.

Conclusions

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.

中文翻译：

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出生体重极低的儿童的白质改变和认知结果

背景

极低出生体重 (VLBW) 婴儿存在白质成熟受阻的风险，但对其影响因素知之甚少，尤其是在学龄前开始出现认知困难时。我们检查了 5 岁 VLBW 和足月 (FT) 儿童的白质微观结构，及其与认知结果和出生体重的关系。

方法

获得了 41 名 VLBW（平均出生体重：1028.6 ± 256.8 g）和 26 名 FT（3295.4 ± 493.9 g）儿童的多壳扩散和 MR 图像。分数各向异性 (FA)、径向扩散率 (RD)、神经突定向分散指数 (ODI) 和密度指数 (NDI) 使用扩散张量和神经突定向分散和密度成像模型进行估计。组间分析使用以组和性别作为解释变量的一般线性模型。还研究了白质微结构、认知结果和出生体重之间的组内关联。

结果

与 FT 儿童相比，VLBW 在广泛的白质区域显示出较低的 FA 和 NDI。在 VLBW 儿童中也发现了较小的非典型 ODI 簇。FT 儿童的组内分析显示，较低的 RD 和较高的 NDI 与词汇习得和工作记忆有关。在 VLBW 儿童中，较高的 FA 和 NDI 以及较低的 RD 和 ODI 与处理速度的提高有关。在两组中，FA 与出生体重呈正相关。

结论

我们的研究结果表明年轻 VLBW 儿童的白质改变，包括轴突密度的广泛降低，这可能反映了持续的髓鞘形成中断。与认知结果的关联也可能突出显示哪些 VLBW 儿童后期认知困难的风险较高。