From the Department of Diagnostic and Interventional Radiology and Molecular Imaging (S.A.M., A.A.M.B.O., A.S.A.-R., A.M.A.-E.), Faculty of Medicine, Ain Shams University, Cairo, Egypt
Research on Children with Special Needs Department (N.H.N., A.K., E.R.A.), Medical Research Division, National Research Centre, Cairo, Egypt.
AJNR Am J Neuroradiol. 2022 Jul;43(7):1042-1047. doi: 10.3174/ajnr.A7535. Epub 2022 Jun 9.
Verbal declarative memory performance relies on frontotemporal connectivity. The uncinate fasciculus is a major association tract connecting the frontal and temporal lobes. Hemispheric asymmetries contribute to various cognitive and neurobehavioral abilities. Here we investigated microstructural alterations and hemispheric asymmetry of the uncinate fasciculus and their possible correlation to memory performance of children with learning disorders attributed to verbal memory deficits.
Two groups of right-handed children with learning disorders attributed to verbal memory deficits and typically developing children ( = 20 and 22, respectively) underwent DTI on a 1.5T scanner. Tractography of the uncinate fasciculus in both hemispheres was performed, and fractional anisotropy and diffusivity indices (radial diffusivity, axial diffusivity, and trace) were obtained. The asymmetry index was calculated. Verbal memory was assessed using subsets of the Stanford Binet Intelligence Scale, 4th edition, a dyslexia assessment test, and the Illinois test of Psycholinguistic Abilities. Correlation between diffusion metrics and verbal memory performance was investigated in the learning disorders group. Also, hemispheric differences in each group were tested, and between-group comparisons were performed.
Children with learning disorders showed absence of the normal left-greater-than-right asymmetry of fractional anisotropy and the normal right-greater-than-left asymmetry of radial diffusivity seen in typically developing children. Correlation with verbal memory subsets revealed that the higher the fractional anisotropy and asymmetry index, the better the rapid naming performance ( <.05) was.
These findings demonstrated microstructural aberrations with reduction of hemispheric asymmetry of the uncinate fasciculus, which could disrupt the normal frontotemporal connectivity in children with learning disorders attributed to verbal memory deficits. This outcome gives more understanding of pathologic mechanisms underlying this disorder.
言语陈述性记忆的表现依赖于额颞叶连接。钩束是连接额叶和颞叶的主要联合束。半球不对称性有助于各种认知和神经行为能力。在这里，我们研究了学习障碍儿童的钩束的微观结构改变和半球不对称性及其与言语记忆缺陷导致的记忆表现的可能相关性。
我们对 20 名患有言语记忆缺陷导致的学习障碍和 22 名发育正常的右利手儿童进行了 1.5T 磁共振弥散张量成像检查。对双侧钩束进行了轨迹追踪，并获得了各向异性分数和弥散指标（径向弥散、轴向弥散和轨迹）。计算了不对称指数。言语记忆采用斯坦福-比奈智力量表第四版的子集、阅读障碍评估测试和心理语言学能力伊利诺伊测试进行评估。在学习障碍组中，研究了弥散指标与言语记忆表现之间的相关性。此外，还测试了每个组之间的半球差异，并进行了组间比较。
学习障碍儿童表现出正常儿童存在的左侧大于右侧的各向异性分数不对称性缺失，以及正常儿童存在的右侧大于左侧的径向弥散不对称性缺失。与言语记忆子集中的相关性显示，各向异性分数和不对称指数越高，快速命名表现越好（<.05）。
这些发现表明，学习障碍儿童的钩束存在微观结构异常，其半球不对称性降低，可能破坏言语记忆缺陷导致的学习障碍儿童的正常额颞叶连接。这一结果为理解该障碍的病理机制提供了更多的认识。
