背景:脑视力障碍(CVI)是早期脑损伤的常见后遗症,损坏,或畸形,是全球儿科人群视觉功能障碍的主要个体原因之一。尽管CVI患者在潜在病因和视觉行为表现方面都是异质性的,在哪些白质通路潜在改变方面,可能存在潜在的相似性。这项探索性研究使用扩散纤维束成像来检查体积的潜在差异,定量各向异性(QA),以及意思,轴向,和径向扩散系数(平均扩散系数(MD),轴向扩散率(AD)和径向扩散率(RD),分别)与通常有视力和发育中的对照组相比,一组患有CVI的年轻人中的背侧和腹侧视觉血流通路。
方法:在10名诊断为CVI的个体的样本中获取了高角度分辨率扩散成像(HARDI)数据(平均年龄=17.3岁,2.97标准偏差(SD),范围14-22岁)和17个对照(平均年龄=19.82岁,3.34SD,范围15-25年)。下纵束(ILF),额枕骨下束(IFOF),枕骨垂直束(VOF),和上纵束的三个分区(SLFI,II,和III)进行虚拟重建和平均气道体积(针对颅内体积进行调整),MD,AD,比较CVI组和对照组的RD值。作为次要分析,进行方差分析(ANOVA)以调查基于病因的潜在差异(即,由于脑室周围白质软化(CVI-PVL)引起的CVI和由于其他原因引起的CVI(CVI-非PVL))。
结果:我们观察到CVI组内有很大程度的变化,将CVI样本作为单一组进行检查时,最大限度地减少了纤维束造影结果的总体组差异。在我们的次要分析中,与对照组和其他原因导致的CVI患者相比,我们观察到CVI-PVL组的气道容积显著减少.我们还观察到QA普遍显著增加,MD,与对照组相比,CVI-PVL中的AD,在CVI-非PVL组中具有混合效应。
结论:这些数据为与视觉感知处理技能有关的关键白质肌束的异常发展提供了初步证据,在患有CVI的个体中通常会受到不同程度的损害。结果还表明,白质变化的严重程度可能部分归因于大脑视觉障碍的根本原因。除了行为测试之外,还需要在更大的样本中进行其他分析,以充分了解白质完整性之间的关系,视觉功能障碍,以及CVI个体的相关原因。
BACKGROUND: Cerebral visual impairment (CVI) is a common sequala of early brain injury, damage, or malformation and is one of the leading individual causes of visual dysfunction in pediatric populations worldwide. Although patients with CVI are heterogeneous both in terms of underlying etiology and visual behavioural manifestations, there may be underlying similarities in terms of which white matter pathways are potentially altered. This exploratory study used diffusion tractography to examine potential differences in volume, quantitative anisotropy (QA), as well as mean, axial, and radial diffusivities (mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD), respectively) focusing on the dorsal and ventral visual stream pathways in a cohort of young adults with CVI compared to typically sighted and developing controls.
METHODS: High angular resolution diffusion imaging (HARDI) data were acquired in a sample of 10 individuals with a diagnosis of CVI (mean age = 17.3 years, 2.97 standard deviation (SD), range 14-22 years) and 17 controls (mean age = 19.82 years, 3.34 SD, range 15-25 years). The inferior longitudinal fasciculus (ILF), inferior fronto-occipital fasciculus (IFOF), vertical occipital fasciculus (VOF), and the three divisions of the superior longitudinal fasciculus (SLF I, II, and III) were virtually reconstructed and average tract volume (adjusted for intracranial volume), MD, AD, and RD were compared between CVI and control groups. As a secondary analysis, an analysis of variance (ANOVA) was carried out to investigate potential differences based on etiology (i.e., CVI due to periventricular leukomalacia (CVI-PVL) and CVI due to other causes (CVI-nonPVL)).
RESULTS: We observed a large degree of variation within the CVI group, which minimized the overall group differences in tractography outcomes when examining the CVI sample as a unitary group. In our secondary analysis, we observed significant reductions in tract volume in the CVI-PVL group compared to both controls and individuals with CVI due to other causes. We also observed widespread significant increases in QA, MD, and AD in CVI-PVL compared to the control group, with mixed effects in the CVI-nonPVL group.
CONCLUSIONS: These data provide preliminary evidence for aberrant development of key white matter fasciculi implicated in visual perceptual processing skills, which are often impaired to varying degrees in individuals with CVI. The results also indicate that the severity and extent of the white matter changes may be due in part to the underlying cause of the cerebral visual impairments. Additional analyses will need to be done in a larger sample alongside behavioural testing to fully appreciate the relationships between white matter integrity, visual dysfunction, and associated causes in individuals with CVI.