Laboratory for Visual Neuroplasticity, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA.
Lab of Neuroimaging and Vision Science, Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
J Integr Neurosci. 2024 Jan 10;23(1):1. doi: 10.31083/j.jin2301001.
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.
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)).
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.
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.
脑性视觉损伤（CVI）是早期脑损伤、损伤或畸形的常见后遗症，也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存在异质性，但在潜在的白质通路可能发生改变方面，可能存在相似之处。本探索性研究使用弥散张量成像（DTI）来检查在患有 CVI 的年轻成年人队列中与正常视力和发育对照组相比，背侧和腹侧视觉流通路的体积、定量各向异性（QA）以及平均、轴向和径向弥散度（平均弥散度（MD）、轴向弥散度（AD）和径向弥散度（RD））的潜在差异。
在一组 10 名 CVI 患者（平均年龄=17.3 岁，2.97 标准差（SD），范围 14-22 岁）和 17 名对照者（平均年龄=19.82 岁，3.34 SD，范围 15-25 岁）中获得高角分辨率弥散成像（HARDI）数据。下纵束（ILF）、下额枕束（IFOF）、垂直枕束（VOF）和上纵束的三个分支（SLF I、II 和 III）被虚拟重建，比较 CVI 和对照组之间的平均束体积（校正颅内体积）、MD、AD 和 RD。作为二次分析，进行方差分析（ANOVA），以根据病因（即脑室周围白质软化症（CVI-PVL）和其他原因（CVI-非 PVL）所致 CVI）研究潜在差异。
当我们将 CVI 样本作为一个整体进行检查时，我们观察到 CVI 组内存在很大程度的变异，这最大限度地减少了组间差异。在我们的二次分析中，我们观察到 CVI-PVL 组与对照组和其他 CVI 患者相比，束体积明显减少。我们还观察到 CVI-PVL 组与对照组相比，QA、MD 和 AD 广泛显著增加，而 CVI-nonPVL 组则存在混合效应。
这些数据提供了初步证据，表明在视觉感知处理技能中涉及的关键白质束的发育异常，在 CVI 患者中，这些技能往往会受到不同程度的损害。结果还表明，白质变化的严重程度和程度部分可能归因于 CVI 的潜在原因。需要在更大的样本中结合行为测试进行额外的分析，以充分了解 CVI 患者的白质完整性、视觉功能障碍和相关病因之间的关系。
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