Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Brain Connect. 2021 Sep;11(7):553-565. doi: 10.1089/brain.2020.0831. Epub 2021 Apr 1.
Previous studies utilized lesion-centric approaches to study the role of the thalamus in language. In this study, we tested the hypotheses that non-lesioned dorsomedial and ventral anterior nuclei (DMVAC) and pulvinar lateral posterior nuclei complexes (PLC) of the thalamus and their projections to the left hemisphere show secondary effects of the strokes, and that their microstructural integrity is closely related to language-related functions. Subjects with language impairments after a left-hemispheric cortical and/or subcortical, early stroke ( = 31, ≤6 months) or late stroke ( = 30, ≥12 months) sparing thalamus underwent the Boston Naming Test (BNT) and diffusion tensor imaging (DTI). The tissue integrity of DMVAC, PLC, and their cortical projections was quantified with DTI. The right-left asymmetry profiles of these structures were evaluated in relation to the time since stroke. The association between microstructural integrity and BNT score was investigated in relation to stroke chronicity with partial correlation analyses adjusted for confounds. In both early stroke and late stroke groups, left-sided tracts showed significantly higher mean diffusivities (MDs), which were likely due to Wallerian degeneration. Higher MD values of the cortical projections from the left PLC (0.5, = 0.005) and DMVAC (0.53, = 0.002) were correlated with lower BNT score in the late stroke but not early stroke group. Nonlesioned thalamic nuclei and thalamocortical pathways show rightward lateralization of the microstructural integrity after a left hemispheric stroke, and this pattern is associated with poorer naming. Impact statement To the best of our knowledge, our study is the first diffusion tensor imaging study suggesting that the thalamic nuclei and pathways of the left hemisphere spared by direct ischemic insult undergo secondary degeneration over time that is associated with poorer picture naming. Our study may pave the way for targeted interventions such as invasive or noninvasive brain stimulation techniques that engage these spared pathways to prevent secondary degeneration and lead to better outcomes in poststroke aphasia.
先前的研究利用病灶为中心的方法来研究丘脑在语言中的作用。在这项研究中，我们测试了以下假设：非病变的丘脑背内侧和腹前核（DMVAC）和丘脑外侧后核（PLC）复合体及其投射到左半球的结构会受到中风的继发性影响，其微观结构完整性与语言相关功能密切相关。患有左半球皮质和/或皮质下、早期中风（ = 31，≤6 个月）或晚期中风（ = 30，≥12 个月）后语言障碍的受试者接受波士顿命名测试（BNT）和弥散张量成像（DTI）检查。使用 DTI 量化 DMVAC、PLC 及其皮质投射的组织完整性。评估这些结构的右-左不对称谱与中风后的时间关系。使用偏相关分析，在调整混杂因素的情况下，研究微观结构完整性与 BNT 评分之间的关联与中风慢性之间的关系。在早期中风和晚期中风组中，左侧束均表现出明显更高的平均弥散度（MD），这可能是由于沃勒变性所致。左侧 PLC（0.5， = 0.005）和 DMVAC（0.53， = 0.002）皮质投射的更高 MD 值与晚期中风组而非早期中风组的 BNT 评分较低相关。左侧半球缺血性损伤后，非病变的丘脑核和丘脑皮质通路的微观结构完整性表现出向右侧偏侧化，这种模式与命名能力下降有关。 本研究首次使用弥散张量成像技术表明，直接缺血性损伤后保留的左侧半球丘脑核和通路会随着时间的推移发生继发性退化，这种退化与图片命名能力下降有关。我们的研究可能为靶向干预提供依据，例如采用侵入性或非侵入性脑刺激技术来利用这些保留的通路，以防止继发性退化，并在中风后失语症中取得更好的结果。
