Max Planck Institute for Human Cognitive and Brain Sciences, Department of Neurology, Leipzig, Germany; Leipzig University of Applied Science, Faculty of Computer Science and Media, Leipzig, Germany; Max Planck Institute for Human Cognitive and Brain Sciences, Methods and Development Group "Brain Networks", Leipzig, Germany; Technische Universität Ilmenau, Instiute of Biomedical Engineering and Informatics, Ilmenau, Germany.
Max Planck Institute for Human Cognitive and Brain Sciences, Methods and Development Group "Brain Networks", Leipzig, Germany; Technische Universität Ilmenau, Advanced Electromagnetics Group, Ilmenau, Germany.
Neuroimage Clin. 2022;35:103071. doi: 10.1016/j.nicl.2022.103071. Epub 2022 Jun 2.
Transcranial direct current stimulation (tDCS) is a promising tool to enhance therapeutic efforts, for instance, after a stroke. The achieved stimulation effects exhibit high inter-subject variability, primarily driven by perturbations of the induced electric field (EF). Differences are further elevated in the aging brain due to anatomical changes such as atrophy or lesions. Informing tDCS protocols by computer-based, individualized EF simulations is a suggested measure to mitigate this variability.
While brain anatomy in general and specifically atrophy as well as stroke lesions are deemed influential on the EF in simulation studies, the influence of the uncertainty in the change of the electrical properties of the white matter due to white matter lesions (WMLs) has not been quantified yet.
A group simulation study with 88 subjects assigned into four groups of increasing lesion load was conducted. Due to the lack of information about the electrical conductivity of WMLs, an uncertainty analysis was employed to quantify the variability in the simulation when choosing an arbitrary conductivity value for the lesioned tissue.
The contribution of WMLs to the EF variance was on average only one tenth to one thousandth of the contribution of the other modeled tissues. While the contribution of the WMLs significantly increased (p≪.01) in subjects exhibiting a high lesion load compared to low lesion load subjects, typically by a factor of 10 and above, the total variance of the EF didnot change with the lesion load.
Our results suggest that WMLs do not perturb the EF globally and can thus be omitted when modeling subjects with low to medium lesion load. However, for high lesion load subjects, the omission of WMLs may yield less robust local EF estimations in the vicinity of the lesioned tissue. Our results contribute to the efforts of accurate modeling of tDCS for treatment planning.
经颅直流电刺激（tDCS）是一种很有前途的增强治疗效果的工具，例如在中风后。所达到的刺激效果表现出很高的个体间变异性，主要是由诱导电场（EF）的干扰引起的。由于解剖结构的变化，如萎缩或病变，衰老大脑中的差异进一步增加。通过基于计算机的个体化 EF 模拟为 tDCS 方案提供信息是减轻这种变异性的一种建议措施。
虽然大脑解剖结构一般，特别是萎缩以及中风病变被认为对模拟研究中的 EF 有影响，但由于白质病变（WML）导致的白质电导率变化的不确定性对 EF 的影响尚未被量化。
对 88 名受试者进行了分组模拟研究，这些受试者被分为四个病变负荷递增的组。由于缺乏关于 WML 电导率的信息，采用不确定性分析来量化在选择病变组织任意电导率值时，模拟中的变异性。
WML 对 EF 方差的贡献平均仅为其他建模组织的十分之一到千分之一。尽管 WML 的贡献在病变负荷高的受试者中（与病变负荷低的受试者相比，p≪.01）显著增加（平均增加 10 倍以上），但 EF 的总方差并未随病变负荷而变化。
我们的结果表明，WML 不会全局地干扰 EF，因此在对病变负荷低至中等的受试者进行建模时可以忽略它们。然而，对于病变负荷高的受试者，忽略 WML 可能会导致在病变组织附近产生不太可靠的局部 EF 估计。我们的研究结果为 tDCS 治疗计划的准确建模工作做出了贡献。
