Unal Gozde, Ficek Bronte, Webster Kimberly, Shahabuddin Syed, Truong Dennis, Hampstead Benjamin, Bikson Marom, Tsapkini Kyrana
Department of Biomedical Engineering, The City College of New York, New York, NY, 10031, USA.
Department of Neurology, Cerebrovascular Division, Johns Hopkins Medicine, 600 N. Wolfe Street, Phipps 488, Baltimore, MD, 21287, USA.
Neurol Sci. 2020 Jul;41(7):1781-1789. doi: 10.1007/s10072-019-04229-z. Epub 2020 Feb 10.
During transcranial direct current stimulation (tDCS), the amount and distribution of current that reaches the brain depends on individual anatomy. Many progressive neurodegenerative diseases are associated with cortical atrophy, but the importance of individual brain atrophy during tDCS in patients with progressive atrophy, including primary progressive aphasia (PPA), remains unclear.
In the present study, we addressed the question whether brain anatomy in patients with distinct cortical atrophy patterns would impact brain current intensity and distribution during tDCS over the left IFG.
We developed state-of-the-art, gyri-precise models of three subjects, each representing a variant of primary progressive aphasia: non-fluent variant PPA (nfvPPA), semantic variant PPA (svPPA), and logopenic variant PPA (lvPPA). We considered two exemplary montages over the left inferior frontal gyrus (IFG): a conventional pad montage (anode over F7, cathode over the right cheek) and a 4 × 1 high-definition tDCS montage. We further considered whether local anatomical features, specifically distance of the cortex to skull, can directly predict local electric field intensity.
We found that the differences in brain current flow across the three PPA variants fall within the distribution of anatomically typical adults. While clustering of electric fields was often around individual gyri or sulci, the minimal distance from the gyri/sulci to skull was not correlated with electric field intensity.
Limited to the conditions and assumptions considered here, this argues against a specific need to adjust the tDCS montage for these patients any more than might be considered useful in anatomically typical adults. Therefore, local atrophy does not, in isolation, reliably predict local electric field. Rather, our results are consistent with holistic head anatomy influencing brain current flow, with tDCS producing diffuse and individualized brain current flow patterns and HD-tDCS producing targeted brain current flow across individuals.
在经颅直流电刺激（tDCS）过程中，到达大脑的电流数量和分布取决于个体解剖结构。许多进行性神经退行性疾病与皮质萎缩有关，但在包括原发性进行性失语（PPA）在内的进行性萎缩患者中，个体脑萎缩在tDCS期间的重要性仍不清楚。
在本研究中，我们探讨了具有不同皮质萎缩模式的患者的脑解剖结构是否会影响左侧额下回tDCS期间的脑电流强度和分布。
我们开发了三位受试者的最先进的、精确到脑回的模型，每位受试者代表原发性进行性失语的一种变体：非流利型原发性进行性失语（nfvPPA）、语义型原发性进行性失语（svPPA）和音韵型原发性进行性失语（lvPPA）。我们考虑了左侧额下回（IFG）上的两种示例性电极放置方式：传统的贴片电极放置方式（阳极置于F7，阴极置于右脸颊）和4×1高清tDCS电极放置方式。我们还进一步考虑了局部解剖特征，特别是皮质到颅骨的距离，是否能直接预测局部电场强度。
我们发现，三种PPA变体之间的脑电流差异落在解剖结构典型的成年人的分布范围内。虽然电场通常聚集在单个脑回或脑沟周围，但脑回/脑沟到颅骨的最小距离与电场强度无关。
限于此处考虑的条件和假设，这表明对于这些患者，没有比解剖结构典型的成年人更有必要调整tDCS电极放置方式。因此，局部萎缩本身并不能可靠地预测局部电场。相反，我们的结果与整体头部解剖结构影响脑电流流动一致，tDCS产生弥散且个体化的脑电流流动模式，而高清tDCS在个体间产生有针对性 的脑电流流动。
