Laboratory for Neuropsychiatry and Neuromodulation, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Boston, Massachusetts 02129, USA; Department of Electrical and Computer Engineering, Iowa State University, 2520 Osborne Drive, Ames, Iowa 50011, USA.
Department of Electrical and Computer Engineering, Iowa State University, 2520 Osborne Drive, Ames, Iowa 50011, USA.
Clin Neurophysiol. 2018 Sep;129(9):1873-1883. doi: 10.1016/j.clinph.2018.04.749. Epub 2018 Jul 6.
To investigate inter-subject variability with respect to cerebrospinal fluid thickness and brain-scalp distance, and to investigate intra-subject variability with different coil orientations.
Simulations of the induced electric field (E-Field) using a figure-8 coil over the vertex were conducted on 50 unique head models and varying orientations on 25 models. Metrics exploring stimulation intensity, spread, and localization were used to describe inter-subject variability and effects of non-brain anatomy.
Both brain-scalp distance and CSF thickness were correlated with weaker stimulation intensity and greater spread. Coil rotations show that for the dorsal portion of the stimulated brain, E-Field intensities are highest when the anterior-posterior axis of the coil is perpendicular to the longitudinal fissure, but highest for the medial portion of the stimulated brain when the coil is oriented parallel to the longitudinal fissure.
Normal anatomical variation in healthy individuals leads to significant differences in the site of TMS, the intensity, and the spread. These variables are generally neglected but could explain significant variability in basic and clinical studies.
This is the first work to show how brain-scalp distance and cerebrospinal fluid thickness influence focality, and to show the disassociation between dorsal and medial TMS.
研究脑脊液厚度和脑颅距离的个体间变异性,并研究不同线圈方向的个体内变异性。
在 50 个独特的头模型上和 25 个模型的不同方向上,使用 8 字形线圈对顶点上方的感应电场(E-Field)进行模拟。使用探索刺激强度、传播和定位的指标来描述个体间变异性和非脑解剖结构的影响。
脑颅距离和 CSF 厚度均与较弱的刺激强度和更大的传播范围相关。线圈旋转表明,对于受刺激大脑的背部部分,当线圈的前后轴垂直于纵裂时,E-Field 强度最高,但当线圈平行于纵裂时,受刺激大脑的内侧部分强度最高。
健康个体的正常解剖结构变异导致 TMS 的部位、强度和传播范围存在显著差异。这些变量通常被忽略,但可以解释基础和临床研究中的显著变异性。
这是第一项展示脑颅距离和脑脊液厚度如何影响聚焦性,并展示 TMS 背侧和内侧之间分离的工作。