McIntyre Cameron C, Mori Susumu, Sherman David L, Thakor Nitish V, Vitek Jerrold L
Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA.
Clin Neurophysiol. 2004 Mar;115(3):589-95. doi: 10.1016/j.clinph.2003.10.033.
The goal of this project was to develop a quantitative understanding of the volume of axonal tissue directly activated by deep brain stimulation (DBS) of the subthalamic nucleus (STN).
The 3-dimensionally inhomogeneous and anisotropic tissue medium surrounding DBS electrodes complicates our understanding of the electric field and tissue response generated by the stimulation. We developed finite element computer models to address the effects of DBS in a homogeneous isotropic medium, and a medium with tissue conductivity properties derived from human diffusion tensor magnetic resonance data. The second difference of the potential distribution generated in the tissue medium was used as a predictor of the volume of tissue supra-threshold for axonal activation.
The model predicts that clinically effective stimulation parameters (-3 V; 0.1 ms; 150 Hz) result in activation of large diameter (5.7 microm) myelinated axons over a volume that spreads outside the borders of the STN. The shape of the activation volume was dependent on the strong dorsal-ventral anisotropy of the internal capsule, and the moderate anterior-posterior anisotropy of the region around zona incerta.
Small deviations ( approximately 1 mm) in the electrode position within STN can substantially alter the shape of the activation volume as well as its spread to neighboring structures.
STN DBS represents an effective treatment for medically refractory movement disorders such as Parkinson's disease. However, stimulation induced side effects such as tetanic muscle contraction, speech disturbance and ocular deviation are not uncommon. Quantitative characterization of the spread of stimulation will aid in the development of techniques to maximize the efficacy of DBS.
本项目的目标是定量了解丘脑底核（STN）深部脑刺激（DBS）直接激活的轴突组织体积。
DBS电极周围三维不均匀且各向异性的组织介质使我们对刺激产生的电场和组织反应的理解变得复杂。我们开发了有限元计算机模型来研究在均匀各向同性介质以及具有源自人类扩散张量磁共振数据的组织电导率特性的介质中DBS的影响。组织介质中产生的电位分布的二阶差分被用作轴突激活阈值以上组织体积的预测指标。
该模型预测，临床有效刺激参数（-3V；0.1ms；150Hz）会导致大直径（5.7微米）有髓轴突在超出STN边界的体积内被激活。激活体积的形状取决于内囊强烈的背腹各向异性以及未定带周围区域适度的前后各向异性。
STN内电极位置的小偏差（约1毫米）会显著改变激活体积的形状及其向相邻结构的扩散。
STN DBS是治疗帕金森病等药物难治性运动障碍的有效方法。然而，刺激引起的副作用如强直性肌肉收缩、言语障碍和眼球偏斜并不罕见。对刺激扩散的定量表征将有助于开发使DBS疗效最大化的技术。
