Abboud S, Bar L, Rosenfeld M, Ring H, Glass I
Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Israel.
Ann Biomed Eng. 1996 Jan-Feb;24(1):75-86. doi: 10.1007/BF02770997.
The left-right asymmetry in the potential amplitude on the scalp was studied in poststroke patients by using flash visual evoked potential (VEP) and a numerical two-dimensional model of the head. The left-right asymmetry of the VEP was measured in three patients after thrombosis, in one after hemorrhage, and in one healthy subject. The numerical model used computed tomography images to define the different compartments of the head. The volume conductor equation for the potential distribution created by a dipole source in the occipital region was solved numerically with use of a finite volume method. Left-right asymmetry was calculated with several values of conductivity of the damaged region. The experimental results revealed a negative asymmetry in the three patients after thrombosis (i.e., the potential amplitude over the ischemic hemisphere was smaller than that over the intact hemisphere), whereas, in the patient after hemorrhage, a positive asymmetry was found. Nonsignificant left-right asymmetry was found in the healthy subject. The numerical model revealed that the electrical conductivity of the damaged tissue has a major effect on the left-right asymmetry. Negative asymmetry, such as that found for patients after thrombosis, was obtained when the conductivity of the damaged region was greater than that of the brain, whereas positive asymmetry (hemorrhage patient) was obtained when that conductivity was smaller than that of the brain. This finding indicates that the left-right asymmetry in the scalp VEP of patients after brain damage may be a result of changes in the conductivity of the volume conductor (the ischemic region) between the source and the electrodes.
通过使用闪光视觉诱发电位（VEP）和头部的二维数值模型，研究了中风后患者头皮上电位振幅的左右不对称性。在3例血栓形成后的患者、1例出血后的患者以及1例健康受试者中测量了VEP的左右不对称性。数值模型使用计算机断层扫描图像来定义头部的不同区域。利用有限体积法对枕区偶极子源产生的电位分布的体积导体方程进行了数值求解。用受损区域的几个电导率值计算左右不对称性。实验结果显示，3例血栓形成后的患者存在负向不对称性（即缺血半球上的电位振幅小于完整半球上的电位振幅），而在出血后的患者中发现了正向不对称性。在健康受试者中未发现明显的左右不对称性。数值模型显示，受损组织的电导率对左右不对称性有主要影响。当受损区域的电导率大于大脑的电导率时，会出现如血栓形成后患者那样的负向不对称性；而当该电导率小于大脑的电导率时，则会出现正向不对称性（出血患者）。这一发现表明，脑损伤后患者头皮VEP的左右不对称性可能是源与电极之间体积导体（缺血区域）电导率变化的结果。
