Department of Medicine (Neurology & Rheumatology), Shinshu University School of Medicine, Asahi 3-1-1 Matsumoto 390-8621, Japan.
Parkinsonism Relat Disord. 2010 Feb;16(2):127-31. doi: 10.1016/j.parkreldis.2009.09.006. Epub 2009 Oct 6.
Transcranial magnetic stimulation (TMS) has been employed in patients with an implanted deep brain stimulation (DBS) device. We investigated the safety of TMS using simulation models with an implanted DBS device.
The DBS lead was inserted into plastic phantoms filled with dilute gelatin showing impedance similar to that of human brain. TMS was performed with three different types of magnetic coil. During TMS (1) electrode movement, (2) temperature change around the lead, and (3) TMS-induced current in various situations were observed. The amplitude and area of each evoked current were measured to calculate charge density of the evoked current.
There was no movement or temperature increase during 0.2 Hz repetitive TMS with 100% stimulus intensity for 1 h. The size of evoked current linearly increased with TMS intensity. The maximum charge density exceeded the safety limit of 30 muC/cm(2)/phase during stimulation above the loops of the lead with intensity over 50% using a figure-eight coil.
Strong TMS on the looped DBS leads should not be administered to avoid electrical tissue injury. Subcutaneous lead position should be paid enough attention for forthcoming situations during surgery.
经颅磁刺激（TMS）已应用于植入深部脑刺激（DBS）装置的患者中。我们使用植入 DBS 装置的模拟模型来研究 TMS 的安全性。
将 DBS 导联插入充满稀释明胶的塑料体模中，其阻抗与人脑相似。使用三种不同类型的磁线圈进行 TMS。在 TMS 过程中（1）观察电极运动，（2）观察导联周围的温度变化，（3）观察各种情况下的 TMS 诱导电流。测量每个诱发电流的幅度和面积，以计算诱发电流的电荷密度。
在 100%刺激强度下，0.2 Hz 重复 TMS 刺激 1 小时期间没有电极运动或温度升高。诱发电流的大小随 TMS 强度呈线性增加。当使用双线圈时，在刺激强度超过 50%的导联环上方，最大电荷密度超过了 30 μC/cm(2)/相的安全限制。
不应在 DBS 导联环上进行强 TMS，以避免电组织损伤。在手术过程中应充分注意皮下导联的位置，以避免出现未来的情况。
