Service de Neurochirurgie, Centre Hospitalier Universitaire d'Amiens, Amiens cedex 1, France.
Acta Neurochir (Wien). 2010 Apr;152(4):689-97. doi: 10.1007/s00701-009-0564-2. Epub 2009 Dec 2.
Exposure to powerful magnetic fields may alter the settings of programmable ventriculoperitoneal shunt valves or even cause permanent damage to these devices. Transcranial magnetic stimulation (TMS) and magnetic resonance imaging both generate a high-intensity, focal magnetic field. To the best of our knowledge, there is no literature data on the compatibility of TMS with neurosurgical implants. The aim of the present in vitro study was to investigate the effects of TMS on four types of pressure-programmable valves (the Strata 2 from Medtronic, the Polaris from Sophysa, the ProGAV from Miethke, and a cylindrical valve from Codman-Hakim).
We used a Magpro X100 stimulator (Medtronic) for monophasic or biphasic TMS via a circular or a figure-of-eight coil. Each valve setting was tested before and after exposure to TMS. Experiment 1: The effect of the coil-valve distance (10, 5, 2.5, and 1 cm) was assessed. Experiment 2: We mimicked in situ stimulation with a human mannequin by placing the valve in a retroauricular position, the TMS circular coil on the apex, and figure-of-eight coil centered over the primary motor area site. Temperature changes were monitored throughout the experiments. Experience 3: TMS-induced valve movements were assessed by using an in-house accelerometric setup.
Our results primarily demonstrated that the Strata 2 and Codman-Hakim valves' settings were perturbed by TMS. There was no heating effect for any of the valves. However, TMS induced movements of the Strata 2, Polaris, and ProGAV valves. Experiment 1: The unsetting frequencies observed for the Strata 2 and the Codman-Hakim valve showed an influence of the distance, the coil model, and the magnetic field characteristics, whereas the Polaris and ProGAV's settings remained unchanged. Experiment 2: Unsetting occurred for Strata 2 valve with the circular coil only, whereas the Polaris, ProGAV, and Codman-Hakim valves' settings remained stable. Experiment 3: The Strata 2, Polaris, and ProGAV valves showed high-amplitude oscillations during TMS under all stimulation conditions, whereas the Codman-Hakim valve did not move.
Our in vitro experiments showed that TMS can interfere with programmable shunt valves by inducing unsetting or movement. This finding suggests that great care must be taken if applying TMS in hydrocephalic, shunted patients.
暴露于强磁场中可能会改变可编程脑室-腹腔分流阀的设置，甚至对这些设备造成永久性损坏。经颅磁刺激（TMS）和磁共振成像都产生高强度、聚焦的磁场。据我们所知，目前尚无关于 TMS 与神经外科植入物兼容性的文献数据。本体外研究的目的是研究 TMS 对四种压力可编程阀（美敦力的 Strata 2、Sophysa 的 Polaris、Miethke 的 ProGAV 和 Codman-Hakim 的圆柱形阀）的影响。
我们使用 Magpro X100 刺激器（美敦力）通过圆形或 8 字形线圈进行单相或双相 TMS。在暴露于 TMS 之前和之后，测试每个阀设置。实验 1：评估线圈-阀距离（10、5、2.5 和 1 cm）的影响。实验 2：我们通过将阀放置于耳后位置、TMS 圆形线圈置于顶点、8 字形线圈置于主要运动区域中心，模拟体内刺激。整个实验过程中监测温度变化。实验 3：使用内部加速度计设置评估 TMS 诱导的阀运动。
我们的结果主要表明，Strata 2 和 Codman-Hakim 阀的设置受到 TMS 的干扰。任何阀门都没有加热效果。然而，TMS 诱导了 Strata 2、Polaris 和 ProGAV 阀的运动。实验 1：Strata 2 和 Codman-Hakim 阀的未设定频率观察到距离、线圈模型和磁场特性的影响，而 Polaris 和 ProGAV 的设置保持不变。实验 2：仅圆形线圈使 Strata 2 阀未设定，而 Polaris、ProGAV 和 Codman-Hakim 阀的设置保持稳定。实验 3：Strata 2、Polaris 和 ProGAV 阀在所有刺激条件下的 TMS 下都显示出高振幅振荡，而 Codman-Hakim 阀没有移动。
我们的体外实验表明，TMS 可以通过引起未设定或运动来干扰可编程分流阀。这一发现表明，在脑积水、分流患者中应用 TMS 时必须格外小心。
