The safety of transcranial magnetic stimulation with deep brain stimulation instruments

Abstract

Objectives: 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. Methods: 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. Results: There was no movement or temperature increase during 0.2Hz repetitive TMS with 100% stimulus intensity for 1 hour. The size of evoked current linearly increased with TMS intensity. The maximum charge density exceeded the safety limit of 30C/cm 2 /phase during stimulation above the loops of the lead with intensity over 50% using a figure-eight coil. Conclusions:Strong TMS on the looped DBS leads should not be administered to avoid electrical tissue injury. Subcutaneous lead position should be pay enough attention for forthcoming situations during surgery.

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines

“…Several ex vivo studies showed that TMS over DBS leads did not induce sufficient current to cause tissue damage or damage to the pulse generator (Kuhn and Huebl, 2011; Kumar et al, 1999), although stimulation over lead loops could potentially produce current large enough to be dangerous (Deng et al, 2010; Shimojima et al, 2010). At least 20 TMS studies in patients with DBS have been published since 2001 (Chen et al, 2001) and no AEs have been reported.…”

Fundamentals of transcranial electric and magnetic stimulation dose: Definition, selection, and reporting practices

“…For example, if TMS is applied to a subject simultaneously receiving some form of transcranial electric stimulation (e.g., tDCS), the TMS magnetic field could potentially induce unintended currents in the scalp electrodes and leads, thus confounding the experimental paradigm and potentially compromising safety. Studies on the interactions between TMS and transcranial electric stimulation devices are currently lacking, but caution is warranted as significant currents induced by TMS in the leads and electrodes of deep brain stimulation implants have been reported (98,99). …”

Transcranial magnetic stimulation combined with high-density EEG in altered states of consciousness

“…Intracranial EEG recordings in patients evaluated for pharmacoresistant epilepsy, for instance, would also extend the spatial capacity of this approach and allow studying of the deeper structures of the thalamocortical networks. Previous studies have demonstrated the safety of using TMS with implanted electrodes, although some recommendations have been released; such as avoiding stimulation near electrodes loops and avoiding repetitive TMS in a chronic setting due to lack of data on potential tissue damage [75].…”