Safety of repetitive transcranial magnetic stimulation in patients with implanted cortical electrodes. An ex-vivo study and report of a case.

OBJECTIVE: To evaluate the safety of repetitive transcranial magnetic stimulation (rTMS) in patients with implanted subdural cortical electrodes. METHODS: We performed ex-vivo experiments to test the temperature, displacement and current induced in the electrodes with single pulse transcranial magnetic stimulation (TMS) from 10 to 100% of stimulator output and tested a typical rTMS protocol used in a clinical setting. We then used rTMS to the motor cortex to treat a patient with refractory post-herpetic neuralgia who had previously been implanted with a subdural motor cortical electrode for pain management. The rTMS protocol consisted of ten sessions of 2000 stimuli at 20Hz and 90% of resting motor threshold. RESULTS: The ex-vivo study showed an increase in the coil temperature of 2°C, a maximum induced charge density of 30.4µC/cm2/phase, and no electrode displacement with TMS. There was no serious adverse effect associated with rTMS treatment of the patient. Cortical tremor was observed in the intervals between trains of stimuli during one treatment session. CONCLUSIONS: TMS was safe in a patient with implanted Medtronic Resume II electrode (model 3587A) subdural cortical electrode. SIGNIFICANCE: TMS may be used as a therapeutic, diagnostic or research tool in patients this type of with implanted cortical electrodes.

Frameless Stereotactic Robot-Assisted Subthalamic Nucleus Deep Brain Stimulation: Case Report.

BACKGROUND: Electrode implantation for deep brain stimulation (DBS) can be performed in numerous ways, but the current "gold standard" is the use of frame-based systems for accuracy. Robotic stereotactic procedures, however, have gained increased interest because of their ease of use and reliability, but there could be concern about their safety in the United States as the result of recent lawsuits (e.g., the da Vinci Surgical System). We report the first DBS implantation performed using a robot (ROSA robotic device) approved by Food and Drug Administration for use in North America. CASE DESCRIPTION: A 56-year-old, right-handed woman with a 12-year history of Parkinson disease is described. She was offered bilateral subthalamic nucleus DBS placement to address motor fluctuations and dyskinesias. DBS electrode implantation was implemented successfully with ROSA robotic stereotactic assistance. Using preoperative magnetic resonance imaging scan acquisitions, we targeted the patient's subthalamic nucleus bilaterally. Bone fiducials were placed and intraoperative computed tomography (CT) imaging was obtained. The magnetic resonance imaging and CT were fused, and the patient was registered to the ROSA software. Trajectories were obtained and a microdrive device was fixed to the robotic arm to advance the electrode to the correct location. Electrodes were then placed bilaterally. Intraoperative CT showed good placement with no complications encountered. CONCLUSIONS: The advantages of robotic assistance in stereotactic procedures are as follows: 1) improved accuracy, 2) "arc-less" approach, and 3) minor adjustments can be made in multiple planes to the entry point without adjustment of a frame. The case demonstrates robotic stereotactic assistance viability as an alternative to traditional frame-based or frameless systems in U.S. hospitals.