MR imaging of implanted depth and subdural electrodes: is it safe?

This study evaluates the safety of imaging chronic epilepsy patients with i ntracranial depth and subdural electrodes by magnetic resonance (MR). To id entify an epileptogenic focus, the precise location of the electrode contac ts is necessary, and MR can provide this information. However, many neurosu rgeons and neuroradiologists are hesitant to scan patients by MR with these implanted, metallic electrodes for fear of electrode displacement, current induction or heating secondary to the strong magnetic field. In the: prese nt study, the subdural electrodes were made of stainless steel with either stainless steel or platinum contacts. The depth electrodes were made of eit her platinum or a nickel-chromium alloy (nichrome). We reviewed 98 cases in which patients with implanted depth electrodes, subdural electrodes, or bo th underwent MR scanning. A total of 143 depth electrodes, 688 subdural str ips, and 38 subdural grids were implanted in the 98 procedures. MK scanning was performed on a 1.5-T unit and consisted of T1, T2, and/or spoiled grad ient echo pulse sequences. There were no documented complications related t o the MR scans. Based on this study and a review of the literature, we feel th;at MR imaging can safely localize intracranial electrodes. (C) 1999 Els evier Science B.V. All rights reserved.