Verification of the Deep Brain Stimulation Electrode Position Using Intraoperative Electromagnetic Localization.

Background: Electromagnetic (EM) localization has typically been used to direct shunt catheters into the ventricle. The objective of this study was to determine if this method of EM tracking could be used in a deep brain stimulation (DBS) electrode cannula to accurately predict the eventual location of the electrode contacts. Methods: The Medtronic AxiEM(TM) system was used to generate the cannula tip location directed to the planned target site. Prior to clinical testing, a series of phantom modelling observations were made. Results: Phantom trials (n = 23) demonstrated that the cannula tip could be accurately located at the target site with an error of between 0.331 +/- 0.144 and 0.6 +/- 0.245 mm, depending on the orientation of the delivery system to the axis of the phantom head. Intraoperative EM localization of the DBS cannula was performed in 84 trajectories in 48 patients. The average difference between the planned target and the EM stylet location at the cannula tip was 1.036 +/- 0.543 mm. The average error between the planned target coordinates and the actual target electrode location (by CT) was 1.431 +/- 0.607 and 1.145 +/- 0.636 mm for the EM stylet location in the cannula (p = 0.00312), indicating that EM localization reflected the position of the target electrode more accurately than the planned target. Conclusions: EM localization can be used to verify the position of DBS electrodes intraoperatively with a high accuracy.