The drift in impedance in deep brain stimulation (DBS), observed primarily within the first 6 months, is in keeping with prior studies and is likely due to surgical micro-lesioning effects and brain parenchyma remodeling at the electrode-tissue interface. This according to a recent study examining retrospective data from 1,764 electrode leads that were drawn from 866 DBS patients enrolled in the University of Florida Institutional Review Board-approved INFORM database and analyzed up to 84 months post-implantation. An exploratory analysis was conducted to identify trends in impedances using a Mann-Kendall test of trend. Researchers found:

• The majority of subjects had Parkinson disease (60.7%).
• The mean age at implantation was 58.7 years old and the mean follow-up time was 36.8 months.
• There were significant fluctuations in the mean impedance of all electrodes analyzed that largely stabilized by 6 months except for the subthalamic nucleus (STN) target, in which fluctuations persisted throughout the duration of follow-up with a continued downward trend.
• The differences in impedance trends over time in the various DBS targets may be due to underlying differences in structure and tissue composition.