• David Satzer, David Lanctin, Lynn E Eberly, and Aviva Abosch.
• Department of Neurosurgery, University of Minnesota, Minneapolis, Minn., USA.
• Stereotact Funct Neurosurg. 2014 Jan 1;92(2):94-102.

BackgroundDeep brain stimulation (DBS) electrode impedance is a major determinant of current delivery to target tissues, but long-term variation in impedance has received little attention.ObjectivesTo assess the relationship between electrode impedance and time in a large DBS patient population and characterize the relationship between contact activity and impedance.MethodsWe collected retrospective impedance and programming data from 128 electrodes in 84 patients with Parkinson's disease, essential tremor or dystonia. Effects of time, contact activity, stimulation voltage and other parameters on impedance were assessed. We also examined impedance changes following contact activation and deactivation.ResultsImpedance decreased by 73 Ω/year (p < 0.001), with 72% of contacts following a downward trend. Impedance was on average 163 Ω lower in active contacts (p < 0.001). Contact activation and inactivation were associated with a more (p < 0.001) and less (p = 0.016) rapid decline in impedance, respectively. Higher stimulation voltages were associated with lower impedance values (p < 0.001). Contact number and electrode model were also significant predictors of impedance.ConclusionsImpedance decreases gradually in a stimulation-dependent manner. These trends have implications for long-term programming, the development of a closed-loop DBS device and current understanding of the electrode-tissue interface.© 2014 S. Karger AG, Basel.

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