Objective: To assess the longitudinal changes in impedance values of CV neurostimulation devices and its possible impact in the clinical outcome of PD patients with STN-DBS.

Background: Deep brain stimulation of the subthalamic nucleus (STN-DBS) has been proven to be a safe and effective symptomatic treatment for in Parkinson’s disease (PD) and others movement disorders. Neurostimulation devices using constant voltage (CV) have been commonly used. In the CV setting, the programmer sets the voltage, but the amount of current delivered may change depending on the impedance variations. The variability of impedances and how they affect clinical outcomes in a significant way is not clear.

Methods: This was an observational prospective pilot study. We collected the impedance and programming data from 124 electrodes in 62 patients with PD in which both parkinsonian features and electrical settings had remained stable during the previous 6 months. Clinical impact was measured with Clinical Global Impressions Scale (CGI) and UPDRS-part IV scores during a 6 months follow-up.

Results: Median impedance was 1017Ω, with an average change of ±1.5% (range 0-66%) between the first and second visit (p=0.51). Changes greater than 5% were seen in 22 electrodes corresponding to 16 patients. In five of these patients (8%), changes in impedance were associated to slight clinical worsening requiring parameter adjustments. The highest change in the impedances (increase of 66% and 36,5%) were seen in the same patient. This increase occurred concomitantly with appearance of motor fluctuations and worsening in 2 points in CGI, requiring parameter adjustments.

Conclusions: In this prospective study we have seen only minimal changes in the impedance of the electrodes with no clinical changes in cohort with patients with PD, suggesting that CV devices are safe. However, we also observed clinical worsening in 5 out of 62 of these patients, attributable to greater increase of impedance. This fact emphasizes that review of impedances is important in patients with DBS and gives value to devices with current-control.

References: Satzer D, Lanctin D, Eberly LE, Abosch A. Variation in Deep Brain Stimulation Electrode Impedance over Years Following Electrode Implantation. Stereotact Funct Neurosurg 2014;92:94–102. doi:10.1159/000358014. Butson C, McIntyre C. Sources and effects impedance during deep brain stimulation. Clin Neurophysiol. 2016; 117 : 447–454. doi:10.1016/j.clinph.2005.10.007.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-electrode-impedance-changes-in-clinical-outcomes-of-patients-with-parkinsons-disease-and-subthalamic-nucleus-deep-brain-stimulation/