Objective: To assess change in resistance and current with voltage and rate changes in Parkinson’s Disease (PD) patients on DBS therapy.

Background: Currently we use constant voltage stimualtors and there is a debate on whether constant current stimulators may have more consistent beneficial effects, as tissue resistance tends to change frequently.

Methods: 44 PD patients who underwent bilateral STN DBS with Activa PC (Medtronic), atleast 6 months prior to study, were assessed for current and resistance changes. The patients were on unipolar stimulation. The contacts were kept constant through the study. Baseline resistance and current were noted in all. Voltage was changed with 0.1mv increments from -0.4 to +0.4 and rate was changed in 10 hertz increments from +20 to -20 of baseline. Variation in current and resistance was evaluated in each individual as well as in the whole group.

Results: Data from 44 patients (88 sides) were analyzed. Mean age was 53.52+14.22; 38 were men. Mean disease duration was 10.78+4.20 years; mean duration post implant was 2.82+1.33 years. Mean resistance with 0.1mV change in amplitude varied from 729 to 1718 ohms (mean right STN – 1246, left – 1181 ohms). Changes in the current delivered with 0.1 mV increments also showed a wide range from -0.08 to 0.37 mA (mean of 0.10 ). The mean of coefficients of variance in resistance (COV) was 0.029 on left side and 0.017 on right side (range: 0.003 to 0.358). There is a trend towards significance (p=0.054). Mean resistance with 10 Hertz change in rate varied from 731 to 1718 ohms (mean right STN – 1181, left – 1246 ohms). The mean of coefficients of variance in resistance (COV) was 0.004 on left side and 0.004 on right side (range: 0.000 to 0.019). There is a trend towards high significance (p=<0.001) with men having more variation. On bifurcating the data based on COV, shorter disease duration, shorter time after DBS, baseline resistance values were significantly associated with COV. Also the left STN has higher resistance than the right STN in both male and female population.

Conclusions: There is significant variation in current delivered and resistance with constant increments in voltage and rate. Hence it is essential to assess these parameters for providing better patient care in constant voltage stimulators.

References: Martinez-Ramirez, D.; Hu, W.; Bona, A.R.; Okun, M.S.; Shukla, A.W. Update on deep brain stimulation in Parkinson’s disease. Transl. Neurodegener. 2015, 4, 12. [CrossRef] [PubMed].

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-changes-in-resistance-on-current-delivered-in-constant-voltage-dbs-stimulator-in-parkinsons-disease/