Abstract
Objectives: To study whether and to what extent the therapeutic impedance and current change under long-term deep brain stimulation (DBS) with constant stimulation settings, which could inform the role of constant current stimulation.Methods: Therapy impedance and current measurements were retrospectively collected from patients with Parkinson’s disease (PD) undergoing DBS of the subthalamic nucleus (STN) or essential tremor (ET) undergoing ventral intermediate nucleus (VIM). Baseline and follow-up measurements were obtained for intervals of at least 6 months without changes in stimulation settings. The single longest interval of constant stimulation for each electrode was included. Temporal trends in impedance and current were analyzed as absolute and relative differences and as the rate of change.Results: Impedance and current data from 79 electrodes (60 in STN, 19 in VIM) in 44 patients (32 with PD, 12 with ET) met inclusion criteria. The duration between baseline and follow-up measurements with constant stimulation settings was 17 months (median, with an interquartile range of 12–26 months) in the mixed group. Therapy impedance decreased by 27 ± 12 Ω/year (mean ± 2 standard errors; p < 0.0001), and therapy current increased at a rate of 0.142 ± 0.063 mA/year (p < 0.0001). Similar results were observed in the STN and VIM subgroups.Conclusions: Impedance decreases gradually over time, even when stimulation settings are kept constant. The rate of decrease is smaller than previously reported, suggesting that changes in stimulation settings contribute to impedance drift. Stimulation-independent impedance drift is gradual but relevant to constant-current programming.
Highlights
Deep brain stimulation (DBS) has proven to be of significant therapeutic benefits for patients with Parkinson’s disease (PD), essential tremor (ET), and dystonia (Vidailhet et al, 2005; Weaver et al, 2009; Follett et al, 2010; Williams et al, 2010; Deuschl et al, 2011)
DBS has traditionally relied on constant-voltage therapy, in which the stimulation voltage is set and current delivery varies according to electrical impedance
There was no difference between the subthalamic nucleus (STN) and ventral intermediate nucleus (VIM) subgroups in the sex distribution, age at disease onset, age at DBS placement, length of study interval, voltage, or pulse width
Summary
Deep brain stimulation (DBS) has proven to be of significant therapeutic benefits for patients with Parkinson’s disease (PD), essential tremor (ET), and dystonia (Vidailhet et al, 2005; Weaver et al, 2009; Follett et al, 2010; Williams et al, 2010; Deuschl et al, 2011). DBS has traditionally relied on constant-voltage therapy, in which the stimulation voltage is set and current delivery varies according to electrical impedance. One of the major reasons for this is the downward drift in impedance over time (Satzer et al, 2014; Hartmann et al, 2015; Wong et al, 2018). Impedance has been reported to immediately decrease after contact activation and higher stimulation voltages have been associated with lower impedance values (Satzer et al, 2014). Since stimulation is associated with lower impedance, it is conceivable that a long-term increase in programmed energy delivery (compensating for disease progression) could entirely account for the observed downward impedance drift over time
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
