Deep Brain Stimulation Impedance Decreases Over Time Even When Stimulation Settings Are Held Constant

Area of Science:

• Neurosurgery
• Biomedical Engineering
• Neurology

Background:

• Deep brain stimulation (DBS) is a key therapy for Parkinson's disease (PD) and essential tremor (ET).
• Understanding impedance and current changes is crucial for optimizing DBS therapy and constant-current stimulation.
• Long-term stability of stimulation parameters requires knowledge of impedance drift.

Purpose of the Study:

• To investigate the extent and nature of therapeutic impedance and current changes during long-term DBS.
• To determine if impedance and current change with constant stimulation settings.
• To inform the application and programming of constant-current DBS.

Main Methods:

• Retrospective analysis of impedance and current data from 79 electrodes in 44 patients (PD and ET).
• Data collected from subthalamic nucleus (STN) for PD and ventral intermediate nucleus (VIM) for ET.
• Analysis focused on intervals of at least 6 months with unchanged stimulation settings, examining temporal trends.

Main Results:

• Therapeutic impedance decreased significantly over time (27 ± 12 Ω/year, p < 0.0001).
• Therapeutic current increased significantly (0.142 ± 0.063 mA/year, p < 0.0001).
• These trends were consistent across STN and VIM subgroups and occurred independently of stimulation setting changes.

Conclusions:

• Impedance decreases gradually over time, even with constant DBS settings.
• The observed impedance drift is slower than previously reported, suggesting stimulation setting changes contribute to drift.
• Stimulation-independent impedance drift is gradual yet significant for effective constant-current DBS programming.