Beta-triggered adaptive deep brain stimulation during reaching movement in Parkinson's disease

Subthalamic nucleus (STN) beta-triggered adaptive deep brain stimulation (ADBS) has been shown to provide clinical improvement comparable to conventional continuous DBS (CDBS) in people with Parkinson's disease (PD) with less energy delivered to the brain and less stimulation induced side-effects. However, several questions remain unanswered. First, there is a normal physiological reduction of STN beta band power just prior to and during voluntary movement. ADBS systems will therefore reduce or cease stimulation during movement and could therefore compromise motor performance compared to CDBS. Second, beta power was smoothed and estimated over time periods of 400ms or longer in most previous ADBS studies. A shorter smoothing period could have the advantage of being more sensitive to changes in beta power which could enhance motor performance. In this study, we addressed these two questions by evaluating the effectiveness of STN beta-triggered ADBS using a standard 400ms and a shorter 200ms smoothing window during reaching movements. Results from 13 people with PD showed that STN beta-triggered ADBS is effective in improving motor performance during reaching movements as it better preserves gamma oscillation than CDBS in people with PD, and that shortening the smoothing window does not result in any additional behavioural benefit. ADBS significantly improved tremor compared with no DBS but was not as effective as CDBS. When developing ADBS systems for PD, it might not be necessary to track very fast beta dynamics; combining beta, gamma, and motor decoding might be more beneficial with additional biomarkers needed for optimal treatment of tremor.