Preliminary evidence from patients with Parkinson's disease (PD) suggests that deep brain stimulation (DBS) might work better, more efficiently, and with fewer side effects when applied in an adaptive manner (aDBS)1-4 In each of these studies aDBS was delivered according to the amplitude of beta oscillations (13-30 Hz) in the subthalamic nucleus (STN), which itself has been shown to correlate with contralateral akinesia and rigidity (AR).5 The key limitations in these clinical aDBS studies are that they have been conducted in the immediate postoperative phase. In this period, clinical testing and stimulation titration are complicated by the "stun" effect, and the optimal chronic DBS settings are not yet known. Furthermore, AR has thus far only been assessed with ordinal clinical scores, a limited and subjective rating system. To circumvent these limitations, we applied aDBS in a PD patient who had been chronically implanted with DBS and already titrated to optimal stimulation parameters and assessed bradykinesia with a validated digital task. aDBS was applied during battery replacement surgery in a 68-year-old patient with a 27-year history of Parkinson's disease who had been implanted with bilateral STN electrodes for 14 years. The patient gave consent to the research protocol, which was approved by the local ethics committee. Bipolar local field potential (LFP) amplitude in the beta range ± 3 Hz was used as biomarker in such a way that conventional DBS was provided only when beta amplitude exceeded an estimated median value (for methods see references 1, 3, and 4). aDBS was applied for 12 minutes to the right STN (contralateral to the most affected side) with matched stimulation parameters to optimized conventional DBS (cDBS), namely, 2.8V, 60-microsecond pulse width, and 135 Hz (with 250-millisecond ramping at onset and offset). Bradykinesia was assessed using a tablet-based version of the validated bradykinesia, akinesia, incoordination (BRAIN) task.6 The BRAIN task assesses the velocity of alternating finger movements between 2 buttons

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Background Beta-based adaptive Deep Brain Stimulation (aDBS) is effective in Parkinson’s disease (PD), when assessed in the immediate post-implantation phase. However, the potential benefits of aDBS in patients with electrodes chronically implanted, in whom changes due to the microlesion effect have disappeared, are yet to be assessed. Methods To determine the acute effectiveness and side-effect profile of aDBS in PD compared to conventional continuous DBS (cDBS) and no stimulation (NoStim), years after DBS implantation, 13 PD patients undergoing battery replacement were pseudo-randomised in a crossover fashion, into three conditions (NoStim, aDBS or cDBS), with a 2-min interval between them. Patient videos were blindly evaluated using a short version of the Unified Parkinson’s Disease Rating Scale (subUPDRS), and the Speech Intelligibility Test (SIT). Results Mean disease duration was 16 years, and the mean time since DBS-implantation was 6.9 years. subUPDRS scores (11 patients tested) were significantly lower both in aDBS (p = <.001), and cDBS (p = .001), when compared to NoStim. Bradykinesia subscores were significantly lower in aDBS (p = .002), and did not achieve significance during cDBS (p = .08), when compared to NoStim. Two patients demonstrated re-emerging tremor during aDBS. SIT scores of patients who presented stimulation-induced dysarthria significantly worsened in cDBS (p = .009), but not in aDBS (p = .407), when compared to NoStim. Overall, stimulation was applied 48.8% of the time during aDBS. Conclusion Beta-based aDBS is effective in PD patients with bradykinetic phenotypes, delivers less stimulation than cDBS, and potentially has a more favourable speech side-effect profile. Patients with prominent tremor may require a modified adaptive strategy.