Martijn Beudel

Background: Adaptive deep brain stimulation (aDBS) is a safe and effective therapy for people with Parkinson's disease (PWP). Utilization of directional aDBS has not been specifically evaluated. Objectives: The goal is to report the first data on the safety, tolerability, and preliminary effectiveness of chronic, directional aDBS in PWP. Methods: A supplemental cohort from the Adaptive DBS Algorithm for Personalized Therapy in Parkinson's Disease Trial received directional aDBS. Participants who were previously receiving stable continuous directional DBS (dDBS) completed an open‐label evaluation of two aDBS modes. Results: Seventeen participants were enrolled, with 15 completing directional aDBS evaluation. The prespecified primary endpoint and post hoc success criterion was met for both directional aDBS modes. On‐time without troublesome dyskinesia was increased, with a median of 1.2 hours/day in directional dual threshold aDBS mode. Stimulation‐related events were similar between dDBS and directional aDBS. All 15 participants chose to continue with directional aDBS chronically. Conclusions: Preliminary data indicates chronic directional aDBS is feasible, tolerable, effective, and safe in PWP. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Adaptive deep brain stimulation (aDBS) can adjust stimulation to the (medication) state of patients with Parkinson’s disease using physiological biomarkers (physiomarkers), but whether individuals share a common physiomarker frequency remains unknown. We quantified levodopa-induced spectral changes (2–100 Hz) in local field potential recordings from the subthalamic nucleus during active DBS (median amplitude 2.0 mA, IQR: [1.6, 2.4]) in 52 PD patients (100 hemispheres). For each hemisphere we assigned the frequency with the largest significant change in spectral power before versus after levodopa intake (median dose 150 mg, IQR: [100, 200]) as the personalized physiomarker using cluster-based permutation tests. Overall, alpha/low-beta (9–20 Hz) power reduction was the most common (35% of physiomarkers) followed by stimulation-entrained gamma (SEG, 62.5 Hz) power increases (19%). Other physiomarkers were identified in theta (4–8 Hz, 8%), high beta (21-30 Hz, 9%), low gamma (31–59 Hz, 10%) or high gamma (66–100 Hz, 12%) bands, most of which increased in power after levodopa intake. Subsequent k-means clustering revealed lower stimulation amplitudes to be associated with alpha/low-beta physiomarkers, while higher stimulation amplitudes and longer disease duration were associated with SEG physiomarkers. These findings contradict the presence of a single generalizable physiomarker frequency and instead argue for individualized selection.

Background: Cervical dystonia (CD) has a varied motor presentation, combining abnormal postures with complex involuntary head movements. Classification of these motor patterns remains imprecise, relying on descriptive terminology without robust definitions. Objectives: To provide a kinematically‐grounded description of the motor phenomenology of CD. Methods: Sixty‐two patients with CD and 32 age‐matched controls were recorded wearing inertial sensors. Voluntary movement was assessed during a head‐turning task, including velocity, range of motion, smoothness, and trajectory. Kinematic metrics were extracted from samples of involuntary movements and cluster analysis was applied to identify different patterns. These were then compared with clinical appraisal of movement phenotype. Exploratory factor analysis was conducted to investigate the relationship between motor characteristics. Results: Voluntary deficits included impaired velocity, range, smoothness, and symmetry, with no evidence of sequence effect. Three distinct clusters of involuntary head movement were identified: low‐frequency oscillations with a sawtooth waveform consisting of alternating fast and slow phases (Cluster 1); erratic mid‐frequency movements with constant changes in speed, waveform profile, and axis (Cluster 2); and high‐frequency sinusoidal movements (Cluster 3). Cluster 2 was specifically associated with a ‘jerky’ clinical phenotype, while Cluster 3 was associated with a ‘tremulous’ phenotype. Factor analysis identified distinct latent components driving variation in voluntary deficits and involuntary movement. Conclusions: CD is characterized by a heterogeneous combination of oscillatory movements and impairments in voluntary head control. Kinematic analysis has the potential to refine disease classification and support the development of objective instrumental outcome measures for clinical assessment and research. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an established treatment for Parkinson's disease (PD). Using 7‐Tesla (7 T) MRI connectivity analysis to visualize the patient‐specific STN motor subdivision, we hypothesize that reprogramming patients who are stimulated outside of this subdivision can improve their motor outcome substantially, without occurrence of adverse effects. Objectives: To determine whether connectivity‐guided reprogramming improves motor outcome in PD patients treated with STN‐DBS. Methods: Patients who underwent STN‐DBS with 7 T MRI probabilistic tractography (2022–2024) were evaluated after standardized follow‐up. Their volume of tissue activated (VTA) was visualized with clinical guided programming. Patients were reprogrammed if their VTA did not overlap with the connectivity‐defined STN motor subdivision. Follow‐up outcome was assessed using the Movement Disorders Society Unified Parkinson's Disease Rating Scale motor part (MDS‐UPDRS III; OFF medication, ON stimulation state) and hours OFF per day (MDS‐UPDRS IV). Results: Twelve patients were included, of whom nine were reprogrammed. Mean MDS‐UPDRS III score after classic programming improved by 16 ± 27% compared to baseline (48 ± 14 to 40 ± 13), and improved significantly further to 42 ± 26% after connectivity‐guided reprogramming (28 ± 8; p = 0.005). Furthermore, OFF time after classic programming decreased from 5 ± 3 h at baseline to 3 ± 2 h, and decreased further to 2 ± 2 h after reprogramming. No stimulation‐induced adverse effects were reported after parameter adjustments. Conclusions: 7 T MRI connectivity‐guided (re)programming of STN‐DBS can provide substantial improvement in motor outcome in PD patients and reduce OFF time, without occurrence of side‐effects. Furthermore, response rate to DBS increases, enhancing overall DBS effectiveness in PD.

Background: Deep brain stimulation (DBS) for Parkinson's disease (PD) primarily improves motor symptoms but leaves non-motor symptoms (NMS) largely unattended. Neurophysiological markers associated with specific symptoms could improve DBS programming. We systematically reviewed the evidence linking basal ganglia local field potentials (LFP) to NMS in PD. Methods: The literature search (Medline, Embase, Scopus, and Web of Science) on August 20, 2024 yielded 1066 records. Studies were included if they focused on patients with idiopathic PD treated with DBS of the subthalamic nucleus (STN) or globus pallidus interna (GPi) and reported on the relationship between LFP data and NMS. The study risk of bias was evaluated using the Prediction Model Risk of Bias Assessment Tool (PROBAST). A narrative synthesis of results was provided. Results: Twenty-one studies were included, focusing on impulse control disorders (n = 8), sleep-wake disorders (n = 5), depressive symptoms (n = 4), cognitive dysfunction (n = 3), hypomania (n = 1) and lower urinary tract symptoms (n = 1). Seven studies had a high risk of bias. Theta and alpha power in the STN were frequently associated with neuropsychiatric symptoms and cognitive function. Beta power in the STN and GPi was linked to sleep-wake disorders and urinary dysfunction. Conclusions: Overall, evidence on basal ganglia physiomarkers of NMS in PD remains limited. Further research is essential to develop patient-specific stimulation paradigms targeting NMS, which could significantly improve the quality of life of individuals with PD. Other: This systematic review was registered with the International Prospective Register of Systematic Reviews (CRD42024495284). There was no specific funding for this study.

Parkinson’s disease patients may experience a different therapeutic effect after replacement of the Medtronic Activa® deep brain stimulation neurostimulator with the newer Percept™ model, which features multiple independent current sources and constant-current control. We analyzed patient-reported therapeutic effect changes after Activa®-to-Percept™ replacements (AP, n=52) across six Dutch DBS-centers, comparing appropriate (AP+, n=36) and inappropriate/no (AP−, n=16) use of the manufacturer’s replacement workflow . Previous Activa®-to-Activa® replacements (AA, n=69) were used as reference. Worsened therapeutic effect was reported in 75.0% of AP−, 44.4% of AP+, and 21.7% of AA replacements (preplacement workflow is not properly used or in complex electrode configurations. We advise to use the workflow, inform the patient and plan closer follow-up appointments.