Kinematic analysis reliably assesses GPi-DBS effectiveness in dystonia

BACKGROUND: Severe forms of generalised (GD) or cervical dystonia (CD) can be effectively treated with deep brain stimulation (DBS) of the globus pallidus interna (GPi). However, objectively assessing DBS effectiveness remains challenging. OBJECTIVE: To identify objective biomarkers of GPi-DBS effectiveness using a minimalistic three-dimensional (3D) kinematic motion capture system in patients with dystonia. METHODS: This retrospective longitudinal study analysed kinematic data from 14 patients before and after GPi-DBS: 7 with GD (3 females; mean age, 34.1±16.5 years; mean Burke-Fahn-Marsden (BFM) 32.9±14.1) and 7 with CD (4 females; mean age, 46.2±9.8 years; mean BFM 10.4±4.4). Parameters included barycentre displacement length, volume, velocity, angular velocity and power spectral density (PSD) in low-frequency (delta and theta) bands. Dystonia severity was assessed using the BFM scale. RESULTS: In the pooled cohort, GPi-DBS significantly reduced dystonia severity, with mean BFM scores decreasing from 21.6±15.4 preoperatively to 14.1±13.1 postoperatively (p=0.011, permutation test). In subgroup analyses, BFM scores decreased significantly in the CD group (p=0.015), while a non-significant trend toward improvement was observed in the GD group (p=0.076). Kinematic analysis in the pooled cohort demonstrated a robust reduction in barycentre angular velocity (p