• Victor Hvingelby, Fareha Khalil, Flavia Massey, Alexander Hoyningen, San San Xu, Joseph Candelario-McKeown, Harith Akram, Thomas Foltynie, Patricia Limousin, Ludvic Zrinzo, and Marie T Krüger.
• Department of Clinical Medicine, Aarhus Universitet, Aarhus, Denmark.
• J. Neurol. Neurosurg. Psychiatr. 2024 Sep 20.

BackgroundSince their introduction in 2015, directional leads have practically replaced conventional leads for deep brain stimulation (DBS) in Parkinson's disease (PD). Yet, the benefits of directional DBS (dDBS) over omnidirectional DBS (oDBS) remain unclear. This meta-analysis and systematic review compares the literature on dDBS and oDBS for PD.MethodsPreferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Database searches included Pubmed, Cochrane (CENTRAL) and EmBase, using relevant keywords such as 'directional', 'segmented', 'brain stimulation' and 'neuromodulation'. The screening was based on the title and abstract.Results23 papers reporting on 1273 participants (1542 leads) were included. The therapeutic window was 0.70 mA wider when using dDBS (95% CI 0.13 to 1.26 mA, p=0.02), with a lower therapeutic current (0.41 mA, 95% CI 0.27 to 0.54 mA, p=0.01) and a higher side-effect threshold (0.56 mA, 95% CI 0.38 to 0.73 mA, p<0.01). However, there was no relevant difference in mean Unified Parkinson's Disease Rating Scale III change after dDBS (45.8%, 95% CI 30.7% to 60.9%) compared with oDBS (39.0%, 95% CI 36.9% to 41.2%, p=0.39), in the medication-OFF state. Median follow-up time for dDBS and oDBS studies was 6 months and 3 months, respectively (range 3-12 for both). The use of directionality often improves dyskinesia, dysarthria, dysesthesia and pyramidal side effects. Directionality was used in 55% of directional leads at 3-6 months, remaining stable over time (56% at a mean of 14.1 months).ConclusionsThese findings suggest that stimulation parameters favour dDBS. However, these do not appear to have a significant impact on motor scores, and the availability of long-term data is limited. dDBS is widely accepted, but clinical data justifying its increased complexity and cost are currently sparse.Prospero Registration NumberCRD42023438056.© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.

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