Objective Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor function, including gait and stability, in people with Parkinson's disease (PD) but differences in DBS contact locations within the STN may contribute to variability in the degree of improvement. Based on anatomical connectivity, dorsal STN may be preferentially involved in motor function and ventral STN in cognitive function.
Methods To determine whether dorsal DBS affects gait and balance more than ventral DBS, a double blind evaluation of 23 PD patients with bilateral STN DBS was conducted. Each participant underwent gait analysis and balance testing off Parkinson's medication under three DBS conditions (unilateral DBS in the dorsal STN region, unilateral DBS in the ventral STN region and both stimulators off) on 1 day.
Results Improvements were seen in Unified Parkinson's Disease Rating Scale (UPDRS)-III scores and velocity in walking trials as fast as possible (Fast gait) and preferred pace (Pref gait), as well as stride length for Fast and Pref gait, with dorsal and ventral stimulation compared with the off condition (post hoc tests, p<0.05). However, there were no differences with dorsal compared to ventral stimulation. Balance, assessed using the multi-item mini-Balance Evaluation Systems Test (mini-BESTest), was similar across conditions.
Conclusions Absence of differences in gait and balance between the dorsal and ventral conditions suggests motor connections involved in gait and balance may be more diffusely distributed in STN than previously thought, as opposed to neural connections involved in cognitive processes, such as response inhibition, which are more affected by ventral stimulation.
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Funding Support was provided by NIH grants RO1NS41509, F31 NS071639, CO6 RR020092 and RR024992 (Washington University Institute of Clinical and Translational Sciences—Brain, Behavioural and Performance Unit), the American Parkinson's Disease Association (APDA), Advanced Center for PD Research at Washington University, the Greater St Louis Chapter of the APDA and the Barnes Jewish Hospital Foundation (Stein Family Fund and the Jack Buck Fund for PD Research).
Competing interests None.
Ethics approval This study was conducted with the approval of the Washington University Human Research Protection Office.
Provenance and peer review Not commissioned; externally peer reviewed.