Brain Advance Access originally published online on October 7, 2008
Brain 2008 131(12):3348-3360; doi:10.1093/brain/awn238
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Bilateral subthalamic stimulation impairs cognitive–motor performance in Parkinson's disease patients
1Department of Biomedical Engineering, Cleveland Clinic, 2Center for Neurological Restoration, Cleveland Clinic, 3Cleveland FES Center, L. Stokes Cleveland VA Medical Center, Cleveland, OH, USA, 4Jacobs Center on Lifelong Learning and Institutional Development, Jacobs University, Bremen, Germany and 5Department of Neuroscience, Cleveland Clinic, Cleveland, OH, USA
Correspondence to: Jay L. Alberts, Department of Biomedical Engineering/ND20, Center for Neurological Restoration, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA E-mail: albertj{at}ccf.org
Deep brain stimulation (DBS) is a surgical procedure that has been shown effective in improving the cardinal motor signs of advanced Parkinson's disease, however, declines in cognitive function have been associated with bilateral subthalamic nucleus (STN) DBS. Despite the fact that most activities of daily living clearly have motor and cognitive components performed simultaneously, postoperative assessments of cognitive and motor function occur, in general, in isolation of one another. The primary aim of this study was to determine the effects of unilateral and bilateral STN DBS on upper extremity motor function and cognitive performance under single- and dual-task conditions in advanced Parkinson's disease patients. Data were collected from eight advanced Parkinson's disease patients between the ages of 48 and 70 years (mean 56.5) who had bilaterally placed STN stimulators. Stimulation parameters for DBS devices were optimized clinically and were stable for at least 6 months prior to study participation. Data were collected while patients were Off anti-parkinsonian medications under three stimulation conditions: Off stimulation, unilateral DBS and bilateral DBS. In each stimulation condition patients performed a cognitive (n-back task) and motor (force tracking) task under single- and dual-task conditions. During dual-task conditions, patients performed the n-back and force-maintenance task simultaneously. Under relatively simple dual-task conditions there were no differences in cognitive or motor performance under unilateral and bilateral stimulation. As dual-task complexity increased, cognitive and motor performance was significantly worse with bilateral compared with unilateral stimulation. In the most complex dual-task condition (i.e. 2-back + force tracking), bilateral stimulation resulted in a level of motor performance that was similar to the Off stimulation condition. Significant declines in cognitive and motor function under modest dual-task conditions with bilateral but not with unilateral STN DBS suggest that unilateral procedures may be an alternative to bilateral DBS for some patients, in particular, those with asymmetric symptomology. From a clinical perspective, these results underscore the need to assess cognitive and motor function simultaneously during DBS programming as these conditions may better reflect the context in which daily activities are performed.
Key Words: Parkinson's disease; deep brain stimulation; force control; cognitive function; dual-task
Abbreviations: DBS, deep brain stimulation; DTL, dual-task loss; GPi, globus pallidus internus; RRMSE, relative root mean square error; STN, subthalamic nucleus; TWR, time within the target range; VTA, volume of tissue activated
Received March 27, 2008. Revised August 27, 2008. Accepted August 29, 2008.