title: Interactive effects of GPI stimulation and levodopa on postural control in Parkinson's disease.
abstract: BACKGROUND
  Postural instability is a major source of disability in idiopathic Parkinson's disease (IPD). Deep brain stimulation of the globus pallidus internus (GPI-DBS) improves clinician-rated balance control but there have been few quantitative studies of its interactive effects with levodopa (L-DOPA). The purpose of this study was to compare the short-term and interactive effects of GPI-DBS and L-DOPA on objective measures of postural stability in patients with longstanding IPD.
  
  
  METHODS
  Static and dynamic posturography during a whole-body leaning task were performed in 10 IPD patients with bilateral GPI stimulators under the following conditions: untreated (OFF); L-DOPA alone; DBS alone; DBS+L-DOPA, and in 9 healthy Control subjects. Clinical status was assessed using the UPDRS and AIMS Dyskinesia Scale.
  
  
  RESULTS
  Static sway was greater in IPD patients in the OFF state compared to the Control subjects and was further increased by L-DOPA and reduced by GPI-DBS. In the dynamic task, L-DOPA had a greater effect than GPI-DBS on improving Start Time, but reduced the spatial accuracy and directional control of the task. When the two therapies were combined, GPI-DBS prevented the L-DOPA induced increase in static sway and improved the accuracy of the dynamic task.
  
  
  CONCLUSIONS
  The findings demonstrate GPI-DBS and L-DOPA have differential effects on temporal and spatial aspects of postural control in IPD and that GPI-DBS counteracts some of the adverse effects of L-DOPA. Further studies on larger numbers of patients with GPI stimulators are required to confirm these findings and to clarify the contribution of dyskinesias to impaired dynamic postural control.
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia; Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Victoria, Australia; The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia. Electronic address: liam.johnson@florey.edu.au.
authors: Liam
authors: L
authors: Johnson
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors: Julian
authors: J
authors: Rodrigues
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia; Centre for Physical Activity and Nutrition Research, Deakin University, Burwood, Victoria, Australia.
authors: Wei-Peng
authors: WP
authors: Teo
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors: Susan
authors: S
authors: Walters
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors: Rick
authors: R
authors: Stell
authors: Western Australian Neuroscience Research Institute, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors: Gary
authors: G
authors: Thickbroom
authors: Institute of Immunology and Infectious Diseases, Murdoch University, Murdoch, Western Australia, Australia.
authors: Frank
authors: F
authors: Mastaglia
mesh_terms: D000368:Aged; D046690:Deep Brain Stimulation / Q000379:methods*; D015259:Dopamine Agents / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D005917:Globus Pallidus / Q000503:physiopathology*; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D004856:Postural Balance / Q000502:physiology*
chemical_list: D015259:Dopamine Agents; D007980:Levodopa
keywords: Deep brain stimulation; Parkinson's disease; Postural instability; Static and dynamic posturography