title: Effect of medication and STN-DBS on postural control in subjects with Parkinson's disease.
abstract: OBJECTIVE
  To assess the effect of disease severity, dopaminergic medication (med) and STN-DBS on postural stability in Parkinson's disease (PD).
  
  
  METHODS
  Postural sway in quiet stance, and the Unified Parkinson's Disease Rating Scale (motor) (UPDRS III) were evaluated in 129 subjects in the off-med state. A subgroup of 28 subjects was studied on-med and after STN-DBS. Postural sway was measured using center of pressure (CoP) root mean square displacement (RMS(CoP)) and mean velocity (V(CoP)) in the anterior-posterior (AP) and medial-lateral (ML) directions.
  
  
  RESULTS
  All CoP parameters were larger in moderate/advanced subjects vs controls (P < 0.001) and early subjects. Only RMS(CoP)ML was larger in early subjects vs controls (P < 0.05). Med, DBS and DBS + med decreased UPDRS III compared to off-med (P < 0.001). RMS(CoP)ML and V(CoP)ML were larger on-med vs off-med and vs DBS (P < 0.001). Compared to controls and PD subjects with normal CoP sway off-med, med increased all CoP parameters (P < 0.01) but DBS returned V(CoP)ML to normal values. For 'abnormal' PD subjects, STN-DBS improved the excessive V(CoP) in ML compared to off and on-med pre-DBS (P < 0.05).
  
  
  CONCLUSIONS
  Postural sway in quiet stance increased with disease severity. Only ML CoP displacement was abnormal in early stage PD, and this may be a compensatory mechanism. Medication increased ML postural sway. In 'normal' PD subjects, STN-DBS reversed medication induced postural instability. Subjects with abnormal balance in quiet stance did not benefit from medication or DBS, except for improvement in ML CoP velocity from DBS. This may serve to reduce postural instability and falling.
authors: Department of Neurology and Neurological Sciences, Rm A343, 300 Pasteur Drive, Stanford University School of Medicine, Stanford, CA 94303, USA. nantelj@stanford.edu
authors: Julie
authors: J
authors: Nantel
authors: Jamie Currie
authors: JC
authors: McDonald
authors: Helen
authors: H
authors: Bronte-Stewart
mesh_terms: D000978:Antiparkinson Agents / Q000009:adverse effects*; D046690:Deep Brain Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000628:therapy*; D004856:Postural Balance / Q000187:drug effects*
chemical_list: D000978:Antiparkinson Agents