title: Effects of STN DBS and auditory cueing on the performance of sequential movements and the occurrence of action tremor in Parkinson's disease.
abstract: BACKGROUND
  Parkinson's disease (PD) patients show a higher ability to perform repetitive movements when they are cued by external stimuli, suggesting that rhythmic synchronization with an auditory timekeeper can be achieved in the absence of intact basal ganglia function. Deep brain stimulation (DBS) is another therapeutic method that improves movement performance in PD and may suppress or enhance action tremor. However, the combined effect of these therapies on action tremor has not been studied yet. In this pilot study, we thus test the effect of both DBS in the subthalamic nucleus (STN) and auditory cueing on movement performance and action tremor.
  
  
  METHODS
  7 PD patients treated with (bilateral) STN DBS were asked to move one hand or foot between two dots, separated by 30 cm as indicated on the table or the floor. The movement frequency was dictated by a metronome with a frequency in the range of 1.6 to 4.8 Hz. Each test was repeated three times for each extremity, with different stimulation settings applied during each repetition. The power spectral density patterns of recorded movements were studied. Tremor intermittency was taken into account by classifying each 2-second window of the recorded angular velocity signals as a tremor or non-tremor window. By determining the phase locking value it was tested whether movement or tremor was synchronized with the auditory cue.
  
  
  RESULTS
  While action tremor presence or absence did not affect the level of synchronization of the movement signal with the auditory cue for the different metronome frequencies, the number of extremities showing action tremor was significantly reduced under external cueing conditions in combination with DBS. In this respect the cueing frequencies of 1.6 and 4.8 Hz showed similar effects, suggesting that the frequency of the cueing signal is not that critical.
  
  
  CONCLUSIONS
  The combination of deep brain stimulation and auditory cueing, which both are proposed to involve the activation of cerebellar circuits, shows an enhanced action tremor reduction in Parkinson's disease.
authors.affiliation: MIRA Institute for Biomedical Engineering and Technical Medicine, University of Twente, Department of Electrical Engineering, Mathematics and Computer Science, Biomedical Signals and Systems group, Zuidhorst 214, P,O, Box 17, 7500 AE Enschede, The Netherlands. t.heida@utwente.nl.
authors.forename: Tjitske
authors.initials: T
authors.lastname: Heida
authors.forename: Eva Christine
authors.initials: EC
authors.lastname: Wentink
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Enrico
authors.initials: E
authors.lastname: Marani
mesh_terms: D000368:Aged; D003463:Cues; D046690:Deep Brain Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D010300:Parkinson Disease / Q000628:therapy*; D010865:Pilot Projects; D020531:Subthalamic Nucleus / Q000502:physiology; D014202:Tremor / Q000628:therapy