title: Long-term evaluation of impedance levels and clinical development in subthalamic deep brain stimulation for Parkinson's disease.
abstract: BACKGROUND
  This study was conducted to better understand the development of clinical efficacy and impedance levels in the long-term course of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD).
  
  
  METHODS
  In this retrospective study of twenty PD patients, the motor part of the Unified Parkinson's Disease Rating Scale was periodically assessed i) after withdrawal of medication and inactivated stimulation, ii) after withdrawal of medication with activated stimulation and iii) after challenge with l-Dopa during activated stimulation up to 13 years after surgery.
  
  
  RESULTS
  STN-DBS with or without medication significantly improved motor function up to 13 years after surgery. The contribution of axial symptoms increased over time. While the stimulation parameters were kept constant, the therapeutic impedances progressively declined.
  
  
  CONCLUSIONS
  STN-DBS in PD remains effective in the long-term course of the disease. Constant current stimulation might be preferable over voltage-controlled stimulation, as it would alleviate the impact of impedance changes on the volume of tissue activated.
authors.affiliation: Department of Neurology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany; Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany. Electronic address: Christian-hartmann@uni-duesseldorf.de.
authors.forename: C J
authors.initials: CJ
authors.lastname: Hartmann
authors.affiliation: Department of Neurology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany; Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Wojtecki
authors.affiliation: Department of Neurosurgery, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Vesper
authors.affiliation: Department of Neurology, Julius-Maximilians-University, Würzburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Volkmann
authors.affiliation: Department of Neurology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany; Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: S J
authors.initials: SJ
authors.lastname: Groiss
authors.affiliation: Department of Neurology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany; Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schnitzler
authors.affiliation: Department of Neurology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany; Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Südmeyer
mesh_terms: D000368:Aged; D046690:Deep Brain Stimulation / Q000379:methods*; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology* / Q000628:therapy*; D012189:Retrospective Studies; D020531:Subthalamic Nucleus / Q000503:physiopathology*; D013995:Time
keywords: Deep brain stimulation; Long-term effects; Parkinson's disease