title: Improvement in Parkinson disease by subthalamic nucleus stimulation based on electrode placement: effects of reimplantation.
abstract: BACKGROUND
  The misplacement of electrodes is a possible explanation for suboptimal response to bilateral subthalamic nucleus (STN) stimulation in patients with Parkinson disease.
  
  
  OBJECTIVE
  To evaluate whether reimplantation of electrodes in the STN can produce improvement in patients with poor results from surgery and with suspected electrode misplacement based on imaging findings.
  
  
  METHODS
  Prospective follow-up study.
  
  
  METHODS
  Academic research.
  
  
  METHODS
  A 1-year postoperative study was undertaken in 7 consecutive patients with Parkinson disease who, despite bilateral STN stimulation, experienced persistent motor disability and who were operated on for reimplantation a median of 16.9 months later.
  
  
  METHODS
  The primary outcome was measured as the change in the Unified Parkinson Disease Rating Scale (UPDRS) motor score 1 year after reimplantation. The secondary outcome was measured as the extent of pharmacologic and electrical treatments required and the threshold at which the first stimulation-induced adverse effect appeared. The distances between the electrode contacts used for chronic stimulation and the STN theoretical effective target, defined as the mean position of the clinically efficient contact from 193 previously implanted electrodes, were compared.
  
  
  RESULTS
  Except for a single patient, all patients displayed improvement following reimplantation. Under off-medication (ie, the patient is taking no medication) condition, STN stimulation improved the basal state UPDRS motor score by 26.7% before reimplantation and by 59.4% at 1 year after reimplantation. The median off-medication Schwab and England score improved from 51% to 76%. The median levodopa equivalent daily dose was reduced from 1202 mg to 534 mg. The stimulation varibles changed from a mean of 2.6 V/73.0 micros/163.0 Hz to 2.8 V/60. 0 micros/ 140.0 Hz. The mean threshold of the first stimulation-induced adverse effect increased from 2.6 to 4.4 V. The mean distance between the contacts used for chronic stimulation and the theoretical effective target decreased from 5.4 to 2.0 mm. This distance correlated inversely with the percentage improvement in theUPDRS motor score.
  
  
  CONCLUSIONS
  Patients demonstrating poor response to STN stimulation as a result of electrode misplacement can benefit from reimplantation in the STN closer to the theoretical target.
authors.affiliation: Department of Neurology, University Hospital A. Michallon, Grenoble, France. anheim@titus.u-strasbg.fr
authors.forename: Mathieu
authors.initials: M
authors.lastname: Anheim
authors.forename: Alina
authors.initials: A
authors.lastname: Batir
authors.forename: Valérie
authors.initials: V
authors.lastname: Fraix
authors.forename: Madjid
authors.initials: M
authors.lastname: Silem
authors.forename: Stéphan
authors.initials: S
authors.lastname: Chabardès
authors.forename: Eric
authors.initials: E
authors.lastname: Seigneuret
authors.forename: Paul
authors.initials: P
authors.lastname: Krack
authors.forename: Alim-Louis
authors.initials: AL
authors.lastname: Benabid
authors.forename: Pierre
authors.initials: P
authors.lastname: Pollak
mesh_terms: D000368:Aged; D001479:Basal Ganglia / Q000503:physiopathology; D046690:Deep Brain Stimulation / Q000295:instrumentation* / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008839:Microelectrodes / Q000592:standards; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology; D038361:Neuronavigation / Q000379:methods / Q000592:standards; D010300:Parkinson Disease / Q000628:therapy*; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D011446:Prospective Studies; D020127:Recovery of Function / Q000502:physiology; D012086:Reoperation; D013238:Stereotaxic Techniques / Q000295:instrumentation / Q000592:standards; D020531:Subthalamic Nucleus / Q000502:physiology* / Q000601:surgery*; D016896:Treatment Outcome