title: A systematic review of studies on anatomical position of electrode contacts used for chronic subthalamic stimulation in Parkinson's disease.
abstract: BACKGROUND
  The dorso-lateral part of the subthalamic nucleus (STN) is considered as the usual target of deep brain stimulation for Parkinson's disease. Nevertheless, the exact anatomical location of the electrode contacts used for chronic stimulation is still a matter of debate. The aim of this study was to perform a systematic review of the existing literature on this issue.
  
  
  METHODS
  We searched for studies on the anatomical location of active contacts published until December 2012.
  
  
  RESULTS
  We identified 13 studies, published between 2002 and 2010, including 260 patients and 466 electrodes. One hundred and sixty-four active contacts (35 %) were identified within the STN, 117 (25 %) at the interface between STN and the surrounding structures, 184 (40 %) above the STN and one within the substantia nigra. We observed great discrepancies between the different series. The contra-lateral improvement was between 37 and 78.5 % for contacts located within the STN, between 48.6 and 73 % outside the STN, between 65.3 and 66 % at the interface. The authors report no clear correlation between anatomical location and stimulation parameters.
  
  
  CONCLUSIONS
  Post-operative analysis of the anatomical location of active contacts is difficult, and all the methods used are debatable. The relationship between the anatomical location of active contacts and the clinical effectiveness of stimulation is unclear. It would be necessary to take into account the volume of the electrode contacts and the diffusion of the stimulation. We can nevertheless assume that the interface between dorso-lateral STN, zona incerta and Forel's fields could be directly involved in the effects of stimulation.
authors.affiliation: Service de Neurochirurgie, CHU de Limoges, 87000, Limoges, France. francois.caire@chu-limoges.fr
authors.forename: François
authors.initials: F
authors.lastname: Caire
authors.forename: Danièle
authors.initials: D
authors.lastname: Ranoux
authors.forename: Dominique
authors.initials: D
authors.lastname: Guehl
authors.forename: Pierre
authors.initials: P
authors.lastname: Burbaud
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Cuny
mesh_terms: D002908:Chronic Disease; D046690:Deep Brain Stimulation / Q000379:methods*; D006801:Humans; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D013238:Stereotaxic Techniques; D013378:Substantia Nigra / Q000503:physiopathology*; D020531:Subthalamic Nucleus / Q000503:physiopathology*