title: Postoperative curving and upward displacement of deep brain stimulation electrodes caused by brain shift.
abstract: BACKGROUND
  Accurate electrode position is important for the efficacy of deep brain stimulation (DBS). Several reports revealed errors during stereotactic surgery due to cerebrospinal fluid (CSF) loss and subdural air invasion. Because subdural air resolves in the weeks after surgery and the brain returns to its original position, DBS electrodes may become displaced postoperatively.
  
  
  OBJECTIVE
  To quantitatively assess postoperative DBS electrode displacement in relation to subdural air invasion.
  
  
  METHODS
  We retrospectively analyzed 14 patients with advanced Parkinson disease and subthalamic nucleus DBS electrodes that underwent immediate postoperative frame-based stereotactic computer tomography (CT) and repeated CT after longer follow-up. We performed volumetric measurements of postoperative subdural air collections on both sides of the brain and determined stereotactic coordinates of the deepest DBS contact on the direct postoperative and follow-up CT.
  
  
  RESULTS
  Subdural air collections measured on average 17+/-24 cm. Consequently, the frontal cortex shifted posteriorly. On follow-up imaging after 16+/-8 months, air collections had resolved and the frontal cortex had returned to its original position, causing anterior curving of the electrodes. The electrodes moved on average 3.3+/-2.5 mm upward along the trajectory. This displacement significantly correlated with the amount of postoperative subdural air.
  
  
  CONCLUSIONS
  Considerable displacement of DBS electrodes may occur in the weeks following surgery, especially in cases with large postoperative subdural air volumes. Postoperative documentation of electrode localization should therefore be repeated after longer follow-up.
authors.affiliation: Department of Neurosurgery, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. p.vandenmunckhof@amc.nl
authors.forename: Pepijn
authors.initials: P
authors.lastname: van den Munckhof
authors.forename: M Fiorella
authors.initials: MF
authors.lastname: Contarino
authors.forename: Lo J
authors.initials: LJ
authors.lastname: Bour
authors.forename: Johannes D
authors.initials: JD
authors.lastname: Speelman
authors.forename: Rob M A
authors.initials: RM
authors.lastname: de Bie
authors.forename: P Richard
authors.initials: PR
authors.lastname: Schuurman
mesh_terms: D000328:Adult; D046690:Deep Brain Stimulation / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D004567:Electrodes, Implanted / Q000009:adverse effects*; D004618:Embolism, Air / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology / Q000601:surgery; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology*; D012189:Retrospective Studies