title: Accuracy of stimulating electrode placement in paediatric pallidal deep brain stimulation for primary and secondary dystonia.
abstract: BACKGROUND
  Accuracy of electrode placement is an important determinant of outcome following deep brain stimulation (DBS) surgery. Data on accuracy of electrode placement into the globus pallidum interna (GPi) in paediatric patients is limited, particularly those with non-primary dystonia who often have smaller GPi. Pallidal DBS is known to be more effective in the treatment of primary dystonia compared with secondary dystonia.
  
  
  OBJECTIVE
  We aimed to determine if accuracy of pallidal electrode placement differed between primary, secondary and NBIA (neuronal degeneration and brain iron accumulation) associated dystonia and how this related to motor outcome following surgery.
  
  
  METHODS
  A retrospective review of a consecutive cohort of children and young people undergoing DBS surgery in a single centre. Fused in frame preoperative planning magnetic resonance imaging (MRI) and postoperative computed tomography (CT) brain scans were used to determine the accuracy of placement of DBS electrode tip in Leskell stereotactic system compared with the planned target. The differences along X, Y, and Z coordinates were calculated, as was the Euclidean distance of electrode tip from the target. The relationship between proximity to target and change in Burke-Fahn-Marsden Dystonia Rating Scale at 1 year was also measured.
  
  
  RESULTS
  Data were collected from 88 electrodes placed in 42 patients (14 primary dystonia, 18 secondary dystonia and 10 NBIA associated dystonia). Median differences between planned target and actual position were: left-side X-axis 1.05 mm, Y-axis 0.85 mm, Z-axis 0.94 mm and Euclidean difference 2.04 mm; right-side X-axis 1.28 mm, Y-axis 0.70 mm, Z-axis 0.70 mm and Euclidean difference 2.45 mm. Accuracy did not differ between left and right-sided electrodes. No difference in accuracy was seen between primary, secondary or NBIA associated dystonia. Dystonia reduction at 1 year post surgery did not appear to relate to proximity of implanted electrode to surgical target across the cohort.
  
  
  CONCLUSIONS
  Accuracy of surgical placement did not differ between primary, secondary or NBIA associated dystonia. Decreased efficacy of pallidal DBS in secondary and NBIA associated dystonia is unlikely to be related to difficulties in achieving the planned electrode placement.
authors: Complex Motor Disorders Service, Evelina Children's Hospital, Guy's & St Thomas' NHS Foundation Trust, Lambeth Palace Road, London, SE1 7EH, UK. Daniel.lumsden@gstt.nhs.uk
authors: Daniel E
authors: DE
authors: Lumsden
authors: Jonathan
authors: J
authors: Ashmore
authors: Geoff
authors: G
authors: Charles-Edwards
authors: Jean-Pierre
authors: JP
authors: Lin
authors: Keyoumars
authors: K
authors: Ashkan
authors: Richard
authors: R
authors: Selway
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D046690:Deep Brain Stimulation / Q000379:methods; D004421:Dystonia / Q000628:therapy*; D004567:Electrodes, Implanted; D005917:Globus Pallidus; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult