title: Tractography-Based Ventral Intermediate Nucleus Targeting: Novel Methodology and Intraoperative Validation.
abstract: The ventral intermediate nucleus of the thalamus is not readily visible on structural magnetic resonance imaging. Therefore, a method for its visualization for stereotactic targeting is desirable.
  
  
  
  The objective of this study was to define a tractography-based methodology for the stereotactic targeting of the ventral intermediate nucleus.
  
  
  
  The lateral and posterior borders of the ventral intermediate nucleus were defined by tracking the pyramidal tract and medial lemniscus, respectively. A thalamic seed was then created 3 mm medial and anterior to these borders, and its structural connections were analyzed. The application of this method was assessed in an imaging cohort of 14 tremor patients and 15 healthy controls, in which we compared the tractography-based targeting to conventional targeting. In a separate surgical cohort (3 tremor and 3 tremor-dominant Parkinson's disease patients), we analyzed the accuracy of this method by correlating it with intraoperative neurophysiology.
  
  
  
  Tractography of the thalamic seed revealed the tracts corresponding to cerebellar input and motor cortical output fibers. The tractography-based target was more lateral (12.5 [1.2] mm vs 11.5 mm for conventional targeting) and anterior (8.5 [1.1] mm vs 6.7 [0.3] mm, anterior to the posterior commissure). In the surgical cohort, the Euclidian distance between the ventral intermediate nucleus identified by tractography and the surgical target was 1.6 [1.1] mm. The locations of the sensory thalamus, lemniscus, and pyramidal tracts were concordant within <1 mm between tractography and neurophysiology.
  
  
  
  The tractography-based methodology for identification of the ventral intermediate nucleus is accurate and useful. This method may be used to improve stereotactic targeting in functional neurosurgery procedures. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital and University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sammartino
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital and University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.
authors.forename: Vibhor
authors.initials: V
authors.lastname: Krishna
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital and University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.
authors.forename: Nicolas Kon Kam
authors.initials: NK
authors.lastname: King
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital and University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.
authors.forename: Andres M
authors.initials: AM
authors.lastname: Lozano
authors.affiliation: Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.|Division of Neurosurgery, Sunnybrook Hospital, Toronto, Canada.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Schwartz
authors.affiliation: Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
authors.forename: Yuexi
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital and University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.
authors.forename: Mojgan
authors.initials: M
authors.lastname: Hodaie
mesh_terms: D056324:Diffusion Tensor Imaging / Q000379:methods* / Q000592:standards; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D009413:Nerve Fibers, Myelinated; D038361:Neuronavigation / Q000379:methods* / Q000592:standards; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000601:surgery; D011712:Pyramidal Tracts / Q000000981:diagnostic imaging*; D014202:Tremor / Q000000981:diagnostic imaging*; D020651:Ventral Thalamic Nuclei / Q000000981:diagnostic imaging* / Q000601:surgery
keywords: essential tremor; functional neurosurgery; stereotactic targeting; tractography; ventral intermedius nucleus