title: A diffusion-based connectivity map of the GPi for optimised stereotactic targeting in DBS.
abstract: The GPi (globus pallidus internus) is an important target nucleus for Deep Brain Stimulation (DBS) in medically refractory movement disorders, in particular dystonia and Parkinson's disease. Beneficial clinical outcome critically depends on precise electrode localization. Recent evidence indicates that not only neurons, but also axonal fibre tracts contribute to promoting the clinical effect. Thus, stereotactic planning should, in the future, also take the individual course of fibre tracts into account.
  
  
  
  The aim of this project is to explore the GPi connectivity profile and provide a connectivity-based parcellation of the GPi.
  
  
  
  Diffusion MRI sequences were performed in sixteen healthy, right-handed subjects. Connectivity-based parcellation of the GPi was performed applying two independent methods: 1) a hypothesis-driven, seed-to-target approach based on anatomic priors set as connectivity targets and 2) a purely data-driven approach based on k-means clustering of the GPi.
  
  
  
  Applying the hypothesis-driven approach, we obtained five major parcellation clusters, displaying connectivity to the prefrontal cortex, the brainstem, the GPe (globus pallidus externus), the putamen and the thalamus. Parcellation clusters obtained by both methods were similar in their connectivity profile. With the data-driven approach, we obtained three major parcellation clusters. Inter-individual variability was comparable with results obtained in thalamic parcellation.
  
  
  
  The three parcellation clusters obtained by the purely data-driven method might reflect GPi subdivision into a sensorimotor, associative and limbic portion. Clinical and physiological studies indicate greatest clinical DBS benefit for electrodes placed in the postero-ventro-lateral GPi, the region displaying connectivity to the thalamus in our study and generally attributed to the sensorimotor system. Clinical studies relating DBS electrode positions to our GPi connectivity map would be needed to complement our findings.
authors.affiliation: INESC TEC and Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
authors.forename: Nadia Moreira
authors.initials: NM
authors.lastname: da Silva
authors.affiliation: Department of Neurology, Klinikum Grosshadern, University of Munich, Germany.
authors.forename: Seyed-Ahmad
authors.initials: SA
authors.lastname: Ahmadi
authors.affiliation: INESC TEC and Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
authors.forename: Sergio Neves
authors.initials: SN
authors.lastname: Tafula
authors.affiliation: INESC TEC and Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
authors.forename: Joao Paulo Silva
authors.initials: JPS
authors.lastname: Cunha
authors.affiliation: INESC TEC and Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
authors.forename: Kai
authors.initials: K
authors.lastname: Bötzel
authors.affiliation: Department of Neurology, Klinikum Grosshadern, University of Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Vollmar
authors.affiliation: Department of Neurology, Klinikum Grosshadern, University of Munich, Germany. Electronic address: verena.rozanski@med.uni-muenchen.de.
authors.forename: Verena Eveline
authors.initials: VE
authors.lastname: Rozanski
mesh_terms: D000328:Adult; D046690:Deep Brain Stimulation / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005917:Globus Pallidus / Q000000981:diagnostic imaging*; D064368:Healthy Volunteers; D006801:Humans
keywords: Connectivity; Deep brain stimulation; basal ganglia; parcellation