title: Deep brain stimulation activation volumes and their association with neurophysiological mapping and therapeutic outcomes.
abstract: OBJECTIVE
  Despite the clinical success of deep brain stimulation (DBS) for the treatment of Parkinson's disease (PD), little is known about the electrical spread of the stimulation. The primary goal of this study was to integrate neuroimaging, neurophysiology and neurostimulation data sets from 10 patients with PD, unilaterally implanted with subthalamic nucleus (STN) DBS electrodes, to identify the theoretical volume of tissue activated (VTA) by clinically defined therapeutic stimulation parameters.
  
  
  METHODS
  Each patient specific model was created with a series of five steps: (1) definition of the neurosurgical stereotactic coordinate system within the context of preoperative imaging data; (2) entry of intraoperative microelectrode recording locations from neurophysiologically defined thalamic, subthalamic and substantia nigra neurons into the context of the imaging data; (3) fitting a three dimensional brain atlas to the neuroanatomy and neurophysiology of the patient; (4) positioning the DBS electrode in the documented stereotactic location, verified by postoperative imaging data; and (5) calculation of the VTA using a diffusion tensor based finite element neurostimulation model.
  
  
  RESULTS
  The patient specific models show that therapeutic benefit was achieved with direct stimulation of a wide range of anatomical structures in the subthalamic region. Interestingly, of the five patients exhibiting a greater than 40% improvement in their Unified PD Rating Scale (UPDRS), all but one had the majority of their VTA outside the atlas defined borders of the STN. Furthermore, of the five patients with less than 40% UPDRS improvement, all but one had the majority of their VTA inside the STN.
  
  
  CONCLUSIONS
  Our results are consistent with previous studies suggesting that therapeutic benefit is associated with electrode contacts near the dorsal border of the STN, and provide quantitative estimates of the electrical spread of the stimulation in a clinically relevant context.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Maks
authors.forename: C R
authors.initials: CR
authors.lastname: Butson
authors.forename: B L
authors.initials: BL
authors.lastname: Walter
authors.forename: J L
authors.initials: JL
authors.lastname: Vitek
authors.forename: C C
authors.initials: CC
authors.lastname: McIntyre
mesh_terms: D001931:Brain Mapping / Q000379:methods*; D046690:Deep Brain Stimulation / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D004292:Dominance, Cerebral / Q000502:physiology; D004567:Electrodes, Implanted; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009415:Nerve Net / Q000503:physiopathology; D009460:Neurologic Examination; D009474:Neurons / Q000502:physiology; D010300:Parkinson Disease / Q000503:physiopathology* / Q000628:therapy*; D013378:Substantia Nigra / Q000503:physiopathology; D020531:Subthalamic Nucleus / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000502:physiology*; D013788:Thalamus / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome