title: A new biomarker for subthalamic deep brain stimulation for patients with advanced Parkinson's disease--a pilot study.
abstract: OBJECTIVE
  Deep brain stimulation (DBS) has become the standard treatment for advanced stages of Parkinson's disease (PD) and other motor disorders. Although the surgical procedure has improved in accuracy over the years thanks to imaging and microelectrode recordings, the underlying principles that render DBS effective are still debated today. The aim of this paper is to present initial findings around a new biomarker that is capable of assessing the efficacy of DBS treatment for PD which could be used both as a research tool, as well as in the context of a closed-loop stimulator.
  
  
  METHODS
  We have used a novel multi-channel stimulator and recording device capable of measuring the response of nervous tissue to stimulation very close to the stimulus site with minimal latency, rejecting most of the stimulus artefact usually found with commercial devices. We have recorded and analyzed the responses obtained intraoperatively in two patients undergoing DBS surgery in the subthalamic nucleus (STN) for advanced PD.
  
  
  RESULTS
  We have identified a biomarker in the responses of the STN to DBS. The responses can be analyzed in two parts, an initial evoked compound action potential arising directly after the stimulus onset, and late responses (LRs), taking the form of positive peaks, that follow the initial response. We have observed a morphological change in the LRs coinciding with a decrease in the rigidity of the patients.
  
  
  CONCLUSIONS
  These initial results could lead to a better characterization of the DBS therapy, and the design of adaptive DBS algorithms that could significantly improve existing therapies and help us gain insights into the functioning of the basal ganglia and DBS.
authors.affiliation: Implant Systems Group, National Information and Communications Technology Australia, Eveleigh, NSW 2015, Australia. School of Electrical Engineering and Telecommunications, The University of New South Wales, NSW 2052, Australia.
authors.forename: Gerrit E
authors.initials: GE
authors.lastname: Gmel
authors.forename: Tara J
authors.initials: TJ
authors.lastname: Hamilton
authors.forename: Milan
authors.initials: M
authors.lastname: Obradovic
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gorman
authors.forename: Peter S
authors.initials: PS
authors.lastname: Single
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Chenery
authors.forename: Terry
authors.initials: T
authors.lastname: Coyne
authors.forename: Peter A
authors.initials: PA
authors.lastname: Silburn
authors.forename: John L
authors.initials: JL
authors.lastname: Parker
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000368:Aged; D015415:Biomarkers; D046690:Deep Brain Stimulation / Q000379:methods*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D010865:Pilot Projects; D020531:Subthalamic Nucleus / Q000502:physiology*
chemical_list: D015415:Biomarkers