title: Effects of subthalamic nucleus stimulation on motor cortex excitability in Parkinson's disease.
abstract: OBJECTIVE
  To study the effects of subthalamic nucleus (STN) stimulation on motor cortex excitability in Parkinson's disease (PD).
  
  
  METHODS
  Fifteen patients were evaluated under off-medication, OFF- and ON-STN conditions, using the UPDRS. We studied the effects of STN stimulation on motor cortex excitability under three conditions (OFF, ON with chronic therapeutic parameters, ON HighV with a voltage set 10% under permanent side effects threshold), using transcranial magnetic stimulation. We measured the central motor conduction time (CMCT), rest and active motor threshold (MT), F-wave persistence and amplitude, silent period (SP), intracortical inhibition and facilitation at 3, 5 and 15 ms interstimulus intervals (ISI).
  
  
  RESULTS
  The UPDRS motor score decreased from 44.4+/-14.0 under OFF, to 15.2+/-8.0 under ON-STN condition. The CMCT and MT did not change across STN conditions. The F-wave parameters were within normal range under STN stimulation. STN stimulation lengthened the SP and induced facilitation at 15 ms ISI compared to the OFF-STN condition.
  
  
  CONCLUSIONS
  Therapeutic STN stimulation modulates cortical excitability in PD. High voltage STN stimulation could also act on spinal excitability.
  
  
  CONCLUSIONS
  At the motor cortical level, STN stimulation may have a direct effect on intracortical interneurons, modifying the balance between excitation and inhibition.
authors.affiliation: Department of Neurology, University Hospital of Grenoble and INSERM U836, Joseph Fourier University, 38000 Grenoble, France. Valerie.Fraix@ujf-grenoble.fr
authors.forename: Valérie
authors.initials: V
authors.lastname: Fraix
authors.forename: Pierre
authors.initials: P
authors.lastname: Pollak
authors.forename: Laurent
authors.initials: L
authors.lastname: Vercueil
authors.forename: Alim-Louis
authors.initials: AL
authors.lastname: Benabid
authors.forename: François
authors.initials: F
authors.lastname: Mauguière
mesh_terms: D000368:Aged; D046690:Deep Brain Stimulation / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology / Q000528:radiation effects; D010300:Parkinson Disease / Q000473:pathology* / Q000628:therapy*; D020531:Subthalamic Nucleus / Q000503:physiopathology* / Q000528:radiation effects; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation