title: Monitoring cortical excitability during repetitive transcranial magnetic stimulation in children with ADHD: a single-blind, sham-controlled TMS-EEG study.
abstract: BACKGROUND
  Repetitive transcranial magnetic stimulation (rTMS) allows non-invasive stimulation of the human brain. However, no suitable marker has yet been established to monitor the immediate rTMS effects on cortical areas in children.
  
  
  OBJECTIVE
  TMS-evoked EEG potentials (TEPs) could present a well-suited marker for real-time monitoring. Monitoring is particularly important in children where only few data about rTMS effects and safety are currently available.
  
  
  METHODS
  In a single-blind sham-controlled study, twenty-five school-aged children with ADHD received subthreshold 1 Hz-rTMS to the primary motor cortex. The TMS-evoked N100 was measured by 64-channel-EEG pre, during and post rTMS, and compared to sham stimulation as an intraindividual control condition.
  
  
  RESULTS
  TMS-evoked N100 amplitude decreased during 1 Hz-rTMS and, at the group level, reached a stable plateau after approximately 500 pulses. N100 amplitude to supra-threshold single pulses post rTMS confirmed the amplitude reduction in comparison to the pre-rTMS level while sham stimulation had no influence. EEG source analysis indicated that the TMS-evoked N100 change reflected rTMS effects in the stimulated motor cortex. Amplitude changes in TMS-evoked N100 and MEPs (pre versus post 1 Hz-rTMS) correlated significantly, but this correlation was also found for pre versus post sham stimulation.
  
  
  CONCLUSIONS
  The TMS-evoked N100 represents a promising candidate marker to monitor rTMS effects on cortical excitability in children with ADHD. TMS-evoked N100 can be employed to monitor real-time effects of TMS for subthreshold intensities. Though TMS-evoked N100 was a more sensitive parameter for rTMS-specific changes than MEPs in our sample, further studies are necessary to demonstrate whether clinical rTMS effects can be predicted from rTMS-induced changes in TMS-evoked N100 amplitude and to clarify the relationship between rTMS-induced changes in TMS-evoked N100 and MEP amplitudes. The TMS-evoked N100 amplitude reduction after 1 Hz-rTMS could either reflect a globally decreased cortical response to the TMS pulse or a specific decrease in inhibition.
authors.affiliation: University Hospital for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, Goethe University, Frankfurt/Main, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Helfrich
authors.forename: Simone S
authors.initials: SS
authors.lastname: Pierau
authors.forename: Christine M
authors.initials: CM
authors.lastname: Freitag
authors.forename: Jochen
authors.initials: J
authors.lastname: Roeper
authors.forename: Ulf
authors.initials: U
authors.lastname: Ziemann
authors.forename: Stephan
authors.initials: S
authors.lastname: Bender
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000503:physiopathology*; D001921:Brain; D016022:Case-Control Studies; D002648:Child; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology / Q000503:physiopathology*; D010919:Placebos; D011930:Reaction Time; D016037:Single-Blind Method; D050781:Transcranial Magnetic Stimulation
chemical_list: D010919:Placebos