title: Triad stimulation frequency for cortical facilitation in cortical myoclonus.
abstract: BACKGROUND
  Abnormally enhanced cortical rhythmic activities have been reported in patients with cortical myoclonus. We recently reported a new triad-conditioning transcranial magnetic stimulation (TMS) method to detect the intrinsic rhythms of the primary motor cortex (M1). Triad-conditioning TMS revealed a 40-Hz intrinsic rhythm of M1 in normal subjects. In this investigation, we study the motor cortical facilitation induced by rhythmic triple TMS pulses (triad-conditioning TMS) in patients with cortical myoclonus.
  
  
  METHODS
  Subjects were 7 patients with cortical myoclonus (28-74 years old) and 13 healthy volunteers (30-71 years old). Three conditioning stimuli over M1 at the intensity of 110% active motor threshold preceded the test TMS at various interstimulus intervals corresponding to 10-200 Hz. The resulting amplitudes of conditioned motor evoked potentials recorded from the contralateral hand muscle were compared with those evoked by the test stimulus alone.
  
  
  RESULTS
  The facilitation at 25 ms (40 Hz) observed in normal subjects was absent in patients with cortical myoclonus. Instead, triad-conditioning TMS induced facilitation at a 40 ms interval (25 Hz) in cortical myoclonus.
  
  
  CONCLUSIONS
  This change in the timing of facilitation may be explained by a shift of the most preferential intrinsic rhythm of M1, or by some dysfunction in the interneuronal network in cortical myoclonus.
authors.affiliation: Department of Neurology, Division of Neuroscience, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan. hanajima-tky@umin.ac.jp
authors.forename: R
authors.initials: R
authors.lastname: Hanajima
authors.forename: Y
authors.initials: Y
authors.lastname: Terao
authors.forename: S
authors.initials: S
authors.lastname: Nakatani-Enomoto
authors.forename: S
authors.initials: S
authors.lastname: Okabe
authors.forename: Y
authors.initials: Y
authors.lastname: Shirota
authors.forename: S
authors.initials: S
authors.lastname: Oominami
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Tsuji
authors.forename: Y
authors.initials: Y
authors.lastname: Ugawa
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001703:Biophysics; D016022:Case-Control Studies; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009207:Myoclonus / Q000473:pathology* / Q000503:physiopathology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000145:classification / Q000379:methods*