title: Changes in cerebrovascular reactivity following low-frequency repetitive transcranial magnetic stimulation.
abstract: OBJECTIVE
  Repetitive Transcranial Magnetic Stimulation (rTMS) potential therapeutic uses have been explored in many conditions including stroke. However, its potential effects on cerebral hemodynamics have not been deeply considered. Transcranial Doppler ultrasonography (TCD) is a promising tool in detecting focal changes of cerebral blood flow velocity (CBFV) and cerebrovascular reactivity (CRV) induced by rTMS. We evaluated possible changes in CBFV and CVR in healthy volunteers.
  
  
  METHODS
  Low-frequency (1 Hz) and Sham rTMS were applied over the motor cortex (M1) of the left hemisphere of healthy volunteers. CBFV and CVR were evaluated in the ipsilateral middle cerebral artery (MCA). CVR to hypercapnia was derived from the breath-holding index (BHI). Subjects were randomly assigned to real or sham stimulation.
  
  
  RESULTS
  Maximal CBFV of MCA tended to decrease after 1 Hz M1 rTMS. Low-frequency 1Hz M1 rTMS increased BHI (measured in MCA) immediately after rTMS, and the observed effect vanished after 15 min when applied over M1. We did not observe any significant change in Pulsatility Index (PI) and Resistance Index (RI) measures in all conditions. No significant changes of above mentioned parameters were observed in the sham stimulation group.
  
  
  CONCLUSIONS
  Low-frequency rTMS induces a significant modulation of CVR in healthy subjects. This effect should be relevant in acute stroke patients with impaired cerebral autoregulation.
authors.affiliation: Stroke Unit, Department of Neuroscience, University of Rome "Tor Vergata", Viale Oxford 81, 00133 Rome, Italy. fabriziosallustio@libero.it
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Sallustio
authors.forename: Silvia
authors.initials: S
authors.lastname: Di Legge
authors.forename: Barbara
authors.initials: B
authors.lastname: Rizzato
authors.forename: Paolo
authors.initials: P
authors.lastname: Stanzione
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002560:Cerebrovascular Circulation / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology; D009044:Motor Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial