title: Effects of intermittent theta burst stimulation on cerebral blood flow and cerebral vasomotor reactivity.
abstract: OBJECTIVE
  To determine whether intermittent theta burst stimulation influences cerebral hemodynamics, we investigated changes induced by intermittent theta burst stimulation on the middle cerebral artery cerebral blood flow velocity and vasomotor reactivity to carbon dioxide (CO(2)) in healthy participants. The middle cerebral artery flow velocity and vasomotor reactivity were monitored by continuous transcranial Doppler sonography. Changes in cortical excitability were tested by transcranial magnetic stimulation.
  
  
  METHODS
  In 11 healthy participants, before and immediately after delivering intermittent theta burst stimulation, we tested cortical excitability measured by the resting motor threshold and motor evoked potential amplitude over the stimulated hemisphere and vasomotor reactivity to CO(2) bilaterally. The blood flow velocity was monitored in both middle cerebral arteries throughout the experimental session. In a separate session, we tested the effects of sham stimulation under the same experimental conditions.
  
  
  RESULTS
  Whereas the resting motor threshold remained unchanged before and after stimulation, motor evoked potential amplitudes increased significantly (P = .04). During and after stimulation, middle cerebral artery blood flow velocities also remained bilaterally unchanged, whereas vasomotor reactivity to CO(2) increased bilaterally (P = .04). The sham stimulation left all variables unchanged.
  
  
  CONCLUSIONS
  The expected intermittent theta burst stimulation-induced changes in cortical excitability were not accompanied by changes in cerebral blood flow velocities; however, the bilateral increased vasomotor reactivity suggests that intermittent theta burst stimulation influences the cerebral microcirculation, possibly involving subcortical structures. These findings provide useful information on hemodynamic phenomena accompanying intermittent theta burst stimulation, which should be considered in research aimed at developing this noninvasive, low-intensity stimulation technique for safe therapeutic applications.
authors: Department of Neurology and Psychiatry, Sapienza University, Viale Dell'Università 30, 00185 Rome, Italy.
authors: Floriana
authors: F
authors: Pichiorri
authors: Edoardo
authors: E
authors: Vicenzini
authors: Francesca
authors: F
authors: Gilio
authors: Elena
authors: E
authors: Giacomelli
authors: Vittorio
authors: V
authors: Frasca
authors: Chiara
authors: C
authors: Cambieri
authors: Marco
authors: M
authors: Ceccanti
authors: Vittorio
authors: V
authors: Di Piero
authors: Maurizio
authors: M
authors: Inghilleri
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D004576:Electromyography; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D017585:Ultrasonography, Doppler, Transcranial; D014666:Vasomotor System / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology
chemical_list: D002245:Carbon Dioxide