title: Prefrontal cortex transcranial magnetic stimulation does not change local diffusion: a magnetic resonance imaging study in patients with depression.
abstract: OBJECTIVE
  To determine whether transcranial magnetic stimulation over the left dorsolateral prefrontal cortex produces pathologic changes or leakage of the blood-brain barrier in patients with depression by using apparent diffusion coefficient magnetic resonance imaging.
  
  
  BACKGROUND
  Transcranial magnetic stimulation is a new technology for noninvasively stimulating the brain. It appears to be a relatively safe technique, with some important exceptions. Its neurobiologic mechanisms of action are poorly understood. One theory to explain its apparent antidepressant effects involves a potential change in local blood-brain barrier settings, allowing passage of peripheral substances directly into brain parenchyma. Knowing whether transcranial magnetic stimulation changes local brain diffusion is important as well from a safety perspective. To test whether transcranial magnetic stimulation changes local brain diffusion, we used apparent diffusion coefficient magnetic resonance imaging in depressed patients undergoing interleaved transcranial magnetic stimulation/functional magnetic resonance imaging over the left prefrontal cortex.
  
  
  METHODS
  Within a 1.5 Tesla magnetic resonance imaging scanner, 14 depressed patients were stimulated with a figure-eight transcranial magnetic stimulation coil over the left prefrontal cortex. Apparent diffusion coefficient magnetic resonance imaging was acquired before, and immediately after, 1 Hertz transcranial magnetic stimulation (147 stimuli) intermittently delivered at a motor threshold of more than 7.35 minutes. Phase maps of the transcranial magnetic stimulation magnetic fields were used to guide region-of-interest placement.
  
  
  RESULTS
  No significant qualitative apparent diffusion coefficient differences were observed before and after 1 Hertz transcranial magnetic stimulation underneath the coil.
  
  
  CONCLUSIONS
  One Hertz transcranial magnetic stimulation over the left dorsolateral prefrontal cortex as applied in this study did not result in pathologic changes or leakage of the blood-brain barrier in patients with depression. If prefrontal transcranial magnetic stimulation at these usage parameters changes local diffusion, it is not an obvious or large effect.
authors.affiliation: Brain Stimulation Laboratory, Medical University of South Carolina, Charleston, South Carolina 29425, USA. lixi@musc.edu
authors.forename: XingBao
authors.initials: X
authors.lastname: Li
authors.forename: Ziad
authors.initials: Z
authors.lastname: Nahas
authors.forename: Mikhael
authors.initials: M
authors.lastname: Lomarev
authors.forename: Stewart
authors.initials: S
authors.lastname: Denslow
authors.forename: Ananda
authors.initials: A
authors.lastname: Shastri
authors.forename: Daryl E
authors.initials: DE
authors.lastname: Bohning
authors.forename: Mark S
authors.initials: MS
authors.lastname: George
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001812:Blood-Brain Barrier; D003865:Major Depressive Disorder / Q000378:metabolism* / Q000473:pathology / Q000628:therapy*; D004058:Diffusion; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D050781:Transcranial Magnetic Stimulation / Q000627:therapeutic use*; D016896:Treatment Outcome; D014867:Water
chemical_list: D014867:Water