MRI study of human brain exposed to weak direct current stimulation of the frontal cortex

Objective: To determine whether weak transcranial direct current stimulation (tDCS), which is an interesting new tool inducing prolonged cortical excitability shifts in humans, induces brain edema, disturbance of the blood-brain barrier or structural alterations of the brain detectable by magnetic resonance imaging (MRI). Methods: In 10 healthy individuals, tDCS, which is known to alter cortical excitability for about 1 h, was applied over motor and prefrontal cortices. Contrast-enhanced T1-, T2-, and diffusion-weighted MRI was performed immediately before, 30 and 60 min after tDCS. Results: MRI performed 30 and 60 min after tDCS did not show pathological signal alterations in pre- and post-contrast-enhanced T1-weighted and diffusion-weighted MR sequences. Conclusions: tDCS protocols which are known to result in cortical excitability changes persisting for an hour after stimulation do not induce brain edema or alterations of the blood-brain barrier or cerebral tissue detectable by MRI. Significance: These results deliver further evidence for the safety of the currently applied tDCS protocols in humans. (C) 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.