Transcranial Direct Current Stimulation Priming of Therapeutic Repetitive Transcranial Magnetic Stimulation: A Pilot Study

Objectives: Repetitive transcranial magnetic stimulation (rTMS) has been shown to be a safe treatment of depression, and research efforts are now largely focused on strategies to enhance its efficacy. Motor cortex experiments suggest that the effects of rTMS can be enhanced by first priming the same cortical area with transcranial direct current stimulation (tDCS). We explored this approach in depressed subjects. Materials and Methods: Seven depressed subjects were given sessions of combined tDCS-rTMS to the left dorsolateral prefrontal cortex, exploring a range of tDCS and rTMS stimulation parameters and inter-stimulation intervals. Effects of repeated stimulation sessions on mood state and neuropsychological functioning were evaluated. Results: Most of the subjects showed little improvement with cathodal tDCS followed by 10-Hz rTMS, although 2 subjects showed marked improvement, one after a single stimulation session. Anodal tDCS followed by rTMS did not lead to any improvement. Preconditioning with tDCS seemed to greatly exacerbate the pain of subsequent rTMS. No adverse effects on neuropsychological functioning were observed. Conclusions: Overall, preconditioning with cathodal tDCS followed by rTMS did not result in greater antidepressant efficacy than rTMS given at similar parameters in open trials, although the dramatic response in 1 subject is encouraging. Outcomes may be highly dependent on the exact stimulation paradigm in which tDCS and rTMS are combined. Researchers should be aware that preconditioning with tDCS may greatly increase the pain experienced with subsequent rTMS.