Transcranial direct current stimulation in mild cognitive impairment: methodology for a randomized controlled trial

Background: Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique that has shown encouraging results regarding performance improvement of normal subjects in tests of executive functions. Moreover, when applied repeatedly in daily sessions, tDCS has shown therapeutic potential in various neuropsychiatric disorders. However, there is a need for double-blind, placebo-controlled studies to determine the true therapeutic potential of this portable, low-cost and non-invasive treatment. Mild cognitive impairment (MCI) of the amnestic subtype may evolve into Alzheimer’s dementia (AD) and pharmacological approaches have not been successful in ameliorating symptoms or halting progression to AD. Here we propose a protocol for studying a possible role for tDCS on improvement of MCI symptoms in older patients.

Methods/Design: This will be a double-blind, placebo-controlled study of the effects of anodal tDCS over the left dorsolateral prefrontal cortex of patients with MCI. Patients aged 60-90 years will be randomly assigned to either real tDCS or sham stimulation. Twenty-minute real or sham tDCS sessions, 5 days a week, will be performed over the course of two weeks. The Rivermead Behavioural Memory Test (RBMT), California Verbal Learning Test, Rey Verbal Auditory Learning Test (RVALT) and Digit Span (WAIS-IV) will be assessed at baseline, after the first and second weeks of treatment, as well as one and three months after the last tDCS session. The primary outcome will be change in test scores over time. Secondary outcomes will be self-reported memory improvement and possible side effects of tDCS.

Discussion: This study will evaluate possible therapeutic applications of tDCS for treatment of MCI. tDCS is a portable and low-cost neuromodulatory technique that has been found to increase performance of both normal subjects and patients in many cognitive tasks. It will also examine the tolerability, program adherence and possible side effects of this novel technique in this age group. The information obtained in this study should be useful in planning further studies in which tDCS could be combined with other treatment modalities, such as cognitive training.