Transcranial Magnetic and Electrical Stimulation in Alzheimer's Disease and Mild Cognitive Impairment: A Review of Randomized Controlled Trials

Alzheimer's disease (AD) and related dementia is an immense personal and public health burden. Available treatments have modest efficacy in reducing symptoms of AD and have no significant impact on the course of the illness. Moreover, attempts to discover novel treatments have to date failed. Noninvasive brain stimulation comprises a suite of interventions that are based on transcranial magnetic or electric stimulation of different brain regions. Promising findings are emerging from two forms of noninvasive brain stimulation: repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). Here, the results from the randomized controlled trials (RCTs) that assessed rTMS or tDCS in AD or in mild cognitive impairment, a clinical state that typically preceded AD, are reviewed. Overall, there are few RCTs, and most of them are limited by small sample sizes. Larger RCTs and additional research are needed to identify the best stimulation parameters for these two interventions.