Therapeutic noninvasive brain stimulation in Alzheimer's disease and related dementias

Alzheimer's disease is a progressive neurodegenerative disease without effective pharmacological treatment. Noninvasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES), are increasingly being investigated for their potential to ameliorate the symptoms of Alzheimer's disease and related dementias (ADRD).

A comprehensive literature review for primary research reports that investigated the ability of TMS/tES to improve cognition in ADRD patients yielded a total of 20 reports since 2016. Eight studies used repetitive TMS and 12 used transcranial direct current stimulation, the most common form of tES. Eight of the studies combined NIBS with cognitive training. Promising results should encourage continued investigation, however there is currently insufficient evidence to support widespread adoption of NIBS-based clinical treatments for ADRD.

NIBS remains an active area of investigation for treatment of ADRD, though the predominance of small, heterogeneous, proof-of-principle studies precludes definitive conclusions. We propose the establishment of a consortium to achieve the benefits of large-scale, controlled studies using biomarker-based diagnostic characterization of participants, development of neurophysiological markers to verify target engagement, and standardization of parameters.