Transcranial Electrical Nerve Stimulation for Dementia: A Systematic Review of Randomized Control Trials

Abstract

Non-invasive brain stimulation is recently gaining interest in brain modulation but transcranial electrical stimulation is yet to receive wide acceptance as a means of managing dementia among the aged. This study reviewed transcranial electrical nerve stimulation and its effectiveness in managing patient with dementia.  The study was carried out over a three months period beginning from April 13th to July 4th, 2020 PubMed, Cochrane, Science direct, Pedro and Google scholar  were searched using keywords including “Transcranial Direct Current Stimulation”, “tDCS”,  “dementia”, “cognitive impairment”. Separate searches was conducted in the same database by replacing Transcranial Direct Current Stimulation (tDCS) with Transcranial Alternating Current Stimulation (tACS). Out of the search hit of 321, 12 germane studies that met the inclusion criteria were pooled and appraised and information therein was synthesized. Out of the 10 papers on tDCS, 7 are on Alzheimer dementia and 4 of the 7 studies supported its efficacy in Alzheimer dementia with clinically important significant improvement observed in cognitive functions. The prefrontal context is the common stimulation area in managing Alzheimer and other type of dementia using tDCS at a current intensity of 1.5 to 2.0 mA. The other three studies out of the 10 papers on tDCS found improvement in cognitive functions including communicating intention processes in vascular and behavioural variant of frontotemporal dementia. One of the two studies on tACS found improvement in biomarkers of Alzheimer's disease at 40Hz (gamma range), and another found improvement in cognitive functions in patients with dementia related to Parkinson's disease at the frequency of 30Hz (Theta range), and this affect is attributable to enhancement in endogenous brain oscillation. This review suggests that Transcranial Electrical Nerve Stimulation is effective in remediating symptoms in mild to moderate dementia as a stand alone or as adjunctive treatment.