Neuropsychological Improvement in Amnestic Mild Cognitive Impairment Following Noninvasive Transcranial Electrical Stimulation: a Case Report

Abstract Objective Amnestic Mild Cognitive Impairment (aMCI) is often a prodromal stage for Alzheimer’s disease, and the few treatments available have limited efficacy in lessening the neuropsychological deficits. Transcranial direct current stimulation (tDCS) is a noninvasive electrical stimulation method with therapeutic potential found in aMCI, but high-definition tDCS (HD-tDCS) is a recent advancement allowing for improved targeting in stimulation and possibly prolonged treatment effects. We present a case report that investigates HD-tDCS-induced neuropsychological changes in aMCI. Method A 78-year-old male with aMCI received 10 HD-tDCS sessions at 1 mA for 20 minutes targeting the dorsal anterior cingulate cortex. He was stable on rivastigmine throughout the trial. Eight neuropsychological tests assessing episodic memory (verbal and visual), attention, executive functioning, and language were completed at baseline, after the 10th session and 3-months later. A change of +/− 10 T-score points from baseline was considered a clinically meaningful difference. Results Significant improvements were observed immediately after HD-tDCS on 4/8 tests, including the Brief Visuospatial Memory Test-Revised (BVMT-R; immediate recall +14; delayed recall +24), semantic fluency (Animals +17), Trail Making Test B (+14), and Stroop Color and Word Interference Trial (+21). At the 3-month follow-up, only the BVMT-R immediate recall remained higher (+16), while the rest were similar to baseline scores. Conclusions Clinically meaningful improvement in neuropsychological functioning was seen following HD-tDCS in this patient with aMCI. However, nearly all the enhancements were diminished 3-months later, returning to baseline. A randomized sham-controlled trial is warranted to confirm the therapeutic effects of HD- tDCS and examine how long effects may persist.