Background/Objectives: Mild cognitive impairment (MCI) is common in Parkinson’s disease (PD) and often precedes dementia. Non-invasive brain stimulation (NIBS) techniques such as transcranial random noise stimulation (tRNS) targeting dorsolateral prefrontal cortex (DLPFC) may offer additional benefits for cognitive and motor functions in PD-MCI patients. Methods: Using a randomized, double-blind, cross-over study, participants with PD-MCI completed two stimulation sessions (real vs. sham) 7 days apart. Cognitive and motor outcomes (MoCA, FAB, FAS, MDS-UPDRS motor) were assessed pre- and post-stimulation; stimulation was administered “online” during executive training. Scores before and after the sessions have been compared, as well as their variations between the two groups. Results: Ten subjects were in the study. Patients undergoing real tRNS showed improvements in global cognition and executive functioning compared to those undergoing sham stimulation, as demonstrated by significant increase in MoCA and FAB scores. In contrast, the motor examination showed no significant differences. Conclusions: This preliminary study showed that a single session of DLPFC-tRNS stimulation produced domain-specific cognitive benefits in PD-MCI patients. Studies with multiple stimulation sessions and larger samples are needed to confirm the effect of this non-pharmacological therapeutic option in PD-MCI.

Background/Objectives: Mild cognitive impairment (MCI) is common in Parkinson’s disease (PD) and significantly impacts quality of life. Non-invasive brain stimulation (NIBS) techniques have emerged as potential therapeutic interventions. This systematic review analyzes the current evidence regarding the efficacy of Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES) on cognitive domains in patients with PD-MCI. Methods: A systematic search was conducted across the PubMed, Scopus, Web of Science, and Medline Ultimate databases up to 20 November 2025. We included studies investigating the effects of NIBS compared to sham stimulation on neuropsychological outcomes in diagnosed PD-MCI patients. Results: Eight studies involving different stimulation protocols were included. Interventions primarily used TMS or tES targeting the left dorsolateral prefrontal cortex (DLPFC). Episodic memory and global cognition were the most responsive domains, assessed with specific neuropsychological scales. Findings for executive functions and attention were heterogeneous, while visuospatial abilities generally showed limited immediate response. Conclusions: NIBS represents a promising but low-certainty-evidence adjunctive therapy for PD-MCI, with improvements found in memory and global cognition. Future research should prioritize larger sample sizes, combined interventions (NIBS plus cognitive rehabilitation), and extended follow-ups to evaluate long-term neuroplasticity.