Targeted review of Parkinson's disease–related fatigue that highlights preliminary evidence for rTMS and tDCS reducing fatigue and improving cognitive processing but notes small sample sizes, heterogeneous protocols, and limited standardized outcomes.

Points to a clinically important, under-treated non-motor symptom and identifies non-invasive brain stimulation as a translational, symptomatic intervention that warrants well-designed randomized trials to optimize parameters and confirm long-term efficacy.

BACKGROUND: Fatigue is a common and debilitating non-motor symptom in Parkinson's disease (PD), significantly impairing patient quality of life and often observed in clinical management. Its pathophysiology involves complex interactions among dopaminergic, non-dopaminergic, and neuroinflammatory pathways. Although fatigue is highly prevalent, evidence-based treatment strategies remain limited. METHODS: This review is based on a targeted literature search focusing on recent advances in research on PD-related fatigue. Using a combination of keywords such as "Parkinson's disease", "fatigue", "non-invasive brain neurostimulation techniques", "repetitive transcranial magnetic stimulation ", and "transcranial direct current stimulation ", relevant articles published between 2000 and 2025 were selected. RESULT: While pharmacological approaches, such as rasagiline, have shown some promise, their therapeutic effects remain inconsistent and limited. Recently, non-invasive brain stimulation (NIBS) techniques, including repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), have emerged as promising non-pharmacological interventions. Preliminary studies indicate that rTMS may help quantify central fatigue through motor evoked potential (MEP) modulation, while tDCS applied to cortical targets like M1 and DLPFC appears to reduce fatigue severity and improve cognitive processing. Despite theirpotential, current evidence is restrained by small sample sizes, heterogeneity in protocols, and a lack of standardized outcome measures. CONCLUSION: This review summarizes the clinical features, diagnostic criteria, and current therapeutic strategies for PD-related fatigue,with a focus on the emerging role of NIBS. Future research should prioritize well-designed, large-scale randomized controlled trials tooptimize stimulation parameters and validate the long-term efficacy of NIBS in fatigue management for PD patients.