Clinical effects of different montages of Transcranial Direct Current Stimulation (tDCS) in patients with Parkinson’s Disease

Background: Parkinson’s disease (PD) is characterized by motor deficits which may not completely respond to the dopaminergic therapy, thus posing a therapeutic challenge. Non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS) have shown promising results as possible alternative of treatment in different neurological disorders including PD. The therapeutic effect of tDCS, which may increase (anodal currents) or decrease (cathodal currents) the cortical excitability level, likely relies on modulation of cortico-subcortical interactions and abnormal patterns of cortical activation. Objective: To investigate safety and therapeutic potential of different montages of tDCS in PD patients with asymmetric motor symptoms. Patients and methods: Patients with asymmetric PD were recruited. While on-treatment, participants underwent 7 separate experimental sessions. The tDCS was applied with the following different electrode montages: anodal and cathodal stimulation of the primary motor cortex (M1) contralateral to the more affected body side, anodal and cathodal stimulation of M1 contralateral to the less affected body side, and sham-stimulation. We evaluated the clinical effects on motor function by means of the MDS-UPDRS, by evaluation of bradykinesia of the arms and by the finger tapping test. All experiments were performed according to a double-blinded design. The dopaminergic medication was continued in all subjects throughout the course of the experiment. Results: 16 patients (8M/8F) were included (aged 58±11.5 years). Compared to baseline and sham stimulation, the motor performances improved in both hands after anodal tDCS of M1 contralateral to the more affected body side. Also the cathodal stimulation of M1 contralateral to the less affected body side was shown to improve the motor performances. Conclusions: Our results confirm the therapeutic potential of tDCS in PD patients, providing useful information on which is the best tDCS montage to apply as a treatment option.