Effectiveness of transcranial direct current stimulation on postural adjustments under external perturbations in patients with Parkinson's disease

Author(s)

Victor Spiandor Beretta

• Document type: Doctoral Thesis
• Press: Rio Claro. 2022-04-20.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2022-03-21
• Advisor: Lilian Teresa Bucken Gobbi; Rodrigo Vitório

Abstract

Background: Patients with Parkinson's disease (PD) demonstrate impairments in postural responses and habituation to external perturbation due to deficits in the functioning of the corticobasal pathways. Although transcranial direct current stimulation (tDCS) modulates the functioning of the corticobasal pathways, it is still unclear whether tDCS can benefit postural responses in patients with PD. Aims: To analyze the effectiveness of different intensities of a single session of tDCS on postural adjustments during habituation to external perturbation (Study 1), and to analyze the effectiveness of eight sessions of tDCS on postural responses in patients with PD (Study 2). Methods: Twenty-four patients with PD participated in Study 1 (crossover) and 20 in Study 2 (clinical trial with two parallel arms). Twenty patients completed the study and were randomly assigned into two groups: 10 in the active tDCS group (a-tDCS) and 10 in the sham group (s-tDCS). In Study 1, anodal tDCS was applied over the primary motor cortex (M1) with intensities of 1mA, 2mA, and sham on three different days (~2 weeks apart) for 20 minutes before assessing postural control. External perturbation (7 trials) was performed by posterior displacement of the support base. In Study 2, eight tDCS sessions were performed over three weeks. From the results of Study 1, the intensity of 2 mA was used in Study 2. Characteristics of active and sham stimulations and the postural control assessments were similar to Study 1. In Study 2, the assessment was performed at the pre, after eight sessions, and one month after the end of the tDCS sessions. The same parameters of electromyographic, center of pressure, and prefrontal cortex (PFC) activity in predictive and reactive postural adjustments were analyzed in both studies. Two-way ANOVA with stimulation condition (1mA x 2mA x sham) and trial (1x2x3x4x5x6x7) factors, with repeated measures, were performed in Study 1. In Study 2, two-way ANOVAs were performed with group (a- tDCS x s-tDCS) and moment (pre x post x follow-up) factors, with repeated measures for the moment. Results: habituation to the perturbation was evidenced regardless of the stimulation condition. Patients with PD had lower latency of the medial gastrocnemius at 2 mA and biceps femoris muscles at 1 mA, and shorter time in an unstable position in both conditions compared to sham. In the reactive adjustments, PFC activity in the non-stimulated hemisphere was lower in the 2 mA condition when compared to sham. In Study 2, a decrease in time in unstable position was observed at the post and follow-up moments in relation to the pre for the a-tDCS group and lower PFC activity in the stimulated hemisphere at the post than pre and follow-up moments. Conclusion: tDCS in M1, mainly with 2 mA, improved the postural responses of patients with PD. However, tDCS was not able to promote habituation to the perturbation in fewer trials. Eight sessions of tDCS seem to improve the balance of patients with PD after and one month after the end of the sessions. (AU)

• FAPESP's process: 18/07385-9 - The effect of transcranial direct current stimulation in the postural adjustments under external perturbation in patients with Parkinson's Disease
• Grantee: Victor Spiandor Beretta
• Support Opportunities: Scholarships in Brazil - Doctorate