Parkinson's disease (PD) is associated with classic motor symptoms such as bradykinesia, rest tremor, muscle rigidity, postural instability, and gait disturbances. They result in reduced gait speed, decreased stride length, increased axial stiffness, and decreased pace that together can trigger difficulties in performing turning. As gait disorders are poorly responsive to levodopa therapy, investigations of additional treatments such as physiotherapy and neuromodulation are of utmost importance. The transcranial direct current stimulation (TDCS) consists of a low intensity electrical current capable of altering the cortical excitability, but its application still brings divergent results and there are no studies that verified the effectiveness of TDCS in turning gait.

To verify the effectiveness of transcranial acute anodic direct current stimulation in the motor cortex region (Cz or C3-Cz-C4) combined with physical therapy in improving gait turning in individuals with PD.

This was a randomized, sham-controlled clinical trial, approved by the Brazilian Registry of Clinical Trials RBR-3mywq86. The sample was composed of 42 individuals diagnosed with idiopathic PD, evaluated in the "on" phase of dopaminergic medication. Participants were divided into four groups: 1) active CBT (Cz) + physical therapy, 2) active CBT (C3-Cz-C4) + physical therapy, 3) sham CBT + physical therapy, and 4) educational lecture + physical therapy. The current intensity was 2mA, applied for 20 minutes prior to the 30-minute physiotherapy session with exercises aimed at improving balance and gait. For the instrumental evaluation of gait turning, the 3D motion analysis system was used in the pre-intervention, post-intervention (immediately after the end of the intervention) and follow up (24 hours after the end of the intervention) moments. For the turning analysis, the patients were instructed to walk at normal speed along a seven-meter walkway and turn around a cone positioned in the middle of the pathway. The following variables were measured: center of mass amplitude, speed, largest radius, number of steps, step length, and cadence. Two-way repeated measures ANOVA was used to compare the groups according to stimulation condition (real, sham, or education), time (pre- and post-intervention), and group vs. time interaction. The significance value adopted was 5%.

No statistically significant differences were found for all gait turning variables when considering the interaction time (pre- and post-intervention) vs. group (active CTE, sham CTE, or Education).

The results of the present study suggest that one session of CBT combined with physical therapy was not effective in improving gait turning in individuals with PD.

CBT has been used as an additional tool to clinical treatment, but future studies are needed to investigate different stimulation strategies (isolated, combined and multitarget), as well as the frequency, intensity, and duration of treatment in improving gait turning in people with PD.