The Effects of Multi-focal Transcranial Direct Current Stimulation (tDCS) on Motor-cognitive Dysfunctions and Freezing of Gait in Patients With Parkinson's Disease: A Randomized Controlled Trial

The current study aim to establish the therapeutic potential of tDCS for freezing of gait (FOG) and motor-cognitive dysfunctions in Parkinson's Disease (PD). FOG phenomenon is often unresponsive to pharmacological and other treatments, especially in the advanced stages of the disease. While it is likely that Transcranial direct current stimulation (tDCS) will provide symptomatic relief, we will also explore, via secondary outcomes, the potential for tDCS to modify disease progression. Support for this possibility stems from the likely mechanisms of action of tDCS.

Based on strong rationale and preliminary findings in previous works, the objectives of the current proposal are to conduct a prospective multi-center, double-blinded, stratified controlled randomized clinical trial, comparing real multifocal tDCS to sham stimulation. The main aim:

• To demonstrate the "short-term" and the longer-term effects of tDCS on FOG severity and frequency.

Participants: A total of 85 patients will be recruited (Hoehn and Yahr Stage 1-3.5) who suffer from FOG, as measured by the new FOG questionnaire (NFOG-Q) and as demonstrated in response to a FOG provoking protocol, who are on stable medications, who have no contraindications to tDCS, and who are between the ages of 40-80. Patients with DBS will not be included.

tDCS intervention: Subjects will be randomized to receive either a real or sham tDCS intervention. Each intervention will consist of 10, 20-minute treatments completed over 2 consecutive weeks (i.e., 5 per week), following previously established protocols. A single, weekly "maintenance" treatment will then be provided for the following 12 weeks (note: for depression, maintenance tDCS is most often provided once every two weeks; we will take a more conservative approach here in this first long-term study for FOG in PD).