Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique that uses surface electrodes placed on the scalp to deliver a low amperage (typically 1.5–2.0 mA) direct current to a targeted cortical region. The mechanism of tDCS, based on current scientific consensus, is that the direct current enhances neural plasticity and enriches any rehabilitative training or learning completed during the treatment session [
1,
2]. Each session of tDCS typically lasts 20 min while the user typically completes simultaneous therapy or training. Greater and more persistent benefit has been observed following multiple stimulation sessions, suggesting a cumulative and long term treatment for maximal benefit. tDCS has been shown to be a safe technique often accompanied by only mild and transient adverse events like skin tingling [
3,
4].
In order to reach participants for long-term study, treatments must be delivered at home. Requiring participants to attend clinic every weekday for treatment is not feasible due to professional and personal obligations alongside any disability they may be managing. Many studies to date in tDCS have been underpowered and are limited to small sample sizes with few sessions studied (i.e., 10 sessions or less) [
3].
We developed a remotely supervised tDCS protocol (RS-tDCS) where participants are able to complete daily 20-min sessions from home while supervised by a study technician using real-time monitoring via videoconference. We have previously verified the feasibility and tolerability of this protocol in a cohort of patients with multiple sclerosis (MS) [
4‐
7]. Our RS-tDCS protocol allows for rapid recruitment and extended study schedules, expanding our sample size and allowing participants to complete 20 tDCS sessions or more, exceeding most studies in tDCS. The RS-tDCS protocol enables easy study of the long-term effects of tDCS in MS and has found significant benefits for mood, fatigue, and cognitive impairment [
8,
9].
Here we expand our RS-tDCS protocol to people with Parkinson’s disease (PD). PD is a chronic, degenerative neurological disorder that can produce a range of motor and non-motor disability [
10]. Many of the pharmacological and surgical therapies are targeted towards improving motor symptoms. Non-motor symptoms such as sleep disturbances, cognitive impairment, depression and fatigue remain a major cause of disability that can lead to overall deteriorations in quality of life [
11,
12]. Recent reports have demonstrated that cognition, such as executive functioning and visuospatial processing, are positively associated with quality of life in PD patients [
13]. For this reason there is growing interest in managing and treating the neuropsychiatric symptoms that occur with the disorder. Neurostimulation techniques such as deep brain stimulation (DBS), transcranial magnetic stimulation (TMS) and tDCS have shown to be effective for ameliorating motor symptoms [
14‐
16] but the efficacy of these modalities for non-motor symptoms is still being studied [
17,
18]. While DBS focuses on deep brain structures that are not thought to be modulated by transcranial neurostimulation, TMS has similar targets to tDCS with both focusing on cortical areas. TMS and tDCS may have similar benefits [
19,
20], but TMS comes with higher costs and no option for home-based, remotely supervised sessions. Furthermore, the combination of tDCS with traditional therapeutic treatment has been used recently to enhance improvement of motor and non-motor symptoms in neurological diseases. In the literature, several studies demonstrated positive effects on motor and cognitive impairments in PD patients after multiple sessions of physical or cognitive training combined simultaneously with tDCS [
21‐
23]. In particular, studies have documented the beneficial effect of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC), alone and in combination with computerized cognitive training, on both mood disturbances and cognitive performance (language, attention and executive functions) [
22,
24,
25].
We planned to expand this RS-tDCS therapy protocol to PD participants, predicting that participants with PD would tolerate RS-tDCS in a similar to those with MS. We recruited participants with PD in an open-label RS-tDCS study following the methods of original study in MS [
6,
7]. Our findings include feasibility, tolerability, and preliminary efficacy of tDCS in people with PD.