Multiple Sessions of Transcranial Direct Current Stimulation in People With Parkinson's Disease

Parkinson's disease (PD) affects approximately 1 million people in the US, with annual health care costs approaching $11 billion. PD results from a loss of dopamine-producing cells in the brain. This decrease in dopamine is associated with shaking, stiffness, slowness, balance/walking problems, thinking, and fatigue which severely impair activities of daily living. Current medical and surgical treatments for PD are either only mildly effective, expensive, or associated with a variety of side-effects. Therefore, the development of practical and effective therapies would have significant benefits. Transcranial direct current stimulation (tDCS) can influence how the brain works. A review of studies concluded that, overall, tDCS improves walking and balance in people with PD (PwPD). However, these studies had mixed results. For example, most have stimulated the frontal brain areas and all have used intensities of 2 mA (milliamperes; a measure of electrical current strength) or less. However, given the vital role of the cerebellum in walking and balance, and in PD impairments, the cerebellum may represent a more effective brain target. A recent review of studies also recommended performing investigations of higher intensity tDCS (greater than 2 mA), to potentially increase stimulation efficacy. No study has investigated the effects of multiple sessions of cerebellar tDCS on gait and balance in PwPD and none have used tDCS intensities greater than 2 mA. Therefore, there is a critical need to determine if repeated sessions of cerebellar tDCS might improve walking and balance in the short- and long-term.