Does transcranial direct current stimulation improve functional locomotion in people with Parkinson's disease? A systematic review and meta-analysis.

The review was not registered before data extraction and analysis were completed. Fourteen of 18 studies reported participants were on medication, and the authors noted medication may confound the tDCS results. Freezing of gait status was not consistent across studies: six excluded severe freezing, while 12 did not report it. The included studies used different brain targets, stimulation intensities, durations, session numbers and concurrent training types, so the optimal protocol is unclear. Only six studies reported long-term outcomes, so the long-term conclusion rests on a smaller evidence base. The authors reported relatively low risk of bias except for selective reporting.

Do not read the small short-term improvement as proof that tDCS alone creates lasting gait benefits in Parkinson's disease. The long-term analysis was not positive, several studies combined tDCS with gait training, treadmill training or physical training, and fourteen of 18 studies reported participants were on medication, so the review cannot separate tDCS from those concurrent factors.