Transcranial direct current stimulation combined with physical or cognitive training in people with Parkinson's disease: a systematic review.
Victor Spiandor Beretta, Núbia Ribeiro Conceição, Priscila Nóbrega-Sousa and 4 others
PMID 32539819WHAT IT FOUND
Adding tDCS to physical or cognitive therapy showed inconsistent benefits.
Cognition and upper limb function improved in some trials, but gait and motor symptoms showed no clear advantage over sham stimulation. Small study sizes and varied protocols limit confidence in these findings.
Key findings
01Five out of six studies reported synergistic effects on cognition at post-test, including improved executive function, attention, and working memory.
02All four studies assessing upper limb function observed synergistic effects, such as reduced freezing during writing and improved motor skill training.
03For motor symptoms assessed by the UPDRS-III, five out of six studies reported similar findings for both active and sham tDCS, indicating no clear additional benefit.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
Most included studies had small sample sizes (n < 24), which limits the generalizability of the findings. tDCS protocols varied widely in stimulation time (7.5 to 30 min), number of sessions (1 to 16), and electrode placement, making direct comparisons difficult. The review excluded open-label studies, which may have omitted other relevant data. The combined interventions varied significantly (e.g., different types of physical or cognitive therapy), confounding the specific contribution of tDCS.
Declared interests
Funded by the São Paulo Research Foundation (FAPESP) and the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES). No commercial conflicts of interest were declared.
The easy way to misread this
Do not interpret the positive findings for cognition or upper limb function as proof that tDCS is an effective standalone or add-on treatment. The evidence comes from small, heterogeneous trials where the addition of tDCS to therapy sometimes showed no benefit over therapy alone, and in one case showed negative effects.