Home›Neurology› tACS shows no significant motor benefit in Parkinson's disease, meta-analysis finds
tACS shows no significant motor benefit in Parkinson's disease, meta-analysis findsTrial Shows No Significant Improvement in Parkinson's With tACS
medRxivPublished August 24, 2026Study authors: Mai, T. T.; Gjishti, T.; Witt, K.; Roheger, M.; Herrmann, C. S.DOI ↗Editorial oversight: Dr. Ji-eun Park, MD · Brain, Mind & Pain
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Key Takeaway
Interpret tACS as lacking consistent motor benefit in Parkinson's; consider protocol heterogeneity.
This meta-analysis synthesized data from small trials of transcranial alternating current stimulation (tACS) in patients with idiopathic Parkinson's disease. The qualitative review included 184 patients, and the meta-analysis pooled data from 146 patients. The primary outcome was motor severity as measured by the Unified Parkinson's Disease Rating Scale (UPDRS).
For overall motor severity, the pooled effect size was small and not statistically significant (SMD = 0.21, 95% CI [-0.10, 0.52], p = 0.097). Similarly, tremor showed no significant difference (SMD = -0.40, 95% CI [-1.97, 1.17], p = 0.478), and short intracortical inhibition also showed no significant difference (MD = 0.00, 95% CI [-0.40, 0.41], p = 0.971).
The authors highlight substantial limitations, including significant between-study heterogeneity (especially for tremor, I2 = 86.1%), small sample sizes, and highly variable stimulation protocols and outcome assessments. They note substantial uncertainty in prediction intervals, and the certainty of evidence is low.
No adverse events were reported, and the intervention was generally well-tolerated. However, the lack of consistent improvements in motor symptoms suggests that current evidence does not support routine clinical use of tACS for motor symptoms in Parkinson's disease. The authors emphasize that these findings are association-only and limited by heterogeneity.
How this fits prior evidence
This meta-analysis adds to prior coverage by addressing a non-pharmacologic intervention for Parkinson's disease. It contrasts with the prior finding that rasagiline and selegiline show comparable efficacy in early Parkinson's, as tACS did not show significant motor benefit. It also extends the context-dependent theme noted for exercise and antioxidants, reinforcing that adjunctive therapies may not consistently outperform control. The null results highlight the need for more standardized protocols, similar to the caution noted for pain as an early indicator.
Researchers looked at the effects of transcranial alternating current stimulation (tACS) on patients with idiopathic Parkinson's disease. This type of treatment uses electrical currents to target specific areas of the brain. The study analyzed data from 146 patients to see if this method could improve motor skills or reduce tremors.
The results showed no statistically significant difference between those receiving active tACS and those in a control group. Specifically, there were no clear improvements in overall motor severity or in the management of tremors. The treatment was generally well-tolerated by participants, with no serious safety concerns reported during the study period.
It is important to note that this evidence comes from a small sample size and varied treatment methods. Because different studies used very different protocols, it is difficult to draw firm conclusions about how tACS works for Parkinson's. Currently, there is not enough consistent evidence to suggest that tACS provides reliable improvements in motor symptoms.
What this means for you:
Current research shows no clear benefit of tACS for motor symptoms or tremors in patients with Parkinson's disease.
Common questions
Does tACS help with tremors in Parkinson's disease?
The study found no statistically significant difference in tremor management between patients who received active tACS and those in a control group. Because of the small sample sizes and inconsistent treatment methods across different studies, the results are not conclusive enough to recommend it as a standard treatment for tremors.
Is transcranial alternating current stimulation safe?
The analysis reported that tACS was generally well-tolerated by patients. No serious adverse events or safety concerns were noted in the data provided. However, because of the high variety in how the treatment was delivered across different studies, individual results may vary.
Why aren't there clearer results for tACS and Parkinson's?
The evidence is currently limited by small sample sizes and significant differences in how each study was conducted. Because the stimulation protocols were so different across studies, it is difficult to determine if a specific method could be effective or not.
Transcranial alternating current stimulation (tACS) is a promising noninvasive intervention for modulating pathological brain oscillations in Parkinson's disease (PD). To evaluate its clinical and neurophysiological efficacy, we searched five databases (Web of Science, PubMed, Scopus, Google Scholar and APA PsycInfo) up to August 31, 2025, for trials employing tACS in patients with idiopathic PD. Risk of bias was assessed using the RoB 2 and ROBINS-I tools. Random-effects meta-analyses were used to calculate standardized (SMD) and unstandardized mean differences (MD) with 95% confidence intervals (CIs). We included 10 studies (184 patients with PD, mean age: 64.9, mean disease duration: 5.2 years) in the qualitative review and seven trials (146 patients with PD, mean age: 65.6, mean disease duration: 5 years) in the meta-analysis. No statistically significant differences favoring active tACS over control were found in overall motor severity (UPDRS: SMD = 0.21, 95% CI [-0.10, 0.52], p = 0.097), tremor (SMD = -0.40, 95% CI [-1.97, 1.17], p = 0.478), or a neurophysiological marker of inhibitory response, represented by short intracortical inhibition (MD = 0.00, 95% CI [-0.40, 0.41], p = 0.971). The prediction intervals indicated substantial uncertainty, and significant between-study heterogeneity was observed, particularly for tremor outcomes (I2 = 86.1%). This variability and limitation in evidence quality is largely driven by small sample sizes, highly heterogeneous stimulation protocols, and varying outcome assessments. Systematically, tACS was generally well-tolerated, with no serious adverse events reported across the included studies; however, formal safety assessment was beyond the scope of this review. Current exploratory evidence shows a lack of consistent improvements in motor symptoms or functions in PD largely due to protocol-level heterogeneity. Future studies should consistently assess the MDS-UPDRS III post-tACS and report its specific subscores alongside neurophysiological measures to enable robust meta-analyses.
