Transcranial direct current stimulation (tDCS): its effect on improving dysphagia in stroke patients

Efficacy of transcranial direct current stimulation in patients with dysphagia after stroke: a systematic review

BACKGROUND

Swallowing is a complex function that can be disrupted after stroke. Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation therapy that recently has been tested to treat stroke-related dysphagia.

METHODS

The authors performed a search in the literature to review the described evidence of the use of tDCS in dysphagia after stroke. Three electronic databases were searched. The risk of bias evaluation was carried out through the RoB-2 tool. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework was also implemented.

RESULTS

Of 265 articles, only nine studies were included in this review. The most common location of the tDCS stimulation was the unaffected hemisphere (44%). Regarding the outcome measure, the Dysphagia Outcome and Severity Scale (DOSS) was the most commonly used (55%). However, due to the high heterogeneity of the protocols, and considering the differences between the types of stroke, the authors opted not to perform a metanalysis. Instead, a systematic review with a thorough analysis of each individual study and the impact of the differences to the outcomes was preferred.

CONCLUSIONS

The final considerations are that even though the majority of studies described benefits from tDCS in post-stroke dysphagia, as they present too many methodological differences, it is not possible to compare them. In addition, many articles included patients with less than 6 months after stroke, which is an important bias as the swallowing function can be recovered spontaneously within this period, turning the certainty of the evidence really low.

Transcranial direct current stimulation for post-stroke dysphagia: a meta-analysis

BACKGROUND

Strokes may cause some swallowing difficulty or associated dysphagia in 25-80% of patients. This phenomenon has been linked to increased morbidity and mortality. Therefore, the aim of this study was to evaluate the efficacy of transcranial direct current stimulation in patients with dysphagia in post-stroke patients.

METHODS

A systematic search in PubMed, Scopus, Web of Science and MEDLINE was conducted. The articles must have to evaluate an intervention that included transcranial direct current stimulation; the sample had to consist exclusively of patients with post-stroke dysphagia; and the experimental design consisted of randomized controlled trial. Difference in mean differences and their 95% confidence interval were calculated as the between-group difference in means divided by the pooled standard deviation. The I2 statistic was used to determine the degree of heterogeneity.

RESULTS

Of the 9 investigations analyzed, all applied transcranial direct current stimulation in combination with conventional dysphagia therapy to the experimental group. All the studies analyzed identified improvements in swallowing function and meta-analysis confirmed their strong effect on reducing the risk of penetration and aspiration (Hedges's g = 0.55). The results showed that participants who received transcranial direct current stimulation significantly improved swallowing function.

CONCLUSIONS

Transcranial direct current stimulation has positive effects in the treatment of poststroke dysphagia by improving swallowing function, oral and pharyngeal phase times and the risk of penetration and aspiration. Furthermore, its combination with conventional dysphagia therapy, balloon dilatation with catheter or training of the swallowing muscles ensures improvement of swallowing function. PROSPERO registration ID CRD42022314949.

Clinical Practice Guidelines for Oropharyngeal Dysphagia

OBJECTIVE

Dysphagia is a common clinical condition characterized by difficulty in swallowing. It is sub-classified into oropharyngeal dysphagia, which refers to problems in the mouth and pharynx, and esophageal dysphagia, which refers to problems in the esophageal body and esophagogastric junction. Dysphagia can have a significant negative impact one's physical health and quality of life as its severity increases. Therefore, proper assessment and management of dysphagia are critical for improving swallowing function and preventing complications. Thus a guideline was developed to provide evidence-based recommendations for assessment and management in patients with dysphagia.

METHODS

Nineteen key questions on dysphagia were developed. These questions dealt with various aspects of problems related to dysphagia, including assessment, management, and complications. A literature search for relevant articles was conducted using Pubmed, Embase, the Cochrane Library, and one domestic database of KoreaMed, until April 2021. The level of evidence and recommendation grade were established according to the Grading of Recommendation Assessment, Development and Evaluation methodology.

RESULTS

Early screening and assessment of videofluoroscopic swallowing were recommended for assessing the presence of dysphagia. Therapeutic methods, such as tongue and pharyngeal muscle strengthening exercises and neuromuscular electrical stimulation with swallowing therapy, were effective in improving swallowing function and quality of life in patients with dysphagia. Nutritional intervention and an oral care program were also recommended.

CONCLUSION

This guideline presents recommendations for the assessment and management of patients with oropharyngeal dysphagia, including rehabilitative strategies.

Dosage consideration for transcranial direct current stimulation in post-stroke dysphagia: A systematic review and network meta-analysis

Objective

This systematic review and network meta-analysis sought to determine the efficacy of different intensities of transcranial direct current stimulation (tDCS) in patients with dysphagia after stroke to improve swallowing function.

Methods

Randomized-controlled trials (RCTs) of tDCS in post-stroke dysphagia were searched from Pubmed, EMBASE, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Service System (SinoMed), Wanfang database, and Chinese Scientific Journals Database (VIP) from databases' inception to June 22, 2022. Article screening, data extraction, and article quality evaluation were completed by 2 independent researchers. Network meta-analysis was performed using Stata.

Results

A final total of 20 studies involving 838 stroke patients were included. The included control interventions were sham tDCS and conventional therapy (CT). Network meta-analysis showed that 20 min of 1.2, 1.4, 1.5, 1.6, and 2 mA anodal tDCS and 30 min of 2 mA anodal tDCS significantly improved post-stroke dysphagia compared with CT (all P < 0.05). In addition, 20 min of 1, 1.4, 1.6, and 2 mA anodal tDCS also significantly improved post-stroke dysphagia compared with sham tDCS (all P < 0.05). Our results demonstrated that 20 min of stimulation at 1.4 mA was the optimal parameters for anodal tDCS and exhibited superior efficacy to CT [SMD = 1.08, 95% CI (0.46, 1.69)] and sham tDCS [SMD = 1.45, 95% CI (0.54, 2.36)].

Conclusion

Different durations and intensities of anodal tDCS are effective in improving post-stroke dysphagia. However, 20 min of tDCS at 1.4 mA may be the optimal regimen.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/#recordDetails, identifier CRD42022342506.

The Effectiveness of Transcranial Stimulation in Improving Swallowing Outcomes in Adults with Poststroke Dysphagia: A Systematic Review and Meta-analysis

Transcranial stimulation has been proposed as an alternative rehabilitation therapy for adults with post-stroke dysphagia (PSD). This systematic review sought to determine the effectiveness of transcranial stimulation in patients with post-stroke dysphagia to improve swallowing function. From inception to January 3, 2021, an extensive search was conducted in PubMed, EMBASE, Cochrane, CINAHL, and Scopus, Web of Science. The randomized controlled trials (RCTs) included studies in adults aged 18 years and older who suffered from post-stroke dysphagia. Using Hedges' g as effect size, meta-analyses were conducted using random-effects models. To investigate potential sources of heterogeneity, subgroup analyses, and multivariable meta-regression analyses were conducted. Sixteen RCTs were included in this review, and 13 RCTs were used for meta-analysis. The meta-analysis showed that a large effect size in improving swallowing function after repetitive Transcranial Magnetic Stimulation (g = - 0.86, 95% CI - 1.57, - 0.16) and medium effect size in Transcranial Direct Current Stimulation (g = - 0.61, 95% CI - 1.04, - 0.17) at post-intervention, respectively. Subgroup and meta-regression analysis indicated that stimulation of the esophagus cortical area and middle-aged adults had a greater effect on swallowing function. The overall certainty of evidence assessed using the GRADE approach was low. Despite the positive results, transcranial stimulation requires additional research to reach definitive conclusions about the optimal stimulation protocol and to achieve the greatest benefit. Future trials should be more rigorous and include a larger sample size to demonstrate the efficacy of transcranial stimulation. Transcranial stimulation enables a more efficacious approach to dysphagia mitigation in PSD rehabilitation.

Neurostimulation in People with Oropharyngeal Dysphagia: A Systematic Review and Meta-Analysis of Randomised Controlled Trials-Part II: Brain Neurostimulation

Objective. To assess the effects of brain neurostimulation (i.e., repetitive transcranial magnetic stimulation [rTMS] and transcranial direct current stimulation [tDCS]) in people with oropharyngeal dysphagia (OD). Methods. Systematic literature searches were conducted in four electronic databases (CINAHL, Embase, PsycINFO, and PubMed) to retrieve randomised controlled trials (RCTs) only. Using the Revised Cochrane risk-of-bias tool for randomised trials (RoB 2), the methodological quality of included studies was evaluated, after which meta-analysis was conducted using a random-effects model. Results. In total, 24 studies reporting on brain neurostimulation were included: 11 studies on rTMS, 9 studies on tDCS, and 4 studies on combined neurostimulation interventions. Overall, within-group meta-analysis and between-group analysis for rTMS identified significant large and small effects in favour of stimulation, respectively. For tDCS, overall within-group analysis and between-group analysis identified significant large and moderate effects in favour of stimulation, respectively. Conclusion. Both rTMS and tDCS show promising effects in people with oropharyngeal dysphagia. However, comparisons between studies were challenging due to high heterogeneity in stimulation protocols and experimental parameters, potential moderators, and inconsistent methodological reporting. Generalisations of meta-analyses need to be interpreted with care. Future research should include large RCTs using standard protocols and reporting guidelines as achieved by international consensus.

Driving Oscillatory Dynamics: Neuromodulation for Recovery After Stroke

Stroke is a leading cause of death and disability worldwide, with limited treatments being available. However, advances in optic methods in neuroscience are providing new insights into the damaged brain and potential avenues for recovery. Direct brain stimulation has revealed close associations between mental states and neuroprotective processes in health and disease, and activity-dependent calcium indicators are being used to decode brain dynamics to understand the mechanisms underlying these associations. Evoked neural oscillations have recently shown the ability to restore and maintain intrinsic homeostatic processes in the brain and could be rapidly deployed during emergency care or shortly after admission into the clinic, making them a promising, non-invasive therapeutic option. We present an overview of the most relevant descriptions of brain injury after stroke, with a focus on disruptions to neural oscillations. We discuss the optical technologies that are currently used and lay out a roadmap for future studies needed to inform the next generation of strategies to promote functional recovery after stroke.