Stroke is classified into several types including ischemic stroke, subarachnoid hemorrhage, and intracerebral hemorrhage. Despite recent improvements in medicine, stroke is one of the leading causes of mortality worldwide (Feigin et al., 2021). Additionally, lengthy sequelae of stroke are frequent, contributing to an increase in social costs (Tsao et al., 2022) by decreasing the quality of life. Stroke is generally categorized into three stages; acute, sub-acute and chronic stage depending on pathological characteristics and post-stroke period (Zhao and Willing, 2018). Acute stage of ischemic stroke is treated with venous thrombolytics injection or thrombectomy whereas hemorrhagic stroke is treated with controlling hemorrhage and removing hematoma. Since majority of people who have suffered a stroke report significant disability even after appropriate acute treatment, rehabilitation treatment plays a critical role in subacute and chronic stage. Conventionally physical therapy, occupational therapy and speech therapy has been recommended for rehabilitation and management of cardiovascular risk factors such as lowering blood pressure is general principles to prevent secondary stroke (Campbell and Khatri, 2020). Despite these conventional medical care, establishment of the optimal rehabilitation intervention has been challenging. Therefore, alternative treatments such as acupuncture, electro-acupuncture and herbal medicine has been gaining attention as a rehabilitation treatment for chronic stage patients.

Traditionally in East Asia, Traditional Chinese Medicine (TCM) has been used for stroke care (Ceniceros and Brown, 1998 Zhang et al., 2022). In the early 19th century, Berlioz from France suggested the clinical application of concurrent use of modern electric therapy and traditional acupuncture and Electroacupuncture (EA) has been used in clinical environment to treat stroke and related disorders since (Macdonald, 1993). Unlike other modality of TCM, EA has the advantage of being standardized by controlling the frequency and intensity of stimulation and has been researched diversely on mechanism and its clinical effect. In animal experiments, EA alleviates ischemic brain damage by regulating apoptosis, inflammation, autophagocytosis, glutamate, mRNA, and other factors (Xing et al., 2018). In clinical applications, EA is an effective treatment for stroke symptoms such as dysphagia (Huang et al., 2020), pain (Xu et al., 2020), aphasia (Shi et al., 2022), and urinary incontinence (Cruz et al., 2022).

The bibliometric analysis method uses mathematical and statistical tools, thereby providing an overview of academic research publications and a quantitative analysis of research trends. This method can identify influential publications, authors, journals, affiliations, and countries and analyze and present topics, methods, and influential keywords (van Eck and Waltman, 2010). There are bibliometric analyses of EA regarding general diseases from 2011 to 2020 (Wei et al., 2022); however, a bibliometric analysis of EA as a treatment for stroke has not yet been conducted. Therefore, in this study, we conducted a bibliometric analysis by year, country, journal, keyword, affiliation, and author of research papers about EA for stroke, which were published in the Web of Science Core Collection Database (WOSCC) in the last 20 years. Network properties between studies and research trends were identified. Therefore, we aimed to propose additional future research directions in the field.

To conduct a bibliometric analysis of EA in patients with stroke, 440 papers published over the last 20 years were reviewed. The number of publications has gradually increased annually. In the first 10 years, starting from 2003, 89 papers were published, and in the last 10 years, 351 papers were published. By 2020, more than 45 papers had been published annually. We believe that this is because EA has been extensively studied and is actively used clinically to treat stroke.

The field of Neurosciences had the most research, followed by the fields of Integrative Complementary Medicine, and Cell Biology. In the field of Neuroscience, research focusing on this mechanism has been actively conducted because of objective and quantitative measurements of the frequency and strength of EA stimulation (Napadow et al., 2005).

Neural Regeneration Research journal had the most numerous publications, followed by Evidence-Based Complementary and Alternative Medicine, and Acupuncture in Medicine. The multiplication of studies in neuroscience is reflected by the published journals. EA treatment is a complementary medical method that has been actively studied.

China published the highest number of studies, followed by Korea and the United StatesIt appears that this is proportionally related to the fact that China is the center of worldwide TCM research. Analysis of clusters showed China and Australia, which recently conducted research in this field actively, was included in the same cluster. Australia conducted studies on the use of EA for the sequelae of stroke. In the early stages, the United States and Taiwan conducted highly cited and influential studies. United States has the highest medical expenditure of post stroke care per patient in the world (Rajsic et al., 2019), and in order to lower this social cost, complementary medicine has been actively researched. In the United States, there was early interest in the combination of Western and Eastern rehabilitation techniques to improve the effectiveness of rehabilitation treatment (Alexander et al., 2004). Appropriate intensity and frequency of EA intervention has been reported to show neuroprotection by up-regulation of the blood flow speed in the infarct site (Zhou et al., 2011) and meta-analysis of acupuncture combined with a conventional rehabilitation approach suggested acupuncture provided additional benefit to motor recovery compared to conventional rehabilitation approach alone. However, some clinical studies failed to demonstrate treatment effect of acupuncture/EA on stroke and inconsistency between studies about effect of EA on stroke remains major obstacle to actively apply EA in rehabilitation program for stroke. This may be the reason why research was actively conducted in the United States in the beginning but has been sluggish recently. Although researches on EA have been increased worldwide, international co-operation width and link strength of collaboration between nations were weak. One of the reasons for the lack of international collaboration might be differences in the frequency of use of acupuncture in clinical settings and controversies over the underlying mechanism of acupuncture. In order to facilitate the growth of the field and sustain high-quality work, researchers need to give effort to multi-national interaction and co-operation in the future. By affiliated institution, Fujian University of Traditional Chinese Medicine published the largest number of studies, followed by Guangzhou University of Chinese Medicine and Air Force Military Medical University. Chen Lidian and Tan Jing published the most papers, followed by Liu Weilin. The three most published authors were affiliated with Fujian University of Traditional Chinese Medicine and were included in author cluster 1, studying mainly the neuroprotective mechanism and anti-inflammatory effects (Lan et al., 2013) of EA for stroke through animal model experiments. By analyzing the top authors, researchers from the same institution cooperated but lacked collaboration with other institutions, nations, or authors. Additional network composition is needed in the future to increase academic status and diversity.

Keyword analysis was performed to identify the research trends and contents of the published papers. The three oldest keywords by average publication year were “neural regeneration, cerebral ischemia, and artery occlusion.” In a previous study, an animal model of ischemic stroke created through the middle cerebral artery and internal carotid artery occlusion and reperfusion was used to verify the nerve regeneration effect of EA (Ma et al., 2020). The three most recent keywords were “autophagy, systematic review, and cognitive impairment.” Studies on the neuroprotective and neuroplastic regulatory effects of EA are continuously in progress, and the autophagic effect of EA-related signal transduction pathway regulation is a recent research topic receiving attention. In clinical research, studies on the sequelae of stroke, such as cognitive disorders (Xie et al., 2022), depression (Wang et al., 2021), and rigidity (Cai et al., 2017) are actively being conducted.

The published research keyword clusters were categorized according to “neuroprotection,” “clinical rehabilitation,” “neuroplasticity,” and “pretreatment-induced tolerance.” The first cluster included “rat,” “apoptosis,” and “mechanism” and was categorized as a “neuroprotection” topic. Neuroprotection focuses on minimizing additional damage of nerve cells after acute brain injury (Chamorro et al., 2021) and EA showed neuroprotective effects against acute brain damage by inducing cell apoptosis, anti-inflammation, and autophagocytosis. As our understandings of the mechanisms and pathology of stroke increases, neuroprotective strategies emerged as hopeful treatment since acute stroke in followed by secondary neuroinflammation and recent studies report neuroinflammation as a key determinant of stroke prognosis (Tao et al., 2020). Nonetheless, there has been no neuroprotective drugs with proven clinical efficacy. EA could display a promising neuroprotective property in stroke individual but additional studies are needed to further elucidate and validate its mechanism and effectiveness. The second cluster consisted of “recovery,” “stimulation,” “rehabilitation,” and “cognitive impairment” and the topic was categorized as “clinical rehabilitation.” Timely rehabilitation treatment from the acute stage of stroke seems to lower risk of physical disability and complication. Also, recent clinical research showed that enhanced functional recovery is possible even in the chronic stage of stroke after 6 months (Zhao and Willing, 2018). Stroke sequelae include neurological and neuropsychological deficits. A human clinical study reported EA showed improvement of functional impairment of sequelae such as dysphagia (Huang et al., 2020) and aphasia (Shi et al., 2022) and improved neuropsychiatric sequelae following stroke, such as cognitive impairment and post-stroke depression (Wang et al., 2021). In the third cluster, “neurogenesis,” “neurotrophic factor,” “proliferation,” and “angiogenesis” was included, and the topic was categorized as “neuroplasticity.” In the sub-acute and chronic stroke brain, voluntary healing occurs and this non-cure healing process happens through brain plasticity (Zhao and Willing, 2018). Neurogenesis, angiogenesis, and synaptic regeneration are important for voluntary neuroplasticity in the brain. Neuroplasticity modifies functional activity by learning through responses to stimulation and plays an important role in functional recovery when impairment occurs because of incomplete nerve cell regeneration. In animal experiments, EA showed regulatory effects on neuroplasticity by accelerating neurogenesis, inducing angiogenesis, and regulating neuroglial cells, such as astrocytes, oligodendrocytes, microglial cells, and neurotrophic factors (Zhang et al., 2021). In the fourth cluster, “expression,” “activation,” “injury,” “rapid tolerance,” and “pretreatment” keywords were included, and the topic was categorized as “pretreatment induced tolerance.” EA pretreatment controls the cannabinoid system, oxidative stress, and growth factors and suppresses cell apoptosis, resulting in neuroprotective effects (Li et al., 2012). Therefore, EA pretreatment can be used as a preventive and initial treatment strategy for patients at risk of ischemic stroke, and many studies have been conducted to prove this neuroprotective effect (Wang et al., 2009). The research included in Cluster 4 focused mainly on verifying the stroke prevention and early neuroprotective mechanisms of EA pretreatment, and there have been almost no clinical studies to date.

Comparing through average publish year, cluster 4 “EA pretreatment induced rapid tolerance” studies were conducted in the past than the other clusters and also showed high average citation. Cluster 2, a “clinical rehabilitation study,” had a more recent average publication year, and the average citation rate was lower than that of the other clusters. Overall, animal model studies have mainly been conducted in the past, and we found that human-subject clinical studies have recently increased in animal experiments.

This study has several limitations. First, only the WOSCC was used as the extraction source for the research papers. WOSCC was used in this study because the database provides high quality and globally influential research papers and details of the research papers needed for bibliometric analysis. If other databases from East Asian countries that were actively studying the field were included as research sources, the results would have been more significant, but this study focus on database which is used worldwide. Second, the number and name of each cluster were discussed between two individual researchers and defined because individual subjectivity can intervene in the process of defining its properties, hindering objectivity; however, researchers may have different views. Considering the research trend on EA about stroke, mechanism of EA on neuroplasticity and its consequent motor recovery might be of interest of future research. Despite major advances in understanding pathophysiology and acute phase stroke intervention, not much progress has been made especially in chronic phase. Because timely intervention is crucial in stroke rehabilitation, EA can be a relatively convenient and cost-efficient intervention especially where Conventionally therapy is not readily available. To achieve this, large scale, high-quality, multicenter or multinational clinical trials must be further conducted to adequately measure the proper effect size. Additionally, analysis of the research trends in various TCM treatment methods, such as manual acupuncture, herbal medicine, and pharmacopucture for stroke could be conducted to provide insight into stroke treatment and rehabilitation.

Using WOSCC as a source, the research trends of 440 papers on EA as a treatment for stroke were analyzed using a bibliometric method, and the results were as follows:

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

HC: Conceptualization, Data curation, Formal analysis, Investigation, Writing – original draft. W-CS: Resources, Writing – review & editing. J-mK: Investigation, Writing – original draft. HK: Methodology, Software, Writing – review & editing. J-HC: Supervision, Validation, Writing – review & editing. M-YS: Supervision, Validation, Writing – review & editing. W-SC: Conceptualization, Project administration, Supervision, Writing – review & editing.