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Treatment on patients with spastic cerebral palsy in the past 30 years: A systematic review and bibliometric analysis

Background: Over the past 30 years, treatments from different disciplines have been applied to spastic cerebral palsy (SCP). However, few bibliometric studies have been conducted to date. This study explored the knowledge base, emerging hotspots, and future trends related to SCP treatment research using bibliometric analysis. Methods: Publications on SCP treatment included in the Web of Science Core Collection database between 1990 and 2020 were retrieved, and Medical Subject Headings terms were extracted from PubMed. Online bibliometric analysis website (http://bibliometric.com/), 2 pieces of software called “CiteSpace” and “VOSViewer” were used for quantitative analysis and knowledge map establishment. Results: A total of 1668 papers were retrieved from 1990 to 2020. The number of publications has increased annually. Developmental Medicine and Child Neurology is the most productive and the highest co-cited journal. The United States has been the largest contributor. Vrije Universiteit Amsterdam ranked first in the number of papers published among institutions that have conducted correlational research. Becher JG and Graham HK should be considered scholars who have made outstanding contributions. The knowledge base of the SCP treatment research field is thoughtfully constructed to promote understanding of the field. Conclusion: This bibliometric study identified global achievements, research hotspots, and trends of SCP treatment. They provide insights into the research field and valuable information for future scientific research and clinical treatment.


Introduction
Cerebral palsy (CP) is defined as a group of permanent disorders of movement and posture development due to non-progressive disturbances that occur in the developing fetal or infant brain. [1] Recent magnetic resonance imaging (MRI) studies have shown that common abnormalities include periventricular white matter lesions, focal ischemic/hemorrhagic lesions, diffuse encephalopathy, basal ganglia damage, and brain malformations. [2] The average prevalence of CP is 2 to 3 per 1000 live births. These values vary in selected patient groups, depending on the risk factors. [3,4] CP is clinically categorized into spastic, dyskinetic, and ataxic CP depending on the predominant motor disorder. Spastic CP (SCP) accounts for up to 80% of CP cases. [5] Children with SCP are prone to motor disorders, comorbidities, and secondary problems caused by motor disorders that threaten their growth, development, and quality of life. [6,7] The past 30 years since William J. Little first described CP have been the most exciting and productive period in the field of treatment. Patients with SCP and their families seek many forms of treatment, especially modalities that have the potential to improve motor function or sensation, such as pharmacotherapy, functional surgery, basic rehabilitation techniques, physical therapy, speech, and psychotherapy. However, the results show that the evidence of beneficial SCP treatment in recent decades is weak. [8,9] Therefore, a comprehensive review of this area is essential for both newcomers and old stagers who can benefit greatly from it. Medicine Bibliometrics is an indispensable tool for studying the knowledge base in an academic field. It uses mathematical and statistical principles to quantitatively analyze the structure of knowledge, active themes, evolutionary trajectories, and emerging trends in a given field by studying literature systems and metrology characteristics. [10] Compared to traditional review methods, bibliometrics provides a more detailed and objective way of analysis to describe the evolution of a field, and can be used to comprehensively explore the impact of a set of research topics, a group of researchers, and a specific paper within the field and predicts the research trends or hotspots. Bibliometrics has been progressively applied to research in different fields, such as medicine and ecology, and has also played a vital role in formulating policy and clinical guidelines for various diseases. [11] To the best of our knowledge, only a few bibliometric analyses have been performed in the field of SCP treatment before this study. We extracted bibliometric indicators from the data, including the number of publications, citation frequency, and Hirsch index, [12] and performed a comprehensive analysis to understand the knowledge base of research on SCP treatment and present future global trends.

Database sources and search strategy
First, Medical Subject Headings terms in the PubMed database were searched to identify search terms. Second, the Web of Science Core Collection (WoSCC) was selected as the original database with a long-standing collection of leading international academic journals that provide detailed publication information, especially references. Therefore, this study evaluated the WoSCC database of over 70.8 million documents. In this study, the searches were limited to articles and reviews, published in English. The literature search was conducted on the same day, October 24, 2021, to avoid bias caused by daily database updates. The detailed search strategy was presented in Table 1.
A total of 1668 documents were obtained (Supplementary material, Supplemental Digital Content, http://links.lww.com/ MD/H883), including 30,570 references. We exported the complete records as plain text format files, and the exported records included a list of authors, article titles, publication dates, keywords, abstracts, and citations. Two researchers conducted screening that showed no duplicates. The above data were downloaded from public database, and no ethical issues were involved in the text. Hence, ethical approval was not necessary.

Statistical analysis
Both CiteSpace and VOSviewer are popular tools used to map scientific knowledge and have been adapted for bibliometric analysis in different disciplinary research areas. [13,14] Therefore, in this study, Citespace V5.8 was applied to analyze the collaborative network of journals, authors, countries, and institutions, as well as the highest cited articles with impact. The VOSviewer 1.6.15, which allows for the visualization of keyword co-occurrence and co-citation clustering, was used to create graphs. Furthermore, an online bibliometric analysis website (http://bibliometric.com/) was also used to visualize the number of publications in different years by country.

Over trend
Over the past 30 years, the number of publications on SCP treatment has been steadily increasing annually, demonstrating growing academic interest in this field (Fig. 1). However, there is a noticeable difference between the periods 1990 to 2005 and 2006 to 2020. The first period grew smoothly, accounting for only 21.6% of the total number of publications with an average of 23 publications per year while the second period accounted for 78.4% with an average of 23 publications per year, reaching 129 publications in 2020. By and large, the publication trend over the past 30 years indicates that the treatment of SCP has received the attention of researchers from various disciplines.

Country distribution
The 1668 published papers were from 76 countries and regions, and the top 5 countries in the number of publications are the United States, the Netherlands, the United Kingdom, China, and Australia. Centrality is an indicator of node importance in a network; a higher centrality suggests a node with a greater impact. The top 5 countries in centrality (Table 2) are the US (0.59), the UK (0.21), France (0.21), Canada (0.2), and Germany (0.14.) Since 1990, the U.S. has published 33.15% of the total number of publications. We can see the participation and enrichment of more countries in this field of research globally in the 21st century.
The analysis in terms of volume and centrality of publications shows that there is no doubt that the United States is the leader in this field (Fig. 2). We found that although developing countries such as China, Turkey, and Brazil published a considerable amount of literature, the intensity of cooperation with other countries was not high (Fig. 3), suggesting that developing countries should enhance international cooperation. Developed countries occupies a high number of seats. The reason for this distribution seems obvious: These developed countries have well-developed disciplines and infrastructure that can support the clinical studies more conveniently and successfully conducted by investigators, and in the meantime offer more new treatments than developing countries to improve current medical stresses when dealing with the health and survival pressures faced by SCP patients and their families.

Institutional analysis
In total 652 institutions published constructive papers. Table 2 lists the top ten productive institutions with specific information. The Vrije Universiteit Amsterdam is the most published institution with 59 articles and a centrality of 0.05, indicating his great effort in this field. Five of the top ten institutions belong to the USA, indicating that American research institutions are crucial Table 1 The topic search queries.

Set
Search in the field of SCP treatment and that they may carry out more in-depth and pioneering work. Notably, 3 of the top ten ranked institutions are comprehensive health care providers. Nemours Alfred I. DuPont Hospital for Children is a major pediatric hospital in the United States and is known for its orthopedic and neurosurgical services. The Royal Children's Hospital Melbourne is a specialized children's hospital in Australia that combines health care and prevention of childhood and adolescent diseases. The Leuven University Hospital is the largest general university hospital in Belgium. These institutions are the mainstay of SCP treatment and have made tremendous contributions to patient nursing and the promotion of innovative therapies. Pediatrics ranked first, which is related to the fact that children are the main patients of SCP. [15] 3.6. Highly co-cited references analysis Table 5 shows the top ten co-cited publications in the field of SCP treatment, which were cited more than 160 times. Six of these were from the journal of Developmental Medicine  and Child Neurology. The most cited article was "A systematic review of interventions for children with developmental medicine and child neurology," published by Novak I from the University of Sydney in Developmental Medicine and Child Neurology in 2013, which has been cited 45 times, with an average of 6.45 times per year. This study systematically described 15 optimal interventions for childhood with CP. [16] Rank's second paper suggested a revised definition of CP and content of the classification. Rank's third paper revealed that selective dorsal rhizotomy combined with physical and occupational therapy resulted in significant improvements in motor function. Strong evidence was shown for botulinum toxin type A for the treatment of lower limb spasticity in CP in a fourth-ranked paper. Critically, randomized controlled trials (RCT) are deemed the most prevalent method for evaluating clinical validity and efficacy. [17] They are the most classical publications with great reference value and formed the theoretical and experiential basis of scientific studies citing them, [18] contributing to a comprehensive understanding of the treatment of CP.

Keyword co-occurrence and co-citation clustering
Keywords reflect a publication's condensed topic and content. The presence of keywords in a series of publications suggests a close thematic relationship. [19] Co-citation clustering can also reveal the knowledge structure and relationship network of a particular domain, because references comprise the knowledge base. [20] Consequently, we combined studies with high significance to determine the core themes and structure of research on SCP treatment. Keyword co-occurrence and co-citation clustering graphs were created using VOSviewer (Figs. 4 and 5). The size of the circle represents the total frequency of the keywords and the line indicates the strength of the relationship between the 2 keywords in the SCP therapeutic area. In Figure 4, it can be seen that these keywords from the 1668 publications can be colored to determine their co-occurrence relationship. Similarly, as shown in Figure 5 the cited literature can be divided into 4 theme clusters with high relevance: Prevention, Diagnosis, Treatment, and Management. To better understand the 4 theme clusters, the representative keywords and cited literature included in each module are listed in Table 6.

Cluster #1(Prevention)
. CP is believed to originate from complex interactions between multiple risk factors. Inflammation before and after preterm birth, infection, hypoxicae, ischemia, and stroke during the antepartum and peripartum periods are major contributors to the risk of CP. [21] The probability of prevalence increases with the accumulation of these risk factors. [22,23] Most of the etiologies and high-risk factors for CP are well known and can be prevented. Adequate prenatal and postnatal care and interventions to prevent intrauterine infections are effective measures for reducing the incidence of preterm birth, low birth weight, and subsequent neurological abnormalities. Magnesium sulfate, [24,25] prenatal corticosteroids, [26] therapeutic hypothermia, [27,28] caffeine, [29] melatonin, [30] erythropoietin, [31] and stem cell [32] have been used in the last 3 decades for the prevention of CP. This has reduced the risk of developing CP. Monitoring procedures of the hip joint in infants also prevent the development of complications due to hip dislocation. [33] The incidence of CP has decreased over time in developed countries (Europe, Australia, the USA, etc.) owing to specific preventive and interventional measures. [34][35][36] However, up to 40% of CP cases do not have an identifiable cause. [37] Genetic etiologies regarding CP are constantly being discovered, and this revolutionary field may lead to the development of new prevention and treatment targets. [38] A revolutionary breakthrough would be made in this field, which would enhance our understanding of the causes of CP.

Cluster #2(Diagnosis)
Diagnosis should be made as early as possible which helps infants access early intervention and effective treatment resources. [39,40] The current literature in this cluster focused mainly on topics related to gait analysis, gross motor function, motor function, quality of life, and graded classification systems. The diagnosis of CP includes clinical diagnosis and assessment of motor function, which involves the use of neuroimaging, standardized neurology, and standardized motor assessment. High-quality evidence demonstrated the accuracy of these diagnostic tools. Before 5 months of corrected age, the most effective tools for predicting risk are The General Movements Assessment, MRI, and The Hammersmith Infant Neurological Examination (HINE) are the most effective methods for predicting CP. MRI and HINE are the most effective methods for predicting the risk of CP after 5 months of corrected age. [41,42] Even if an assessment of General Movements Assessment or MRI is not available in some low-and middle-income countries, it can be used for fairly accurate early diagnoses such as gait analysis, HINE, or cranial ultrasound, which provides objective information about the severity. [41][42][43] Clinicians need to identify motor disorders and screen for comorbidities that often accompany CP and provide timely prevention and intervention. The combination of at least 2 tools for accurate diagnosis is recommended because it allows  patients to receive specific interventions and treatments as early as possible. [44] There is growing evidence that specific early interventions can maximize neural cell plasticity, and minimize deleterious modifications to muscle development and bone growth, [45] and the subsequent need for surgery. [46] To better assess prognosis, many functional classification systems have been developed, [47] the most widely used is the Gross Motor Function Classification System.

Cluster #3(Treatment)
The treatment of SCP is centered on specific symptoms of movement disorder. Spasticity is the most common movement disorder and has been the focus of recent academic literature. The major research in this cluster concentrated efforts on botulinum toxin, intrathecal baclofen, surgery, physiotherapy, effectiveness, and reliability. Treatment should consider the functional level and expectations of the families of patients with CP and select appropriate interventions to be performed within the International Classification of Functioning, Disability and Health. Initial treatment approaches included physiotherapy to improve spasticity, [48] which has been shown to improve large muscle motor skills and gait. [49] A recent study showed that repeated injections of Abobo botulinum toxin reduced muscle tone and significantly reduced upper limb spasticity in children with CP. [50,51] This is an attractive approach for improving spasticity in children with CP because it enables less invasive treatments. In addition, alternative treatment explored in the literature include intrathecal baclofen), [52] selective dorsal rhizotomy (intrathecal baclofen therapy is not available), [53] and extracorporeal shockwave therapy has been applied to the treatment of spasticity. [54] There are some limitations, however, it is still evaluating the effectiveness and reliability of these therapies by RCT. [8] Since the aim of treatment has tended to improve the quality of life of patients and their families rather than focusing simply on the improvement of individual functional indicators. The treatment should therefore focus on the management of a variety of comorbidities to seek a better quality of life.

Cluster #4(Management).
The ultimate goal of management is to improve the quality of life and social participation status of the patient and their caregivers beyond that achieved with standard therapy alone. [55] Relevant issues in this cluster included following keywords: Management, strength, gait, adults, comorbidities, balance, and quality of life. CP may be regarded as a static brain lesion that cause permanent motor impairment with ongoing comorbidities and secondary conditions. [56,57] The management of CP is strongly associated with evidence-based targeted interventions. Traditional evidence-based medical treatment for pain, epilepsy, sleep, vision, and hearing problems in CP has been suggested to improve child's outcome. [58] This implies that multidisciplinary involvement in management and rehabilitation planning, as well as long-term monitoring, is required. It seems especially important for individuals with CP to evaluate motor function by observing muscle strength and balance ability, and thus determine whether they can participate more in social activities. Hence, strength training and fitness programs should be a part of their daily lives, such as robot-assisted gait and treadmill training. [59,60] Equally significant, support from parents is indispensable in management because they assist patients with Table 5 The top 10 co-cited publications.

Burst keywords analysis
CiteSpace has a burst detection module that can be used to determine the decrease or growth in a topic by detecting large changes in keywords over time. High-breaking keywords indicate that the interest of researchers is growing rapidly. The emergence, evolution, and decline of research topics and themes, as well as the shift in the focus of research hotspots, could be described by the introduction of burst analysis. [62,63] Figure 6 shows the top 29 keywords with high intensity and their dynamic evolution in the area of SCP treatment from 1990 to 2020. The blue line represents the time interval, and the red line represents the time of the keyword burst. Muscle strength, muscle spasticity, interrater reliability, balance, intervention, individual, intrathecal baclofen therapy, classification system, and multilevel surgery may be research hotspots in the future. Overall, burst keyword analysis revealed a clear evolutionary progression of SCP treatment. First, the features of the overall study changed from macroscopic observations of clinical efficacy to more specific indicators. In the early stages, research on SCP treatment mainly focused on the rehabilitation of selective dorsal rhizotomy, botulinum toxin A, and baclofen, and gait analysis has been applied to clinical diagnosis and curative effect evaluation to improve patient management. [43] Scholars have redirected their emphasis to deeper comprehension and more specific content as a result of the rapid advancement of different disciplines such as motor function, muscle strength, feet, ankles, and upper limbs. This has led to the extension of research topics that are in line with modern scientific consensus. This includes the exploration and utilization of new therapies (induction of movement therapy, femoral de-rotation osteotomy, intrathecal baclofen), evaluation of the validity and reliability of clinical therapy based on RCT, and the establishment of a classification system and criteria for CP.
Second, SCP treatment research has evolved to represent various age-related characteristics, such as the burst words infant, young adult, and age. SCP is inevitably a lifelong disease owing to its incurable nature. Early studies focused on infants and children and considered SCP a pediatric disease. Healthcare faces difficulties in successfully transferring services from children to adults, with some neglect by adult patients. [64] To address these challenges, experts from different domains are actively helping researchers better define the etiology of CP and improve nursing standard for adult patients with SCP. Comprehensive care Figure 4. The network of keywords co-occurrence. Each circle represents a keyword; the larger the area of the circle; the more often this keyword appears, and the same color between different circles means that these keywords usually appear together, probably on the same research topic, and thus can be defined as a cluster.
for adult patients with SCP is mirrored in general hospitals and adjuvant therapies have been expanded outside medical facilities. [65] Third, the quality of life of the patients and their caregivers have been valued. In 2001, the World Health Organization published the International Classification of Functioning, Disability and Health, which emphasized that the purpose of treatment is not only to repair the disability and promote functional activity, but also to recognize that personal and environmental factors are indispensable for the well-being of individuals. [66] This initiative has had a huge influence on the direction of research, and social care has begun to emphasize quality of life. [67] The study of controlling muscle tone, increasing muscle strength, and improving gait posture has been transformed into a core point of SCP treatment, thus promoting functional activities and facilitating patient participation. Treatment goals and management of CP have shifted from treating impairment and disabilities to integrating elements of health, activity, and social participation.
Fourth, the planning, implementation, and verification of multidisciplinary services is a trend of SCP treatment. Emergent words included multiple surgeries, randomized controlled trials, and interrater reliability. On the 1 hand, the patient is an individual, Figure 5. The network of co-citation clusters. Each title is a reference, and the relevance of each title is similar or different in color. The same color indicates high relevance, probably for the same research topic, and thus can be defined as a cluster. Table 6 Four clusters and their representative keywords and cited literature.

Clusters
Keywords Cited reference Prevention Prevention, Stroke, brain injury, complications, hip joint and he/she should pay attention to a personalized treatment plan when he/she is treated. On the other hand, a patient is also a social group, and he needs help from society and more participation in social activities. Patients faced unpredictable clinical problems due to physical and psychological deficits. Involving a multidisciplinary team to refine various aspects of care, started in well-equipped and staffed institutions, can improve the appropriate diagnosis and treatment of patients with CP and ensure improved long-term results. [68] Efforts should be made to provide and sustain such medical services in developing countries. In addition, using an RCT to verify the validity and reliability of therapies is an integral part of the SCP treatment.

Discussion
This quantitative analysis identified trends in the treatment of SCP that can be considered when designing a treatment program. Evidence-based interventions can significantly improve the health of patients with SCP. Monitoring and ensuring these benefits, from suggestion to reality, is the joint effort of patients, caregivers, clinicians, and social workers. There is indeed a long way to go before the ultimate goal of SCP can be cured. [8] In addition, we found a research gap between developed and developing countries, in terms of the volume of publications, countries, and research institutions. This gap was reflected in the clinic, for example, the prevalence rate in high-income countries is 1.7 to 3.1 per 1000 live births, while it is higher in low-income countries. [69] Constraints on the availability of public resources for health care in developing countries limit access to necessary services. [70] The greater health and survival pressures on individuals with SCP and their families have forced countries to look for new ways to improve the current health care pressure. The following recommendations, which are based on the findings of the bibliometric analysis, may be useful for researchers and public health policymaking.

The significance of CP prevention
CP should be regarded as a public health priority for prevention to avoid a significant economic burden. [71] As pointed out by Nana Amankwah, Canadian dollars were about $11,700 for children with CP aged 1 to 4 years versus about $600 for those without the condition, and their quality of life was poor. [72] Moreover, children with CP in developing countries face greater economic, geographic, and social barriers in accessing medical and rehabilitative interventions. prevention would significantly reduce its prevalence. [21] However, the prevention of CP is infinitely challenging because it results from the interaction of multiple factors along a causal pathway. Many epidemiological studies are currently underway, [73] most of them are populationor registry-based and focus on identifying risk factors that will ultimately lead to the implementation of prevention strategies.

Seeking new treatments
At present, traditional therapies such as physical therapy, drug intervention, orthopedics, and neurosurgery are still mainstream, but the beneficial evidence is weak. There is an urgent need to discover new, safe and alternative approaches to deal with the current weak evidence of therapeutic benefits. Traditional Chinese medicine (TCM), including acupuncture, massage, Chinese herbal medicine, and other TCM methods, has attracted considerable attention for the treatment of CP. Specifically, TCM established individualized therapy to achieve the desired therapeutic effect by thoroughly considering the characteristics of each patient's symptoms. In line with some studies' reports on the benefits of enhancing nerve recovery and relieving spasms with TCM methods, [74,75] it was quite common in East Asian nations to use Chinese medicine to treat patients with CP. [76] More importantly, Acupuncture has emerged as a cost-effective and available treatment modality and could dramatically decrease health care expenditures. [77,78]

Information collection and sharing platform construction
Although CP is the most common childhood disability, its etiology remains complex and unknown. A large population base is needed to assemble a sufficient number of cases to answer the research questions, as the prevalence of CP is not very high even in moderately severe ischemic-hypoxic neonates and preterm infants, posing many difficulties for research. [79] Over the past decade, countries and institutions worldwide have made clearified the importance of information collection platform. [80] By collecting information on children with CP, aggregating data, analyzing changes in regional clinical practice, accessing healthcare, and further refining the way children with CP are described. [4] Simultaneously, a standard definition and classification system for CP have been established to provide targeted intervention activities for patients. To this end Europe, the United States, and Canada have established CP registry management organizations. This facilitated linking changes in prevalence to changes in prenatal, perinatal, and postnatal care to identify CP and its risk factors, and could also provide a sound basis for future treatment, management, and prevention of CP.

Update of social care model
Increasing evidence has shown that good parental care results are not applicable in low-and middle-income countries, and that the quality of life of patients and their caregivers is even worse. [81,82] Community-based health worker program is popular all over the world. [83] Community-based medical care and prevention provided by highly-skilled community members who have received different levels of formal or technical education is a highly effective and feasible nursing model for infants with CP. This model is highly scalable, transferable, and can be popularized in developing countries. [84] Therefore, equal emphasis should be placed on involving the local communities in the treatment and management of patients with CP. Skilled social workers and community workers can integrate better into the nursing teams. Such a public network can not only train parents with the latest medical and health knowledge to prevent CP [85] but can also help patients with CP learn and alleviate psychological disorders (e.g., depression, post-treatment stress disorder) to improve their health status and quality of life. [86] Community-based complementary therapies are being developed. [65]

Limitation
To our knowledge, this is the first study to perform a bibliometric analysis and visual display of SCP treatment. Our study had some limitations. First, owing to the limitation of the software, we only searched and analyzed English learning in WoSCC. Second, there are few documents from developing countries. However, these differences may not have changed the overall trends of this study.

Conclusion
Through a bibliometric analysis of 1668 related publications published from 1990 to 2020, this study attempts to outline the research hotspots and valuable viewpoints in the field of SCP treatment, as well as the global development trend of SCP treatment. The field of SCP treatment has entered a rapid development stage, which has attracted considerable attention worldwide. A total of 76 countries or regions contributed to this field. Most of the research was conducted in developed countries such as North America and Europe, and some developing countries also participated in it. More targeted research on people with SCP in developing countries is required. The research basement showed 4 theme clusters (prevention, diagnosis, treatment, and management) because the clustering pattern, is offered to better grasp the current global achievements and perspectives on future development. Finally, hot spots and trends could be confirmed by observing burst words, which may help shape the scientific research of researchers and clinical treatment planning of patients.