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Syringomyelia is a chronic, progressive disease of the spinal cord. Syringomyelia is an etiologically diverse affliction caused by disturbance of normal cerebrospinal fluid flow dynamics. Lesions are characterized by the formation of tubular cavities in the gray matter of the spinal cord and gliosis; however, the etiology is unknown and treatment methods differ. Many existing studies have focused on the relationship between other diseases and syringomyelia. There is a lack of comprehensive and objective reports on the research status of syringomyelia. Therefore, this study aimed to conduct a bibliometric analysis to quantify studies on Syringomyelia and trending issues in the last 20 years.
Methods
Articles were acquired from the Web of Science Core Collection database. We used the Library Metrology online analysis platform, BICOMB, gCLUTO, CiteSpace bibliometrics tools for analysis, VOSviewer 1.6.16 (Nees Jan van Eck and Ludo Waltman, 2010), and Microsoft Excel 2019 to perform bibliometric analysis and visualization. Individual impact and collaborative information were quantified by analyzing annual publications, journals, co-cited journals, countries/regions, institutions, authors, and co-cited authors. We then identified the trending research areas of syringomyelia by analyzing the co-occurrence of keywords and co-cited references.
Results
From January 2003 to August 2022, 9,556 authors from 66 countries published a total of 1,902 research articles on syringomyelia in 518 academic journals. Most publications come from the United States, China, the United Kingdom, and Japan, with the United States dominating. Nanjing University and the University of Washington are the most active institutions, Dr. Claire Rusbridge has published the most papers, and Miholat has the most co-citations. The Journal of Neurosurgery has the highest number of co-cited articles, which are mainly in the fields of neurology, surgery, and biology. High-frequency keywords included syringomyelia, Chiari-I malformation, children, surgical treatment, and spinal cord.
Conclusions
The number of articles on syringomyelia has increased steadily over the past two decades. At present, research on syringomyelia is mainly focused on the age of onset, potential therapeutic interventions, surgical treatment, avoidance of recurrence, and delay of pain. The use of surgical treatment of the disease and the mechanism of further treatment are the current hot research topics. The correlation between trauma and congenital factors, translational application, the effect of surgical treatment, postoperative recurrence, and complications are further hot research areas. These may provide ideas for further research into a radical cure for syringomyelia
Syringomyelia (Syr) is an etiologically diverse affliction caused by a disturbance of normal cerebrospinal fluid (CSF) flow dynamics. It is a fluid-filled cavity anatomically located in the spinal cord parenchyma or central canal [
]. Most lesions are located between C2 and T9; however, they can descend to the conus medullaris, or extend upward into the brain stem (i.e., syringobulbia). Estimates of prevalence vary widely, from 1.94 per 100,000 in Japan to 8.4 per 100,000 in Western countries. In children, Syr usually occurs in the context of congenital malformations, most commonly CM-I and tethered spinal cords; however, it can also develop many years after meningitis, spinal trauma, or intramedullary and extramedullary tumors [
]. Syr mainly presents with sensory symptoms, such as pain and temperature insensitivity and in most often identified under coincidental circumstances [
Roser F, Ebner FH, Sixt C, Hagen JMV, Tatagiba MS. Defining the line between hydromyelia and syringomyelia. A differentiation is possible based on electrophysiological and magnetic resonance imaging studies. Acta Neurochir (Wien). 2010;152(2):213-219; discussion 219. 10.1007/s00701-009-0427-x.
The natural course of Syr is variable and unpredictable, with both stable and progressive phases. Even skilled neurosurgeons currently do not fully understand the natural history of Syr. The clinical course of the disease continues to progress over months to years, with rapid deterioration in the early stages and then a gradual slowing of the increase in severity [
Syrinx size and duration of symptoms predict the pace of progressive myelopathy: retrospective analysis of 103 unoperated cases with craniocervical junction malformations and syringomyelia.
]. In addition, sudden head shaking and prolonged coughing may cause a sudden onset of symptoms in previously asymptomatic patients, which may be due to increased tonsillar descent [
]. Due to the increased use of magnetic resonance imaging (MRI) in routine assessments of back and neck pain, the discovery of Syr is becoming more common. As mentioned above, it is usually associated with CM, medial basilar obstruction, atlantopivot dislocation, or arachnoid adhesions; other CSF circulation disorders have been associated with other spinal deformities [
]. Thus, pro-oxidative and antioxidant processes occurring in the central nervous system (CNS) may be reflected in the components of the CSF and blood. A better understanding of the underlying molecular pathways associated with Syr formation will be beneficial in reaching the goal of treating and preventing Syr.
], there is no established animal model of Syr associated with lumbosacral spinal lipoma, with few studies on simulated animal experiments.
Although a quantitative overview can be done through many methods, such as a traditional review, systematic review, main path analysis, or evidence map [
], only bibliometrics enables us to qualitatively and quantitatively analyze the contribution and cooperation of authors, institutions, countries, and journals, and to evaluate the knowledge base and trending research topics at the same time [
It is an encouraging task to explore new methods for automated data analysis to acquire knowledge in any medical field, especially in an extremely challenging disease such as Syr. Through bibliometric methods and tools, we can perform a macro analysis based on a large amount of reported data, which has become an important method to accurately grasp the development in trends of a research field. However, at present, there are no bibliometric studies on neurosyringomyelia. In this paper, through a comprehensive analysis of the relevant literature and external characteristics of Syr, we summarized various data from articles on Syr and to help identify valuable future directions. Therefore, this study aimed to quantify the number of Syr studies using multiple bibliometrics platforms including the Library Metrology online analysis platform, BICOMB, gCLUTO, CiteSpace, and VOSviewer. Furthermore, we identified trending research questions over the past 2 years, which may help to generate hypotheses for future research in the field of Syr.
2. Methods
2.1 Data search and download
Based on the expanded database of the Science Citation Index, a bibliometric analysis was carried out. In the Web of Science database, we set the subject word (search title, abstract, author, and keywords, etc.) as: syringomyelia; time: 2003–2022; and article types: original articles and reviews. Excluded articles including meeting abstracts, editorial material, letters, proceedings papers, corrections, new items, book chapters, retracted publications, and reprints. Two doctors simultaneously performed the abovementioned search using different devices and the literature related to neurosyringomyelia was obtained.
2.2 Data collection
The data, including fully recorded and quoted references, was downloaded from the Web of Science and imported into the Online Analysis Platform of Bibliometrics (https://bibliometric.com/) and CiteSpace (version 6.1.R3, Drexel University, USA). CiteSpace is an excellent tool for collaborative network analysis, linking various publication functions. Once the imported data was downloaded from the Web of Science database, the relevant category was selected to analyze the relationship between countries, institutions, authors, and so on. By obtaining keywords with a high citation rate, the research frontiers and emerging trends in this field could be predicted [
道客巴巴. CiteSpace II Detecting and visualizing emerging trends and transient patterns in scientific literature (2006). Accessed October 20, 2022. https://www.doc88.com/p-6621592881869.html.
We included publishing characteristics such as countries, institutions, journals and authors in our analysis. The 2022 version of the Journal Citation Reports (JCR) and impact factor (IF), as important indicators to measure the scientific value of research, were also included in the analysis [
]. In the Online Analysis Platform of Bibliometrics, we analyzed changes in the volume of articles and the cooperative relationships of various countries. In CiteSpace, we connected all kinds of publication characteristics through collaborative network analysis. Furthermore, we obtained highly cited keywords to predict the research frontiers and emerging trends in this field.
3. Results
3.1 Search results of related studies
The flow chart of the search is shown in Fig. 1. According to our strategy, a total of 1902 relevant articles were retrieved from 2003 to 2022.
3.2 Contributions of countries and institutions to global publications
A total of 1902 articles on syringomyelia were published in various countries during the two decades. The number of articles fluctuates to a certain extent, which may be related to research hotspots and other issues in that year. However, the number of articles tended to increase every 5 years. The largest number of articles were published in 2020 (120 articles), and the lowest were in 2005 and 2014 (69 articles). Over the past two decades, the United States (Fig. 2) has made the most significant contribution to Syr research, followed by China, the United Kingdom, and Japan.
Fig. 2Contribution of related literature trends of syringomyelia; the number of published studies in the top 10 countries and the growth trend of the top 10 countries/regions from 2003 to 2022. Graph generated using the Library Metrology online analysis platform.
The international cooperation analysis showed that the United States cooperated most frequently with other countries. While China was ranked second and rising in the number of articles published, it had less cooperation with other countries (Fig. 3A).The network density of Syr studies was only 0.0041 (Fig. 3B), which means that the research teams are relatively scattered across several institutions and do not cooperate closely enough. Among the 10 institutions, only Cornell University (0.07) has a centrality greater than 0.05. In general, most institutions had a low influence and lacked cooperation.
Fig. 3The distribution of countries/regions and institutions. (A) Cooperative relationships among countries/regions (the area represents the number of articles, and the connection represents the cooperative relationship. Conducted by online analysis platform of Bibliometrics). (B) Cooperative relationships among institutions (conducted by CiteSpace (version 6.1.R3, Drexel University)).
In the past 20 years, 414 journals have published literature in the field of Syr. Of the 1902 articles on Syr identified in our study, the top 10 journals published 708 (37.22 %) (Table 1). In terms of the number of publications, the top three were Children’s Nervous System (IF = 1.532), Journal of Neurosurgery (IF = 3.968), and World Neurosurgery (IF = 2.221). In terms of citations, the top three were the Journal of Neurosurgery (IF = 5.408), Neurosurgery (IF = 5.315), and Children’s Nervous System (IF = 1.532). According to the 2022 JCR, the first two journals are in Q1.
Table 1Top 10 most active journals with articles in neurosyringomyelia research (sorted by count).
Over the course of two decades, 6814 authors were involved in the study of neurosyringomyelia. Of these, 61 authors published at least 10 or more articles; Rusbridge, C, of the University of Surrey, published the most articles related to neurosyringomelia (n = 45), followed by Tubbs, RS (n = 38), and Oakes, WJ (n = 37) (Table 2). The different colors represent the five author clusters (Fig. 4). Active cooperation usually exists in the same cluster, such as Biston, L and Stoodley, MA. There was also cooperation between two nodes linked in different clusters.
Table 2The top 10 most productive authors contributing to the publication of syringomyelia research.
Fig. 4(A) The network map of productive authors. Conducted by CiteSpace (version 6.1.R, Drexel University). (B) Authors with more than six publications (cluster graph). The size of the nodes reflects the frequency of symbiosis of authors, links indicate symbiosis between authors, link thickness is proportional to the number of publications co-authored by both researchers, and nodes of the same color represent the same cluster.
We used BICOMB to extract and statistically analyze the data downloaded from the Web of Science. For a more comprehensive analysis, we included keywords with frequencies greater than or equal to 15 and generated a follow-up analysis matrix. According to the 25 most frequently cited terms from 2003 to 2022, the time trend and time chart of hotspot transfer were analyzed (Fig. 5). Through “gCLUTO”, we used the biclustering method to sort four different clusters and used mountain (Fig. 6A) and matrix visualization (Fig. 6B) to map the relationship between the source literature and keywords. Mountain visualization provides a more intuitive understanding of the contents of high-dimensional datasets; peaks 0–3 represent different clusters. Peak, volume, altitude, and color are all used to depict information about the associated category. The distance between a pair of peaks on a plane indicates the relative similarity of their categories. The altitude of each peak is positively correlated with the internal similarity of the categories. The size of the peak is proportional to the number of main keywords contained in the category. Finally, the color of the peak represents the standard deviation within the category. Red indicates a low deviation, while blue indicates a higher deviation. In matrix visualization, the column tags represent source literatures and row tags represent keywords. The cluster trees on the left represent frequent keyword associations and the cluster trees above represent literature associations. The matrix values were represented graphically, and their colors describe the frequency at which keywords appear in a literature. The color gradually deepens from white to red, indicating a gradual increase in significance. The above-mentioned high-frequency words were divided into four categories, and the representative literatures of each category were studied and summarized. Finally, we identified four hotspots:
Fig. 5The top 25 terms with the strongest citation bursts during 2003 to 2022. Conducted by CiteSpace (version 6.1.R3, Drexel University).
Fig. 6Biclustering of highly frequent major keywords and literature on syringomyelia. Mountain visualization (A) and matrix visualization (B). Conducted by gCLUTO (version 1.0, University of Minnesota).
Through statistical and quantitative analysis, we report that the number of research articles on Syr has fluctuated to a certain extent over the past 20 years. Although the research direction of Syr is relatively wide, a summary and analysis of the research hotspots is lacking. In this paper, four clusters were obtained by dual cluster analysis. Focusing on the discussion and interpretation of these clusters will help to identify valuable future directions.
Cluster 2 focuses on the symptoms and diagnosis of Syr. Syr is defined morphologically on MRI as the presence of a single or multiple fluid-filled cavities (syrinx) in the spinal cord parenchyma and/or the spinal sphere. As observed in the word matrix of BICOMB, many authors still raise questions and opinions on the definition, diagnosis, and classification of Syr. Not every fluid-filled cavitation of the spinal cord should be diagnosed as Syr. In studies conducted before the advent of modern neuroimaging, the prevalence ranged from 3.3 to 8.5 per 100,000 [
]. In the Russian Federation, the incidence of Syr was reported to be approximately 10 per 100 000, with most cases occurring in men over the age of 30–35 years [
Klimov VS, Gulay YuS, Evsyukov AV, Moysak GI. Syringosubarachnoid shunting in treatment of syringomyelia: a literature review and a clinical case report. Vopr Neirokhirurgii Im NN Burdenko. 2017;81(3):58. 10.17116/neiro201781358-65.
Ciaramitaro P, Garbossa D, Peretta P, et al. Syringomyelia and Chiari Syndrome Registry: advances in epidemiology, clinical phenotypes and natural history based on a North Western Italy cohort. :11.
Adult Syr can be broadly divided into those associated with CM-I and those not associated with CM-I (no-CM-I). The latter includes asymptomatic, isolated Syr [
]. Typical clinical signs of Syr include sensory retardation, sensory disturbances, or pain from movement, Furthermore, scoliosis can occur in up to 67 % of cases [
]. CM-I-associated Syr is a very complex pathology; most theories regarding its formation/persistence and progression involve dynamic factors of CSF circulation, volume changes in the contents of the spinal canal, heart-related pulsations, abdominal pressure, and a reduction of the posterior cranial fossa [
Batzdorf U. Primary spinal syringomyelia. Invited submission from the joint section meeting on disorders of the spine and peripheral nerves, March 2005. J Neurosurg Spine. 2005;3(6):429-435. 10.3171/spi.2005.3.6.0429.
]. The increased use of MRI has improved the ability to diagnose CM and Syr, which has led to an increase in the reporting of asymptomatic and low-symptom cases. Therefore, more standardized definitions, diagnostic criteria, and treatment options are needed [
]. In addition, it has been reported that newly diagnosed Syr often occurs during the treatment of children with CM-I who were not found to have Syr prior to treatment [
Advances in technology and the implementation of the CSF velocity coding sequence two decades ago has helped us to understand the basic characteristics of CSF motion along the neural axis and to diagnose and evaluate Syr [
], which was used to describe a picture of Syr occurring in the absence of abnormalities at the level of the foramen magnum. A third possible cause is infectious disease, which is more common in meningitis due to tuberculosis and listeria [
]. In addition, iatrogenic causes may also contribute to Syr, such as cases arising after postoperative arachnoiditis or diagnostic procedures (lumbar puncture, myelography) [
]. There is a common origin of disturbance of normal CSF circulation in these conditions.
In the past two decades, many experts have proposed hypotheses on the pathogenesis of Syr. David N. Levine (2004) criticized the existing pathogenesis of Syr caused by foramen magnum lesions and formulated a new hypotheses [
The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis.
], stating that reduced compliance of the posterior spinal veins associated with decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and the formation of Syr. During the bibliometric process, we found that Rusbridge, C., attempted to explore the pathogenesis of Syr through model experiments.
Through further investigation of the intraoperative findings of CM-I, the following intradural pathologies were recorded: opacified arachnoid, thickened arachnoid, arachnoid granulations, ischemic and gliotic tonsils, inferior descent of the fourth ventricle and cervicomedullary junction (CMJ), tonsillar cysts, medialized tonsils, tonsil overlying and obstructing the foramen of Magendie, intertonsillar and tonsil to CMJ arachnoid adhesions, vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie, and arachnoid veils or webs obstructing or occluding the foramen of Magendie [
]. These pathologies may also be closely related to the occurrence and development of Syr. The pathological entity seems to block the CSF channel and the flow of the CSF through the metapore and foramen magnum [
Honored guest presentation: lifetime experiences and where we are going: Chiari I with syringohydromyelia–controversies and development of decision trees.
]. Cluster 1 emphasizes the treatment of Syr. For two decades, prevention of the onset and delay of pain have been the most important considerations for Syr patients regardless of the treatment modality [
Zhang Z xing, Feng D xu, Li P, et al. Surgical treatment of scoliosis associated with syringomyelia with no or minor neurologic symptom. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 2015;24(7):1555-1559. 10.1007/s00586-014-3692-1.
]. Recovery of the patient’s function and social independence should be the ultimate goal of treatment. For patients with isolated Syr, such as those with only a single symptom resembling pain or sensory disturbance, conservative treatment of symptoms can be selected. The purpose of surgical treatment is to determine the etiology of the obstruction and restore normal CSF circulation. The common shunt has a high failure rate and recurrence rate (a recurrence rate as high as 92 % in 3 years [
] reviewed the literature published up to 2015, covering a total of 410 patients. Factors influencing the recurrence of clinical symptoms were compared, and age (older age, greater risk of recurrence) and type of intervention (in which shunting was associated with a sevenfold higher risk of clinical recurrence than undergoing spider omentolysis) were detected as statistically significant risk factors for clinical recurrence. For asymptomatic CM-I patients with Syr, the decision whether to operate is primarily based on the clinical context, which is related to the progression of neurological symptoms; however, some instrumental diagnostic data are thought to be helpful in supporting surgical planning. In CM-I with Syr, bony decompression and duraplasty is preferable, regardless of symptoms. This theory has received 100 % agreement from international experts.CSF leaks are considered a worrying complication, deserving prompt treatment (85 %) to avoid infections and arachnoiditis in all cases, except for asymptomatic non-growing CSF collections. CSF leaks may also cause iatrogenic hypotension with or without subdural collections, a complication that is difficult to treat, as recently described [
Subdural Fluid Collection and Hydrocephalus After Foramen Magnum Decompression for Chiari Malformation Type I: Management Algorithm of a Rare Complication.
]. In asymptomatic children with incidentally discovered CM-I and Syr, surgery is indicated in cases with a syrinx larger than 5–8 mm, and a smaller syrinx increasing in size. This statement was endorsed by 82 % of the panel [
] reported that the rate of Syr improvement in CM-I children was 0 % with conservative treatment; however, the improvement rate after surgical treatment increased to 87.5 %. Therefore, children with Syr should be appropriately selected as surgical patients due to the high rates of clinical and radiographic improvement. For patients with post-traumatic Syr, spinal cord untethering with expansile duraplasty is the preferred first-line surgical technique [
], which may provide a new direction for the treatment of Syr, insight into the pathogenesis of Syr and its main clinical manifestations, and help to further explore the mechanism of disease recurrence and complications.
Cluster 3 emphasized the prognosis and recurrence of Syr. Syr accounts for 5 % of paraplegic patients [
]. Improving the prognosis and preventing recurrence are enduring goals in the treatment of Syr. Among Syr patients treated with surgery, retrospective studies have shown that Decompression of the epidural bone-ligament has no significant effect on Syr patients, while Syr patients treated with posterior fossa decompression have an improvement rate of 67.3–87.5 % and a reoperation rate of 10 %. For CM-I patients with Syr, the prognosis of surgical treatment is significantly worse [
Comparison of Three Different Cranio-Cervical Decompression Procedures in Children with Chiari Malformation Type I: Does the Surgical Technique Matter?.
]. A summary by Schuster et al. found that the incidence of recurrent/residual Syr after surgical decompression ranged from 0 to 22 %, with an average of 6.7 % [
]. Therefore, further exploration in the future is required to avoid complications and recurrence, and to provide effective treatment when symptoms occur.
In conclusion, we summarized the literature related to Syr from 2003 to 2022, including source countries and institutions, authors, published journals, etc. Based on these publications, we analyzed the research hotspots and predicted future trends. Reviewing previous studies on Syr, we discussed the four aspects of Syr and identified the key research topics. We fully and specifically discussed the shortcomings of these priorities and the importance of achieving breakthroughs in these priorities for the treatment of Syr patients. We believe that our research will help to determine the valuable future direction of Syr research, and that the mentioned hot spots will undergo major breakthroughs in the future.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding
This work was supported by grants from the Natural Science Research Project of Anhui Universities (No. KJ2021ZD0078), Postgraduate Innovation Scheme Fund (No. Byycx22094), and 512 Talent Cultivation Program (No. by51202206).
Roser F, Ebner FH, Sixt C, Hagen JMV, Tatagiba MS. Defining the line between hydromyelia and syringomyelia. A differentiation is possible based on electrophysiological and magnetic resonance imaging studies. Acta Neurochir (Wien). 2010;152(2):213-219; discussion 219. 10.1007/s00701-009-0427-x.
Syrinx size and duration of symptoms predict the pace of progressive myelopathy: retrospective analysis of 103 unoperated cases with craniocervical junction malformations and syringomyelia.
道客巴巴. CiteSpace II Detecting and visualizing emerging trends and transient patterns in scientific literature (2006). Accessed October 20, 2022. https://www.doc88.com/p-6621592881869.html.
Klimov VS, Gulay YuS, Evsyukov AV, Moysak GI. Syringosubarachnoid shunting in treatment of syringomyelia: a literature review and a clinical case report. Vopr Neirokhirurgii Im NN Burdenko. 2017;81(3):58. 10.17116/neiro201781358-65.
Ciaramitaro P, Garbossa D, Peretta P, et al. Syringomyelia and Chiari Syndrome Registry: advances in epidemiology, clinical phenotypes and natural history based on a North Western Italy cohort. :11.
Batzdorf U. Primary spinal syringomyelia. Invited submission from the joint section meeting on disorders of the spine and peripheral nerves, March 2005. J Neurosurg Spine. 2005;3(6):429-435. 10.3171/spi.2005.3.6.0429.
The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis.
Honored guest presentation: lifetime experiences and where we are going: Chiari I with syringohydromyelia–controversies and development of decision trees.
Zhang Z xing, Feng D xu, Li P, et al. Surgical treatment of scoliosis associated with syringomyelia with no or minor neurologic symptom. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. 2015;24(7):1555-1559. 10.1007/s00586-014-3692-1.
Subdural Fluid Collection and Hydrocephalus After Foramen Magnum Decompression for Chiari Malformation Type I: Management Algorithm of a Rare Complication.
Comparison of Three Different Cranio-Cervical Decompression Procedures in Children with Chiari Malformation Type I: Does the Surgical Technique Matter?.
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