Background and purpose The number of citations that an article has received can be used to evaluate its impact on the scientific community. This study aimed to identify the 100 most cited articles in the field of neurointervention and to analyze their characteristics.
Materials and methods We selected the 669 journals that were considered potentially to publish neurointervention articles based on the database of Journal Citation Reports. Using the Web of Science citation search tool, we identified the 100 most cited articles relevant to neurointervention within the selected journals. Each article was evaluated for several characteristics including publication year, journal, journal category, impact factor, number of citations, number of citations per year, authorship, department, institution, country, type of article, and topic.
Results The number of citations for the top 100 articles ranged from 1912 to 170 (mean 363.4) and citations per year ranged from 271.0 to 4.1 (mean 40.0). The majority of articles were published in clinical neurology journals (63%), were published in 2000–2009 (39%), originated in the USA (45%), were original articles (95%), and dealt with endovascular treatment of cerebral aneurysm (42%). The Department of Radiology, University of California School of Medicine (n=12) was the leading institution and Viñuela F (n=11) was the most prolific author.
Conclusions Our study presents a detailed list and analysis of the 100 most cited articles in the field of neurointervention and provides a historical perspective on the scientific progress in this field.
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Neurointervention, also known as interventional neuroradiology or interventional neurosurgery, is a relatively new medial subspecialty that uses minimally invasive techniques principally to treat disorders of the blood vessels of the brain, head and neck, and spinal cord.1 Neurointervention has rapidly developed over the past decades with advances in imaging modalities, catheters and other devices, and interventional techniques.1 ,2 This progress can be demonstrated through many landmark articles published by many pioneers in the scientific literature.2
A citation is the acknowledgment that one scientiﬁc article (the cited article) has been referenced by another article (the citing article). The number of citations (ie, how many times a given article is counted in the reference lists of subsequent articles) can be used to evaluate the influence of an article on its field and to determine the relative importance of medical journals by means of the journal impact factor (IF).3 ,4 Therefore, reviewing the most cited articles (so-called ‘citation classics’) offers the reader an interesting insight into the history and development of the specialty.
There have been many studies to identify the most cited articles in various medical ﬁelds including general surgery,5 anesthesiology,6 neurosurgery,7 obstetrics and gynecology,8 orthopedics,9 rehabilitation,10 and radiology.11 To our knowledge, however, the bibliometric analysis of the most cited articles in the ﬁeld of neurointervention has not yet been reported.
The purpose of the present study was therefore to identify the 100 most cited articles in the field of neurointervention and to analyze the characteristics of these articles.
Materials and methods
Institutional review board approval was not necessary as our study was a bibliometric analysis that did not involve human subjects.
Two reviewers (JYL and HJJ, neurointerventionalists with 10 and 5 years' experience, respectively) independently conducted journal selection, article identification, and analysis. In cases of disagreement, a third reviewer (DYY, a neurointerventionalist with 20 years' experience) was included in the discussion until consensus was achieved.
Selection of journals
To identify the most cited neurointervention articles, journals listed under the following five subject categories of the Institute for Scientific Information (ISI) Web of Knowledge Journal Citation Reports (JCR) Science Edition 2014 (Thomson Reuters, New York, New York, USA) were evaluated for inclusion: ‘Clinical Neurology’ (192 journals), ‘Medicine, General & Internal’ (154 journals), ‘Neuroimaging’ (14 journals), ‘Neuroscience’ (252 journals), and ‘Radiology, Nuclear medicine & Medical imaging’ (125 journals). The subject category of ‘Medicine, General & Internal’ was included in our study because it contains high IF interdisciplinary journals that cover a broad spectrum of scientific research. An additional search was performed on the JCR database for journals including the title word ‘neuro*’ or ‘intervention*’ (an asterisk replaces any number of characters) regardless of the subject category, and 253 journals were identified. After excluding 321 duplicated journals, a total of 669 journals were considered journals potentially publishing neurointervention articles and were included in this study. No restrictions were made in terms of the language or IF of the journal.
Identification of the 100 most cited articles
To identify the most cited articles, each of the 669 journals was then searched separately using the ‘Cited Reference Search’ in the Science Citation Index Expanded of the ISI Web of Knowledge-Web of Science (Thomson Reuters) on January 2016. The ISI Web of Knowledge-Web of Science is a multidisciplinary database providing the overall citation counts from published scientific articles since 1945. Articles from each journal with more than 100 citations were recorded and compiled into a single database. These articles were then ranked in descending order based on citation number and reviewed to determine if they were relevant to neurointervention.
A neurointervention article was defined as any study which met all of the following three conditions: (1) focused on techniques, outcomes or complications of endovascular treatment for cerebrovascular disease; (2) described interventional procedures of the intracranial arteries, extracranial portion of the internal carotid artery and vertebral artery, external carotid artery and its branches, common carotid artery, spinal artery, or intracranial veins; and (3) had any relevance or impact on most neurointerventionalists' daily clinical practice. No restrictions were placed on the patient's age or language for our study. Articles were excluded if they explored basic science research (ie, pathophysiology, hemodynamics, or biochemistry), dealt purely with conservative management or surgery, or focused on diagnostic imaging to evaluate indication or outcome of neurointerventional treatment. Some article types such as abstracts, letters, editorial materials, corrections, discussions, and book reviews were also excluded.
Analysis of articles
We searched the National Library of Medicine's PubMed database to obtain the full texts of the 100 most cited articles that were available online. For those where electronic copies were unavailable, the articles were obtained in printed format from local or overseas libraries.
The 100 most cited articles were reviewed and the following information was extracted according to their specific characteristics: (1) year of publication; (2) journal title; (3) journal category (clinical neurology, neuroscience, radiology/imaging, or interdisciplinary); (4) IF of journal (based on the 2014 science edition of the ISI JCR); (5) number of citations; (6) number of citations per year (calculated by total number of citations over the number of years and months since publication); (7) authorship; (8) department (radiology, neurosurgery, neurology, not separated or multispecialty groups (eg, department of neurological sciences, department of neuroradiology and neurosurgery, service of endovascular therapy), or others); (9) institution; (10) country; (11) type of article (original article (reports that investigated clearly stated objectives or hypotheses and contained specifically articulated methods and results sections), review, technical note, methodological study, guideline/consensus statement, systematic review/meta-analysis, or case report); and (12) topic.
For the purpose of our study, the department, institution, and country of origin were defined by the affiliation provided for the first author. If the first author had an affiliation to more than one institution or group name, the corresponding author's affiliation was used for the origin of the article.
The present study adopted a descriptive research approach by means of bibliometric analysis.
The online supplementary table lists the 100 most cited neurointervention articles in descending order according to the number of citations received. The number of citations for the top 100 articles ranged from 1912 to 170 (mean±SD 363.4±300.5; median 242) and four articles were cited more than 1000 times. Furlan et al12 published the top-ranking article, which was a randomized controlled trial published in 1999 and described the clinical efficacy and safety of intra-arterial recombinant prourokinase in patients with acute middle cerebral artery occlusion.
The number of citations per year ranged from 271.0 to 4.1 (mean 40.0±53.5; median 19.6). The number of citations per year produced significant shifts in rank for the top 100 list (mean absolute rank change 18.1±14.9; range −73 to +50). The article with the most citations per year since publication was a randomized trial published in 2015 by Berkhemer et al13 on intra-arterial treatment for acute ischemic stroke.
Of the 669 journals included in our bibliometric analysis, only 16 provided articles in our top 100 list: Journal of Neurosurgery (n=23) and Stroke (n=22) contained the most articles. The leading journal categories were clinical neurology (n=63), followed by radiology/imaging (n=19), and interdisciplinary (n=18) (table 1). Articles were published from 1973 to 2015, with the most productive decades being the 2000s (n=39) and the 1990s (n=33) (table 2).
We found 11 frequent authors who contributed five or more of the most cited articles. This list was led by Viñuela F, who authored or co-authored 11 of the articles. The most frequent first author was Higashida RT (n=5), followed by Fiorella D (n=4) (table 3). With regard to specialty contribution, radiology departments produced the most articles (n=38), followed by neurology (n=21), neurosurgery (n=20), not separated or multispecialty groups (n=15), and others (n=6). The institution with the greatest number of articles was the Department of Radiology, University of California School of Medicine (USA) (n=12) (table 4). The 100 articles originated from just 15 countries. The majority of the articles originated in the USA (n=45), followed by France (n=14) and Germany (n=10) (table 5).
Type of article was most frequently original article (n=95), 62 of which were clinical observational studies and 30 were comparative clinical trials (table 6). The most common topic was endovascular treatment of cerebral aneurysm (n=42) followed by intra-arterial thrombolysis or thrombectomy (n=22) (table 7).
The number of citations is a reliable objective indicator of the quality and impact of an individual article.3 An article ranked in the highest percentile of citations is usually called a ‘citation classic’, which clearly means an article with the highest impact on their field.14 In this paper we present the 100 most cited articles in the field of neurointervention. Although the number of citations is not a perfect method to assess the quality of an article, the list of the most cited articles is useful for several reasons.15 ,16 It offers the reader an interesting insight into how the specialty has developed over time. Moreover, it can also present useful information about scientific progress such as authors, institutions, journals, topics, and trends of academic research.
One can hypothesize that citation rates for each specialty might depend on the size of the scientific community. However, although neurointervention is a young and very small field, the number of citations in our study (range 170–1912; mean 363.45) is slightly lower than that observed in neurosurgical journals7 (range 287–1.515; mean 452.6) and comparable to that in interventional radiology17 (range 200–2497; mean 320.7). It may be explained by the fact that a significant proportion (18%) of the articles in our list was published in high-impact interdisciplinary journals. These journals have wider readership and prestige than specialty journals and therefore appeal to researchers of various subspecialties.18
The total number of citations of an article could be dependent on its publication year because citations accumulate over time. Generally, scientific articles are not cited until one or two years after publication, reach a peak after 3–10 years, and show a decreasing trend thereafter.19 This pattern of citations in scientific literature may result in underestimation of recently published articles irrespective of their actual impact.20 To overcome this problem we used an alternative measure of citations, which was calculated by dividing the total number of citations by the number of years and months since publication. This method can be used for evaluating the current relevance of the article on the scientific community, regardless of publication year. Our results showed significant shifts in rank between the total number of citations and the number of citations per year for the 100 most cited articles. Articles with a high total citation count but low number of citations per year may be of historical importance and may not reflect the current impact. In contrast, articles with both high total citation count and number of citations per year may still retain relevance for current researchers.
The most productive decade of neurointerventional research in the top 100 was 2000–2009, with 39 articles. This result is different from those in other medical fields, which revealed that a majority of highly cited articles were published in 1980–19896–10 or 1990–1999.11 This is likely to reflect the relatively recent evolution and development in the field of neurointervention.
Our study also showed that the USA dominates the list of the 100 most cited articles with 45 contributions. This result is in line with previous citation analyses in many medical fields, reflecting the strong influence of the USA on medical research. However, our neurointervention citation classic list is less concentrated in the USA than other disciplines in which the proportion of the USA ranged from 57% to 69%.5 ,6 ,8–11
A strength of our study was that we compiled a comprehensive list of the most cited neurointervention articles across wide medical disciplines. The majority of previous citation classic studies restricted their searches only to their own specialty journals to gain the most cited articles.5–11 Consequently, top-cited articles that were originally published in other specialty or interdisciplinary journals may have been excluded from the list. In our study, a total of 669 journals potentially publishing neurointervention articles were included for analysis, therefore achieving a more representative list of most cited articles. Various journals under clinical neurology (n=63), radiology/imaging (n=19), or interdisciplinary (n=18) categories published the top 100 neurointervention articles. This tendency may reflect the impact of neurointervention articles on various medical disciplines. At present, neurointerventional therapy of cerebrovascular disease promises to be a greatly expanding field across neurosurgery, radiology, and neurology.2
With regard to the type of articles, our results showed that original articles accounted for 95% of all neurointervention citation classics, which is higher than those of previous studies (51–92%) on top cited articles in other medical fields.5–11 This finding may indicate neurointerventionalists' preference for citing high level clinical evidence rather than review articles or expert opinion.
Endovascular treatment of aneurysm and thrombolysis/thrombectomy for acute arterial occlusion were the most common topics in the top 100 list. This highlights the high prevalence and importance of these diseases within the neurointerventional specialty.
The citation analysis presented in this study has some inherent limitations that warrant discussion. There are a number of factors that can influence the overall number of citations of an article. First, ‘obliteration by incorporation’ is one important flaw with citation analyses. It describes the phenomenon that information from some highly influential or classic articles becomes integrated into common knowledge and thus these articles are not necessary to cite.14 For this reason, the true landmark articles in a particular field may not be found in the most cited articles list but rather in the references of the other classic articles. Second, another problem of citation behavior is so-called ‘incomplete citing’, which describes the situation where the reasons for citing specific articles may not be entirely appropriate. There are various types of conscious or unconscious incomplete citing biases that may affect citation counts, such as self-citation (ie, authors citing their own previous work), in-house citation (ie, citing articles of colleagues in a network of authors), omission bias (ie, tendency to cite articles supporting the interpretation of one's own results rather than to cite sources contradictory to one's own results), citing articles published in high-IF journals, preference to cite review articles or full-length articles, and language bias towards English.19 ,21 ,22
This study presents a detailed list of the 100 most cited articles in the field of neurointervention. Our findings provide an insight into historical developments and information pertaining to the dissemination of knowledge in neurointervention.
Contributors ESK: study design, data acquisition, data analysis, data interpretation, manuscript preparation. DYY: study design, data acquisition, data analysis, data interpretation, manuscript revision, final approval of manuscript. HJK: data acquisition, data analysis. HJJ: data acquisition, data analysis, data interpretation. JYL: data acquisition, data analysis, data interpretation. B-MC: data analysis, data interpretation. KL: data interpretation, manuscript revision.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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