Highest cited papers published in Neurology India: An analysis for the years 1993–2014
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.185362
Source of Support: None, Conflict of Interest: None
Context: The highest cited papers published in a journal provide a snapshot of the clinical practice and research in that specialty and/or region.
Keywords: Articles; citation analysis; highest cited; neurology; Neurology India; neuroscience; neurosurgery; ranking
The papers published in a journal pertaining to a particular scientific discipline provide a vignette of the status of science in that discipline. If a journal largely represents one geographic area, the papers published therein have the added property of being representative of the diseases and conditions that are of clinical concern and/or form the focus of research in that country or region. This is the reason why several journals contain articles that present data regarding the “best papers” they have published. Such lists would also provide an idea about the impact of a particular journal in the relevant field. The techniques used to determine the “best papers” published in a journal vary but are usually based on citation counts. Citation counts and metrics are often used to measure the impact of a paper or journal. Such analyses are based on the premise that a more “useful” paper would be cited more than a less useful one. Evidently, these metrics neither measure the impact of a paper at the level of an individual physician's practice habits nor do they account for variations in citation habits across scientific disciplines. Despite these major (and much discussed) shortcomings, analysis of citation metrics remains the most intuitive technique for quantitative analysis of the impact of a paper or journal.
Neurology India (ISSN 0028–3886) is the official publication of the Neurological Society of India. The journal was founded in 1952 and is thus currently in its 64th year of publication. The journal is indexed in all major indexing services and caters to all clinical, paraclinical, and basic neuroscience specialties. The journal follows the open access model, and all published articles are deposited with PubMed Central. This study analyzes papers published in Neurology India between 1993 and 2014 and identifies the highest cited papers and their attributes. It is hoped that this data will provide a summary of the best science that has been published in Neurology India over the past two decades.
The online archives of Neurology India were accessed, and the table of contents for each issue beginning with issue 41(1) in 1993 to issue 62(2) in 2014, was downloaded. Each published item was categorized as belonging to one of three subject domains: Neurology (NE), neurosurgery (NS), or other neurosciences (ON). The ON category included all allied specialties such as neuroradiology, neuropathology, microbiology, neuroanesthesia, psychology, rehabilitation, as well as all translational research papers, multispecialty papers, and basic neurosciences research. Next, the papers were classified as original papers, review articles, case reports, letters to the editor, or others (editorial, commentary, etc.). The number of citations received by each published item was determined by searching on Google Scholar. Of the various databases that can be used for citation analysis (such as Scopus, Web of Science, and Google Scholar), we opted to use Google Scholar due to ease of use and free availability, making the analyses readily reproducible. It is evident that the ages of the published items included in this analysis would vary between approximately 1 year (for those papers published in 2014) and 22 years (papers published in 1993). The papers would thus have had varying amounts of time to accumulate citations. To compensate for this, the total number of citations received by a paper was normalized to its age as follows -
Where CPY is the citations per year for a published item and the age of a published item is given by the simple relation age of the paper = 2015 − year of publication. The relationship between age of the paper and the number of times it had been cited is displayed in [Figure 1]; this graph has an approximately Gaussian distribution. Papers were then ranked separately on the basis of the total number of citations they had received and based on CPY. The top 100 papers on each rank list were analyzed in greater detail.
Between the years 1993 (issue 41:1) and 2014 (issue 62:6), 100 issues of Neurology India had been published and 3244 published papers were found to be suitable for inclusion in the present analysis from these issues. The subject-wise distribution of published items was NE - 1286 (39.6%), NS - 1571 (48.4%), and ON - 387 (11.9%). Case reports (n = 938, 28.9%) and letters to the editor (n = 1019, 31.4%) together formed 60.3% of all the published items, original articles (n = 923) formed 28.4% and review articles (n = 194) formed 5.98% of all published items. The distribution of the various types of papers across subject domains is displayed in [Table 1].
The 3244 items published since 1993 had received a total of 23,603 citations; this amounts to 7.28 citations per published item on an average. When normalized to the ages of the published items, the mean CPY per published item was 1.005 ± 1.44 (median 0.5, range 0–17.8). The citations received by papers grouped according to publication type and subject are displayed in [Table 2]. One-way ANOVA showed that papers in both ON and NE groups had received significantly higher citations than those in the NS group (F = 15.15, P < 0.001). Interestingly, original articles had received a lower mean number of CPY (1.72 ± 1.76) when compared with review articles (2.38 ± 2.61); this difference was significant on an independent samples t-test (t = −3.369, P = 0.001). Nearly a quarter of the published items (n = 785, 24.2%) had never been cited. The characteristics of the published items that had never been cited are displayed in [Table 3].
The top 100 articles ranked by the total number of citations
Papers were ranked on the basis of the total number of citations they had received since publication, and the top 100 papers from this list are displayed in [Table 4]. The attributes of these articles are displayed in [Table 5]. The various types of articles (based on the type of data presented in the paper) represented in the top 100 were basic lab research - 4 (3.9%), cadaver studies - 4 (3.9%), clinical articles - 55 (54.5%), epidemiologic studies - 8 (7.9%), radiologic investigations - 7 (6.9%), and review articles - 23 (22.7%). The top 5 countries represented in these 101 papers were: India - 80 papers (79.2%), USA - 5 (4.9%), China and Turkey - 4 each (3.9%), Iran and France - 2 (1.98%) each, and 1 paper each from the UK, Germany, Australia, and Italy. The 5 institutes that had the highest number of papers in the top 100 were Sanjay Gandhi Post Graduate Institute of Medical Education and Research (SGPGI), Lucknow, and Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh - 9 papers each, Christian Medical College (CMC), Vellore - 8 papers, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram - 7 papers, Seth GS Medical College, Mumbai - 5 papers, and National Institute of Mental Health and Neurosciences (NIMHANS) and CARE Hospitals, Hyderabad - 4 papers each. Three of the top 5 papers on this list were from India and one each from China and the USA.,,,, The major themes covered in these 100 top cited papers were infection (18), vascular (14), spine (12), trauma (6), nutritional disorders (5), epilepsy (5), autoimmune diseases (5), and craniovertebral junction (CVJ) diseases (5).
When review articles were excluded, the top 100 cited papers included 23 case reports, 1 letter to the editor, 1 commentary, and 75 original articles. The top cited paper had been cited 139 times as of the time of this analysis. The authors studied the role of inflammation in causing brain edema in a rodent model of intracerebral hemorrhage. The second highest cited paper originating from Seth GS Medical College, was a cadaveric study of the anatomical relation of the vertebral artery to C1 and C2 (115 citations, published in 2004). The third most cited paper, originating from L. V. Prasad Eye Institute, Hyderabad, dealt with the isolation and characterization of rat bone marrow stromal cells (published 2010, 92 citations). A review cum clinical series on the application of neuronavigation from the University of Erlangen-Nuremberg, Germany, published in 2002 was the 4th highest cited paper (published 2002, 88 citations). A clinical series that detailed the neurological manifestations and management of patients with Vitamin B12 deficiency from CMC Vellore (published 2005, 76 citations) was the 5th most cited paper. The other papers in the top 10 dealt with epilepsy, anatomy of the CVJ, Chikungunya infection, and the epidemiology of neurologic disorders in West Bengal. Thus, 8 of the top 10 papers on this list originated from India.,,,
The top 100 articles - normalized to citations per year
When papers were ranked by how many cites they had received per year (CPY) since publication, it was found that 55 papers in the top 100 of this rank list were common with the rank list based on total citations. The other 45 papers on the CPY rank list, however, did not figure on the total citations rank list. To explore this phenomenon further, we looked at the ages of the papers on both rank lists. The mean age of the top 101 papers on the total citations rank list was 10.97 ± 3.25 years whereas the mean age of the papers on the CPY rank list was 6.6 ± 3.36 years. This difference was significant on a t-test (t = −9.4, P < 0.001). Thus, younger papers that had begun to be cited highly each year but had not had enough time to accrue a large number of total citations had been left out of the total citations rank list. The CPY rank list is displayed in [Table 6].
The attributes of these 100 top ranked papers is displayed in [Table 7]. Sixty-five (65%) of the papers on the CPY rank list were original articles, 30 were review articles, and 5 were case reports. The subject areas covered by these papers were vascular (20), infection (18), oncology and spine - 8 each, and congenital conditions and trauma - 7 each. India (64), Turkey (9), China (9), USA (7), and France (3) were the top 5 publishing countries. All India Institute of Medical Sciences (AIIMS), New Delhi (8), PGIMER Chandigarh (6), NIMHANS (6), CMC Vellore (5) and SCTIMST, and Thiruvananthapuram (5) were the institutes with the most number of papers on this rank list. The paper with the highest CPY was a basic science research paper from the L. V. Prasad Eye Institute, published in 2010 and had received a total of 92 citations over 5 years (CPY = 18.4). This paper dealt with a technique of isolation and characterization of bone marrow stem cells. Two of the top 5 papers on this list were from India and one each from Mexico, the UK, and China., 7, ,,
When review articles were eliminated, there were 9 case reports, 1 letter to the editor, 2 commentaries, and 88 original papers in the CPY top 100 rank list. Four of the top 10 papers with the highest annual citation rates since publication were common to the top 10 on the total citations rank list.,,, The remaining 6 included a large series of patients with cerebral venous sinus thrombosis from the Nizam's Institute of Medical Sciences, Hyderabad (published 2012, 32 citations), a case series from Turkey on the etiological factors for peripheral nerve injuries (published 2009, 59 citations), a study on the outcomes following spontaneous intracerebral haemorrhage from the AIIMS, New Delhi (published 2013, 19 citations), a case report of dengue-related hypokalemic paralysis from SGPGI, Lucknow (published 2010, 42 citations), assessment of indocyanine green angiography for aneurysm surgery from China (published 2009, 49 citations), and a report of sleep disorders in South India from NIMHANS (published 2012, 23 citations).,,,,, Thus, 7 of the top papers on this list were from India, 2 from China and one from Turkey.
In this analysis, we identified the highest cited papers published in Neurology India since 1993 - the year that online archiving of the journal's contents commenced. These rank lists provide information about the papers published in Neurology India that have had the maximum impact on neuroscience research and practice across the globe. After eliminating self-citations, the top 5 countries from which authors had cited papers published in Neurology India (besides India) were the USA, China, Turkey, the UK, and Germany. [Figure 2] provides a depiction of the global impact of articles published in Neurology India.
Several prior studies have looked at the highest cited clinical neuroscience papers published in neurology and neurosurgical journals and in nonneurological and nonneurosurgical high-impact general medical journals., Many studies have also mapped the progress of research and treatment in a specific subspecialty (e.g., skull base surgery or stereotactic and functional NS) or even of a specific disease or condition (e.g., epilepsy, anorexia nervosa, depression, multiple sclerosis, etc.) using citation analysis.,,,, However, in several of these analyses, authors have used raw total citation counts to rank papers. One of the major problems with ranking papers merely on the basis of the total number of citations is that older papers have had more time to accrue citations than more recent ones. Thus, more recent papers that have been showing a trend toward being highly cited may be left out of this rank list simply because they have been published more recently. The graph displaying the relationship between the age of published items and the number of citations they had accrued for Neurology India is displayed in [Figure 1]. This graph is approximately in the shape of a bell-shaped normal distribution, with citations gradually peaking between 6 and 16 years postpublication. Recent analyses have taken cognizance of this issue and have normalized the number of citations received to the age of the paper. In this analysis, we have ranked papers both ways – on the basis of raw total citations and age normalized CPY. Only 50% of the papers in the top 100 were the same – the younger papers with high annual citation rates were ignored by the raw citation count rank list.
Attributes of the highest cited papers
The majority of papers in both rank lists (80% on the total citations rank list and 64% in the CPY rank list) were from India. China, Turkey, and the USA were the countries with the next highest numbers of papers in the top 100. SGPGI (Lucknow), PGIMER (Chandigarh), CMC (Vellore), SCTIMST (Thiruvananthapuram), Seth GS Medical College (Mumbai), NIMHANS (Bangalore), and AIIMS (New Delhi) were the institutes that had published the most number of papers ranked in the top 100.
Most common themes
The most common themes found among the highest cited papers on the total citation rank list were infection, vascular, oncology, and spine. The other common themes were trauma, nutritional diseases, congenital conditions, epilepsy, and autoimmune diseases. A similar study found that the disciplines represented among the 100 highest cited papers published in NS journals were vascular diseases (43%), trauma (27%), functional NS (13%), and oncology (12%). This study did not include pure spine surgery journals, which explains the absence of articles related to this discipline. No similar journal-wide studies were found for neurology journals.
Papers related to infectious disease accounted for 18 papers out of the top 100 on both rank lists. These papers pertained to neurologic syndromes resulting from viral diseases such as dengue and chikungunya, nervous system tuberculosis, mycoses, neurocysticercosis, and postsurgical infections. The second most frequent theme represented in the top 100 was vascular disease (14% of the top 100 in the total citations rank list and 20% on the CPY rank list) [Table 5]. Three of the 14 papers on the total citations rank list dealt with the epidemiology of stroke. Most of the clinical papers dealt with stroke, and cortical venous thrombosis – these are vascular diseases that are highly prevalent in India.
Spine was the third highest represented subject (12 papers in the total citations rank list and 8 on the CPY rank list). Except for one cadaver study, the other papers were all clinical studies or review articles. There were 6 papers pertaining to neurotrauma in the top 100. Notable is the fact that no papers reporting nation-wide epidemiologic data pertaining to brain and spine trauma have been published in Neurology India over the past two decades. Autoimmune diseases (including Guillain–Barre syndrome, multiple sclerosis), congenital diseases (cysts, muscular dystrophies, etc.), CVJ surgery, epilepsy, and nutritional diseases (mostly Vitamin B12 deficiency) were each represented by 5 papers.
Stroke and infectious diseases indeed form the major burden of neurologic disease in India. However, other conditions which are also a significant cause for morbidity and mortality, especially trauma, were grossly underrepresented in the highest cited published items in Neurology India. Most of the high quality clinical and research work in these fields is possibly published in international journals with a wider reach. It is also of concern that the allied specialties were underrepresented in Neurology India. This could be due to the availability of subspecialty journals in these disciplines. Active efforts would need to be made to present data from these specialties in Neurology India, so as to make its scope truly comprehensive vis-a-vis the neurosciences. Also, several clinicians and researchers tend to publish nationally relevant data in international journals. This affects the availability of these data to clinicians and researchers within India itself as well as the visibility of Neurology India as a journal that is a vehicle for good data. This should be an issue for future discussion and debate.
The 100 highest cited papers published in Neurology India present a good snapshot of the neurologic diseases of major concern in India. Stroke (and other cerebrovascular diseases) and infections form a large proportion of the disease burden in India and are adequately represented in the journal, whereas other areas of concern such as trauma are not. Publication of such nationally relevant data in international journals could limit its availability within India and reduce the impact of such data within the country. Neurology India should position itself as the vehicle for the dissemination of such important data.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]