Background It is widely acknowledged that there is a global divide on health care and health research known as the 10/90 divide.
Background
It is widely acknowledged that there is a global divide on health care and health research known as the 10/90 divide.Methods A retrospective survey of articles published in the BMJ, Lancet, NEJM, Annals of Internal Medicine & JAMA in a calendar year to examine the contribution of the developing world to medical literature. We categorized countries into four regions: UK, USA, Other Euro-American countries (OEAC) and (RoW). OEAC were European countries other than the UK but including Australia, New Zealand and Canada. RoW comprised all other countries.
Methods
A retrospective survey of articles published in the BMJ, Lancet, NEJM, Annals of Internal Medicine & JAMA in a calendar year to examine the contribution of the developing world to medical literature. We categorized countries into four regions: UK, USA, Other Euro-American countries (OEAC) and (RoW). OEAC were European countries other than the UK but including Australia, New Zealand and Canada. RoW comprised all other countries.Results The average contribution of the RoW to the research literature in the five journals was 6.5%. In the two British journals 7.6% of the articles were from the RoW; in the three American journals 4.8% of articles were from RoW. The highest proportion of papers from the RoW was in the Lancet (12%). An analysis of the authorship of 151 articles from RoW showed that 104 (68.9%) involved authorship with developed countries in Europe or North America. There were 15 original papers in these journals with data from RoW but without any authors from RoW.
Results
The average contribution of the RoW to the research literature in the five journals was 6.5%. In the two British journals 7.6% of the articles were from the RoW; in the three American journals 4.8% of articles were from RoW. The highest proportion of papers from the RoW was in the Lancet (12%). An analysis of the authorship of 151 articles from RoW showed that 104 (68.9%) involved authorship with developed countries in Europe or North America. There were 15 original papers in these journals with data from RoW but without any authors from RoW.Conclusions There is a marked under-representation of countries in high-impact general medical journals. The ethical implications of this inequity and ways of reducing it are discussed.
Conclusions
There is a marked under-representation of countries in high-impact general medical journals. The ethical implications of this inequity and ways of reducing it are discussed.

Background National and international bodies concerned with research ethics need to confront the greatest ethical challenge-the enormous inequities in global health research [ 1 ]. Thus, less than 10% of the world's research resources are earmarked for 90% of the health problems [ 2 ]. Though 93% of the world's burden of preventable mortality occurs in developing countries, too little research funding is targeted to health problems in those countries [ 3 ]. This divide in research funding is mirrored by concerns regarding a divide in the proportion of publications arising from medical research in developing countries. A recent survey of six leading psychiatric journals revealed that only 6% of the articles originated from, or described data arising from, regions of the world that accounted for over 90% of the global population [ 4 ]. Following this paper, the issue of under-representation of developing countries was debated and discussed in many journals and by journal editors [ 5 - 7 ]. The aim of this study is to investigate the publication bias beyond the field of psychiatry to determine the overall contribution of different regions of the world to the medical literature published in high-impact journals and, in particular, to quantify the developing world's contribution.
Background
National and international bodies concerned with research ethics need to confront the greatest ethical challenge-the enormous inequities in global health research [ 1 ]. Thus, less than 10% of the world's research resources are earmarked for 90% of the health problems [ 2 ]. Though 93% of the world's burden of preventable mortality occurs in developing countries, too little research funding is targeted to health problems in those countries [ 3 ]. This divide in research funding is mirrored by concerns regarding a divide in the proportion of publications arising from medical research in developing countries. A recent survey of six leading psychiatric journals revealed that only 6% of the articles originated from, or described data arising from, regions of the world that accounted for over 90% of the global population [ 4 ]. Following this paper, the issue of under-representation of developing countries was debated and discussed in many journals and by journal editors [ 5 - 7 ].The aim of this study is to investigate the publication bias beyond the field of psychiatry to determine the overall contribution of different regions of the world to the medical literature published in high-impact journals and, in particular, to quantify the developing world's contribution.Methods The method used is the same as that which was used by two of the authors (AS and VP) in a recent survey of the international representation in the psychiatric literature [ 4 ]. A retrospective survey was conducted of all issues in one calendar year (the most recent, complete set available in the medical library in Colombo where data collection took place) of the following journals: BMJ, Lancet, NEJM, Annals of Internal Medicine & JAMA. These journals were selected because they have the highest impact amongst general medical journals [ 8 ]. These journals lay claim to their global legitimacy for many reasons: frequent publication, high impact, long history, credibility of the publisher, large numbers of full time editorial staff, membership of the International Committee of Medical Journal Editors, and influential joint statements [ 9 ]. The year for which data was collected was 2000 for all journals, except JAMA for which it was 1999 (all issues in year 2000 were not available). All articles, excluding the specified ones in each journal were reviewed. In the BMJ we excluded obituaries, multi-media, personal views, Minerva, news and soundings. In the Lancet we excluded Dissecting Room and news. In the Annals, we excluded on Being a doctor, Current clinical issues, Medical writings, Book notes, Ad Libitum and persona. In the NEJM, we excluded book reviews, This week in the journal and Abstracts. In JAMA, we excluded Medical news and Perspectives, Peace of my mind, JAMA hundred years ago, Abstracts, FDA, CDC, poetry and medicines, Books journals, New media, World in medicine and the section titled "from the JAMA websites". In the Lancet, editorials and commentaries were pooled together, because the commentaries in the Lancet resemble editorials in the other journals in terms of their contents. None of the other four journals had commentaries section. For the allocation of regions of the world, we categorized countries into four regions: UK, USA, OEAC (Other Euro-American countries) and RoW (Rest of the World). OEAC were European countries other than the UK but including Australia, New Zealand and Canada. RoW comprised all other countries including Eastern Europe, Central and South America, Asia and Africa. We scrutinized each article to examine the country of the authors' affiliation address with a view to categorizing them into relevant regions of the world. All authors were noted including multiple authors in large multi-center studies. We also scrutinized the methods section of all the original articles to ascertain the origin of data with special emphasis on whether the research was carried out in RoW countries. The affiliation of the first, last and corresponding authors was also noted. We worked with a negative bias against the USA and the UK from where the journals originated. Therefore articles, which included authors from the RoW, were considered as arising from the RoW even if the first author is from the UK, USA or OEAC. Similarly, articles from the OEAC, which involved collaborations from the UK or USA, were included in the OEAC category. In the event of a collaborative study between the USA and the UK, the allocation to region was based on the institutional affiliation of the first author. The RoW category included collaborative studies between any country in the RoW and developed nations. In some cases the origin of the author was difficult, particularly when there were two places named as their attached institutions. For an example when one was in USA while the other is in Kenya. We used our best guess in these instances. For an example the two authors AS and VP in this paper were based in RoW at the time we did this research but were employed in UK but with strong affiliations to the RoW countries where they were born and did their research. Attempts to analyse the nationality of the authors was therefore abandoned.
Methods
The method used is the same as that which was used by two of the authors (AS and VP) in a recent survey of the international representation in the psychiatric literature [ 4 ]. A retrospective survey was conducted of all issues in one calendar year (the most recent, complete set available in the medical library in Colombo where data collection took place) of the following journals: BMJ, Lancet, NEJM, Annals of Internal Medicine & JAMA. These journals were selected because they have the highest impact amongst general medical journals [ 8 ]. These journals lay claim to their global legitimacy for many reasons: frequent publication, high impact, long history, credibility of the publisher, large numbers of full time editorial staff, membership of the International Committee of Medical Journal Editors, and influential joint statements [ 9 ]. The year for which data was collected was 2000 for all journals, except JAMA for which it was 1999 (all issues in year 2000 were not available). All articles, excluding the specified ones in each journal were reviewed. In the BMJ we excluded obituaries, multi-media, personal views, Minerva, news and soundings. In the Lancet we excluded Dissecting Room and news. In the Annals, we excluded on Being a doctor, Current clinical issues, Medical writings, Book notes, Ad Libitum and persona. In the NEJM, we excluded book reviews, This week in the journal and Abstracts. In JAMA, we excluded Medical news and Perspectives, Peace of my mind, JAMA hundred years ago, Abstracts, FDA, CDC, poetry and medicines, Books journals, New media, World in medicine and the section titled "from the JAMA websites". In the Lancet, editorials and commentaries were pooled together, because the commentaries in the Lancet resemble editorials in the other journals in terms of their contents. None of the other four journals had commentaries section.For the allocation of regions of the world, we categorized countries into four regions: UK, USA, OEAC (Other Euro-American countries) and RoW (Rest of the World). OEAC were European countries other than the UK but including Australia, New Zealand and Canada. RoW comprised all other countries including Eastern Europe, Central and South America, Asia and Africa. We scrutinized each article to examine the country of the authors' affiliation address with a view to categorizing them into relevant regions of the world. All authors were noted including multiple authors in large multi-center studies. We also scrutinized the methods section of all the original articles to ascertain the origin of data with special emphasis on whether the research was carried out in RoW countries. The affiliation of the first, last and corresponding authors was also noted. We worked with a negative bias against the USA and the UK from where the journals originated. Therefore articles, which included authors from the RoW, were considered as arising from the RoW even if the first author is from the UK, USA or OEAC. Similarly, articles from the OEAC, which involved collaborations from the UK or USA, were included in the OEAC category. In the event of a collaborative study between the USA and the UK, the allocation to region was based on the institutional affiliation of the first author. The RoW category included collaborative studies between any country in the RoW and developed nations.In some cases the origin of the author was difficult, particularly when there were two places named as their attached institutions. For an example when one was in USA while the other is in Kenya. We used our best guess in these instances. For an example the two authors AS and VP in this paper were based in RoW at the time we did this research but were employed in UK but with strong affiliations to the RoW countries where they were born and did their research. Attempts to analyse the nationality of the authors was therefore abandoned.Results The contribution of the RoW to the research literature surveyed in these five high-impact journals was 6.5%. In the two British journals, 7.6% of the articles were from the RoW, whilst the proportion in the three American journals was 4.8%. This averages hides the fact that there is considerable variation between journals; thus, around 3.5% of articles in the two journals of national medical associations of the UK (BMJ) and USA (JAMA) were from the RoW as compared to 12% in the Lancet articles (Table  1 ). Indeed, more than half the articles from the RoW were published in just one journal, the Lancet (Table  2 ). Table 1 The contribution of regions to the research literature in five leading journals BMJ Lancet NEJM JAMA ANNALS Total Editorials 261 350 4 124 102 39 876 UK 160 61.4% 167 47.7% 10 8.0% 02 1.9% 01 2.4% 340 38.8% USA 38 14.6% 87 24.9% 97 78.3% 97 95.0% 35 90.0% 354 40.4% OEAC 1 56 21.4% 89 25.4% 14 11.3% 02 1.9% 03 7.6% 164 18.7% RoW 2 07 2.6% 07 2.0 % 03 2.4% 01 0.9% 00 0.0% 18 2.6% Original papers 322 307 218 227 115 1189 UK 216 67.0% 66 21.5 % 06 2.7% 04 1.8% 03 2.6% 295 24.8% USA 22 7.0% 38 12.4% 107 49.1% 173 76.2% 81 70.4% 421 35.4% OEAC 76 23.6% 136 44.3 % 78 35.8% 42 18.5% 23 20.0% 355 29.9% RoW 08 2.4% 67 21.8% 27 12.4% 08 3.5% 08 7.0% 118 9.9% Correspondence 1118 1043 5 894 605 251 3911 UK 829 74% 374 35.8% 30 3.4% 13 2.1% 04 1.6% 1250 32% USA 69 6% 141 13.5% 601 67.2% 506 83.6% 183 72.9% 1500 38.4% OEAC 174 16% 400 38.3% 212 23.7% 71 11.7% 49 19.5% 906 23.2% RoW 46 4% 128 12.2% 51 5.7% 15 2.5% 15 6.0% 255 6.5% Review articles 286 50 65 36 66 503 UK 195 68.2% 17 34% 04 6.2% 01 2.7% 01 1.6% 218 43.3% USA 29 10.2% 15 30% 48 73.8% 28 78.0% 61 92.4% 181 36% OEAC 54 18.8% 14 28% 13 20.0% 04 11.1% 04 6.0% 89 17.7% RoW 08 2.8% 04 08% 00 0.0% 03 8.2% 00 0.0% 15 3% Others 3 47 208 149 145 27 576 UK 31 66.0% 68 32.8% 03 02.0% 00 00.0% 00 00.0% 102 17.7% USA 08 17.0% 34 16.3% 118 79.3% 120 82.7% 25 92.6% 305 53% OEAC 04 8.5% 78 37.5% 22 14.7 % 16 11.0% 01 3.7% 121 21% RoW 04 8.5% 28 13.4% 06 4.0% 09 6.2% 01 3.7% 48 8.3% Global total 2034 1958 1450 1115 498 7055 RoW total 73 3.6% 234 12% 87 6% 36 3.2% 24 4.8% 454 6.4 % 1. OEAC (Other Euro-American countries), OEAC were European countries other than the UK, Australia, New Zealand and Canada. 2. RoW comprised all other countries (i.e. all countries in Eastern Europe, Central and South America, Asia and Africa) 3. Others include: for  The Lancet : case reports, view points, public letters, essays, public health, violence in health, department of medical history, the world, world ideas, health and human rights, development of ethics, eponymous, clinical picture, reportage, adverse drug reactions, personal papers, medicine and law, personal papers; for the  JAMA : Patients relationships, grand rounds, clinical cross roads, rational clinical examinations, medicine and media, commentary, updates, letters from counters, public opinion and health, medical literature, health law and ethics, clinical cross roads; for the  NEJM : images, clinical problem solving, case records from Massachusetts general hospital, clinical implications of basic research, sounding board, clinical problem solving, special articles, for the  BMJ : drug point, practice and results, quality of life, history, practice point, lessons of every week; for the  Annals : past present and future, time and medicine, social means of medicine, technology of time, personal time, media and publication, NIH conference, in the balance, abroad. 4. The Lancet had 52 editorials and 298 commentaries. Editorials were written in house. 5. The Lancet had 262 research letters. We did not include these either in the correspondence or with the Original papers category. Other journals did not have such a category to compare. Table 2 Proportion of articles contributed by different regions of the RoW category to the total number of editorials, original articles and reviews. BMJ Lancet NEJM JAMA Annals Total 1 (%) India 2 1 2 0 0 05 (3) China 2 5 6 1 1 15 (10) Other Asian 6 8 3 2 0 19 (12) Sub Saharan Africa 8 25 2 1 0 36 (24) Latin America 2 11 4 5 2 24 (16) Middle East/North Africa 0 6 1 0 0 07 (5) Japan 0 8 5 0 4 17 (11) Israel 3 6 4 1 0 14 (9) Multi national 0 8 3 2 1 15 (10) Total 2  (%) 23 (15) 78 (52) 30 (20) 12 (8) 8 (5) 151 1 The % figures in this column represent the contribution of the specific country or region to the RoW papers in the table 2 The % figures in this row represent the contribution of the specific journal to the total RoW papers in the table. Note: This analysis only includes Original Articles, Editorials and Review Papers Within journals, variations in regional contributions from other regions were also notable. Thus, the proportion of articles from the UK was highest in the two journals published in the UK (BMJ and Lancet) while the proportion of articles from the USA was highest in the three journals published in the USA. Table  2  shows the relative contribution of different regions of the RoW category to the total number of editorials, original articles and reviews. Two developed countries (Japan and Israel) contribute a fifth of the literature from RoW, while the two most populous countries in the world (India and China) contribute about 13% together. A detailed analysis of the authorship of the 151 RoW articles showed that 104 (68.9%) involved collaborative authorship with developed countries in Europe or North America; only 43 (31.1%) were entirely independent efforts from the RoW. There were 118 original papers with at least one author from the RoW. Forty-five (38%) of them had a first author from the RoW; 32 (27%) had a last author from the RoW; and 36 (30%) had a corresponding author from the RoW. Only 25 (21%) of them had first, last and corresponding authors all from the RoW. There were 15 original papers in these journals with data from the RoW but without any authors from the RoW; of these 15, nine were in Lancet, four in BMJ and one each in JAMA and NEJM. Thus, the majority of the original articles originating from the RoW had contribution from the developed world authors.
Results
The contribution of the RoW to the research literature surveyed in these five high-impact journals was 6.5%. In the two British journals, 7.6% of the articles were from the RoW, whilst the proportion in the three American journals was 4.8%. This averages hides the fact that there is considerable variation between journals; thus, around 3.5% of articles in the two journals of national medical associations of the UK (BMJ) and USA (JAMA) were from the RoW as compared to 12% in the Lancet articles (Table  1 ). Indeed, more than half the articles from the RoW were published in just one journal, the Lancet (Table  2 ).The contribution of regions to the research literature in five leading journals1. OEAC (Other Euro-American countries), OEAC were European countries other than the UK, Australia, New Zealand and Canada.2. RoW comprised all other countries (i.e. all countries in Eastern Europe, Central and South America, Asia and Africa)3. Others include: for  The Lancet : case reports, view points, public letters, essays, public health, violence in health, department of medical history, the world, world ideas, health and human rights, development of ethics, eponymous, clinical picture, reportage, adverse drug reactions, personal papers, medicine and law, personal papers; for the  JAMA : Patients relationships, grand rounds, clinical cross roads, rational clinical examinations, medicine and media, commentary, updates, letters from counters, public opinion and health, medical literature, health law and ethics, clinical cross roads; for the  NEJM : images, clinical problem solving, case records from Massachusetts general hospital, clinical implications of basic research, sounding board, clinical problem solving, special articles, for the  BMJ : drug point, practice and results, quality of life, history, practice point, lessons of every week; for the  Annals : past present and future, time and medicine, social means of medicine, technology of time, personal time, media and publication, NIH conference, in the balance, abroad.The LancetJAMANEJMBMJAnnals4. The Lancet had 52 editorials and 298 commentaries. Editorials were written in house.5. The Lancet had 262 research letters. We did not include these either in the correspondence or with the Original papers category. Other journals did not have such a category to compare.Proportion of articles contributed by different regions of the RoW category to the total number of editorials, original articles and reviews.BMJLancetNEJMJAMAAnnalsTotal(%)Total1 The % figures in this column represent the contribution of the specific country or region to the RoW papers in the table2 The % figures in this row represent the contribution of the specific journal to the total RoW papers in the table.Note: This analysis only includes Original Articles, Editorials and Review PapersWithin journals, variations in regional contributions from other regions were also notable. Thus, the proportion of articles from the UK was highest in the two journals published in the UK (BMJ and Lancet) while the proportion of articles from the USA was highest in the three journals published in the USA. Table  2  shows the relative contribution of different regions of the RoW category to the total number of editorials, original articles and reviews. Two developed countries (Japan and Israel) contribute a fifth of the literature from RoW, while the two most populous countries in the world (India and China) contribute about 13% together. A detailed analysis of the authorship of the 151 RoW articles showed that 104 (68.9%) involved collaborative authorship with developed countries in Europe or North America; only 43 (31.1%) were entirely independent efforts from the RoW.There were 118 original papers with at least one author from the RoW. Forty-five (38%) of them had a first author from the RoW; 32 (27%) had a last author from the RoW; and 36 (30%) had a corresponding author from the RoW. Only 25 (21%) of them had first, last and corresponding authors all from the RoW. There were 15 original papers in these journals with data from the RoW but without any authors from the RoW; of these 15, nine were in Lancet, four in BMJ and one each in JAMA and NEJM. Thus, the majority of the original articles originating from the RoW had contribution from the developed world authors.Discussion This study presents findings of a survey of articles published in five high-impact general medical journals with the objective of describing the developing world's contribution to research literature over a single calendar year. Our way of classifying countries into developed (UK, USA, OEAC) and developing countries (RoW) has obvious inadequacies but we followed the same method adopted in an earlier paper [ 4 ]. Other euro-American countries (OEAC) shared many cultural and economic features. Rest of the world (RoW) included Eastern Europe, which although culturally related to Western Europe was not economically on the same level, and Japan, which was highly developed economically but did not share many cultural factors with OEAC. The key finding of our survey is that, only 6.5% of the publications in these journals have authors from countries where 90% of the world's population lives. There is a severe under representation of biomedical research from a vast section of the world in these five journals. In addition, there are a small but significant number of articles with data from the developing world without a single author from these countries. This is a troublesome finding that some would refer as 'safari research'. It is a separate ethical issue and journal editors need to look at it carefully. The reasons for under representation of researchers based in developing countries may include research barriers such as lack of funding, poor facilities, limited technical support and inadequate training. Many researchers from developing countries do not speak English as their first language. Fear of rejection by the journals, uncertainty about which journal would be best to publish research, a lack of the culture of publication, competing clinical commitments, different ministry and donor driven agendas for research, are some of the unseen barriers facing developing country researchers (10). The editors of leading medical journals may not have paid sufficient attention to these barriers, real and perceived, that clinical researcher in developing countries face [ 11 ]. We acknowledge that many developing country researchers choose to publish their work in national or regional journals that are not as high-impact as the journals we have reviewed. However, many researchers, irrespective of the country of their origin, also prefer to publish their work in journals with a high impact factor and circulation. This, inevitably, leads to a focus on leading journals published from the UK or USA. However, journals may be under some pressure to publish material, which is relevant to the majority of their readership. Thus, it is not surprising that journals from the UK have the majority of articles from UK institutions and similarly, journals from the USA tend to have most of their articles from US institutions. The BMJ admits that although the BMJ aspires to be more international, they cannot forget that they reach 80% doctors in Britain [ 12 ]. However all these journals are financially highly successful in global markets. Their international success brings responsibilities to the global community they serve and profits from [ 11 ]. Our findings are in agreement with other published findings in this area [ 13 ]. In a study of randomised controlled trials published in leading medical journals many of the diseases afflicting the south are understudied [ 14 ]. Even in the field of tropical medicine there were few contributions originating from countries with a low human development index (HDI) [ 15 ]. Another study, where the number of biomedical articles were normalized to the number of publications per million population, also shows an under representation of Asia, Africa and South America. The authors demonstrated that the number of biomedical publications increase according to the economic ranking of the country [ 16 ]. The same authors have shown in a similar study that publications per million population are more closely related to gross national product (GNP) and research and development expenditure [ 17 ]. The inescapable conclusion of this research is that USA, UK and other European countries dominate biomedical research, in part because of their wealth and investment in research. Irrespective of the method used to categorize countries in developing world, (by GNP, HDI or any other method), generation of new knowledge in biomedical research in these nations is insufficient. In a recent Nature paper on science publications Japan occupies 4th place, Israel 15th, China 19th, and India 22nd in the rank order of nations based on their share of top 1% of highly cited publications. Unsurprisingly the USA and UK occupies the two top positions [ 18 ]. There are many reasons to strive for a more just international distribution of biomedical research in leading journals. The burden of disease in the world falls heavily on developing countries and the pattern of this burden is likely to change in the next twenty years. Diseases like TB, HIV, Malaria, Dengue, and viral hemorrhagic fevers are now no longer tropical with increase in international travel, global warming, refugees, economic and military intervention and conflicts. Newly emerging infections from tropics such as SARS and bird flu can have devastating effects far away from tropics. In addition, diseases such as diabetes and obesity can no longer be considered as diseases in the developed world. As the impact and burden of these diseases are more in developing countries more research publications are needed from South. Clinicians and policy makers in many developing countries have limited access to international journals because medical libraries often need to make a choice from a number of journals due to financial constraints. Often, it is the high-impact journal, which is subscribed to. Thus, the proportion of international representation in these leading journals may be a crucial factor in influencing health policies in many countries. The importance of research goes well beyond its impact on health policies [ 11 ]. Thus, research on the epidemiology and management of diseases in different health systems raises the probability of identifying risk factors for diseases and identifying innovative approaches to their management. This fact was well reflected in the multi-center eclampsia trial [ 19 ]. Until this trial was carried out in Africa, South America and India, the subject of using magnesium sulfate in the management of eclampsia was controversial. The other good example is the only meningitis B vaccine in the world, which was developed by the Carlos J. Finlay Institute in Cuba and now saves lives all over the world [ 20 ]. Providing free journals electronically to the developing countries is a commendable step in correcting the thirst for new information [ 21 ]. However the one-way flow of information by making journals electronically free to developing world is unlikely to be sufficient [ 22 ]. By providing journals free to 'RoW', and propagating research which has been conducted in countries where only 10% of the disease burden is experienced is itself a moral and ethical issue. Ultimately, we believe that strengthening the health research capacity in developing world and providing reasonable opportunities for publications arising from the developing world are critical, not only for achieving biomedical research publication equity, but also advancing medical science.
Discussion
This study presents findings of a survey of articles published in five high-impact general medical journals with the objective of describing the developing world's contribution to research literature over a single calendar year.Our way of classifying countries into developed (UK, USA, OEAC) and developing countries (RoW) has obvious inadequacies but we followed the same method adopted in an earlier paper [ 4 ]. Other euro-American countries (OEAC) shared many cultural and economic features. Rest of the world (RoW) included Eastern Europe, which although culturally related to Western Europe was not economically on the same level, and Japan, which was highly developed economically but did not share many cultural factors with OEAC.The key finding of our survey is that, only 6.5% of the publications in these journals have authors from countries where 90% of the world's population lives. There is a severe under representation of biomedical research from a vast section of the world in these five journals. In addition, there are a small but significant number of articles with data from the developing world without a single author from these countries. This is a troublesome finding that some would refer as 'safari research'. It is a separate ethical issue and journal editors need to look at it carefully.The reasons for under representation of researchers based in developing countries may include research barriers such as lack of funding, poor facilities, limited technical support and inadequate training. Many researchers from developing countries do not speak English as their first language. Fear of rejection by the journals, uncertainty about which journal would be best to publish research, a lack of the culture of publication, competing clinical commitments, different ministry and donor driven agendas for research, are some of the unseen barriers facing developing country researchers (10). The editors of leading medical journals may not have paid sufficient attention to these barriers, real and perceived, that clinical researcher in developing countries face [ 11 ].We acknowledge that many developing country researchers choose to publish their work in national or regional journals that are not as high-impact as the journals we have reviewed. However, many researchers, irrespective of the country of their origin, also prefer to publish their work in journals with a high impact factor and circulation. This, inevitably, leads to a focus on leading journals published from the UK or USA. However, journals may be under some pressure to publish material, which is relevant to the majority of their readership. Thus, it is not surprising that journals from the UK have the majority of articles from UK institutions and similarly, journals from the USA tend to have most of their articles from US institutions. The BMJ admits that although the BMJ aspires to be more international, they cannot forget that they reach 80% doctors in Britain [ 12 ]. However all these journals are financially highly successful in global markets. Their international success brings responsibilities to the global community they serve and profits from [ 11 ].Our findings are in agreement with other published findings in this area [ 13 ]. In a study of randomised controlled trials published in leading medical journals many of the diseases afflicting the south are understudied [ 14 ]. Even in the field of tropical medicine there were few contributions originating from countries with a low human development index (HDI) [ 15 ]. Another study, where the number of biomedical articles were normalized to the number of publications per million population, also shows an under representation of Asia, Africa and South America. The authors demonstrated that the number of biomedical publications increase according to the economic ranking of the country [ 16 ]. The same authors have shown in a similar study that publications per million population are more closely related to gross national product (GNP) and research and development expenditure [ 17 ]. The inescapable conclusion of this research is that USA, UK and other European countries dominate biomedical research, in part because of their wealth and investment in research. Irrespective of the method used to categorize countries in developing world, (by GNP, HDI or any other method), generation of new knowledge in biomedical research in these nations is insufficient. In a recent Nature paper on science publications Japan occupies 4th place, Israel 15th, China 19th, and India 22nd in the rank order of nations based on their share of top 1% of highly cited publications. Unsurprisingly the USA and UK occupies the two top positions [ 18 ].There are many reasons to strive for a more just international distribution of biomedical research in leading journals. The burden of disease in the world falls heavily on developing countries and the pattern of this burden is likely to change in the next twenty years. Diseases like TB, HIV, Malaria, Dengue, and viral hemorrhagic fevers are now no longer tropical with increase in international travel, global warming, refugees, economic and military intervention and conflicts. Newly emerging infections from tropics such as SARS and bird flu can have devastating effects far away from tropics. In addition, diseases such as diabetes and obesity can no longer be considered as diseases in the developed world. As the impact and burden of these diseases are more in developing countries more research publications are needed from South.Clinicians and policy makers in many developing countries have limited access to international journals because medical libraries often need to make a choice from a number of journals due to financial constraints. Often, it is the high-impact journal, which is subscribed to. Thus, the proportion of international representation in these leading journals may be a crucial factor in influencing health policies in many countries. The importance of research goes well beyond its impact on health policies [ 11 ]. Thus, research on the epidemiology and management of diseases in different health systems raises the probability of identifying risk factors for diseases and identifying innovative approaches to their management. This fact was well reflected in the multi-center eclampsia trial [ 19 ]. Until this trial was carried out in Africa, South America and India, the subject of using magnesium sulfate in the management of eclampsia was controversial. The other good example is the only meningitis B vaccine in the world, which was developed by the Carlos J. Finlay Institute in Cuba and now saves lives all over the world [ 20 ].Providing free journals electronically to the developing countries is a commendable step in correcting the thirst for new information [ 21 ]. However the one-way flow of information by making journals electronically free to developing world is unlikely to be sufficient [ 22 ]. By providing journals free to 'RoW', and propagating research which has been conducted in countries where only 10% of the disease burden is experienced is itself a moral and ethical issue.Ultimately, we believe that strengthening the health research capacity in developing world and providing reasonable opportunities for publications arising from the developing world are critical, not only for achieving biomedical research publication equity, but also advancing medical science.Competing interests We would like to state here that our conflict of interest if at all would be due to the fact that we come from the developing world.
Competing interests
We would like to state here that our conflict of interest if at all would be due to the fact that we come from the developing world.Authors' contributions All authors were involved in all the components of this paper, right from the start, in formulating and developing the idea, collecting the data, drafting the first version and revising it and approving the final version.
Authors' contributions
All authors were involved in all the components of this paper, right from the start, in formulating and developing the idea, collecting the data, drafting the first version and revising it and approving the final version.Pre-publication history The pre-publication history for this paper can be accessed here:
Pre-publication history
The pre-publication history for this paper can be accessed here:


Background The carotid body paraganglioma (chemodectoma) is a relatively rare neoplasm of obscure origin. These are usually benign and commonly present as asymptomatic cervical mass.
Background
The carotid body paraganglioma (chemodectoma) is a relatively rare neoplasm of obscure origin. These are usually benign and commonly present as asymptomatic cervical mass.Patients and methods Records of 12 patients (9 female and 3 male) with carotid body tumors treated between 1982 and 2003, treated at our center were retrospectively reviewed. Data on classification, clinical presentation, and surgical treatment were extracted from the case records. Surgical complications and treatment outcome were noted and survival was calculated by actuarial method. The literature on carotid body paraganglioma was reviewed.
Patients and methods
Records of 12 patients (9 female and 3 male) with carotid body tumors treated between 1982 and 2003, treated at our center were retrospectively reviewed. Data on classification, clinical presentation, and surgical treatment were extracted from the case records. Surgical complications and treatment outcome were noted and survival was calculated by actuarial method. The literature on carotid body paraganglioma was reviewed.Results The average age of the patients was 52 years (range 30–78 years). Eight of these cases presented as a large asymptomatic non-tender neck mass, and two each presented with dysphagia, and hoarseness of voice. As per Shamblin classification seven of tumors were type II and 5 were types III. In 7 cases subadventitial tumor excision was performed, while in 5 associated resection of both external and internal carotid arteries was carried out. The artery was repaired by end-to-end anastomosis in one case, with Dacron graft in one case, and with saphenous vein graft in 3 cases. There was no operative mortality. After a mean follow-up of 6.2 years (range 6 months to 20 years), there were no signs of tumor recurrence in any of the cases.
Results
The average age of the patients was 52 years (range 30–78 years). Eight of these cases presented as a large asymptomatic non-tender neck mass, and two each presented with dysphagia, and hoarseness of voice. As per Shamblin classification seven of tumors were type II and 5 were types III. In 7 cases subadventitial tumor excision was performed, while in 5 associated resection of both external and internal carotid arteries was carried out. The artery was repaired by end-to-end anastomosis in one case, with Dacron graft in one case, and with saphenous vein graft in 3 cases. There was no operative mortality. After a mean follow-up of 6.2 years (range 6 months to 20 years), there were no signs of tumor recurrence in any of the cases.Conclusions Surgical excision is the treatment of choice for carotid body paragangliomas although radiation therapy is an option for patients who are not ideal candidates for surgery. For the tumors that are in intimate contact with carotid arteries, the treatment by vascular surgeon is recommended.
Conclusions
Surgical excision is the treatment of choice for carotid body paragangliomas although radiation therapy is an option for patients who are not ideal candidates for surgery. For the tumors that are in intimate contact with carotid arteries, the treatment by vascular surgeon is recommended.

Background Paraganglioma arising from the carotid body are relatively rare tumors but constitute majority of head and neck paragangliomas (60–70%) [ 1 - 6 ]. The term paraganglia was first used by Kohn in the early twentieth century and is the most appropriate nomenclature from an embryologic standpoint [ 3 - 5 ]. Other terms such as carotid body tumor, glomus tumor, chemodectomas, and nonchromaffin tumor are less accurate terms and therefore should be best avoided [ 7 - 13 ]. The neoplasm present as asymptomatic neck mass. We report our experience with surgically treated carotid body tumors.
Background
Paraganglioma arising from the carotid body are relatively rare tumors but constitute majority of head and neck paragangliomas (60–70%) [ 1 - 6 ]. The term paraganglia was first used by Kohn in the early twentieth century and is the most appropriate nomenclature from an embryologic standpoint [ 3 - 5 ]. Other terms such as carotid body tumor, glomus tumor, chemodectomas, and nonchromaffin tumor are less accurate terms and therefore should be best avoided [ 7 - 13 ]. The neoplasm present as asymptomatic neck mass. We report our experience with surgically treated carotid body tumors.Patients and methods Between 1982 and 2003, 12 patients (9 female and 3 male) with carotid body paraganglioma were surgically treated at the Institute for Cardiovascular Diseases, Serbian Clinical Centre. Mean age of the patients was 52 years (range 30–78 years). The records of these patients were retrospectively reviewed for clinical presentation, diagnostic work-up, surgical treatment, and outcome. Descriptive data was presented as frequency and percentage. Survival was calculated by actuarial method. World literature on carotid body paraganglioma was reviewed. The articles were extracted using the key words carotid body and paraganglioma. All the patients were followed-up periodically every 6 months for the first year, yearly for next 5 years, thereafter only select patients were followed. The patients who had undergone carotid artery repair were followed-up with yearly duplex scanning; two patients were followed by a computerized tomography (CT) scan, and one by regular magnetic resonance (MR) imaging.
Patients and methods
Between 1982 and 2003, 12 patients (9 female and 3 male) with carotid body paraganglioma were surgically treated at the Institute for Cardiovascular Diseases, Serbian Clinical Centre. Mean age of the patients was 52 years (range 30–78 years). The records of these patients were retrospectively reviewed for clinical presentation, diagnostic work-up, surgical treatment, and outcome. Descriptive data was presented as frequency and percentage. Survival was calculated by actuarial method. World literature on carotid body paraganglioma was reviewed. The articles were extracted using the key words carotid body and paraganglioma.All the patients were followed-up periodically every 6 months for the first year, yearly for next 5 years, thereafter only select patients were followed. The patients who had undergone carotid artery repair were followed-up with yearly duplex scanning; two patients were followed by a computerized tomography (CT) scan, and one by regular magnetic resonance (MR) imaging.Results Eight cases presented as large non-tender neck masses located just anterior to the sternocleidomastoid muscle, two patients presented with dysphagia due to hypoglossal nerve compression, while two other had hoarseness of voice. The duplex ultrasonography and selective carotid angiography were used for diagnosis in the eleven cases, CT in five, and MR imaging in three cases (Figure  1  and  2 ). In one case the diagnosis was established on intraoperative exploration. Figure 1 Selective carotid angiography showed carotid body paraganglioma. The typical separation (''lyre sign") of external and internal carotid arteries, are presented. Figure 2 Selective carotid angiography showed hypervascularization of the carotid body paraganglioma mostly from the external carotid artery. Intraoperatively on exploration of the neck seven of the cases showed a medium size tumor intimately associated and compressing carotid vessels (Shamblin II), and a large tumor involving carotid vessels in five cases (Shamblin III). In 7 cases of Shamblin II carotid body paraganglioma a subadventitial tumor excision was performed while in other 5 cases both external and internal carotid arteries were resected. One of these was repaired by end-to-end anastomosis, one with interposition of Dacron ®  graft, and other 3 were repaired with reversed saphenous vein graft. The histological examination showed no signs of malignancy in any of the tumors. In two cases transient hypoglossal nerve palsy was noticed. Another patient had unexpected postoperative hoarseness of voice due to the transient vagus nerve palsy. All these three cases subsequently recovered. There was no operative mortality. The patients were followed-up from the 6 months to 20 years (mean 6.2 year) no local, regional or distant metastasis was noticed. The actuarial survival was 100%.
Results
Eight cases presented as large non-tender neck masses located just anterior to the sternocleidomastoid muscle, two patients presented with dysphagia due to hypoglossal nerve compression, while two other had hoarseness of voice. The duplex ultrasonography and selective carotid angiography were used for diagnosis in the eleven cases, CT in five, and MR imaging in three cases (Figure  1  and  2 ). In one case the diagnosis was established on intraoperative exploration.Intraoperatively on exploration of the neck seven of the cases showed a medium size tumor intimately associated and compressing carotid vessels (Shamblin II), and a large tumor involving carotid vessels in five cases (Shamblin III). In 7 cases of Shamblin II carotid body paraganglioma a subadventitial tumor excision was performed while in other 5 cases both external and internal carotid arteries were resected. One of these was repaired by end-to-end anastomosis, one with interposition of Dacron ®  graft, and other 3 were repaired with reversed saphenous vein graft.The histological examination showed no signs of malignancy in any of the tumors. In two cases transient hypoglossal nerve palsy was noticed. Another patient had unexpected postoperative hoarseness of voice due to the transient vagus nerve palsy. All these three cases subsequently recovered. There was no operative mortality. The patients were followed-up from the 6 months to 20 years (mean 6.2 year) no local, regional or distant metastasis was noticed. The actuarial survival was 100%.Discussion The carotid body was first described by von Haller in 1743 [ 14 ]. It is highly specialized organ located at the common carotid artery bifurcation. Its feeding vessels run primarily from the external carotid artery. The function of the carotid body is related to autonomic control of the respiratory and cardiovascular systems, as well as blood temperature [ 3 , 10 , 12 , 15 - 23 ]. Paraganglioma is a relatively rare neoplasm occurring in carotid body [ 1 - 6 ]. The carotid body paraganglioma is more common in women [ 2 - 5 , 20 , 25 - 28 ]. The incidence of bilateral carotid body lesions is approximately 10%. Most of these lesions are benign however malignant behavior is often encountered. For diagnosis of malignant carotid body paraganlioma there are no clear histological characteristics that differentiate it from benign lesions. This diagnosis is reserved for the tumors with local, regional and distant metastasis. The rate of malignancy is reported to be 6–12.5% of all cases [ 3 - 5 , 9 , 11 , 29 - 35 ]. The 7–9% of the cases are hereditary [ 2 , 4 , 20 , 25 - 28 , 36 ]. None of our cases were bilateral or hereditary. Carotid body paraganglioma often present as slow growing, non-tender neck masses located just anterior to the sternocleidomastoid muscle at the level of the hyoid. The tumor is mobile in the lateral plane but its mobility is limited in the cephalocaudal direction [ 3 - 5 , 13 - 15 , 21 , 26 , 36 - 38 ]. Occasionally the tumor mass may transmit the carotid pulse or demonstrate a bruit or thrill [ 39 ]. Because of its location in close approximation to carotid vessels and X-XII cranial nerves, tumors enlargement causes progressive symptoms such as dysphagia (two of our cases), odynophagia, hoarseness of voice (two of our cases) or other cranial nerve deficits [ 2 - 5 , 14 , 26 , 27 , 32 , 37 , 40 ]. The patients may give a history suggestive of symptoms associated with catecholamine production such as fluctuating hypertension, blushing, obstructive sleep apnea and palpitations [ 3 - 5 , 10 , 14 , 15 , 21 - 23 , 37 ]. Size of the tumor has a great importance not only for its clinical manifestations but also for treatment. In 1971, Shamblin introduced a classification system based on tumors size [ 41 ]. They classified small tumors that could be easily dissected away from the vessels as group I. Group II (7 of our cases) included paragangliomas of medium size that were intimately associated and compressed carotid vessels, but could be separated with careful subadventitial dissection. Group III consisted of (5 of our cases) tumors that were large and typically encased the carotid artery requiring partial or complete vessel resection and replacement. Histologically, carotid body paraganglioma resemble the normal architecture of the carotid body. The tumors are highly vascular, and between the many capillaries are clusters of cells called Zellballen [ 41 ]. The carotid angiography is the most useful diagnostic test for paragangliomas. The angiography demonstrates tumor blood supply and widening of the carotid bifurcation by a well-defined tumor blush ("lyre sign"), which is classic pathognomonic angiographic finding [ 5 , 8 , 37 - 39 , 42 , 43 ]. MR and contrast CT are more effective non-invasive imagining modalities comparing with duplex ultrasonography, especially for small tumors [ 3 , 37 - 39 , 42 - 45 ]. Radioimmunodetection of carotid body paraganglioma by  111 In labeled anti-CEA antibody is also described in literature [ 9 , 46 ]. The differential diagnosis includes other tumors in this area, carotid artery aneurysms and elongation. For this reason using of precutaneous fine-needle aspiration for preoperative diagnosis of carotid body paraganglioma, can be very dangerous [ 47 ]. Resection of carotid body paraganglioma carries inherent risks of injury to the cranial nerves, carotid arteries as well excessive blood loss. Reigner first attempted resection of a carotid body paraganglioma in 1880, but the patients did not survive [ 48 ]. Maydel was the first to remove a carotid body paraganglioma successfully in 1886, but the patient became aphasic and hemiplegics due to internal carotid artery ligature [ 49 ]. In 1903, Scudder performed the first successful removal of carotid body paraganglioma [ 50 ]. The surgical excision with careful subadventitial dissection is treatment of choice for most carotid body paragangliomas (Shamblin I and II) [ 2 - 6 , 14 - 18 , 34 , 37 - 40 , 43 ]. The Shamblin III of carotid body paraganglioma requires resection of the external and/or internal carotid artery. If the internal carotid is encased in tumor or damaged during resection, immediate repair/replacement should be performed [ 15 , 37 , 39 , 40 , 42 , 43 , 51 , 52 ]. The second problem during tumor excision is bleeding, which sometimes can be massive. In such cases clamping of all carotid arteries is useful, with placement of internal carotid shunt [ 18 , 35 , 37 ]. Having in mind our experience with surgical treatment of both carotid body gangliomas as well as carotid stenosis, we recommend Pruitt-Inahara double balloon occlusive internal carotid shunt [ 37 ]. The placement of this shunt through incision on the common carotid artery contributes to the adequate bleeding control from the common and internal carotid arteries, as well as brain protection. This procedure gave a clean and dry operative field during tumor removal [ 3 , 37 ]. Some other articles recommend angiographic embolization preoperatively [ 3 , 23 , 37 , 42 , 53 - 55 ]. The Preoperative embolization of a carotid body paraganglioma can be performed by ethanol or polyvinyl alcohol. The finally result is a complete devascularization [ 55 ]. Earlier the carotid body paragangliomas were considered radioresistant [ 34 ]. However, more recent studies indicate good responses to radiation therapy [ 11 , 30 ]. Most authors recommend radiotherapy for giant and recurrent carotid body paragangliomas, and with malignant carotid body paragangliomas metastatic to the regional lymph nodes [ 8 , 33 - 36 ]. The modern surgical techniques have reduced the risk of postoperative stroke in carotid body paraganglioma resection to less than 5% [ 37 , 40 , 56 ]. However, the incidence of cranial nerve injury remains strikingly high, ranging from 20% to 40% [ 37 , 38 , 48 , 56 , 57 ]. In 20% of patients the neurological deficits is permanent. We found two (18%) transient hypoglossal, and one transient vagus nerve damage. recurrence after complete resection occurs in approximately 6% of patients [ 15 , 37 , 39 , 40 , 42 , 43 , 51 , 52 ]. In our study however, there were no recurrences. The patients with internal carotid artery reconstruction should undergo duplex scanning periodically to identify graft stenosis.
Discussion
The carotid body was first described by von Haller in 1743 [ 14 ]. It is highly specialized organ located at the common carotid artery bifurcation. Its feeding vessels run primarily from the external carotid artery. The function of the carotid body is related to autonomic control of the respiratory and cardiovascular systems, as well as blood temperature [ 3 , 10 , 12 , 15 - 23 ]. Paraganglioma is a relatively rare neoplasm occurring in carotid body [ 1 - 6 ].The carotid body paraganglioma is more common in women [ 2 - 5 , 20 , 25 - 28 ]. The incidence of bilateral carotid body lesions is approximately 10%. Most of these lesions are benign however malignant behavior is often encountered. For diagnosis of malignant carotid body paraganlioma there are no clear histological characteristics that differentiate it from benign lesions. This diagnosis is reserved for the tumors with local, regional and distant metastasis. The rate of malignancy is reported to be 6–12.5% of all cases [ 3 - 5 , 9 , 11 , 29 - 35 ]. The 7–9% of the cases are hereditary [ 2 , 4 , 20 , 25 - 28 , 36 ]. None of our cases were bilateral or hereditary.Carotid body paraganglioma often present as slow growing, non-tender neck masses located just anterior to the sternocleidomastoid muscle at the level of the hyoid. The tumor is mobile in the lateral plane but its mobility is limited in the cephalocaudal direction [ 3 - 5 , 13 - 15 , 21 , 26 , 36 - 38 ]. Occasionally the tumor mass may transmit the carotid pulse or demonstrate a bruit or thrill [ 39 ]. Because of its location in close approximation to carotid vessels and X-XII cranial nerves, tumors enlargement causes progressive symptoms such as dysphagia (two of our cases), odynophagia, hoarseness of voice (two of our cases) or other cranial nerve deficits [ 2 - 5 , 14 , 26 , 27 , 32 , 37 , 40 ]. The patients may give a history suggestive of symptoms associated with catecholamine production such as fluctuating hypertension, blushing, obstructive sleep apnea and palpitations [ 3 - 5 , 10 , 14 , 15 , 21 - 23 , 37 ].Size of the tumor has a great importance not only for its clinical manifestations but also for treatment. In 1971, Shamblin introduced a classification system based on tumors size [ 41 ]. They classified small tumors that could be easily dissected away from the vessels as group I. Group II (7 of our cases) included paragangliomas of medium size that were intimately associated and compressed carotid vessels, but could be separated with careful subadventitial dissection. Group III consisted of (5 of our cases) tumors that were large and typically encased the carotid artery requiring partial or complete vessel resection and replacement. Histologically, carotid body paraganglioma resemble the normal architecture of the carotid body. The tumors are highly vascular, and between the many capillaries are clusters of cells called Zellballen [ 41 ].The carotid angiography is the most useful diagnostic test for paragangliomas. The angiography demonstrates tumor blood supply and widening of the carotid bifurcation by a well-defined tumor blush ("lyre sign"), which is classic pathognomonic angiographic finding [ 5 , 8 , 37 - 39 , 42 , 43 ]. MR and contrast CT are more effective non-invasive imagining modalities comparing with duplex ultrasonography, especially for small tumors [ 3 , 37 - 39 , 42 - 45 ]. Radioimmunodetection of carotid body paraganglioma by  111 In labeled anti-CEA antibody is also described in literature [ 9 , 46 ]. The differential diagnosis includes other tumors in this area, carotid artery aneurysms and elongation. For this reason using of precutaneous fine-needle aspiration for preoperative diagnosis of carotid body paraganglioma, can be very dangerous [ 47 ].Resection of carotid body paraganglioma carries inherent risks of injury to the cranial nerves, carotid arteries as well excessive blood loss. Reigner first attempted resection of a carotid body paraganglioma in 1880, but the patients did not survive [ 48 ]. Maydel was the first to remove a carotid body paraganglioma successfully in 1886, but the patient became aphasic and hemiplegics due to internal carotid artery ligature [ 49 ]. In 1903, Scudder performed the first successful removal of carotid body paraganglioma [ 50 ]. The surgical excision with careful subadventitial dissection is treatment of choice for most carotid body paragangliomas (Shamblin I and II) [ 2 - 6 , 14 - 18 , 34 , 37 - 40 , 43 ]. The Shamblin III of carotid body paraganglioma requires resection of the external and/or internal carotid artery. If the internal carotid is encased in tumor or damaged during resection, immediate repair/replacement should be performed [ 15 , 37 , 39 , 40 , 42 , 43 , 51 , 52 ]. The second problem during tumor excision is bleeding, which sometimes can be massive. In such cases clamping of all carotid arteries is useful, with placement of internal carotid shunt [ 18 , 35 , 37 ]. Having in mind our experience with surgical treatment of both carotid body gangliomas as well as carotid stenosis, we recommend Pruitt-Inahara double balloon occlusive internal carotid shunt [ 37 ]. The placement of this shunt through incision on the common carotid artery contributes to the adequate bleeding control from the common and internal carotid arteries, as well as brain protection. This procedure gave a clean and dry operative field during tumor removal [ 3 , 37 ]. Some other articles recommend angiographic embolization preoperatively [ 3 , 23 , 37 , 42 , 53 - 55 ]. The Preoperative embolization of a carotid body paraganglioma can be performed by ethanol or polyvinyl alcohol. The finally result is a complete devascularization [ 55 ]. Earlier the carotid body paragangliomas were considered radioresistant [ 34 ]. However, more recent studies indicate good responses to radiation therapy [ 11 , 30 ]. Most authors recommend radiotherapy for giant and recurrent carotid body paragangliomas, and with malignant carotid body paragangliomas metastatic to the regional lymph nodes [ 8 , 33 - 36 ].The modern surgical techniques have reduced the risk of postoperative stroke in carotid body paraganglioma resection to less than 5% [ 37 , 40 , 56 ]. However, the incidence of cranial nerve injury remains strikingly high, ranging from 20% to 40% [ 37 , 38 , 48 , 56 , 57 ]. In 20% of patients the neurological deficits is permanent. We found two (18%) transient hypoglossal, and one transient vagus nerve damage. recurrence after complete resection occurs in approximately 6% of patients [ 15 , 37 , 39 , 40 , 42 , 43 , 51 , 52 ]. In our study however, there were no recurrences. The patients with internal carotid artery reconstruction should undergo duplex scanning periodically to identify graft stenosis.Conclusion Early operative management is warranted to avoid the possibility of eventual metastasis and progressive local invasion to the point of inoperability. In case of tumors intimately contact with carotid arteries, the treatment by vascular surgeon is recommended.
Conclusion
Early operative management is warranted to avoid the possibility of eventual metastasis and progressive local invasion to the point of inoperability. In case of tumors intimately contact with carotid arteries, the treatment by vascular surgeon is recommended.Competing interests The author(s) declare that they have no competing interests.
Competing interests
The author(s) declare that they have no competing interests.Funding source Nil
Funding source
NilAuthors' contributions LBD:  Preperation of draft manuscript VBD:  Literature search, data collection DMV:  Study design, data analysis, interpretation, preparation of draft RPS:  Study coordination, data interpretation, manuscript preperation SND:  Manuscript editing, preparation of final manuscript for publication All authors read and approved the manuscript.
Authors' contributions
LBD:  Preperation of draft manuscriptLBD:VBD:  Literature search, data collectionVBD:DMV:  Study design, data analysis, interpretation, preparation of draftDMV:RPS:  Study coordination, data interpretation, manuscript preperationRPS:SND:  Manuscript editing, preparation of final manuscript for publicationSND:All authors read and approved the manuscript.