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View and Review • Arq. Neuro-Psiquiatr. 78 (09) • Sept 2020 • https://doi.org/10.1590/0004-282X20200016   copy

Deep brain stimulation treatment in dystonia: a bibliometric analysis

Estimulação cerebral profunda no tratamento de distonia: uma análise bibliométrica

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Background:

Dystonia is a heterogeneous disorder that, when refractory to medical treatment, may have a favorable response to deep brain stimulation (DBS). A practical way to have an overview of a research domain is through a bibliometric analysis, as it makes it more accessible for researchers and others outside the field to have an idea of its directions and needs.

Objective:

To analyze the 100 most cited articles in the use of DBS for dystonia treatment in the last 30 years.

Methods:

The research protocol was performed in June 2019 in Elsevier’s Scopus database, by retrieving the most cited articles regarding DBS in dystonia. We analyzed authors, year of publication, country, affiliation, and targets of DBS.

Results:

Articles are mainly published in Movement Disorders (19%), Journal of Neurosurgery (9%), and Neurology (9%). European countries offer significant contributions (57% of our sample). France (192.5 citations/paper) and Germany (144.1 citations/paper) have the highest citation rates of all countries. The United States contributes with 31% of the articles, with 129.8 citations/paper. The publications are focused on General outcomes (46%), followed by Long-term outcomes (12.5%), and Complications (11%), and the leading type of dystonia researched is idiopathic or inherited, isolated, segmental or generalized dystonia, with 27% of articles and 204.3 citations/paper.

Conclusions:

DBS in dystonia research is mainly published in a handful of scientific journals and focused on the outcomes of the surgery in idiopathic or inherited, isolated, segmental or generalized dystonia, and with globus pallidus internus as the main DBS target.

Keywords:
Bibliometrics; Deep Brain Stimulation; Dystonia

RESUMO

Introdução:

A distonia é uma doença heterogênea que, quando refratária ao tratamento medicamentoso, pode ter uma resposta favorável à estimulação encefálica profunda (EEP). Uma forma prática de ter uma visão desta área de pesquisa é por meio de análise bibliométrica, pois permite aos pesquisadores e terceiros a terem uma ideia das tendências e necessidades da área.

Objetivo:

Analisar os 100 artigos mais citados no tratamento de distonia pelo uso de EEP nos últimos 30 anos.

Métodos:

O protocolo de pesquisa foi realizado em junho de 2019 através da base de dados Scopus da Elsevier, em que se obteve os artigos mais citados na área de tratamento de distonia com EEP. Analisaram-se variáveis como autores, ano de publicação, país, afiliação, e alvos de EEP.

Resultados:

Os artigos foram principalmente publicados principalmente na Movement Disorders (19%), no Journal of Neurosurgery (9%), e na Neurology (9%). Os países europeus oferecem contribuições significativas (57% da amostra). A França (192,5 citações/artigo) e a Alemanha (144,1 citações/artigo) possuem as mais altas taxas de citações dentre todos os países. Os Estados Unidos contribuem com 31% dos artigos da amostra (129,8 citações/artigo). As publicações focaram em Desfechos gerais (46%), seguido de Desfechos a longo prazo (12,5%), e Complicações (11%). O principal tipo de distonia pesquisado foi distonia generalizada ou segmentar, idiopática ou hereditária, isolada, abrangendo 27% dos artigos e 204,3 citações/artigo.

Conclusões:

A pesquisa de EEP em distonia é publicada em seletos periódicos científicos e foca nos desfechos da cirurgia, nas distonias generalizadas ou segmentares, idiopáticas ou hereditárias, isoladas, sendo o globus pallidus internus o principal alvo da EEP.

Palavras-chave:
Bibliometria; Estimulação Encefálica Profunda; Distonia

INTRODUCTION

Dystonia is a heterogeneous movement disorder characterized by sustained or intermittent muscle contractions leading to abnormal movements and postures11. Albanese A, Bhatia K, Bressman SB, Delong MR, Fahn S, Fung VS, et al. Phenomenology and classification of dystonia: a consensus update. Mov Disord. 2013 Jun;28(7):863-73. https://doi.org/10.1002/mds.25475
https://doi.org/https://doi.org/10.1002/... . It can be classified by its clinical characteristics, including body distribution (focal, segmental, multifocal, generalized, or hemidystonia) and associated features (isolated or combined); and etiology (idiopathic, inherited or acquired)11. Albanese A, Bhatia K, Bressman SB, Delong MR, Fahn S, Fung VS, et al. Phenomenology and classification of dystonia: a consensus update. Mov Disord. 2013 Jun;28(7):863-73. https://doi.org/10.1002/mds.25475
https://doi.org/https://doi.org/10.1002/... . The treatment of dystonia is aimed at providing symptomatic relief for the motor symptoms, improving pain, and avoiding musculoskeletal complications such as joint contractures22. Cury RG, Kalia SK, Shah BB, Jimenez-Shahed J, Prashanth LK, Moro E. Surgical treatment of dystonia. Expert Rev Neurother. 2018 May;18(6):477-92. https://doi.org/10.1080/14737175.2018.1478288
https://doi.org/https://doi.org/10.1080/... . Medical treatment is usually limited to the side effects and has small symptomatic relief33. Comella CL. Dystonia: Then and now. Parkinsonism Relat Disord. 2018 Jan;46 Suppl 1:S66-S69. https://doi.org/10.1016/j.parkreldis.2017.06.025
https://doi.org/https://doi.org/10.1016/... . Botulinum toxin is a good option for focal dystonia; however, in generalized and segmental dystonia, it may have a limited effect due to its dose limits.

In general, most dystonic patients are selected for surgical treatment when the pharmacological treatment has revealed inadequate response; therefore, an individualized approach is the norm. Ablative procedures were largely performed in dystonia, before the advent of deep brain stimulation (DBS). Nowadays, pallidotomy is usually an option, for instance in acquired static dystonia and in status dystonicus. DBS should be considered in the inherited or idiopathic generalized dystonias that do not have reasonable symptomatic control with medication and in which disabilities impact patient’s QoL. In inherited or idiopathic segmental and focal dystonias and other acquired forms like tardive dyskinesia or cerebral palsy, it should be considered when refractory to pharmacological treatments22. Cury RG, Kalia SK, Shah BB, Jimenez-Shahed J, Prashanth LK, Moro E. Surgical treatment of dystonia. Expert Rev Neurother. 2018 May;18(6):477-92. https://doi.org/10.1080/14737175.2018.1478288
https://doi.org/https://doi.org/10.1080/... . DBS, usually targeting the globus pallidus internus (GPi), has a response in idiopathic or inherited isolated segmental or generalized dystonia that varies between 43-65%22. Cury RG, Kalia SK, Shah BB, Jimenez-Shahed J, Prashanth LK, Moro E. Surgical treatment of dystonia. Expert Rev Neurother. 2018 May;18(6):477-92. https://doi.org/10.1080/14737175.2018.1478288
https://doi.org/https://doi.org/10.1080/... . GPi is the most common target; however, initially, thalamic targets were used22. Cury RG, Kalia SK, Shah BB, Jimenez-Shahed J, Prashanth LK, Moro E. Surgical treatment of dystonia. Expert Rev Neurother. 2018 May;18(6):477-92. https://doi.org/10.1080/14737175.2018.1478288
https://doi.org/https://doi.org/10.1080/... . Recently, the subthalamic nucleus (STN) is also being considered a viable target44. Lin S, Wu Y, Li H, Zhang C, Wang T, Pan Y, et al. Deep brain stimulation of the globus pallidus internus versus the subthalamic nucleus in isolated dystonia. J Neurosurg. 2019 Mar:1-12. https://doi.org/10.3171/2018.12.JNS181927
https://doi.org/https://doi.org/10.3171/... ,55. Schjerling L, Hjermind LE, Jespersen B, Madsen FF, Brennum J, Jensen SR, Let al. A randomized double-blind crossover trial comparing subthalamic and pallidal deep brain stimulation for dystonia. J J Neurosurg. 2013 Dec;119(6):1537-45. https://doi.org/10.3171/2013.8.JNS13844
https://doi.org/https://doi.org/10.3171/... .

A practical way to identify which are the most influential authors, journals, and countries in a particular field is through a bibliometric analysis66. Ramos MB, Koterba E, Rosi Junior J, Teixeira MJ, Figueiredo EG. A Bibliometric analysis of the most cited articles in Neurocritical Care Research. Neurocrit Care. 2019 Oct;31(2):365-72. https://doi.org/10.1007/s12028-019-00731-6
https://doi.org/https://doi.org/10.1007/... . It makes it more accessible for researchers and others outside the field to have an overview of its directions and needs77. King NK, Tam J, Fasano A, Lozano AM. The most cited works in Essential Tremor and Dystonia. Tremor Other Hyperkinet Mov (N Y). 2016 Apr;6:310. https://doi.org/10.7916/D8NG4QHP
https://doi.org/https://doi.org/10.7916/... . The literature does present bibliometric analysis on various themes, such as neurocritical care66. Ramos MB, Koterba E, Rosi Junior J, Teixeira MJ, Figueiredo EG. A Bibliometric analysis of the most cited articles in Neurocritical Care Research. Neurocrit Care. 2019 Oct;31(2):365-72. https://doi.org/10.1007/s12028-019-00731-6
https://doi.org/https://doi.org/10.1007/... , back pain88. Huang W, Wang L, Wang B, Yu L, Yu X. Top 100 cited articles on back pain research: a citation analysis. Spine (Phila Pa 1976). 2016 Nov;41(21):1683-92. https://doi.org/10.1097/BRS.0000000000001736
https://doi.org/https://doi.org/10.1097/... , essential tremor77. King NK, Tam J, Fasano A, Lozano AM. The most cited works in Essential Tremor and Dystonia. Tremor Other Hyperkinet Mov (N Y). 2016 Apr;6:310. https://doi.org/10.7916/D8NG4QHP
https://doi.org/https://doi.org/10.7916/... , Parkinson’s disease99. Xue JH, Hu ZP, Lai P, Cai DQ, Wen ES. The 100 most-cited articles in Parkinson's disease. Neurol Sci. 2018 Sep;39(9):1537-45. https://doi.org/10.1007/s10072-018-3450-y
https://doi.org/https://doi.org/10.1007/... , and deep brain stimulation1010. Hu K, Moses ZB, Xu W, Williams Z. Bibliometric profile of deep brain stimulation. Br J Neurosurg. 2017 Oct;31(5):587-92. https://doi.org/10.1080/02688697.2017.1324109
https://doi.org/https://doi.org/10.1080/... .

We analyzed the 100 most cited articles on the use of DBS for dystonia treatment in the last 30 years. We evaluated authors’ information, their affiliation, and the country of the corresponding author. Additionally, we investigated which were the most cited journals and their impact factors, the used DBS targets (when applicable), and the dystonia classification (also, when applicable). Articles were divided into primary or secondary (i.e., reviews and guidelines) articles.

METHODS

Search protocol

The used database for article selection was Elsevier’s Scopus, and the search protocol was performed in June 2019. The exact input was TITLE ("dystonia" AND (“DBS” OR “Deep brain stimulation”)) OR ABS ("dystonia" AND (“DBS” OR “Deep brain stimulation”)) AND PUBYEAR>1988. This terminology translated to publications which possessed the terms dystonia and DBS or deep brain stimulation in either the article’s title or abstract and have been published in the last 30 years (i.e., since 1989). After screening the search results based on pertinence, the 100 most cited were used in this study. Impact factor (IF) data of journals were retrieved from InCites Journal Citation Reports (Clarivate Analytics), and both 2017 IF and 5-year IF were collected. Lastly, the h index of authors was obtained from Scopus, as well.

Bibliometric analysis

After selecting the 100 most cited articles, we obtained additional information regarding these publications within our sample. At first, all the authors, year of publication, journal and its impact factor, country, and affiliation of the corresponding author were retrieved. All articles were also categorized, when mentioned, regarding the targets of DBS. The publications were divided into primary researches (i.e., original articles) and secondary researches, such as reviews, and guidelines; the classification of dystonia, if applicable; and into specific themes, such as complications, outcomes, pathophysiology, physiology, surgical approach, targets, ethics, types of stimulation and treatment. Categorized articles in outcomes were further classified into general aspects, long-term outcomes, dystonic tremor outcomes, and predictors of outcome.

RESULTS

General results

Our search led to 337 hits ranging from zero to 679 citations (mean of 30.2). The 100 most cited articles have a mean of 130.4 citations (70-679), and the top 10, a mean of 311.2 (203-679), which have been detailed in Table 1. The most cited article was from Vidailhet et al.1111. Vidailhet M, Vercueil L, Houeto JL, Krystkowiak P, Benabid AL, Cornu P, et al. Bilateral deep-brain stimulation of the globus pallidus in primary generalized dystonia. N Engl J Med. 2005 Feb;352(5):459-67. https://doi.org/10.1056/NEJMoa042187
https://doi.org/https://doi.org/10.1056/... .

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Table 1.
Top ten cited publications in deep brain stimulation in dystonia.

Journals and impact factor

Movement Disorders (2017 IF=8.324) accounts for 19 of the articles in our sample, summing up 2071 citations, and 12 articles were from primary research (1,262 citations). New England Journal of Medicine (2017 IF=79.260) was the second most cited journal while having only two articles in the top 100, both of them from primary research; they were cited 1276 times. The Journal of Neurosurgery was the third most cited journal, with nine publications, all of them from primary research. This material accounted for 1,247 citations.

Country and affiliation

All of the corresponding author countries in our samples were from the Northern Hemisphere. They were divided primarily in Europe and North America, but also in Asia. “DBS in dystonia” research is highly prevalent in Europe, which accounted for 57 articles in our sample. Germany, France, and the United Kingdom display a large production of material. Germany accounted for 25 articles (3,203 citations), 18 from primary research (2,438 citations). France summed up to 15 articles (2,647 citations), 12 from primary research (2,309). Moreover, the United Kingdom had 10 articles (1,086 citations), in which eight were from primary research. The United States was another country in which publications were majorly present. The country has the most articles than any other in the sample: 31 articles (3,834 citations), 19 from primary research (2,466 citations).

The most prolific affiliations are the University of Sorbonne (France), the Kiel University (Germany), and the University of Montpellier (France). The three institutions account for 16% of the 100 most cited articles in “DBS in dystonia”. Both University of Sorbonne and Kiel University display five articles, although the first has four primary research publications, and the latter two. However, the total citations from the University of Sorbonne are 1,300 (1,221 from primary research), and the Kiel University 1,036 (696 from primary research). The University of Montpellier has six articles, all of them from primary research, summing up 789 citations.

Year

Although we researched articles since 1989, the most cited ones were only included from 1999 on. After then, all years, until 2014, had highly cited publications, with a peak from 2005-2007, in which 33% of our sample’s articles reside, summing up to 39% of total citations.

Authors

The three most cited first authors were Vidailhet (h index of 66), Kupsch (h index of 63), and Volkmann (h index of 61), as seen in Table 2. The three altogether represent 18% of all citations in our sample. Vidailhet displayed four articles (1,222 citations), three from primary research (1,143 citations). Kupsch has a single highly cited, primary research article with 597 citations. Lastly, Volkmann had four articles (547 citations), two of which were from primary research (256 citations).

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Table 2.
Ten most cited first authors and all authors in deep brain stimulation in dystonia research.

Another analysis was performed according to any placement of authors during publications. In this analysis, the most cited authors were Pollak (h index of 83), Volkmann (h index of 61), and Benabid (h index of 88). Pollak appeared in seven articles (1,646 citations), six from primary research (1,520 citations). Volkmann was included in nine publications (1,625 citations), five of which are primary research articles (1,334 citations). Benabid was in six articles (1,568 citations), five of which were from primary research (1,442 citations).

Categories

The articles were then categorized, and primary research articles accounted for 72% of our samples. The most present categories were articles that discussed General outcomes from DBS, which included 33 articles (5,044 citations). We separated from these general overviews the ones that investigated the Long-term Outcomes (more than 18 months), which was the second most discussed topic (9 articles, 1,327 citations). The third most present category was Complications, which had eight articles summing 996 citations.

The other 28 articles in our sample were from secondary research; most of them were Reviews, and only one a Guideline. Most of the secondary researches focused on Treatment aspects using DBS (13 articles, 1,508 citations), and other minor focus were given to Pathophysiology (3 articles, 388 citations) and General outcomes (3 articles, 294 citations).

DBS Targets

As reported in Figure 1, we detailed how DBS targets were applied in the different publications listed in the 100 most cited articles in “DBS in dystonia”. There were 31 articles in which this analysis was not applicable, as the target was either not mentioned or DBS treatment was not specified in a general manner. Doubtlessly, the most mentioned target was the GPi, which appeared in 60 articles (8,255 citations), 54 of which being from primary research (7,662 citations). Thalamic targets were, then, the most present ones. In total, 10 articles mentioned thalamic targets: five of which did not specify a precise target, three focused on the Ventral intermediate nucleus (VIM), one on the Ventrolateral thalamic nucleus (VLp), and one on the Ventral-oralis complex (Vo). The total citations for thalamic targets were 1,126. Additionally, seven articles were focusing on the Subthalamic nucleus (STN, 663 citations), five of which were from primary research (461 citations). One primary research article focused on the Caudal Zona Incerta (cZi) and had 143 citations.

Figure 1.
Pie charts indicating the distribution of (A) articles and (B) citations for different deep brain stimulation targets.

Dystonia classification

In the most cited articles, the description of dystonia classification was only observed in primary articles (Table 3). A fraction of them (18, under Miscellaneous) did present different kinds of dystonia in the study. The most common dystonia investigated was idiopathic or inherited, isolated, segmental or generalized dystonia, which presented 16 articles (3,269 citations), followed by idiopathic, isolated, focal dystonia, with 11 publications (1,238 citations).

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Table 3.
Citation and publication profile according to the type of dystonia in the 100 most cited articles in deep brain stimulation in dystonia research.

DISCUSSION

Our analysis indicated that the 10 most cited journals in DBS in dystonia accounted for almost three-quarters of all articles and citations in our sample. They are majorly published in Movement Disorders (19%), the Journal of Neurosurgery (9%), Neurology (9%), Brain (8%), and The Lancet Neurology (7%). However, the journals with most cited articles were the New England Journal of Medicine (average of 638 citations per paper), The Lancet Neurology (152.1 citations/paper), and the European Journal of Neurology (146.5 citations/paper).

DBS in dystonia is mainly researched in the Northern Hemisphere. In the top 100 most cited articles in this theme, there were no countries outside of it. European countries offer significant contributions (57% of our sample). France and Germany have the highest citation rates of all countries. When considering primary research articles, France displays 192.5 citations/paper, and Germany 144.1 citations/paper. The United States also contributes to 31% of the articles, with 129.8 citations/paper.

Most primary research articles focus on General outcomes (46%), followed by Long-term outcomes (12.5%), and Complications (11%). Few publications in our sample tried to find Predictors of outcome (2.8%) or compared different Targets (1.4%). When we analyzed the used DBS targets for dystonia treatment, the classic GPi corresponded to 77% of the publications, STN, which is a hopeful new option of treatment44. Lin S, Wu Y, Li H, Zhang C, Wang T, Pan Y, et al. Deep brain stimulation of the globus pallidus internus versus the subthalamic nucleus in isolated dystonia. J Neurosurg. 2019 Mar:1-12. https://doi.org/10.3171/2018.12.JNS181927
https://doi.org/https://doi.org/10.3171/... ,55. Schjerling L, Hjermind LE, Jespersen B, Madsen FF, Brennum J, Jensen SR, Let al. A randomized double-blind crossover trial comparing subthalamic and pallidal deep brain stimulation for dystonia. J J Neurosurg. 2013 Dec;119(6):1537-45. https://doi.org/10.3171/2013.8.JNS13844
https://doi.org/https://doi.org/10.3171/... ,5656. Moro E, Gross RE, Krauss JK. What's new in surgical treatment for dystonia? Mov Disord. 2013 Jun 15;28(7):1013-20. https://doi.org/10.1002/mds.25550
https://doi.org/https://doi.org/10.1002/... , totalized 9%, and thalamic targets 13%, though mainly used for dystonic tremor5656. Moro E, Gross RE, Krauss JK. What's new in surgical treatment for dystonia? Mov Disord. 2013 Jun 15;28(7):1013-20. https://doi.org/10.1002/mds.25550
https://doi.org/https://doi.org/10.1002/... ,5757. Fasano A, Bove F, Lang AE. The treatment of dystonic tremor: a systematic review. J Neurol Neurosurg Psychiatry. 2014 Jul;85(7):759-69. https://doi.org/10.1136/jnnp-2013-305532
https://doi.org/https://doi.org/10.1136/... .

As expected, most articles analyzed idiopathic or inherited, isolated, segmental or generalized dystonia (27% with an average of 204.3 citations/paper), which is the most studied kind of dystonia and has, usually, the most improvement after DBS treatment5858. Moro E, LeReun C, Krauss JK, Albanese A, Lin JP, Walleser Autiero S, et al. Efficacy of pallidal stimulation in isolated dystonia: a systematic review and meta-analysis. Eur J Neurol. 2017 Apr;24(4):552-60. https://doi.org/10.1111/ene.13255
https://doi.org/https://doi.org/10.1111/... . Idiopathic, isolated, focal dystonia is also highly prevalent (18.5%, 112.6 citations/paper) in our sample.

Similarly to other bibliometric analysis, our study has limitations. Scopus possesses greater coverage and specificity when compared to Web of Science and Google Scholar; however, we employed it as a single database for article retrieval66. Ramos MB, Koterba E, Rosi Junior J, Teixeira MJ, Figueiredo EG. A Bibliometric analysis of the most cited articles in Neurocritical Care Research. Neurocrit Care. 2019 Oct;31(2):365-72. https://doi.org/10.1007/s12028-019-00731-6
https://doi.org/https://doi.org/10.1007/... ,5959. Falagas ME, Pitsouni EI, Malietzis GA, Pappas G. Comparison of PubMed, Scopus, Web of Science, and Google Scholar: strengths and weaknesses. FASEB J. 2008 Feb;22(2):338-42. https://doi.org/10.1096/fj.07-9492LSF
https://doi.org/https://doi.org/10.1096/... ,6060. Martín-Martín A, Orduna-Malea E, Thelwall M, López-Cózar ED. Google Scholar, Web of Science, and Scopus: a systematic comparison of citations in 252 subject categories. J Informetr. 2018;12(4):1160-77. https://doi.org/10.1016/j.joi.2018.09.002
https://doi.org/https://doi.org/10.1016/... . Moreover, articles published after 2014 did not displayed in our sample, possibly because more recent articles are still accumulating citations. Nevertheless, this context does not undervalue their potential.

DBS in dystonia research is mainly focused on selected, Northern Hemisphere countries. They are mostly published in a handful of scientific journals and mainly focusing on outcomes of the surgery, with GPi as DBS target, and in idiopathic or inherited, isolated, segmental or generalized dystonia. This bibliometric analysis might assist unfamiliar researchers and practitioners in obtaining an overview of this particular domain.

REFERENCES

Publication Dates

  • Publication in this collection
    29 May 2020
  • Date of issue
    Sept 2020

History

  • Reviewed
    15 Nov 2019
  • Received
    30 Dec 2019
  • Accepted
    27 Jan 2020
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