Accepted on 21 Mar 2016
Submitted on 26 Mar 2015
The study of the most cited works in a particular field gives an indication of the most impactful advances, developments, and discoveries that have been instrumental in driving research in that discipline.1,2 This analysis also offers insight into where the field has been, where the unmet needs are, and where the field may be heading.1 Such snapshots of the most important works have previously been generated for several areas of neurology and neurosurgery.1,3–8 A recent study examined citations related to essential tremor (ET),8 but a similar analysis has however not yet been carried out for dystonia. Importantly, no study has compared the literature in the two different but linked fields of ET and dystonia. Here we compared and contrasted these two research areas to produce a more comprehensive review and identify the most highly cited ET and dystonia articles.
We used a search strategy similar to one we have previously used for bibliometric analysis in other fields.1,9 A search was performed in January 2016 using the bibliometric database ISI Web of Science for articles published between 1900 and 2015 using the topic search terms “(essential OR benign OR familial) and tremor*” for ET. For dystonia, the search terms were “dystoni* OR meige syndrome OR writer cramp OR torticollis.” Alternative terms were also searched to identify additional citations: “professional cramp OR musician cramp OR eyelid opening apraxia OR Brueghel syndrome OR Oppenheim disease.” The “OR” is a Boolean operator to find records containing any of the terms, and the parentheses were used to define operator precedence such that the expression inside the parentheses is executed first. The asterisk was included as a wild card character. The search terms for ET returned 4,578 articles with the earliest published in 1903. The search terms for dystonia returned 18,839 articles with the earliest published in 1901. The two results were separately sorted by number of citations from highest to lowest and were manually examined to identify the top 100 cited articles related to the field. Articles were considered “citation classics” if they received 400 or more citations as previously defined.2
We first conducted a broad search to identify the relative publication activity across each of the main movement disorders as identified by PubMed (Table 1). Relative to Parkinson’s disease (PD), the number of papers identified in PubMed on dystonia was approximately one fifth and on ET was approximately one twentieth.
Table 1
| Disorder(Search Term)1 | Number of Citations in PubMed (up to December 31, 2015) |
|---|---|
| “Parkinson’s disease” | 59,140 |
| “Essential tremor” | 2,930 |
| “Dystonia” | 12,978 |
| “Myoclonus” | 8,969 |
| “Chorea” | 6,742 |
| “Tic” | 5,952 |
| “Tics” | 3,502 |
1
Each search term was entered as indicated in PubMed for the period of January 1, 1900 to December 31, 2015.
The 100 most cited articles showed that the number of citations per article for ET ranged from 79 to 846 (median 100) compared to a range from of 137 to 560 (median 179) for dystonia. The articles were ranked by citations, and those articles that were ranked in the top 100 are shown in Table 2 for ET and Table 3 for dystonia. Out of these articles, there were four citation classics receiving 400 or more citations for ET10–13 and six citation classics for dystonia,14–19 representing 0.09% and 0.03% of all search results, respectively.
Table 2
| Absolute Number | Rank | Citations | Paper | Category |
|---|---|---|---|---|
| 1 | 1 | 846 | Benabid AL, Pollak P, Gervason C, et al. Long-term suppression of tremor by chronic stimulation of the ventral intermediate thalamic nucleus. Lancet 1991;337:403–406 | Clinical: Surgery |
| 2 | 2 | 809 | Deuschl G, Bain P, Brin M. Consensus statement of the Movement Disorder Society on tremor. Mov Disord 1998;13 Supplement:2–23 | Clinical: Classification |
| 3 | 3 | 652 | Benabid AL, Pollak P, Gao DM, et al. Chronic electrical stimulation of the ventralis intermedius nucleus of the thalamus as a treatment of movement disorders. J Neurosurg 1996;84:203–214 | Clinical: Surgery |
| 4 | 4 | 484 | Schuurman PR, Bosch DA, Bossuyt PMM, et al. A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor. N Engl J Med 2000;342:461–468 | Clinical: Surgery |
| 5 | 5 | 294 | Koller W, Pahwa R, Busenbark K, et al. High-frequency unilateral thalamic stimulation in the treatment of essential and Parkinsonian tremor. Ann Neurol 1997;42:292–299 | Clinical: Surgery |
| 6 | 6 | 291 | Limousin P, Speelman JD, Gielen F, et al. Multicentre European study of thalamic stimulation in parkinsonian and essential tremor. J Neurol Neurosurg Psychiatry 1999;66:289–296 | Clinical: Surgery |
| 7 | 7a | 220 | Louis ED, Ottman R, Hauser WA. How common is the most common adult movement disorder? Estimates of the prevalence of essential tremor throughout the world. Mov Disord 1998;13:5–10 | Review |
| 8 | 7b | 220 | Critchley M. Observations on essential (heredo-familial) tremor. Brain 1949;72:113–139 | Review |
| 9 | 8 | 215 | Benabid AL, Benazzouz A, Hoffmann D, et al. Long-term electrical inhibition of deep brain targets in movement disorders. Mov Disord 1998;13 Supplement:119–125 | Clinical: Surgery |
| 10 | 9 | 214 | Bain PG, Findley LJ, Thompson PD, et al. A study of hereditary essential tremor. Brain 1994;117:805–824 | Review |
| 11 | 10 | 212 | Blond S, Caparros-Lefebvre D, Parker F, et al. Control of tremor and involuntary movement-disorders by chronic stereotaxic stimulation of the ventral intermediate thalamic nucleus. J Neurosurg 1992;77: 62–68 | Clinical: Surgery |
| 12 | 11 | 212 | Lou JS, Jankovic J. Essential tremor: clinical correlates in 350 patients. Neurology 1991;41:234–238 | Clinical: Classification |
| 13 | 12 | 210 | Louis ED, Faust PL, Vonsattel JP, et al. Neuropathological changes in essential tremor: 33 cases compared with 21 controls. Brain 2007;130:3297–3307 | Lab: Patho-physiology |
| 14 | 13 | 198 | Deuschl G, Raethjen J, Lindemann M, et al. The pathophysiology of tremor. Muscle Nerve 2001;24:716–735 | Review |
| 15 | 15 | 177 | Jenkins IH, Bain PG, Colebatch JG, et al. A positron emission tomography study of essential tremor: evidence for overactivity of cerebellar connections. Ann Neurol 1993;34:82–90 | Lab: Patho-physiology |
| 16 | 15 | 174 | Bain PG, Findley LJ, Atchison P, et al. Assessing tremor severity. J Neurol Neurosurg Psychiatry 1993;56:868–873 | Clinical: Classification |
| 17 | 16 | 172 | Brooks DJ, Playford ED, Ibanez V, et al. Isolated tremor and disruption of the nigrostriatal dopaminergic system: an 18F-dopa PET study. Neurology 1992;42:1554–1560 | Lab: Patho-physiology |
| 18 | 17 | 169 | Jankovic J, Cardoso F, Grossman RG, et al. Outcome after stereotaxic thalamotomy for parkinsonian, essential, and other types of tremor. Neurosurgery 1995;37:680–686 | Clinical: Surgery |
| 19 | 18 | 167 | Rajput AH, Offord KP, Beard CM, et al. Essential tremor in Rochester, Minnesota: a 45-year study. J Neurol Neurosurg Psychiatry 1984;47:466–470 | Epidemiology |
| 20 | 19 | 166 | Tasker RR. Deep brain stimulation is preferable to thalamotomy for tremor suppression. Surg Neurol 1998;49:145–153 | Clinical: Surgery |
| 21 | 20 | 164 | Benito-León J, Bermejo-Pareja F, Morales JM, et al. Prevalence of essential tremor in three elderly populations of central Spain. Mov Disord 2003;18:389–394 | Epidemiology |
| 22 | 21a | 158 | Deuschl G, Wenzelburger R, Loffler K, et al. Essential tremor and cerebellar dysfunction: clinical and kinematic analysis of intention tremor. Brain 2000;123:1568–1580 | Review |
| 23 | 21b | 158 | Louis ED. Essential tremor. Lancet Neurol 2005;4:100–110 | Review |
| 24 | 22 | 154 | Gulcher JR, Jonsson P, Kong A, et al. Mapping of a familial essential tremor gene, FET1, to chromosome 3q13. Nat Genet 1997;17:84–87 | Lab: Genetic studies |
| 25 | 23 | 149 | Koller WC, Busenbark K, Miner K, et al. The relationship of essential tremor to other movement-disorders: report on 678 patients. Ann Neurol 1994;35:717–723 | Epidemiology |
| 26 | 24 | 142 | Louis ED, Ferreira JJ. How common is the most common adult movement disorder? Update on the worldwide prevalence of essential tremor. Mov Disord 2010;25:534–541 | Review |
| 27 | 25 | 138 | Elble RJ. Physiological and essential tremor. Neurology 1986;36:225–231 | Clinical: Classification |
| 28 | 26 | 131 | Ondo W, Jankovic J, Schwartz K, et al. Unilateral thalamic deep brain stimulation for refractory essential tremor and Parkinson’s disease tremor. Neurology 1998;51:1063–1069 | Clinical: Surgery |
| 29 | 27a | 128 | Geraghty JJ, Jankovic J, Zetusky WJ. Association between essential tremor and Parkinson’s disease. Ann Neurol 1985;17:329–333 | Epidemiology |
| 30 | 27b | 128 | Winkler GF, Young RR. Efficacy of chronic propranolol therapy in action tremors of familial, senile or essential varieties. New Engl J Med 1974;290:984–988 | Clinical: Medicine |
| 31 | 28a | 127 | Higgins JJ, Pho LT, Nee LE. A gene (ETM) for essential tremor maps to chromosome 2p22–p25. Mov Disord 1997;12:859–864 | Review |
| 32 | 28b | 127 | Koller WC, Lyons KE, Wilkinson SB, et al. Long-term safety and efficacy of unilateral deep brain stimulation of the thalamus in essential tremor. Mov Disord 2001;16:464–468 | Clinical: Surgery |
| 33 | 29 | 126 | Colebatch JG, Findley LJ, Frackowiak RSJ, et al. Preliminary-report: activation of the cerebellum in essential tremor. Lancet 1990;336:1028–1030 | Lab: Patho-physiology |
| 34 | 30a | 125 | Rehncrona S, Johnels B, Widner H, et al. Long-term efficacy of thalamic deep brain stimulation for tremor: Double-blind assessments. Mov Disord 2003;18:163–170 | Clinical: Surgery |
| 35 | 30b | 125 | Wills AJ, Jenkins IH, Thompson PD, et al. Red nuclear and cerebellar but no olivary activation-associated with essential tremor: a positron emission tomographic study. Ann Neurol 1994;36:636–642 | Lab: Patho-physiology |
| 36 | 31 | 123 | Zesiewicz TA, Elble R, Louis ED, et al. Practice parameter: Therapies for essential tremor – Report of the quality standards subcommittee of the American Academy of Neurology. Neurology 2005;64:2008–2020 | Clinical: Classification |
| 37 | 32a | 121 | Bucher SF, Seelos KC, Dodel RC, et al. Activation mapping in essential tremor with functional magnetic resonance imaging. Ann Neurol 1997;41:32–40 | Lab: Patho-physiology |
| 38 | 32b | 121 | Stolze H, Petersen G, Raethjen J, et al. The gait disorder of advanced essential tremor. Brain 2001;124:2278–2286 | Clinical: Classification |
| 39 | 33a | 118 | Benito-León J, Louis ED. Essential tremor: emerging views of a common disorder. Nat Clin Pract Neurol 2006;2:666–678 | Review |
| 40 | 33b | 118 | Dogu O, Sevim S, Camdeviren H, et al. Prevalence of essential tremor – Door-to-door neurologic exams in Mersin Province, Turkey. Neurology 2003;61:1804–1806 | Epidemiology |
| 41 | 34a | 116 | Benamer HTS, Patterson J, Grosset DG, et al. Accurate differentiation of Parkinsonism and essential tremor using visual assessment of [I-123]-FP-CIT SPECT imaging: The [I-123]-FP-CIT study group. Mov Disord 2000;15:503–510 | Clinical: Classification |
| 42 | 34b | 116 | Rautakorpi I, Takala J, Marttila RJ, et al. Essential tremor in a Finnish population. Acta Neurol Scand 1982;66:58–67 | Epidemiology |
| 43 | 35 | 115 | Louis ED, Ottman R, Ford B, et al. The Washington Heights-Inwood Genetic Study of Essential Tremor: Methodologic issues in essential-tremor research. Neuroepidemiology 1997;16:124–133 | Lab: Genetic studies |
| 44 | 36 | 113 | Critchley E. Clinical manifestations of essential tremor. J Neurol Neurosurg Psychiatry 1972;35:365–372 | Clinical: Classification |
| 45 | 37a | 112 | Lombardi WJ, Woolston DJ, Roberts JW, et al. Cognitive deficits in patients with essential tremor. Neurology 2001;57:785–790 | Clinical: Classification |
| 46 | 37b | 112 | Benito-León J, Louis ED, Bermejo-Pareja F. Population-based case-control study of cognitive function in essential tremor. Neurology 2006;66:69–74 | Epidemiology |
| 47 | 38 | 102 | Jankovic J, Schwartz K, Clemence W, et al. A randomized, double-blind, placebo-controlled study to evaluate botulinum toxin type A in essential hand tremor. Mov Disord 1996;11:250–256 | Clinical: Medicine |
| 48 | 39a | 101 | Wilms H, Sievers J, Deuschl G. Animal models of tremor. Mov Disord 1999;14:557–571 | Review |
| 49 | 39b | 101 | Bain P, Brin M, Deuschl G, et al. Criteria for the diagnosis of essential tremor. Neurology 2000;54:S7–S7 | Clinical: Classification |
| 50 | 39c | 101 | Sydow O, Thobois S, Alesch F, et al. Multicentre European study of thalamic stimulation in essential tremor: a six year follow up. J Neurol Neurosurg Psychiatry 2003;74:1387–1391 | Epidemiology |
| 51 | 40a | 99 | Asenbaum S, Pirker W, Angelberger P, et al. [I-123]beta-CIT and SPECT in essential tremor and Parkinson’s disease. J Neural Transm (Vienna) 1998;105:1213–1228 | Clinical: Classification |
| 52 | 40b | 99 | Growdon JH, Shahani BT, Young RR. Effect of alcohol on essential tremor. Neurology 1975;25:259–262 | Lab: Patho-physiology |
| 53 | 40c | 99 | Alesch F, Pinter MM, Helscher RJ, et al. Stimulation of the ventral intermediate thalamic nucleus in tremor dominated Parkinson’s disease and essential tremor. Acta Neurochir (Wien) 1995;136:75–81 | Clinical: Surgery |
| 54 | 41 | 98 | Hornabrook RW, Nagurney JT. Essential tremor in Papua, New Guinea. Brain 1976;99:659–672 | Epidemiology |
| 55 | 42a | 97 | Rajput AH, Rozdilsky B, Ang L, et al. Clinicopathological observations in essential tremor: report of 6 cases. Neurology 1991;41:1422–1424 | Lab: Patho-physiology |
| 56 | 42b | 97 | Lee RG, Stein RB. Resetting of tremor by mechanical perturbations – a comparison of essential tremor and Parkinsonian tremor. Ann Neurol 1981;10:523–531 | Clinical: Medicine |
| 57 | 43 | 96 | Marshall J. Observations on essential tremor. J Neurol Neurosurg Psychiatry 1972;25:122–125 | Clinical: Classification |
| 58 | 44a | 95 | Gironell A, Kulisevsky J, Barbanoj M, et al. A randomized placebo-controlled comparative trial of gabapentin and propranolol in essential tremor. Arch Neurol 1999;56:475–480 | Clinical: Medicine |
| 59 | 44b | 95 | Louis ED, Zheng W, Jurewicz EC, et al. Elevation of blood beta-carboline alkaloids in essential tremor. Neurology 2002;59:1940–1944 | Lab: Patho-physiology |
| 60 | 44c | 95 | Singer C, Sanchezramos J, Weiner WJ. Gait abnormality in essential tremor. Mov Disord 1994;9:193–196 | Clinical: Classification |
| 61 | 44d | 95 | Benito-León J, Bermejo-Pareja F, Louis ED. Incidence of essential tremor in three elderly populations of central Spain. Neurology 2005;64:1721–1725 | Epidemiology |
| 62 | 44e | 95 | Raethjen J, Lindemann M, Schmaljohann H, et al. Multiple oscillators are causing Parkinsonian and essential tremor. Mov Disord 2000;15:84–94 | Lab: Patho-physiology |
| 63 | 44f | 95 | Stefansson H, Steinberg S, Petursson H, et al. Variant in the sequence of the LINGO1 gene confers risk of essential tremor. Nat Genet 2009;41:277–279 | Lab: Genetic studies |
| 64 | 45a | 94 | Busenbark KL, Nash J, Nash S, et al. Is essential tremor benign? Neurology 1991;41:1982–1983 | Epidemiology |
| 65 | 45b | 94 | Louis ED, Shungu DC, Chan S, et al. Metabolic abnormality in the cerebellum in patients with essential tremor: a proton magnetic resonance spectroscopic imaging study. Neurosci Lett 2002;333:17–20 | Lab: Patho-physiology |
| 66 | 45c | 94 | Hariz MI, Shamsgovara P, Johansson F, et al. Tolerance and tremor rebound following long-term chronic thalamic stimulation for parkinsonian and essential tremor. Stereotact Funct Neurosurg 1999;72:208–218 | Clinical: Surgery |
| 67 | 46a | 93 | Kumar R, Lozano AM, Sime E, et al. Long-term follow-up of thalamic deep brain stimulation for essential and Parkinsonian tremor. Neurology 2003;61:1601–1604 | Clinical: Surgery |
| 68 | 46b | 93 | Boecker H, Wills AJ, Ceballos-Baumann A, et al. The effect of ethanol on alcohol responsive essential tremor: a positron emission tomography study. Ann Neurol 1996;39:650–658 | Lab: Patho-physiology |
| 69 | 47a | 92 | Louis ED, Barnes L, Albert SM, et al. Correlates of functional disability in essential tremor. Mov Disord 2001;16:914–920 | Clinical: Classification |
| 70 | 47b | 92 | Hubble JP, Busenbark KL, Wilkinson S, et al. Deep brain stimulation for essential tremor. Neurology 1996;46:1150–1153 | Clinical: Surgery |
| 71 | 47c | 92 | Rajput A, Robinson CA, Rajput AH. Essential tremor course and disability – A clinicopathologic study of 20 cases. Neurology 2004;62:932–936 | Lab: Patho-physiology |
| 72 | 47d | 92 | Bermejo-Pareja F, Louis ED, Benito-León J. Risk of incident dementia in essential tremor: A population-based study. Mov Disord 2007;22:1573–1580 | Epidemiology |
| 73 | 48 | 91 | Louis ED, Ottman R. How familial is familial tremor? The genetic epidemiology of essential tremor. Neurology 1996;46:1200–1205 | Review |
| 74 | 49a | 90 | Louis ED, Marder K, Cote L, et al. Differences in the prevalence of essential tremor among elderly African-Americans, whites, and Hispanics in northern Manhattan, NY. Arch Neurol 1995;52:1201–1205 | Epidemiology |
| 75 | 49b | 90 | Findley LJ, Koller WC. Essential tremor: a review. Neurology 1987;37:1194–1197 | Review |
| 76 | 49c | 90 | Hellwig B, Haussler S, Schelter B, et al. Tremor-correlated cortical activity in essential tremor. Lancet 2001;357:519–523 | Lab: Patho-physiology |
| 77 | 50a | 88 | Helmchen C, Hagenow A, Miesner J, et al. Eye movement abnormalities in essential tremor may indicate cerebellar dysfunction. Brain 2003;126:1319–1332 | Lab: Patho-physiology |
| 78 | 50b | 88 | Hallett M, Dubinsky RM. Glucose-metabolism in the brain of patients with essential tremor. J Neurol Sci 1993;114:45–48 | Lab: Patho-physiology |
| 79 | 50c | 88 | Louis ED, Ford B, Frucht S, et al. Risk of tremor and impairment from tremor in relatives of patients with essential tremor: a community-based family study. Ann Neurol 2001;49:761–769 | Epidemiology |
| 80 | 51a | 87 | Jeanneteau F, Funalot B, Jankovic J, et al. A functional variant of the dopamine D-3 receptor is associated with risk and age-at-onset of essential tremor. Proc Natl Acad Sci U S A 2006;103:10753–10758 | Lab: Genetic studies |
| 81 | 51b | 87 | Jefferson D, Jenner P, Marsden CD. Beta-adrenoreceptor antagonists in essential tremor. J Neurol Neurosurg Psychiatry 1979;42:904–909 | Clinical: Medicine |
| 82 | 52a | 86 | Benito-León J, Louis ED, Bermejo-Pareja F. Elderly-onset essential tremor is associated with dementia. Neurology 2006;66:1500–1505 | Clinical: Classification |
| 83 | 52b | 86 | Deuschl G, Elble R. Essential tremor–neurodegenerative or nondegenerative disease towards a working definition of ET. Mov Disord 2009;24:2033–2041 | Review |
| 84 | 53a | 86 | Shahed J, Jankovic J. Exploring the relationship between essential tremor and Parkinson’s disease. Parkinsonism Relat Disord 2007;13:67–76 | Review |
| 85 | 53b | 86 | Leehey MA, Munhoz RP, Lang AE, et al. The fragile X premutation presenting as essential tremor. Arch Neurol 2003;60:117–121 | Lab: Genetic studies |
| 86 | 54a | 85 | Koller W, Biary N, Cone S. Disability in essential tremor: effect of treatment. Neurology 1986;36:1001–1004 | Clinical: Medicine |
| 87 | 54b | 85 | Deng H, Le W, Jankovic J. Genetics of essential tremor. Brain 2007;130:1456–1464 | Review |
| 88 | 55a | 84 | Gasparini M, Bonifati V, Fabrizio E, et al. Frontal lobe dysfunction in essential tremor: a preliminary study. J Neurol 2001;248:399–402 | Lab: Patho-physiology |
| 89 | 55b | 84 | Shill HA, Adler CH, Sabbagh MN, et al. Pathologic findings in prospectively ascertained essential tremor subjects. Neurology 2008;70:1452–1455 | Lab: Patho-physiology |
| 90 | 56 | 83 | Koller WC, Vetere-Overfield B. Acute and chronic effects of propranolol and primidone in essential tremor. Neurology 1989;39:1587–1588 | Clinical: Medicine |
| 91 | 57a | 82 | Jain S, Lo SE, Louis ED. Common misdiagnosis of a common neurological disorder : how are we misdiagnosing essential tremor? Arch Neurol 2006;63:1100–1104 | Clinical: Classification |
| 92 | 57b | 82 | Jankovic J. Essential tremor: a heterogeneous disorder. Mov Disord 2002;17:638–644 | Clinical: Classification |
| 93 | 57c | 82 | Troster AI, Woods SP, Fields JA, et al. Neuropsychological deficits in essential tremor: an expression of cerebello-thalamo-cortical pathophysiology? Eur J Neurol 2002;9:143–151 | Lab: Patho-physiology |
| 94 | 57d | 82 | Axelrad JE, Louis ED, Honig LS, et al. Reduced Purkinje cell number in essential tremor. Arch Neurol 2008;65:101–107 | Lab: Patho-physiology |
| 95 | 58 | 81 | Brin MF, Lyons KE, Doucette J, et al. A randomized, double masked, controlled trial of botulinum toxin type A in essential hand tremor. Neurology 2001;56:1523–1528 | Clinical: Medicine |
| 96 | 59a | 80 | Wills AJ, Jenkins IH, Thompson PD, et al. A positron emission tomography study of cerebral activation-associated with essential and writing tremor. Arch Neurol 1995;52:299–305 | Lab: Patho-physiology |
| 97 | 59b | 80 | Louis ED, Ford B, Lee H, et al. Diagnostic criteria for essential tremor: a population perspective. Arch Neurol 1998;55:823–828 | Clinical: Classification |
| 98 | 59c | 80 | Kralic JE, Criswell HE, Osterman JL, et al. Genetic essential tremor in gamma-aminobutyric acidA receptor alpha 1 subunit knockout mice. J Clin Invest 2005;115:774–779 | Lab: Genetic studies |
| 99 | 60a | 79 | Cleeves L, Findley LJ, Koller W. Lack of association between essential tremor and Parkinson’s disease. Ann Neurol 1988;24: 23–26 | Epidemiology |
| 100 | 60b | 79 | Tan EK, Matsuura T, Nagamitsu S, et al. Polymorphism of NACP-Rep1 in Parkinson’s disease: An etiologic link with essential tremor? Neurology 2000;54: 1195–1198 | Lab: Genetic studies |
Table 3
| Absolute Number | Rank | Citations | Paper | Category |
|---|---|---|---|---|
| 1 | 1 | 560 | Ozelius LJ, Hewett JW, Page CE, et al. The early-onset torsion dystonia gene (DYT1) encodes an ATP binding protein. Nat Genet 1997;17:40–48 | Lab: Genetic studies |
| 2 | 2 | 537 | Burke RE, Fahn S, Marsden CD, et al. Validity and reliability of a rating-scale for the primary torsion dystonias. Neurology 1985;35:73–77 | Clinical: Classification |
| 3 | 3 | 523 | Ichinose H, Ohye T, Takahashi E, et al. Hereditary progressive dystonia with marked diurnal fluctuation caused by mutations in the GTP cyclohydrolase-I gene. Nat Genet 1994;8:236–242 | Lab: Genetic studies |
| 4 | 4 | 491 | Berardelli A, Rothwell JC, Hallett M, et al. The pathophysiology of primary dystonia. Brain 1998;121:1195–1212 | Lab: Patho-physiology |
| 5 | 5 | 453 | Tsui JKC, Stoessl AJ, Eisen A, et al. Double-blind-study of botulinum toxin in spasmodic torticollis. Lancet 1986;2:245–247 | Clinical: Medicine |
| 6 | 6 | 438 | Vidailhet M, Vercueil L, Houeto JL, et al. Bilateral deep-brain stimulation of the globus pallidus in primary generalized dystonia. N Engl J Med 2005;352:459–467 | Clinical: Surgery |
| 7 | 7 | 391 | Ridding MC, Sheean G, Rothwell JC, et al. Changes in the balance between motor cortical excitation and inhibition in focal, task specific dystonia. J Neurol Neurosurg Psychiatry 1995;59:493–498 | Clinical: Medicine |
| 8 | 8 | 363 | Burke RE, Fahn S, Jankovic J, et al. Tardive dystonia: late-onset and persistent dystonia caused by anti-psychotic drugs. Neurology 1982;32:1335–1346 | Lab: Patho-physiology |
| 9 | 9 | 362 | Kupsch A, Benecke R, Mueller J, et al. Pallidal deep-brain stimulation in primary generalized or segmental dystonia. N Engl J Med 2006;355:1978–1990 | Clinical: Surgery |
| 10 | 10 | 320 | Sheehy MP, Marsden, CD. Writers cramp -a focal dystonia. Brain 1982;105: 461–480 | Clinical: Classification |
| 11 | 11 | 312 | Risch N, de Leon D, Ozelius L, et al. Genetic-analysis of idiopathic torsion dystonia in Ashkenazi Jews and their recent descent from a small founder population. Nat Genet 1995;9:152–159 | Lab: Genetic studies |
| 12 | 12 | 311 | Byl NN, Merzenich MM, Jenkins WM. A primate genesis model of focal dystonia and repetitive strain injury 1. Learning-induced dedifferentiation of the representation of the hand in the primary somatosensory cortex in adult monkeys. Neurology 1996;47:508–520 | Lab: Patho-physiology |
| 13 | 13 | 292 | Vitek JL, Chockkan V, Zhang JY, et al. Neuronal activity in the basal ganglia in patients with generalized dystonia and hemiballismus. Ann Neurol 1999;46:22–35 | Lab: Patho-physiology |
| 14 | 14 | 282 | Berardelli A, Rothwell JC, Day BL, et al. Patho-physiology of blepharospasm and oromandibular dystonia. Brain 1985;108:593–608 | Lab: Patho-physiology |
| 15 | 15 | 279 | Siebner HR, Tormos JM, Ceballos-Baumann AO, et al. Low-frequency repetitive transcranial magnetic stimulation of the motor cortex in writer’s cramp. Neurology 1999;52:529–537 | Clinical: Medicine |
| 16 | 16 | 259 | Jankovic J, Orman J. Botulinum-a toxin for cranial-cervical dystonia: a double-blind, placebo-controlled study. Neurology 1987;37:616–623 | Clinical: Medicine |
| 17 | 17a | 255 | Elbert T, Candia V, Altenmuller E, et al. Alteration of digital representations in somatosensory cortex in focal hand dystonia. Neuroreport 1998;9:3571–3575 | Lab: Patho-physiology |
| 18 | 17b | 255 | Jankovic J, Schwartz K, Donovan DT. Botulinum toxin treatment of cranial-cervical dystonia, spasmodic dysphonia, other focal dystonias and hemifacial spasm. J Neurol Neurosurg Psychiatry 1990;53:633–639 | Clinical: Medicine |
| 19 | 17c | 255 | Coubes P, Roubertie A, Vayssiere N, et al. Treatment of DYT1-generalised dystonia by stimulation of the internal globus pallidus. Lancet 2000;355:2220–2221 | Clinical: Surgery |
| 20 | 18 | 248 | Zimprich A, Grabowski M, Asmus F, et al. Mutations in the gene encoding epsilon-sarcoglycan cause myoclonus-dystonia syndrome. Nat Genet 2001;29:66–69 | Lab: Genetic studies |
| 21 | 19 | 246 | Brin MF, Fahn S, Moskowitz C, et al. Localized injections of botulinum toxin for the treatment of focal dystonia and hemifacial spasm. Mov Disord 1987;2:237–254 | Clinical: Medicine |
| 22 | 20 | 242 | Nutt JG, Muenter MD, Aronson A, et al. Epidemiology of focal and generalized dystonia in Rochester, Minnesota. Mov Disord 1988;3:188–194 | Epidemiology |
| 23 | 21 | 234 | Greene P, Kang U, Fahn S, et al. Double-blind, placebo-controlled trial of botulinum toxin injections for the treatment of spasmodic torticollis. Neurology 1990;40:1213–1218 | Clinical: Medicine |
| 24 | 22 | 233 | Jankovic J, Leder S, Warner D, et al. Cervical dystonia: clinical findings and associated movement-disorders. Neurology 1991;41:1088–1091 | Epidemiology |
| 25 | 23 | 231 | Greene P, Fahn S, Diamond B. Development of resistance to botulinum toxin type-a in patients with torticollis. Mov Disord 1994;9:213–217 | Clinical: Medicine |
| 26 | 24 | 230 | Chan J, Brin MF, Fahn S. Idiopathic cervical dystonia : clinical characteristics. Mov Disord 1991;6:119–126 | Clinical: Classification |
| 27 | 25 | 226 | Jun AS, Brown MD, Wallace DC. A mitochondrial-DNA mutation at nucleotide pair-14459 of the NADH dehydrogenase subunit-6 gene associated with maternally inherited Leber hereditary optic neuropathy and dystonia. Proc Natl Acad Sci U S A 1994;91:6206–6210 | Lab: Genetic studies |
| 28 | 26a | 225 | Lance JW. Familial paroxysmal dystonic choreoathetosis and its differentiation from related syndromes. Ann Neurol 1977;2:285–293 | Clinical: Classification |
| 29 | 26b | 225 | Brin MF, Lew MF, Adler CH, et al. Safety and efficacy of NeuroBloc (botulinum toxin type B) in type A-resistant cervical dystonia. Neurology 1999;53:1431–1438 | Clinical: Medicine |
| 30 | 27 | 224 | Siebner HR, Dressnandt J, Auer C, et al. Continuous intrathecal baclofen infusions induced a marked increase of the transcranially evoked silent period in a patient with generalized dystonia. Muscle Nerve 1998;21:1209–1212 | Clinical: Medicine |
| 31 | 28 | 222 | Nakashima K, Rothwell JC, Day BL, et al. Reciprocal inhibition between forearm muscles in patients with writers cramp and other occupational cramps, symptomatic hemidystonia and hemiparesis due to stroke. Brain 1989;112:681–697 | Lab: Patho-physiology |
| 32 | 29 | 221 | Bara-Jimenez W, Catalan MJ, Hallett M, et al. Abnormal somatosensory homunculus in dystonia of the hand. Ann Neurol 1998;44: 828–831 | Lab: Patho-physiology |
| 33 | 30a | 220 | Ceballos-Baumann AO, Passingham RE, Warner T, et al. Overactive prefrontal and underactive motor cortical areas in idiopathic dystonia. Ann Neurol 1995;37:363–372 | Lab: Patho-physiology |
| 34 | 30b | 220 | Brashear A, Lew MF, Dykstra DD, et al. Safety and efficacy of NeuroBloc (botulinum toxin type B) in type A-responsive cervical dystonia. Neurology 1999;53:1439–1446 | Clinical: Medicine |
| 35 | 31 | 217 | Breakefield XO, Blood AJ, Li Y, et al. The pathophysiological basis of dystonias. Nat Rev Neurosci 2008;9:222–234 | Review |
| 36 | 32 | 213 | Ozelius L, Kramer PL, Moskowitz CB, et al. Human-gene for torsion dystonia located on chromosome 9q32–q34. Neuron 1989;2:1427–1434 | Lab: Genetic studies |
| 37 | 33 | 211 | Koehler CM, Leuenberger D, Merchant S, et al. Human deafness dystonia syndrome is a mitochondrial disease. Proc Natl Acad U S A 1999;96:2141–2146 | Clinical: Classification |
| 38 | 34 | 210 | Hallett, M. Is dystonia a sensory disorder? Ann Neurol 1995;38:139–140 | Clinical: Classification |
| 39 | 35’ | 206 | Jankovic J, Ford J. Blepharospasm and orofacial cervical dystonia: clinical and pharmacological findings in 100 patients. Ann Neurol 1983;13:402–411 | Epidemiology |
| 40 | 36a | 205 | Jankovic J, Schwartz K. Botulinum toxin injections for cervical dystonia. Neurology 1990;40:277–280 | Clinical: Medicine |
| 41 | 36b | 205 | Coubes P, Cif L, El Fertit H, et al. Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results. J Neurosurg 2004;101:189–194 | Clinical: Surgery |
| 42 | 37a | 193 | Jankovic J, Vanderlinden C. Dystonia and tremor induced by peripheral trauma: predisposing factors. J Neurol Neurosurg Psychiatry 1988;51:1512–1519 | Lab: Patho-physiology |
| 43 | 37b | 193 | Eidelberg D, Moeller JR, Antonini A, et al. Functional brain networks in DYT1 dystonia. Ann Neurol 1998;44:303–312 | Lab: Patho-physiology |
| 44 | 38 | 192 | Lozano AM, Kumar R, Gross RE, et al. Globus pallidus internus pallidotomy for generalized dystonia. Mov Disord 1997;12:865–870 | Clinical: Surgery |
| 45 | 39 | 189 | Brown A, Bernier G, Mathieu M, et al. The mouse dystonia musculorum gene is a neural isoform of bullous pemphigoid antigen-1. Nat Genet 1995;10:301–306 | Lab: Genetic studies |
| 46 | 40 | 185 | Kaji R, Rothwell JC, Katayama M, et al. Tonic vibration reflex and muscle afferent block in writers cramp. Ann Neurol 1995;38:155–162 | Clinical: Medicine |
| 47 | 41 | 183 | Marsden CD. Blepharospasm-oromandibular dystonia syndrome (Brueghel’s syndrome). A variant of adult-onset torsion dystonia. J Neurol Neurosurg Psychiatry 1976;39:1204–1209 | Clinical: Classification |
| 48 | 42 | 181 | Ikoma K, Samii A, Mercuri B, et al. Abnormal cortical motor excitability in dystonia. Neurology 1996;46:1371–1376 | Clinical: Medicine |
| 49 | 43 | 180 | Quartarone A, Bagnato S, Rizzo V, et al. Abnormal associative plasticity of the human motor cortex in writer’s cramp. Brain 2003;126:2586–2596 | Clinical: Medicine |
| 50 | 44 | 179 | Bressman SB, Sabatti C, Raymond D, et al. The DYT1 phenotype and guidelines for diagnostic testing. Neurology 2000;54:1746–1752 | Lab: Genetic studies |
| 51 | 45 | 178 | Zuber M, Sebald M, Bathien N, de Recondo J, Rondot P. Botulinum antibodies in dystonic patients treated with type-a botulinum toxin – frequency and significance. Neurology 1993;43:1715–1718 | Clinical: Medicine |
| 52 | 46 | 176 | Muenter MD, Sharpless NS, Tyce GM, et al. Patterns of dystonia (I-D-I and D-I-D) in response to l-dopa therapy for Parkinson’s disease. Mayo Clin Proc 1977;3:163–174 | Clinical: Medicine |
| 53 | 47 | 175 | Marsden CD, Harrison MJ. Idiopathic torsion dystonia (dystonia musculorum deformans). A review of forty-two patients. Brain 1974; 97:793–810 | Review |
| 54 | 48 | 174 | Kumar R, Dagher A, Hutchison WD, et al. Globus pallidus deep brain stimulation for generalized dystonia: clinical and PET investigation. Neurology 1999;53:871–874 | Lab: Patho-physiology |
| 55 | 49 | 173 | Goodchild RE, Kim CE, Dauer WT. Loss of the dystonia-associated protein torsinA selectively disrupts the neuronal nuclear envelope. Neuron 2005;48:923–932 | Lab: Genetic studies |
| 56 | 50 | 171 | Cohen LG, Hallett M. Hand cramps – clinical-features and electromyographic patterns in a focal dystonia. Neurology 1988;38:1005–1012 | Clinical: Classification |
| 57 | 51 | 170 | Blitzer A, Brin MF, Stewart CF. Botulinum toxin management of spasmodic dysphonia (Laryngeal dystonia): A 12-year experience in more than 900 patients. Laryngoscope 1998;108:1435–1441 | Clinical: Medicine |
| 58 | 52a | 169 | Dauer WT, Burke RE, Greene P, et al. Current concepts on the clinical features, aetiology and management of idiopathic cervical dystonia. Brain 1998;121:547–560 | Review |
| 59 | 52b | 169 | Irani SR, Michell AW, Lang B, et al. Faciobrachial dystonic seizures precede Lgi1 antibody limbic encephalitis. Ann Neurol 2011;69:892–900 | Lab: Patho-physiology |
| 60 | 52c | 169 | Gelb DJ, Lowenstein DH, Aminoff MJ. Controlled trial of botulinum toxin injections in the treatment of spasmodic torticollis. Neurology 1989;39:80–84 | Clinical: Medicine |
| 61 | 53 | 167 | Burke RE, Fahn S, Gold AP. Delayed-onset dystonia in patients with static encephalopathy. J Neurol Neurosurg Psychiatry 1980;43:789–797 | Clinical: Classification |
| 62 | 54a | 165 | Waddy HM, Fletcher NA, Harding AE, et al. A genetic-study of idiopathic focal dystonias. Ann Neurol 1991;29:320–324 | Lab: Genetic studies |
| 63 | 54b | 165 | Krauss JK, Pohle T, Weber S, et al. Bilateral stimulation of globus pallidus internus for treatment of cervical dystonia. Lancet 1999;354:837–838 | Clinical: Surgery |
| 64 | 55 | 164 | Odergren T, Hjaltason H, Kaakkola S, et al. A double blind, randomised, parallel group study to investigate the dose equivalence of Dysport (R) and Botox (R) in the treatment of cervical dystonia. J Neurol Neurosurg Psychiatry 1998;64:6–12 | Clinical: Medicine |
| 65 | 56a | 163 | Simpson DM, Gracies JM, Graham HK, et al. Assessment: Botulinum neurotoxin for the treatment of spasticity (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology 2008;70:1691–1698 | Review |
| 66 | 56b | 163 | Bressman SB, de Leon D, Brin MF, et al. Idiopathic dystonia among Ashkenazi Jews: evidence for autosomal dominant inheritance. Ann Neurol 1989;26:612–620 | Lab: Genetic studies |
| 67 | 57a | 162 | Jin H, May M, Tranebjaerg L, et al. A novel X-linked gene, DDP, shows mutations in families with deafness (DFN-1), dystonia, mental deficiency and blindness. Nat Genet 1996;14:177–180 | Lab: Genetic studies |
| 68 | 57b | 162 | Nygaard TG, Marsden CD, Fahn S. Dopa-responsive dystonia: long-term treatment response and prognosis. Neurology 1991;41:174–181 | Clinical: Medicine |
| 69 | 58a | 161 | Rupniak NMJ, Jenner P, Marsden, CD. Acute dystonia induced by neuroleptic drugs. Psychopharmacology (Berl) 1986;88:403–419 | Lab: Patho-physiology |
| 70 | 58b | 161 | Vidailhet M, Vercueil L, Houeto JL, et al. Bilateral, pallidal, deep-brain stimulation in primary generalised dystonia: a prospective 3 year follow-up study. Lancet Neurol 2007;6:223–229 | Clinical: Surgery |
| 71 | 58c | 161 | Newton MR, Berkovic SF, Austin MC, et al. Dystonia, clinical lateralization, and regional blood-flow changes in temporal-lobe seizures. Neurology 1992;42:371–377 | Epidemiology |
| 72 | 58d | 161 | Aguiar PD, Sweadner KJ, Penniston JT, et al. Mutations in the Na+/K+-ATPase alpha 3 gene ATP1A3 are associated with rapid-onset dystonia Parkinsonism. Neuron 2004; 43:169–175 | Lab: Genetic studies |
| 73 | 58e | 161 | Silberstein P, Kuhn AA, Kupsch A, et al. Patterning of globus pallidus local field potentials differs between Parkinson’s disease and dystonia. Brain 2003;126:2597–2608 | Lab: Patho-physiology |
| 74 | 59 | 160 | Lew MF, Adornato BT, Duane DD, et al. Botulinum toxin type B: A double-blind, placebo-controlled, safety and efficacy study in cervical dystonia. Neurology 1997; 49:701–707 | Clinical: Medicine |
| 75 | 60 | 159 | Albanese A, Bhatia K, Bressman SB, et al. Phenomenology and classification of dystonia: A consensus update. Mov Disord 2013;28:863–873 | Clinical: Classification |
| 76 | 61a | 157 | Abbruzzese G, Marchese R, Buccolieri A; et al. Abnormalities of sensorimotor integration in focal dystonia – A transcranial magnetic stimulation study. Brain 2001;124:537–545 | Lab: Patho-physiology |
| 77 | 61b | 157 | Kotagal P, Lüders H, Morris HH, et al. Dystonic posturing in complex partial seizures of temporal-lobe onset: a new lateralizing sign. Neurology 1989:39:196–201 | Lab: Patho-physiology |
| 78 | 62a | 155 | Jankovic J, Vuong KD, Ahsan, J. Comparison of efficacy and immunogenicity of original versus current botulinum toxin in cervical dystonia. Neurology 2003;60:1186–1188 | Clinical: Medicine |
| 79 | 62b | 155 | Vercueil L, Pollak P, Fraix V, et al. Deep brain stimulation in the treatment of severe dystonia. J Neurol 2001;248:695–700 | Clinical: Surgery |
| 80 | 63a | 154 | Kothary R, Clapoff S, Brown A, Campbell R, Peterson A, Rossant J. A transgene containing lacz inserted into the dystonia locus is expressed in neural tube. Nature 1988;335:435–437 | Lab: Genetic studies |
| 81 | 63b | 154 | Byrnes ML, Thickbroom GW, Wilson SA, et al. The corticomotor representation of upper limb muscles in writer’s cramp and changes following botulinum toxin injection. Brain 1998;121:977–988 | Clinical: Medicine |
| 82 | 64a | 152 | Rajput AH, Gibb WR, Zhong XH, et al. Dopa-responsive dystonia – pathological and biochemical observations in a case. Ann Neurol 1994;35:396–402 | Clinical: Medicine |
| 83 | 64b | 152 | Krack P, Pollak P, Limousin P, et al. From off-period dystonia to peak-dose chorea – The clinical spectrum of varying subthalamic nucleus activity. Brain 1999; 122:1133–1146 | Clinical: Classification |
| 84 | 64c | 152 | Knappskog PM, Flatmark T, Mallet J, et al. Recessively inherited l-dopa-responsive dystonia caused by a point mutation (q381k) in the tyrosine-hydroxylase gene. Hum Mol Genet 1995;4:1209–1212 | Lab: Genetic studies |
| 85 | 65 | 151 | Kessler KR, Skutta M, Benecke R. Long-term treatment of cervical dystonia with botulinum toxin A: efficacy, safety, and antibody frequency. J Neurol 1999;246:265–274 | Clinical: Medicine |
| 86 | 66a | 150 | Ceballos-Baumann AO, Sheean G, Passingham RE, et al. Botulinum toxin does not reverse the cortical dysfunction associated with writer’s cramp . A PET study. Brain 1997;120:571–582 | Lab: Patho-physiology |
| 87 | 66b | 150 | Nygaard TG, Wilhelmsen KC, Risch NJ, et al. Linkage mapping of dopa-responsive dystonia (drd) to chromosome 14q. Nat Genet 1993;5:386–391 | Lab: Genetic studies |
| 88 | 65a | 149 | Tempel LW, Perlmutter JS. Abnormal cortical responses in patients with writer’s cramp. Neurology 1993;43:2252–2257 | Lab: Patho-physiology |
| 89 | 65b | 149 | Agostino R, Berardelli A, Formica A, et al. Sequential arm movements in patients with Parkinson’s disease, Huntington’s disease and dystonia. Brain 1992;115:1481–1495 | Clinical: Classification |
| 90 | 66a | 146 | Blackie JD, Lees AJ. Botulinum toxin treatment in spasmodic torticollis. J Neurol Neurosurg Psychiatry 1990;53:640–643 | Clinical: Medicine |
| 91 | 66b | 146 | Lugaresi E, Cirignotta F. Hypnogenic paroxysmal dystonia: epileptic seizure or a new syndrome? Sleep 1981;4:129–138 | Clinical: Classification |
| 92 | 67 | 143 | Leube B, Rudnicki D, Ratzlaff T, et al. Idiopathic torsion dystonia: Assignment of a gene to chromosome 18p in a German family with adult onset, autosomal dominant inheritance and purely focal distribution. Hum Mol Genet 1996;5:1673–1677 | Lab: Genetic studies |
| 93 | 68a | 142 | Fahn S. High dosage anticholinergic therapy in dystonia. Neurology 1983;33:1255–1261 | Clinical: Medicine |
| 94 | 68b | 142 | Cohen LG, Hallett M, Geller, BD, et al. Treatment of focal dystonias of the hand with botulinum toxin injections. J Neurol Neurosurg Psychiatry 1989;52:355–363 | Clinical: Medicine |
| 95 | 69a | 141 | Chen R, Wassermann EM, Canos M, et al. Impaired inhibition in writer’s cramp during voluntary muscle activation. Neurology 1997;49:1054–1059 | Clinical: Medicine |
| 96 | 69b | 141 | Goodchild RE, Dauer WT. Mislocalization to the nuclear envelope: An effect of the dystonia-causing torsinA mutation. Proc Natl Acad Sci U S A 2004;101:847–852 | Lab: Genetic studies |
| 97 | 70 | 140 | Paisan-Ruiz C, Bhatia KP, Li A, et al. Characterization of PLA2G6 as a locus for dystonia-parkinsonism. Ann Neurol 2009; 65:19–23 | Lab: Genetic studies |
| 98 | 71 | 138 | Ondo WG, Desaloms JM, Jankovic J, et al. Pallidotomy for generalized dystonia. Mov Disord 1998;13:693–698 | Clinical: Surgery |
| 99 | 72a | 137 | Quartarone A, Siebner HR, Rothwell JC. Task-specific hand dystonia: can too much plasticity be bad for you? Trends Neurosci 2006;29:192–199 | Review |
| 100 | 72b | 137 | DeVries DD, Went LN, Bruyn GW, et al. Genetic and biochemical impairment of mitochondrial complex I activity in a family with Leber hereditary optic neuropathy and hereditary spastic dystonia. Am J Hum Genet 1996;58:703–771 | Lab: Patho-physiology |
For further analysis of the most cited works, each article was classified into one of seven categories: epidemiology, laboratory genetic studies, laboratory pathophysiological studies, clinical classification, clinical medical therapies, clinical surgical therapies, and review articles. The numbers of articles in each category by field of study (ET and dystonia) are shown in Figure 1.
Studies were included in this category if they described the epidemiology of the condition including prevalence, incidence, comparisons, and trends over time. For ET, there were 15 studies in this category. Out of these, eight studies investigated the incidences of ET in different regions or countries. The remaining seven examined the association of ET with dementia, PD, and other functional measures. By comparison, there were only four dystonia articles in this category. These studies investigated the prevalence of dystonia in different population subgroups.
This broad category included new description of the disease, new diagnostic features, its classification into subtypes, as well as condition-specific measures and rating scales. There were 18 articles in this category, including one citation classic for ET.11 Similarly, there were 13 articles for dystonia and one citation classic.16
Studies were included in this category if they were genetic studies. There were seven studies for ET, including investigations in the familial essential tremor gene FET1, fragile X premutation, variants in the sequences of the LINGO1 gene and the dopamine D-3 receptor, GABA(A) alpha 1 receptor knockout, polymorphism of NACP-Rep1, and methodologic issues in ET research. For dystonia, there were 19 studies including two citation classics.14,15 These two genetic studies were the first and third most highly ranked articles by citations in the dystonia field. There were five studies on the early onset dystonia gene (DYT1),;four on idiopathic dystonia; two on the genetics of dopa-responsive dystonia; one on Leber optic atrophy and dystonia; one on lacZ transgene insertion; and one each on mutations of the deafness/dystonia peptide (DDP) gene, GTP cyclohydrolase-1 gene, epsilon sarcoglycan gene, dystonia musculorum gene, Na+/K+-ATPase alpha 3 gene, and phospholipase A2 group VI (PLA2G6) gene.
Studies investigating the pathophysiologic mechanisms underlying ET and dystonia were included in this category. There were 21 studies for ET, including 10 that employed imaging techniques. There were four studies on the physiology of ET, five on pathology, and the remaining studies on pharmacology or biochemical analysis of cerebrospinal fluid. For dystonia, there were 20 studies with 13 on neurophysiology, six on imaging, and one on pharmacology.
Only those studies dealing with the application of medical and nonsurgical treatments were included in this category. For ET, there were eight articles on medical treatment with two studies on propranolol and primidone, and one study each on gabapentin and propranolol, on propranolol alone, on alcohol, on botulinum toxin, and on mechanical displacement. For dystonia, there were 30 articles including one citation classic.18 The effect of botulinum toxin was investigated in 19 out of the 30 articles. The remaining articles included five studies on transcranial magnetic stimulation; three studies on levodopa; and one study each on baclofen, lidocaine, and anticholinergic treatment.
Only those studies that dealt primarily with surgical treatment were included in this category. In several studies, the primary aim of the surgical treatment was for tremor whose etiology could either be due to PD or ET; these were also included. For ET, there were 16 articles with three citation classics.10,12,13 There was one article on the effect of thalamotomy and two articles comparing thalamotomy with deep brain stimulation (DBS); the 13 remaining articles investigated the effects of thalamic stimulation of the ventral intermediate nucleus. For dystonia, there were nine articles on surgical therapies, all of which were studies of globus pallidus internus (GPi) DBS.
There were 15 review articles for ET: seven on the general aspects of ET and the remainder reviewing the treatment, pathophysiology, and effect of electrical stimulation. For dystonia, there were five reviews of pathophysiology or diagnostic features.
The publication year of the most cited articles are summarized in Figure 2. This showed that there was a peak of the most cited articles for ET for articles published between 2000 and 2004, and for dystonia between 1995 and 1999. The most cited articles were published in 38 journals. The top 10 journals by numbers of articles published and numbers of citations per articles are shown in Figure 3. The top 10 journals accounted for 162 (81%) of the combined 200 most cited articles.
The most highly cited articles in the fields of ET and dystonia were identified (Tables 2 and 3). By category, the most cited studies were those on pathophysiology followed by medical treatments, clinical classification, genetic studies, surgical treatments, review articles, and epidemiology studies.
Comparing ET and dystonia, there are very similar proportions of articles in the most cited on pathophysiology and clinical classification categories. Nevertheless, the two fields diverge in other subfields because ET is characterized by a larger number of studies describing the epidemiology of the condition, whereas dystonia has a much higher representation of genetic studies. This is likely an indication of the greater understanding and contribution of genetic factors to dystonia compared to ET, which is—by contrast—a much more common condition but probably characterized by a wide spectrum of possible etiologies, making genetic studies very difficult. Moreover, there is a predominance of surgical treatment for ET, whereas medical treatment predominates for dystonia.
Trends over time showed that the peak period of when the most cited papers were published was between 1995 and 2005, with dystonia peaking 5 years before ET. This is in line with our previous work looking at the most cited papers in the functional neurosurgery literature, which showed a similar peak in the 1990s.6 The proposed reasons for the peak during this time are likely similar, namely that this period was particular active and productive with significant success in elucidating the causes and diagnosis of these conditions, and effective treatments such as deep brain stimulation or botulinum toxin were developed for dystonia. Another possible reason for the proposed peak may be a fundamental feature of contemporary research whereby older publications are no longer cited because they have been replaced by new studies that have replicated the findings and superseded them.6 At the same time, more recent studies have not had time to become established as a most cited article, for example the more recent discovery of the DYT6 gene.20
The majority of the most cited articles were generally published in specialized journals such as Neurology, Annals of Neurology, Movement Disorders, Brain, Journal of Neurology, Neurosurgery, and Psychiatry, among others (Figure 3). However, articles published in the more general medical journals such as the New England Journal of Medicine or Lancet tend to receive more citations per article published. This also corresponded to their higher overall journal impact factor (Figure 3). An exception were articles published in the Journal of Neurosurgery, which received on average 356 citations per articles, more than would be expected by the journal’s impact factor. These were attributable to contributions from three studies on deep brain stimulation.12,21,22 This suggests that the publication of important clinical therapeutic studies in a specialized journal is also able to achieve significant impact.
The choice of ISI Web of Science, which indexes over 15,000 journals, over Google Scholar, which indexes a wider range of academic documents may also have had an effect on our findings. However, our previous reviews in other fields yielded very similar results using these two search engines when the study field was small.6,9 Another limitation is that the search terms may not have yielded all possible results despite our inclusion of broad terms. For the ISI Web of Science search engine, it is possible to perform either a title- or topic-based search. The former would only search for the search term in the title of the article, whereas a topic-based search would also include the abstract. Given the small size of the ET and dystonia fields, a topic-based search was selected to retrieve all possible results as described in the methods section. This is particularly important for ET, as many of the studies would also include patients with parkinsonian tremor. By contrast, a citation analysis study on ET using a title-based search would yield fewer results.8 Finally, the list of most cited papers changes with time and is therefore a snapshot of the current state of research.
We performed an analysis to identify the most cited ET and dystonia papers. There are fewer citation classics compared to PD, confirming that this is a smaller field of research. Compared to dystonia, areas of research in ET such as genetics, neurophysiology, and medical treatment are underrepresented. The peak of citations for ET is also lagging by about 5 years. These findings suggest that further work remains to be carried out to improve our understanding of the basic science of ET.
1 Acknowledgements: None.
2 Financial Disclosures: None.
3 Conflicts of interest: Dr. King has no conflicts of interest, including relevant financial interests, activities, relationships, and affiliations.
4 Dr. Fasano has given expert testimony for Medtronic, has received honoraria from serving scientific board of Abbvie, Boston Scientific, and UCB pharma and has received honoraria from TEVA, UCB pharma, Medtronic, Abbvie, Boston Scientific, Novartis, and Chiesi Farmaceutici.
5 Dr. Lozano receives consulting fees from Medtronic, Boston Scientific, St. Jude, and Ely Lilly and holds an interest in Functional Neuromodulation.
6 Ethics Statement: Not applicable for this Review.
Ponce, FA and Lozano, AM (2011). The most cited works in Parkinson’s disease. Mov Disord 26: 380–390. 10.1002/mds.23445 [PubMed]
Garfield, E (1987). 100 citation classics from the Journal of the American Medical Association. JAMA 257: 52–59, DOI: https://doi.org/10.1001/jama.1987.03390010056028 [PubMed]
Ponce, FA and Lozano, AM (2010). Highly cited works in neurosurgery. Part II: the citation classics. J Neurosurg 112: 233–246, DOI: https://doi.org/10.3171/2009.12.JNS091600 [PubMed]
Ponce, FA and Lozano, AM (2010). Highly cited works in neurosurgery. Part I: the 100 top-cited papers in neurosurgical journals. J Neurosurg 112: 223–232. 10.3171/2009.12.JNS091599 [PubMed]
Ibrahim, GM, Snead, OC 3rd, Rutka, JT and Lozano, AM (2012). The most cited works in epilepsy: trends in the “citation classics. Epilepsia 53: 765–770, DOI: https://doi.org/10.1111/j.152-1167.2012.03455.x [PubMed]
Lipsman, N and Lozano, AM (2012). Measuring impact in stereotactic and functional neurosurgery: an analysis of the top 100 most highly cited works and the citation classics in the field. Stereotact Funct Neurosurg 90: 201–209, DOI: https://doi.org/10.1159/000337170 [PubMed]
Heros, RC (2010). Highly cited works in neurosurgery. J Neurosurg 112: 220–222, DOI: https://doi.org/10.3171/2009.11.JNS091706 [PubMed]
Benito-León, J and Louis, ED (2013). The top 100 cited articles in essential tremor. Tremor Other Hyperkinet Mov, : 3. pii:tre-03-186-4307-1.
Lipsman, N, Woodside, DB and Lozano, AM (2014). Trends in anorexia nervosa research: an analysis of the top 100 most cited works. Eur Eat Disord Review 22: 9–14. 10.1002/erv.2270
Benabid, AL Pollak, P Gervason, C et al. (1991). Long-term suppression of tremor by chronic stimulation of the ventral intermediate thalamic nucleus. Lancet 337: 403–406. [PubMed]
Deuschl, G, Bain, P and Brin, M (1998). Consensus statement of the Movement Disorder Society on tremor. Ad Hoc Scientific Committee. Mov Disord 13: 2–23, DOI: https://doi.org/10.1002/mds.870131303 [PubMed]
Benabid, AL Pollak, P Gao, DM et al. (1996). Chronic electrical stimulation of the ventralis intermedius nucleus of the thalamus as a treatment of movement disorders. J Neurosurg 84: 203–214, DOI: https://doi.org/10.3171/jns.1996.84.2.0203 [PubMed]
Schuurman, PR Bosch, DA Bossuyt, PM et al. (2000). A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor. N Engl J Med 342: 461–468, DOI: https://doi.org/10.1056/NEJM200002173420703 [PubMed]
Ozelius, LJ Hewett, JW Page, CE et al. (1997). The early-onset torsion dystonia gene (DYT1) encodes an ATP binding protein. Nat Genet 17: 40–48, DOI: https://doi.org/10.1038/ng0997-40 [PubMed]
Ichinose, H Ohye, T Takahashi, E et al. (1994). Hereditary progressive dystonia with marked diurnal fluctuation caused by mutations in the GTP cyclohydrolase-I gene. Nat Genet 8: 236–242, DOI: https://doi.org/10.1038/ng1194-236 [PubMed]
Burke, RE, Fahn, S, Marsden, CD, Bressman, SB, Moskowitz, C and Friedman, J (1985). Validity and reliability of a rating-scale for the primary torsion dystonias. Neurology 35: 73–77, DOI: https://doi.org/10.1212/WNL.35.1.73 [PubMed]
Berardelli, A, Rothwell, JC, Hallett, M, Thompson, PD, Manfredi, M and Marsden, CD (1998). The pathophysiology of primary dystonia. Brain 121: 1195–1212, DOI: https://doi.org/10.1093/brain/121.7.1195 [PubMed]
Tsui, JK, Stoessl, AJ, Eisen, A, Calne, S and Calne, DB (1986). Double-blind study of botulinum toxin in spasmodic torticollis. Lancet 2: 245–247. [PubMed]
Vidailhet, M Vercueil L Houeto, JL et al. (2005). Bilateral deep-brain stimulation of the globus pallidus in primary generalized dystonia. N Engl J Med 352: 459–467, DOI: https://doi.org/10.1056/NEJMoa042187 [PubMed]
Fuchs, T Gavarini, S Saunders-Pullman, R et al. (2009). Mutations in the THAP1 gene are responsible for DYT6 primary torsion dystonia. Nat Genet 41: 286–288, DOI: https://doi.org/10.1038/ng.304 [PubMed]
Blond, S Caparros-Lefebvre, D Parker, F et al. (1992). Control of tremor and involuntary movement-disorders by chronic stereotaxic stimulation of the ventral intermediate thalamic nucleus. J Neurosurg 77: 62–68, DOI: https://doi.org/10.3171/jns.1992.77.1.0062 [PubMed]
Coubes, P Cif, L El Fertit, H et al. (2004). Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results. J Neurosurg 101: 189–194, DOI: https://doi.org/10.3171/jns.2004.101.2.0189 [PubMed]