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What is impact?

Matthew C Kiernan

The word impact is in peril of becominghackneyed terminology. In modernparlance its meaning appears to haveundergone more costume changes thanLady Gaga on a whistle-stop tour! And inthe world of medical publishing the defi-nition of impact is nowhere more nebu-lous than where a ground breaking paper,and a review that merely cites a groundbreaking paper, are measured using thesame impact criteria.

How then does one judge the impact ofa publication, both at the time and

thereafter? For instance, in high turnoverpublications such as daily newspapers,initial impact may be phenomenal,although transitory, from front pagescoop, to fish and chips wrapping in thespace of a single day. When consideringmedicine, and particularly medical publi-cations, presumably the desired impactwould mean that manuscripts were read,information conveyed and subsequentlyadopted by the reader, and as a conse-quence, practice was changed with thereasonable hope and anticipation thatpatient outcomes would improve.

When considering the role of JNNP insuch a process, in addition to immediateimpact, the journals current high standinghas been built up over close to a century ofpublishing the worlds seminal neurosci-ence publications.1 As proof of longevityand ongoing relevance, akin to openingbottles of wine from an established cellarfor the palate of the connoisseur, thesuccess of the journals immense archive

built up from 1920 is refl

ected through ourachievement of the longest citation half-life of any journal across the clinicalneurosciences. In other words, the originalJNNP manuscripts continue to be heavilycited, many in the thousands,2 3 with somenotching up more than 10 000 citations,4

further serving to reinforce the journalsstanding as a neuroscience trailblazer.

How then does a manuscript becomehighly cited, a critical work from whichothers model and further develop theirtheories and practice? To help us under-stand the process, in this issue of

JNNP we launch Impact Commentaries(figure 1), a monthly series which willprovide a modern perspective on some ofthe most highly cited JNNP papers of alltime. Where possible, we have approachedthe authors of the original study. In thoseinstances where the author is no longeralive, we have asked key opinion leaders tocomment on the original science andsubsequent course of the findingspresented, to decipher the reasons behindthe success of each publication. In additionto providing pearls of wisdom, these

commentaries provide newcomers, such asneurology trainees, with an opportunity toput the discoveries and developments intoan historical context. Unfortunately, it isall too rare to have the opportunity to getthe long view from the original author ofresearch that in retrospect has beena blockbuster. With our new monthlyImpact Commentaries, we will focus onthe opinions that set the scene and then gobeyond the research study to discover howit influenced important developments inthe field, in some cases over many deca-desda perspective that newcomer journals

are unable to provide.

While looking at impact from the past,JNNP continues to be excited about thefuture. Our ultimate goal is to identify keynew developments and potential futurediscoveries in the constantly evolvingworld of neuroscience. The past year hasseen JNNP receive more than 3000

submissions, although the higher submis-sion rates inevitably generate greaterselectivity. Already, a significant propor-tion of these recently published manu-scripts, covering the entire realm ofclinical neuroscience, are well on the wayto becoming citation classics in their ownright.5e16Add to this reviews from expe-rienced clinician researchers, regularpodcasts and the recently launched JNNPblog, and a very 21st century notion ofimpact begins to develop.

Borrowing a sentiment from the musi-cian Brian Eno, once youve shocked, you

cant shock again with the same tune.This year at JNNP we will be embracingthat old rockers conviction by bothexamining why the papers that shapedthe world of neuroscience did so andseeking out the future classics that willmake their impact on the brain and mindsciences. We look forward to an excitingand challenging year ahead.

Competing interests None.

Provenance and peer review Commissioned; not

externally peer reviewed.

Accepted 28 October 2011

J Neurol Neurosurg Psychiatry 2012;83:1e2.doi:10.1136/jnnp-2011-301738

REFERENCES1. Kiernan MC. The realm of neurologydpast, present

and future. J Neurol Neurosurg Psychiatry2011;82:1.

2. Scoville WB, Milner B. Loss of recent memory after

bilateral hippocampal lesions. J Neurol Neurosurg

Psychiatry1957;20:11e21.

3. Hughes AJ, Daniel SE, Kilford L, et al. Accuracy of

clinical-diagnosis of idiopathic Parkinsons-diseaseda

clinicopathological study of 100 cases. J Neurol

Neurosurg Psychiatry 1992;55:181e4.

4. Hamilton M. A rating scale for depression. J Neurol


5. Buse DC, Manack A, Serrano D, et al.

Sociodemographic and comorbidity profiles of chronic

migraine and episodic migraine sufferers. J Neurol


6. Jankovic J, Jimenez-Shahed J, Brown LW.

A randomised, double-blind, placebo-controlled

study of topiramate in the treatment of Tourette

syndrome. J Neurol Neurosurg Psychiatry2010;81:70e3.

7. Fleuren JF, Voerman GE, Erren-Wolters CV, et al.

Stop using the Ashworth Scale for the assessment of

spasticity. J Neurol Neurosurg Psychiatry2010;81:46e52.

8. Fois AF, Wotton CJ, Yeates D, et al. Cancer in

patients with motor neuron disease, multiple

sclerosis and Parkinsons disease: record linkage

studies. J Neurol Neurosurg Psychiatry2010;81:215e21.

Figure 1 Impact Commentaries, launched inthis months issue, provide a modern perspec-

tive on the most highly cited JNNP papers ofall time.

Correspondence to Professor M C Kiernan,Editor-in-Chief of JNNP, Neuroscience Research

Australia, Barker Street, Randwick, Sydney, NSW 2031,Australia; [email protected]

J Neurol Neurosurg Psychiatry January 2012 Vol 83 No 1 1

Editorial commentaries

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9. Logroscino G, Traynor BJ, Hardiman O, et al.

Incidence of amyotrophic lateral sclerosis in

Europe. J Neurol Neurosurg Psychiatry2010;81:385e90.

10. Topakian R, Barrick TR, Howe FA, et al. Blood-brain

barrier permeability is increased in normal-appearing

white matter in patients with lacunar stroke and

leucoaraiosis. J Neurol Neurosurg Psychiatry2010;81:192e7.

11. Ibarretxe-Bilbao N, Ramirez-Ruiz B, Junque C, et al.Differential progression of brain atrophy in Parkinsons

disease with and without visual hallucinations.

J Neurol Neurosurg Psychiatry2010;81:650e7.

12. Uncini A, Manzoli C, Notturno F, et al. Pitfalls in

electrodiagnosis of Guillain-Barre syndrome subtypes.

J Neurol Neurosurg Psychiatry2010;81:1157e63.

13. Douglass CP, Kandler RH, Shaw PJ, et al. An

evaluation of neurophysiological criteria used in the

diagnosis of motor neuron disease. J Neurol


14. Zampieri C, Salarian A, Carlson-Kuhta P, et al. Theinstrumented timed up and go test: potential

outcome measure for disease modifying therapies in

Parkinsons disease. J Neurol Neurosurg Psychiatry2010;81:171e6.

15. Kagi G, Bhatia KP, Tolosa E. The role of DAT-SPECT in

movement disorders. J Neurol Neurosurg Psychiatry2010;81:5e12.

16. Charlton RA, Schiavone F, Barrick TR, et al. Diffusion

tensor imaging detects age related white matter

change over a 2 year follow-up which is associated

with working memory decline. J Neurol NeurosurgPsychiatry2010;81:13e19.

The expanding phenotype ofCLIPPERS: is it a disease ora syndrome?

Jun-ichi Kira

Chronic lymphocytic inflammation withpontine perivascular enhancementresponsive to steroids (CLIPPERS) isa newly named pontine-centric inflam-matory disorder.1 The cardinal feature ofthe disease is punctate gadoliniumenhancement peppering the pons onMRI. The unique MRI features of thisdisorder have attracted many neurologistsattention leading to the publication of

several case reports recently.2e5

The biop-sied pontine pathology from the originalstudy revealed a marked perivascular andparenchymal CD3-postive T-cell inflam-mation without any specific pathology.1

However, because of the lack of a specificbiomarker and long-term follow-up, thenosological position of CLIPPERS is still tobe established.

The paper by Simon and colleagues6

(see page 15) reports five additional casesof CLIPPERS with detailed pathology andlong-term evaluation, expanding the clin-ical, neuroimaging and pathological

phenotype of this disorder: (1) cognitiveimpairment was seen in four of five casesalong with cerebral atrophy in three ofthem; (2) MRI lesions were distributednot only in the pons but also in thebrachium ponti and cerebellum, which

later culminated in severe atrophy of thecerebellum and brachium ponti; (3)prominent CD4-positive T lymphocytic aswell as histiocytic infiltrates wereobserved, involving both small arteriesand veins but with few B cells. Neuro-axonal injury was also found but therewas no evidence of vasculitis (destructionof the vessel wall with fibrinoid necrosis).6

Based on the distribution of MRI lesions,

Simon and colleagues propose an amend-ment of the disorder to chronic lympho-cytic inflammation with pontocerebellarperivascular enhancement responsiveto steroids (CLIPPERS).6 Lesions mayoccur in the spinal cord, basal ganglia orcerebral white matter. The perivasculargadolinium enhancement pattern andsteroid-responsiveness indicate the auto-immune/inflammatory nature of thiscondition. These authors6 and others1

carried out extensive laboratory andpathological surveys to exclude specificcauses for the condition, such as sarcoid-

osis, histiocytosis, lymphoma, gran-ulomatosis, multiple sclerosis, isolatedangiitis of the central nervous system,Lyme disease, Whipple disease, Bickerstaffbrainstem encephalitis, Behcets diseaseand Sjgrens syndrome, suggesting thatCLIPPERS is an independent diseaseentity.

However, there appears to be someoverlap with other autoimmune/inflam-matory brainstem-predominant encepha-litis, especially brainstem type ofneuro-Behcets disease and Sjgrens

syndrome. Pittock and colleagues

1

foundno evidence of systemic illness; however,

Simon and colleagues6 reported additionalsubclinical systemic findings in somecases, namely antinuclear antibody SS-A,lymphocytic conjunctival infiltrate,lymphocytic sialadenitis and parotiduptake on gallium scan. Neuro-Behcetsdisease is well known and frequentlyaffects the pons and cerebellum. Thisdisease occasionally presents withoutapparent mucocutaneo-ocular manifesta-tions,7 8 showing progressive cerebellarataxia and prominent pontine and cere-bellar atrophy. Such patients can alsobenefit from early steroid therapy. Cogni-tive impairment, first described by Simonand colleagues6 in CLIPPERS, is alsofrequently encountered in Behcetsdisease. On MRI, enhancement of lesionsin the pons and middle cerebellar pedun-cles frequently shows a mottled non-confluent pattern similar to that ofCLIPPERS.9e11At the chronic stage, severe

atrophy of the basis pontis and cerebellumis common. Pathologically, Behcetsdisease shows perivascular infiltration of Tcells and macrophages/monocytes withfew B cells, mainly involving venules butalso occasionally small arteries.12 Exami-nations of needle reaction, HLA-DR51 andinterleukin 6 in the cerebrospinal fluid areessential to differentiate brainstem type ofneuro-Behcets disease from CLIPPERS. Sofar, all cases with CLIPPERS have beenreported from Western countries. Behcetsdisease is prevalent in Mediterraneancountries, the Middle East and Japan. It is

interesting to know whether there is anyracial preponderance for this condition.

Cerebellar and brainstem involvementhas also been repeatedly reported in Sjg-rens syndrome,13e15 while sicca symp-toms may not be clinically overt. MRIfeatures of brainstem involvement inprimary Sjgrens syndrome occasionallypresents punctate gadolinium-enhancingfoci peppering the pons, middle cerebellarpeduncles, cerebellar hemispheres andvermis, and mesencephalon, which arequite similar to those of CLIPPERS.15 The

subclinical involvement of exocrine glandsfound in some CLIPPERS cases6 suggests

Department of Neurology, Neurological Institute,Graduate School of Medical Sciences, Kyushu University,Japan

Correspondence to Professor Jun-ichi Kira,Department of Neurology, Neurological Institute,Graduate School of Medical Sciences, Kyushu University,

Fukuoka 812-8582, Japan;[email protected]

2 J Neurol Neurosurg Psychiatry January 2012 Vol 83 No 1

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doi: 10.1136/jnnp-2011-3017382012 83: 1-2J Neurol Neurosurg Psychiatry

Matthew C KiernanWhat is impact?

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