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Pallidotomy for Parkinson disease: a review of contemporary literature

Ahmed Alkhani and Andres M. Lozano

Object. The authors conducted an evidence-based review of contemporary published articles on pallidotomy to obtain an appraisal of this procedure in the treatment of Parkinson disease (PD).

Methods. A search of the Pubmed database performed using the key word “pallidotomy” yielded 263 articles cited between January 1, 1992, and July 1, 1999. Articles that included original, nonduplicated descriptions of patients with PD treated with radiofrequency pallidotomy were selected.

In 85 articles identified for critical review, 1959 patients with PD underwent pallidotomies at 40 centers in 12 countries. There were 1735 unilateral (88.6%) and 224 bilateral procedures (11.4%). The mean age of the patients was 61.4 ± 3.6 years and the mean duration of PD symptoms in these patients was 12.3 ± 1.9 years. Microelectrode recordings were used in 46.2% of cases. Outcomes were objectively documented using the Unified Parkinson Disease Rating Scale (UPDRS) in 501 (25.6%) of the cases at 6 months and in 218 (11.1%) of the cases at 1 year. There was a consensus on the benefits of pallidotomy for off period motor function and on period, drug-induced dyskinesias, with variations in the extent of symptomatic benefit across studies. At the 1-year assessment, the mean improvement in the UPDRS motor score during off periods was 45.3% and the mean improvement in contralateral dyskinesias during on periods was 86.4%. The overall mortality rate was 0.4% and the rate of persistent adverse effects was estimated at 14%. Major adverse events, including intracerebral hemorrhages, contralateral weakness, and visual field defects, occurred in 5.3% of patients reported.

Conclusions. Unilateral pallidotomy is effective and relatively safe in the treatment of PD; however, limited data are available on the long-term outcome of this procedure.

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Familial intracranial aneurysms

Andrés M. Lozano and Richard Leblanc

✓ The authors report seven individuals from two families, all of whom had aneurysmal subarachnoid hemorrhage. These cases and all reported cases of familial aneurysms (243 aneurysms in 177 patients from 74 families) were submitted to computer-aided multivariate analysis to determine if the aneurysms or the patients who harbor them differ from sporadic aneurysm cases. Familial aneurysms rupture at a smaller size (mean diameter 10.5 mm), and when the patient is younger (mean age 42.3 years and decennial age at peak incidence 40 to 49 years). There is a similar sex distribution (male to female ratio 48:52), a similar incidence of multiple aneurysms (21.5%), and a similar predominance of females over males with multiple aneurysms (2.2:1). Anterior communicating artery aneurysms occur less often in familial cases (19%) than in sporadic cases. In sibling pairs the aneurysms occur at the same or at mirror sites, and rupture within the same decade twice as frequently as randomly selected nonfamilial aneurysm patient pairs. The occurrence of aneurysms at identical and mirror sites is more frequent in familial cases and appears to be a function of the degree of kinship between affected individuals. These observations suggest a genetic basis for the pathogenesis of familial intracranial aneurysms.

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Highly cited works in neurosurgery. Part I: the 100 top-cited papers in neurosurgical journals

A review

Francisco A. Ponce and Andres M. Lozano

Object

The number of citations a published article receives is a measure of its impact in the scientific community. This study identifies and characterizes the current 100 top-cited articles in journals specifically dedicated to neurosurgery.

Methods

Neurosurgical journals were identified using the Institute for Scientific Information Journal Citation Reports. A search was performed using Institute for Scientific Information Web of Science for articles appearing in each of these journals. The 100 top-cited articles were selected and analyzed.

Results

The 100 most cited manuscripts in neurosurgical journals appeared in 3 of 13 journals dedicated to neurosurgery. These included 79 in the Journal of Neurosurgery, 11 in the Journal of Neurology, Neurosurgery and Psychiatry, and 10 in Neurosurgery. The individual citation counts for these articles ranged from 287 to 1515. Seventy-seven percent of articles were published between 1976 and 1995. Representation varied widely across neurosurgical disciplines, with cerebrovascular diseases leading (43 articles), followed by trauma (27 articles), stereotactic and functional neurosurgery (13 articles), and neurooncology (12 articles). The study types included 5 randomized trials, 5 cooperative studies, 1 observational cohort study, 69 case series, 8 review articles, and 12 animal studies. Thirty articles dealt with surgical management and 12 with nonsurgical management. There were 15 studies of natural history of disease or outcomes after trauma, 11 classification or grading scales, and 10 studies of human pathophysiology.

Conclusions

The most cited articles in neurosurgical journals are trials evaluating surgical or medical therapies, descriptions of novel techniques, or systems for classifying or grading disease. The time of publication, field of study, nature of the work, and the journal in which the work appears are possible determinants of the likelihood of citation and impact.

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Erratum: Highly cited works in neurosurgery. Part II: the citation classics

A review

Francisco A. Ponce and Andres M. Lozano

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Neurostimulation for chronic noncancer pain: an evaluation of the clinical evidence and recommendations for future trial designs

Robert J. Coffey and Andres M. Lozano

Object

Neurostimulation to treat chronic pain includes approved and investigational therapies directed at the spinal cord, thalamus, periaqueductal or periventricular gray matter, motor cortex, and peripheral nerves. Persistent pain after surgery and work-related or neural injuries are common indications for such treatments. In light of the risks, efforts, costs, and expectations associated with neurostimulation therapies, a careful reexamination of the methods used to gather evidence for this treatment’s long-term efficacy is in order.

Methods

The authors combed English-language publications to determine the nature of the evidence supporting the efficacy of neurostimulation therapies for chronic noncancer pain. To formulate recommendations for the design of future studies, the results of their analysis were compared with established guidelines for the evaluation of medical evidence.

Evidence supporting the efficacy of neurostimulation has been collected predominantly from retrospective series or from prospective studies whose design or methods of analysis make them subject to limited interpretation. To date, there has been no successful clinical study focused on establishing the efficacy of neurostimulation for pain and incorporating sufficient numbers of participants, matched control groups, sham stimulation, randomization, prospectively defined end points, and methods for controlling experimental bias. Currently available data provide little support for the common practices of psychological or pharmacological screening or trial stimulation to predict and/or improve long-term results.

Conclusions

These findings do not diminish the value of previous investigations or positive patient experiences and do not mean that the treatments are ineffective; rather, they reveal that new data are required to answer the questions raised in and by previous study data. Future analyses of emerging neurostimulation modalities for pain should, whenever feasible, require unambiguous diagnoses as an entry criterion and should involve the use of randomization, parallel control groups that receive sham stimulation, and blinding of patients, investigators, and device programmers. Given the chronicity of patient symptoms and stimulation therapies, efficacy should be studied for 1 year or longer after device implantation. Meticulous study methods are especially important to evaluate new therapies like motor cortex and occipital nerve stimulation.

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Highly cited works in neurosurgery. Part II: the citation classics

A review

Francisco A. Ponce and Andres M. Lozano

Object

The term “citation classic” has been used in reference to an article that has been cited more than 400 times. The purpose of this study is to identify such articles that pertain to clinical neurosurgery.

Methods

A list of search phrases relating to neurosurgery was compiled. A topic search was performed using the Institute for Scientific Information Web of Science for phrases. Articles with more than 400 citations were identified, and nonclinical articles were omitted. The journals, year of publication, topics, and study types were analyzed.

Results

There were 106 articles with more than 400 citations relating to clinical neurosurgery. These articles appeared in 28 different journals, with more than half appearing in the Journal of Neurosurgery or the New England Journal of Medicine. Fifty-three articles were published since 1990. There were 38 articles on cerebrovascular disease, 21 on stereotactic and functional neurosurgery, 21 on neurooncology, 19 on trauma, 4 on nontraumatic spine, 2 on CSF pathologies, and 1 on infection. There were 29 randomized trials, of which 86% appeared in the New England Journal of Medicine, Lancet, or the Journal of the American Medical Association, and half concerned the prevention or treatment of stroke. In addition, there were 16 prospective studies, 15 classification or grading systems, and 7 reviews. The remaining 39 articles were case series, case reports, or technical notes.

Conclusions

More than half of the citation classics identified in this study have been published in the past 20 years. Case series, classifications, and reviews appeared more frequently in neurosurgical journals, while randomized controlled trials tended to be published in general medical journals.

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Editorial

Psychosurgery

Andres M. Lozano

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Academic impact and rankings of American and Canadian neurosurgical departments as assessed using the h index

Clinical article

Francisco A. Ponce and Andres M. Lozano

Object

The authors undertook a study to estimate the relative academic impact of neurosurgical departments in Canada and the US using the h index, a measure of the number of citations received by a collection of work.

Methods

The study included 99 departments of neurosurgery with residency programs participating in the US National Residency Matching Program, and the 14 analogous Canadian programs. Three types of h indices were determined—one reflecting the cumulative work attributed to a neurosurgical department, h(c); one restricted to the cumulative work published over the past 10 years, h(10); and one limited to work published in 2 major North American neurosurgical journals, hNS(10). For an article to be included, attribution to a neurosurgical department had to appear in the address field in the database Thomson's ISI Web of Science. The three h indices were compared with each other, and their relation to other measures such as size of the department, degrees held by the faculty, and research funding was examined.

Results

Significant correlations were found between the citation indices and faculty size, number of publications and the types of degrees held by the faculty, and funding by the US NIH. Three types of authorship were identified: neurosurgeon, nonclinician researcher, and nonneurosurgeon clinical affiliate. The degree to which the latter 2 nonneurosurgeon categories contributed to the departmental h index varied among departments and can confound interdepartmental comparison. Limiting articles to those published in neurosurgical journals appeared to correct for the influence of nonneurosurgeons in departmental impact and reflect neurosurgeon-driven scholarship.

Conclusions

The h index may be useful in evaluating output across neurosurgery departments.

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The academic productivity and impact of the University of Toronto Neurosurgery Program as assessed by manuscripts published and their number of citations

Christopher S. Lozano, Joseph Tam, Abhaya V. Kulkarni, and Andres M. Lozano

OBJECT

Recent works have assessed academic output across neurosurgical programs using various analyses of accumulated citations as a proxy for academic activity and productivity. These assessments have emphasized North American neurosurgical training centers and have largely excluded centers outside the United States. Because of the long tradition and level of academic activity in neurosurgery at the University of Toronto, the authors sought to compare that program's publication and citation metrics with those of established programs in the US as documented in the literature. So as to not rely on historical achievements that may be of less relevance, they focused on recent works, that is, those published in the most recent complete 5-year period.

METHODS

The authors sought to make their data comparable to existing published data from other programs. To this end, they compiled a list of published papers by neurosurgical faculty at the University of Toronto for the period from 2009 through 2013 using the Scopus database. Individual author names were disambiguated; the total numbers of papers and citations were compiled on a yearly basis. They computed a number of indices, including the ih(5)-index (i.e., the number of citations the papers received over a 5-year period), the summed h-index of the current faculty over time, and a number of secondary measures, including the ig(5), ie(5), and i10(5)-indices. They also determined the impact of individual authors in driving the results using Gini coefficients. To address the issue of author ambiguity, which can be problematic in multicenter bibliometric analyses, they have provided a source dataset used to determine the ih(5) index for the Toronto program.

RESULTS

The University of Toronto Neurosurgery Program had approximately 29 full-time surgically active faculty per year (not including nonneurosurgical faculty) in the 5-year period from 2009 to 2013. These faculty published a total of 1217 papers in these 5 years. The total number of citations from these papers was 13,434. The ih(5)-index at the University of Toronto was 50.

CONCLUSIONS

On the basis of comparison with published bibliometric data of US programs, the University of Toronto ranks first in terms of number of publications, number of citations, and ih(5)-index among neurosurgical programs in North America and most likely in the world.

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Familial Cerebral Aneurysms and Type III Collagen Deficiency