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Ryan P. Lee, Raymond Xu, Pooja Dave, Sonia Ajmera, Jock C. Lillard, David Wallace, Austin Broussard, Mustafa Motiwala, Sebastian Norrdahl, Carissa Howie, Oluwatomi Akinduro, Garrett T. Venable, Nickalus R. Khan, Douglas R. Taylor, Brandy N. Vaughn and Paul Klimo Jr.

OBJECTIVE

There has been an increasing interest in the quantitative analysis of publishing within the field of neurosurgery at the individual, group, and institutional levels. The authors present an updated analysis of accredited pediatric neurosurgery training programs.

METHODS

All 28 Accreditation Council for Pediatric Neurosurgery Fellowship programs were contacted for the names of pediatric neurosurgeons who were present each year from 2011 through 2015. Faculty names were queried in Scopus for publications and citations during this time period. The 5-year institutional Hirsch index [ih(5)-index] and revised 5-year institutional h-index [ir(5)-index] were calculated to rank programs. Each publication was reviewed to determine authorship value, tier of research, clinical versus basic science research, subject matter, and whether it was pediatrics-specific. A unique 3-tier article classification system was introduced to stratify clinical articles by quality and complexity, with tier 3 being the lowest tier of publication (e.g., case reports) and tier 1 being the highest (e.g., randomized controlled trials).

RESULTS

Among 2060 unique publications, 1378 (67%) were pediatrics-specific. The pediatrics-specific articles had a mean of 15.2 citations per publication (median 6), whereas the non–pediatrics-specific articles had a mean of 23.0 citations per publication (median 8; p < 0.0001). For the 46% of papers that had a pediatric neurosurgeon as first or last author, the mean number of citations per publication was 12.1 (median 5.0) compared with 22.5 (median 8.0) for those in which a pediatric neurosurgeon was a middle author (p < 0.0001). Seventy-nine percent of articles were clinical research and 21% were basic science or translational research; however, basic science and translational articles had a mean of 36.9 citations per publication (median 15) compared with 12.6 for clinical publications (median 5.0; p < 0.0001). Among clinical articles, tier 1 papers had a mean of 15.0 citations per publication (median 8.0), tier 2 papers had a mean of 18.7 (median 8.0), and tier 3 papers had a mean of 7.8 (median 3.0). Neuro-oncology papers received the highest number of citations per publication (mean 25.7). The most common journal was the Journal of Neurosurgery: Pediatrics (20%). MD/PhD faculty members had significantly more citations per publication than MD faculty members (mean 26.7 vs 14.0; p < 0.0001) and also a higher number of publications per author (mean 38.6 vs 20.8). The median ih(5)- and ir(5)-indices per program were 14 (range 5–48) and 10 (range 5.6–37.2), respectively. The mean ir(5)/ih(5)-index ratio was 0.8. The top 5 fellowship programs (in descending order) as ranked by the ih(5)-index corrected for number of faculty members were The Hospital for Sick Children, Toronto; Children’s Hospital of Pittsburgh; University of California, San Francisco Benioff Children’s Hospital; Seattle Children’s Hospital; and St. Louis Children’s Hospital.

CONCLUSIONS

About two-thirds of publications authored by pediatric neurosurgeons are pediatrics-specific, although non–pediatrics-specific articles averaged more citations. Most of the articles authored by pediatric neurosurgeons are clinical, with basic and translational articles averaging more citations. Neurosurgeons with PhD degrees averaged more total publications and more citations per publication. In all, this is the most advanced and informative analysis of publication productivity in pediatric neurosurgery to date.

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Paul Klimo Jr., L. Madison Michael II, Garrett T. Venable and Douglas R. Taylor

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Douglas R. Taylor, Garrett T. Venable, G. Morgan Jones, Jacob R. Lepard, Mallory L. Roberts, Nabil Saleh, Said K. Sidiqi, Andrew Moore, Nickalus Khan, Nathan R. Selden, L. Madison Michael II and Paul Klimo Jr.

OBJECT

Various bibliometric indices based on the citations accumulated by scholarly articles, including the h-index, g-index, e-index, and Google’s i10-index, may be used to evaluate academic productivity in neurological surgery. The present article provides a comprehensive assessment of recent academic publishing output from 103 US neurosurgical residency programs and investigates intradepartmental publishing equality among faculty members.

METHODS

Each institution was considered a single entity, with the 5-year academic yield of every neurosurgical faculty member compiled to compute the following indices: ih(5), cumulative h, ig(5), ie(5), and i10(5) (based on publications and citations from 2009 through 2013). Intradepartmental comparison of productivity among faculty members yielded Gini coefficients for publications and citations. National and regional comparisons, institutional rankings, and intradepartmental publishing equality measures are presented.

RESULTS

The median numbers of departmental faculty, total publications and citations, ih(5), summed h, ig(5), ie(5), i10(5), and Gini coefficients for publications and citations were 13, 82, 716, 12, 144, 23, 16, 17, 0.57, and 0.71, respectively. The top 5 most academically productive neurosurgical programs based on ih(5)-index were University of California, San Francisco, University of California, Los Angeles, University of Pittsburgh, Brigham & Women’s Hospital, and Johns Hopkins University. The Western US region was most academically productive and displayed greater intradepartmental publishing equality (median ih[5]-index = 18, median Ginipub = 0.56). In all regions, large departments with relative intradepartmental publishing equality tend to be the most academically productive. Multivariable logistic regression analysis identified the ih(5)-index as the only independent predictor of intradepartmental publishing equality (Ginipub ≤ 0.5 [OR 1.20, 95% CI 1.20–1.40, p = 0.03]).

CONCLUSIONS

The ih(5)-index is a novel, simple, and intuitive metric capable of accurately comparing the recent scholarly efforts of neurosurgical programs and accurately predicting intradepartmental publication equality. The ih(5)-index is relatively insensitive to factors such as isolated highly productive and/or no longer academically active senior faculty, which tend to distort other bibliometric indices and mask the accurate identification of currently productive academic environments. Institutional ranking by ih(5)-index may provide information of use to faculty and trainee applicants, research funding institutions, program leaders, and other stakeholders.

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Douglas R. Taylor and Jason A. Weaver

Radiosurgery for primary and metastatic tumors of the central nervous system is increasing in utility and intensity. Known complications in the brain include radiation necrosis and the well-documented phenomenon of pseudoprogression. Known complications of radiosurgery to spinal column tumors include radiation myelopathy and delayed vertebral compression fractures; however, the concept of pseudoprogression of spinal column tumors has not been previously described. The authors review 2 cases of spinal metastasis treated with stereotactic radiosurgery (SRS) and attempt to define the concept of spine tumor pseudoprogression.

Two patients who had undergone SRS to the spine for metastatic disease presented in early follow-up (3 and 7 weeks) with symptomatic complaints consisting of axial pain, radicular pain, or evidence of cord compression. In both patients, MRI revealed evidence of tumor enlargement. In one patient, the lesion had grown by 9 mm and 7.7 mm in the axial and sagittal planes, respectively. In the other patient, the tumor growth resulted in a 5-mm decrease in spinal canal diameter with epidural compression and right foraminal encroachment. Because of the absence of progressive neurological deficit, myelopathy, mechanical symptomatology of instability, or vertebral compression fracture, the first patient was treated expectantly with a corticosteroid taper and had improvement of symptoms at 1 month and near-total radiographic resolution of the tumor. In the second patient, worsening symptoms suggested a need for surgical intervention to address presumed radiosurgical failure and tumor progression. During surgery, only necrotic tumor cells were observed, without viable tumor. Follow-up imaging over 1 year showed ongoing local control.

To their knowledge, the authors report the first description of pseudoprogression involving spinal column metastasis in the literature and aim to alert the treating physician to this clinical situation. Unlike brain tumor pseudoprogression, spine tumor pseudoprogression is a relatively early posttreatment phenomenon, measured in days to 2 months. The authors believe that the acute inflammatory response associated with tumor necrosis and disruption of the tumor capillary integrity caused by radiotherapy is an important component in the development of pseudoprogression. Future studies will be fundamental in assigning clinical significance, defining the incidence and predictors, and affecting future management of this phenomenon.

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Paul Klimo Jr., Garrett T. Venable, Nickalus R. Khan, Douglas R. Taylor, Brandon A. Shepherd, Clinton J. Thompson and Nathan R. Selden

Object

The application of bibliometric techniques to academic neurosurgery has been the focus of several recent publications. The authors provide here a detailed analysis of all active pediatric neurosurgeons in North America and their respective departments.

Methods

Using Scopus and Google Scholar, a bibliometric profile for every known active pediatric neurosurgeon in North America was created using the following citation metrics: h-, contemporary h-, g-, and e-indices and the m-quotient. Various subgroups were compared. Departmental productivity from 2008 through 2013 was measured, and departments were ranked on the basis of cumulative h- and e-indices and the total number of publications and citations. Lorenz curves were created, and Gini coefficients were calculated for all departments with 4 or more members.

Results

Three hundred twelve pediatric neurosurgeons (260 male, 52 female) were included for analysis. For the entire group, the median h-index, m-quotient, contemporary h-, g-, and e-indices, and the corrected g- and e-indices were 10, 0.59, 7, 18, 17, 1.14, and 1.01, respectively; the range for each index varied widely. Academic pediatric neurosurgeons associated with fellowship programs (compared with unassociated neurosurgeons), academic practitioners (compared with private practitioners), and men (compared with women) had superior measurements. There was no significant difference between American and Canadian pediatric neurosurgeons. The mean Gini coefficient for publications was 0.45 (range 0.18–0.70) and for citations was 0.53 (range 0.25–0.80).

Conclusions

This study represents the most exhaustive evaluation of academic productivity for pediatric neurosurgeons in North America to date. These results should serve as benchmarks for future studies.

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Nickalus R. Khan, Clinton J. Thompson, Douglas R. Taylor, Garrett T. Venable, R. Matthew Wham, L. Madison Michael II and Paul Klimo Jr.

Object

Bibliometrics is defined as the study of statistical and mathematical methods used to quantitatively analyze scientific literature. The application of bibliometrics in neurosurgery is in its infancy. The authors calculate a number of publication productivity measures for almost all academic neurosurgeons and departments within the US.

Methods

The h-index, g-index, m-quotient, and contemporary h-index (hc-index) were calculated for 1225 academic neurosurgeons in 99 (of 101) programs listed by the Accreditation Council for Graduate Medical Education in January 2013. Three currently available citation databases were used: Google Scholar, Scopus, and Web of Science. Bibliometric profiles were created for each surgeon. Comparisons based on academic rank (that is, chairperson, professor, associate, assistant, and instructor), sex, and subspecialties were performed. Departments were ranked based on the summation of individual faculty h-indices. Calculations were carried out from January to February 2013.

Results

The median h-index, g-index, hc-index, and m-quotient were 11, 20, 8, and 0.62, respectively. All indices demonstrated a positive relationship with increasing academic rank (p < 0.001). The median h-index was 11 for males (n = 1144) and 8 for females (n = 81). The h-index, g-index and hc-index significantly varied by sex (p < 0.001). However, when corrected for academic rank, this difference was no longer significant. There was no difference in the m-quotient by sex. Neurosurgeons with subspecialties in functional/epilepsy, peripheral nerve, radiosurgery, neuro-oncology/skull base, and vascular have the highest median h-indices; general, pediatric, and spine neurosurgeons have the lowest median h-indices. By summing the manually calculated Scopus h-indices of all individuals within a department, the top 5 programs for publication productivity are University of California, San Francisco; Barrow Neurological Institute; Johns Hopkins University; University of Pittsburgh; and University of California, Los Angeles.

Conclusions

This study represents the most detailed publication analysis of academic neurosurgeons and their programs to date. The results for the metrics presented should be viewed as benchmarks for comparison purposes. It is our hope that organized neurosurgery will adopt and continue to refine bibliometric profiling of individuals and departments.

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Douglas R. Taylor, Scott D. Wait, James W. Wheless and Frederick A. Boop

Neurocutaneous melanosis (NCM) is a rare, congenital neuroectodermal dysplasia generally resulting in early death from neurological decline due to leptomeningeal involvement. Nonmeningeal CNS epileptogenic lesions presenting in later childhood in the absence of leptomeningeal disease are rare. This report summarizes a rare presentation and curative epilepsy surgery.

The authors discuss the case of a 14-year-old girl with NCM who originally presented with intractable partial-onset seizures. The MRI, PET, and SPECT studies subsequently revealed a focal epileptogenic source in the right temporal lobe. Results of video-electroencephalography monitoring concurred with the imaging findings, and a right temporal lobectomy was performed including the medial structures. Following surgery, histopathological features of the lesion included multiple scattered mononuclear cells with brown pigmentation in the amygdala specimen. The patient remains seizure free 2 years postresection, and no longer needs medication for seizure management.

This patient presented with an atypical CNS manifestation of NCM that is curable by epilepsy surgery. Her intractable epilepsy developed secondary to amygdalar neuromelanosis, which had no associated leptomeningeal melanosis, an uncommon occurrence. As evidenced by the lack of seizure activity following resection, the patient's quality of life greatly improved after neurological surgery.