Vestibular Schwannoma Koos Grade 1

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Vestibular Schwannoma Koos Grade 1

Vestibular Schwannoma Koos grading scale 1 involves only the internal auditory canal without extension into the cerebellopontine angle (CPA).

– These tumors are typically less than 1 cm in diameter.

Clinical features

– They often present with early symptoms such as unilateral hearing loss, tinnitus (ringing in the ears), or a sensation of fullness in the ear.

Treatment

Treatment for a Koos Grade 1 vestibular schwannoma is typically aimed at preserving hearing and avoiding damage to surrounding structures.

Common management options include:

1. Observation with regular imaging, particularly if the tumor is asymptomatic or if the patient’s age and general health suggest that intervention is not immediately necessary.

2. Surgical resection to remove the tumor, especially if symptoms are progressive or if the tumor is growing.

3. Stereotactic radiosurgery (such as Gamma Knife), which is often used for tumors that are difficult to access surgically or when hearing preservation is a priority.

For Koos Grade I vestibular schwannomas, there is typically no compression of critical structures, and treatment options often involve active surveillance or SRS rather than surgery. These small tumors may not cause immediate symptoms and can often be monitored with regular imaging to track any growth.

Prognosis

The prognosis for Koos Grade 1 vestibular schwannomas is generally good, particularly when they are treated early. However, given the slow-growing nature of many Koos Grade I schwannomas, the necessity and timing of intervention remain topics of ongoing debate in neurosurgery, with individualized treatment being essential

Prospective observational studies

This study by Levivier et al. 1) presents an argument for early intervention with Gamma Knife Surgery (GKS) in patients with Koos grade I vestibular schwannomas (VS), suggesting it as a superior approach to the “wait and see” strategy. However, a critical examination reveals substantial limitations and questions regarding the validity of these recommendations, particularly concerning the study’s methodology and interpretation of results.

1. Short Follow-Up Period and Limited Long-Term Data: The mean follow-up in this study was a mere 1.3 years, with a range from 0.6 to 3.6 years, which is alarmingly short given the slow-growing nature of vestibular schwannomas. Tumors in this early stage often exhibit minimal or no growth over years, making this follow-up insufficient to draw conclusions about long-term outcomes, especially in terms of tumor control and cranial nerve preservation. With such limited follow-up, any claims regarding the benefits of early GKS are speculative at best.

2. Lack of Comparison with Observation Group: The study fails to include a direct comparison group of patients managed with observation, which is a common approach for small, asymptomatic, or minimally symptomatic Koos I tumors. Without this essential control, the assertion that early GKS is preferable to a “wait and see” strategy lacks robust evidence. This absence is particularly significant, as previous studies have shown that many Koos I VS can be safely observed without immediate intervention.

3. Inconsistent Hearing Preservation Results and Dose Concerns: The reported hearing preservation rate of 85% appears promising; however, the authors overlook the fact that hearing can often be maintained in Koos I tumors without intervention, as tumor growth rates are typically low. Additionally, the study does not adequately discuss the risks of radiation exposure to the cochlea and the potential for hearing deterioration over time, especially given the mean cochlear dose of 4.1 Gy, which could have cumulative adverse effects.

4. Overstatement of Preliminary Data: The authors prematurely advocate for early GKS based on “preliminary data,” which lacks the rigor and maturity required for such a definitive recommendation. Promoting early intervention based on short-term data may expose patients to unnecessary risks, especially considering that many Koos I tumors remain asymptomatic or progress very slowly. The recommendation for early GKS is therefore premature, and further research with a longer follow-up is essential before suggesting that patients with asymptomatic or minimally symptomatic tumors should undergo early intervention.

5. Methodological Concerns in Dosimetric Analysis: The study’s focus on dosimetric factors, while important, appears overly simplistic in suggesting that cochlear dose alone can predict hearing preservation. Hearing outcomes in VS are multifactorial, and the authors’ narrow focus on dose metrics overlooks other critical factors that could influence outcomes, such as baseline hearing quality, individual patient anatomy, and the biological response to radiation.

Conclusion: In summary, this study’s recommendation for early GKS in Koos I vestibular schwannomas is founded on weak preliminary data, a limited follow-up, and an absence of a control group for observation. The authors’ enthusiasm for early intervention is unwarranted without more robust, long-term evidence. Until such data is available, it would be prudent to adhere to a conservative approach of observation for Koos I tumors, reserving intervention for cases where there is documented tumor progression or symptomatic deterioration.

Retrospective cohort studies

The VISAS-K1 study is a multicenter retrospective analysis comparing stereotactic radiosurgery (SRS) with active surveillance in the management of Koos grade I vestibular schwannomas (VS). The study aimed to evaluate the safety and efficacy of SRS versus observation for these small, intracanalicular tumors.

Study Design and Methods:

Participants: The study included 142 patients with Koos grade I VS, divided into two groups: those who underwent SRS and those who were observed without immediate intervention.

Matching: Propensity score matching was utilized to balance demographics, tumor size, and audiometric data between the two groups, aiming to reduce selection bias.

Follow-up: The median follow-up period was 36 months, with some patients monitored up to 8 years.

Key Findings:

Tumor Control:

The SRS group achieved a 100% tumor control rate at both 5 and 8 years. In contrast, the observation group had control rates of 48.6% at 5 years and 29.5% at 8 years, indicating a significant advantage for SRS in preventing tumor progression. Hearing Preservation:

Preservation of serviceable hearing was comparable between the two groups. At 5 years, 70.1% of patients in the SRS group and 53.4% in the observation group maintained serviceable hearing, with no statistically significant difference (P = .33). Neurological Function:

Patients in the SRS group had a reduced likelihood of developing tinnitus (odds ratio [OR] = 0.46, P = .04), vestibular dysfunction (OR = 0.17, P = .002), and overall cranial nerve dysfunction (OR = 0.49, P = .03) at the last follow-up compared to those under observation. Conclusions:

The VISAS-K1 study suggests that SRS offers superior tumor control and a lower risk of cranial nerve dysfunction for patients with Koos grade I vestibular schwannomas, without compromising hearing preservation, compared to active surveillance. These findings support the consideration of SRS as a primary treatment option for this patient population 2).

Critical Considerations:

Study Design Limitations: As a retrospective analysis, the study may be subject to selection biases and unmeasured confounding factors, despite efforts to balance groups through propensity score matching.

Follow-up Duration: The median follow-up of 36 months may not fully capture long-term outcomes, especially given the slow-growing nature of vestibular schwannomas.

Outcome Measures: The assessment of cranial nerve function and hearing preservation relies on clinical evaluations that may vary between centers, potentially affecting the consistency of reported outcomes.

In summary, while the VISAS-K1 study provides valuable insights into the management of small vestibular schwannomas, its retrospective nature and potential biases necessitate cautious interpretation of the results. Prospective, randomized controlled trials with standardized outcome assessments are needed to confirm these findings and guide clinical decision-making.

1)

M. Levivier, C. Tuleasca, Mercy G, Schiappacasse L, M. Zeverino, Maire R. Should Koos grade I vestibular schwannomas be treated early with gamma knife surgery? A subgroup analysis in a series of 190 consecutive patients. Neurochirurgie. 2014;60(6):331-331. doi:https://doi.org/10.1016/j.neuchi.2014.10.028‌
2)

Bin-Alamer O, Abou-Al-Shaar H, Peker S, Samanci Y, Pelcher I, Begley S, Goenka A, Schulder M, Tourigny JN, Mathieu D, Hamel A, Briggs RG, Yu C, Zada G, Giannotta SL, Speckter H, Palque S, Tripathi M, Kumar S, Kaur R, Kumar N, Rogowski B, Shepard MJ, Johnson BA, Trifiletti DM, Warnick RE, Dayawansa S, Mashiach E, Vasconcellos FN, Bernstein K, Schnurman Z, Alzate J, Kondziolka D, Sheehan JP. Vestibular Schwannoma Koos Grade I International Study of Active Surveillance Versus Stereotactic Radiosurgery: The VISAS-K1 Study. Neurosurgery. 2024 Nov 6. doi: 10.1227/neu.0000000000003215. Epub ahead of print. PMID: 39503441.

The Peritumoral Brain Zone in Glioblastoma

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The article “The Peritumoral Brain Zone in Glioblastoma: A Review of the Pretreatment Approach,” published in *Pol J Radiol* (October 2024), attempts to explore the role of advanced imaging in understanding the peritumoral brain zone (PTZ) in glioblastoma, a highly aggressive and common form of brain tumor. Although the topic is undoubtedly of great importance in neurooncology, the review falls short in several critical areas that undermine its overall contribution to the field.

### Lack of Original Insight

The review essentially reiterates well-established facts about glioblastoma and its clinical challenges, particularly the difficulty in delineating tumor margins for complete resection. While it acknowledges the role of advanced imaging technologies in preoperative planning, the content feels redundant. Much of the information provided could be found in earlier foundational studies, and the article fails to introduce truly novel or groundbreaking ideas that would push the field forward. Readers hoping for fresh perspectives on how imaging can revolutionize treatment planning or innovative therapeutic strategies may be left disappointed.

### Inadequate Depth and Technical Analysis

The article briefly mentions several advanced neuroimaging techniques, such as diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), perfusion-weighted imaging (PWI), and proton magnetic resonance spectroscopy (1H MRS), yet it provides little detailed explanation on how these technologies could be practically applied to improve glioblastoma treatment. The authors reference these methods without delving into their technical intricacies or discussing how these imaging tools can overcome current clinical limitations. For instance, the article fails to adequately explore the potential of chemical exchange saturation transfer (CEST) imaging in mapping the PTZ, which has been an emerging area of interest. Without a deep dive into the challenges and breakthroughs of these technologies, the review reads more like a surface-level summary rather than a meaningful contribution to the scientific community.

### Flawed Structure and Organization

One of the most striking weaknesses of the article is its lack of cohesion and poor structure. The sections on imaging techniques and their implications for glioblastoma management feel disjointed. The transitions between topics are abrupt, and the review doesn’t offer a clear progression from one idea to the next. This lack of flow makes it difficult for the reader to follow the authors’ arguments and understand how each piece of information builds upon the previous one. Additionally, while the article mentions the critical issue of radioresistance in glioblastoma, it does not offer any substantial discussion of how imaging might inform therapeutic strategies to overcome this challenge.

### Missed Opportunity for Clinical Relevance

While the article touches on the importance of preoperative imaging for glioblastoma resection, it misses an important opportunity to translate this knowledge into actionable clinical insights. It fails to address practical challenges clinicians face when using these imaging techniques, such as cost, accessibility, and the need for multidisciplinary collaboration. Furthermore, the review does not adequately discuss how the integration of these imaging methods could change the trajectory of patient outcomes in a meaningful way. There is no discussion on how imaging could influence patient management decisions in a real-world setting, nor is there any mention of how emerging imaging technologies could be incorporated into clinical practice or trials.

### Repetitive and Lackluster Writing

Lastly, the writing style is somewhat repetitive, particularly when describing the heterogeneous nature of glioblastomas and the PTZ. These points are restated multiple times without adding substantial value to the narrative. This redundancy not only makes the article less engaging but also detracts from the potential to provide in-depth analysis or novel insights.

### Conclusion

Overall, the article fails to meet the expectations set by its title. Rather than offering a comprehensive, cutting-edge review of the peritumoral brain zone in glioblastoma, it recycles outdated information and lacks the depth needed to provide valuable insights for clinicians or researchers. While the use of advanced imaging techniques is undoubtedly an exciting area of research, this review misses the mark in providing a clear and innovative perspective on how these tools can be used to improve the treatment of glioblastoma. Researchers and clinicians looking for substantive guidance or new avenues of research will find little to take away from this article.

Follow up of infants with skull fractures by neurosurgeons due to the risk of growing fractures; is it needed?

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The article “Follow up of infants with skull fractures by neurosurgeons due to the risk of growing fractures; is it needed?” published in *Br J Neurosurg* provides a retrospective analysis of skull fractures in infants under one year of age and aims to determine the necessity of follow-up for those at risk of growing skull fractures. While the study touches on a potentially important issue in pediatric neurosurgery, it suffers from numerous critical weaknesses, rendering its conclusions unsubstantiated and ultimately unconvincing.

Firstly, the methodology of the study is deeply flawed. The authors utilize a single-center retrospective design, which inherently limits the generalizability of the results. The absence of referral data from 2008-2013 further undermines the reliability of the findings, as it introduces a significant gap in the dataset. The small sample size (n=246) and the even smaller subset of patients who developed growing skull fractures (n=2) further exacerbate this issue, making it difficult to draw any meaningful conclusions about risk factors or the need for follow-up care. The study’s reliance on a small number of cases renders its results statistically insignificant and unrepresentative of the larger population.

Moreover, the study presents a highly superficial analysis of the factors associated with growing skull fractures. While the authors note a significant difference in fracture splay distance and elevation/depression distance, these variables alone are insufficient to predict the development of a growing skull fracture. The study fails to consider a broad range of potential confounders, such as underlying genetic factors, comorbidities, or the presence of other cranial injuries, that could influence the likelihood of fracture progression. This lack of comprehensive data analysis weakens the study’s conclusions and renders the identified risk factors (fracture displacement over 4mm and elevation/depression distance over 3mm) overly simplistic.

The study’s findings also raise serious questions about the clinical relevance of its results. The authors suggest that resources and investigations should focus on children with fractures that exceed specific thresholds in displacement and elevation/depression, which seems like a reasonable approach at first glance. However, the study does not provide adequate evidence to support this recommendation. With only two cases of growing skull fractures in the entire sample, the claim that these thresholds are indicative of a “significantly greater risk” is premature and unsubstantiated. The low incidence of growing skull fractures in the study (a mere 1.1% of the total sample) calls into question whether follow-up for all fractures, regardless of severity, is justified.

Furthermore, the authors make sweeping recommendations about resource allocation based on minimal data, failing to acknowledge the potential risks of overtreatment. With so few cases of growing skull fractures observed, it is highly questionable whether the vast resources and investigations required to follow up on every infant with a skull fracture are justified. The study does not adequately address the costs, both in terms of healthcare resources and patient well-being, associated with frequent follow-ups for an extremely rare condition.

Lastly, the study’s conclusions lack critical perspective. While the authors recommend focusing on infants with fractures meeting certain criteria, they fail to adequately discuss the potential harms of over-monitoring and over-intervention. It is essential to balance the need for follow-up with the avoidance of unnecessary medical interventions, particularly when dealing with vulnerable populations such as infants.

In conclusion, while the study raises an important clinical question, it ultimately fails to provide robust evidence to justify its claims. The flawed methodology, small sample size, lack of comprehensive data analysis, and unsubstantiated recommendations make this paper far from conclusive. The need for follow-up in cases of skull fractures in infants remains an open question, and this study does little to advance our understanding of which children truly require ongoing monitoring. Without more rigorous research, the recommendations presented in this study should be viewed with caution and skepticism.

Anti-Inflammatory Thrombolytic JX10 (TMS-007) in Late Presentation of Acute Ischemic Stroke

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The investigational drug TMS-007 (now branded JX10), developed as a novel thrombolytic agent for acute ischemic stroke, has been heralded for its potential to expand the therapeutic window for treatment. However, despite the initial enthusiasm surrounding its clinical development, there are numerous critical flaws in both the study design and the interpretation of the findings that undermine its promise as a groundbreaking stroke therapy.

First, the methodology of the Phase 2a study raises substantial concerns. While the randomized, double-blind, placebo-controlled design is theoretically robust, the small sample size (90 patients) severely limits the generalizability of the findings. With such a small cohort, the study lacks statistical power to make definitive conclusions about the true efficacy and safety of JX10. Moreover, the stratification of patients by dose (1, 3, or 6 mg/kg) and gender (with a skewed distribution of females across doses) introduces an additional layer of complexity and potential bias that goes unaddressed in the analysis. This lack of statistical rigor leaves the results open to question.

The primary endpoint, the incidence of symptomatic intracranial hemorrhage (sICH), demonstrated no significant difference between JX10 and placebo (0% vs. 2.6%, respectively). The authors highlight this as a favorable outcome, but the fact that such a small incidence of sICH was observed in both groups calls into question the clinical relevance of this outcome. With so few patients experiencing a clinically meaningful event, the observed lack of difference between groups is not as compelling as it may initially appear. This failure to show a significant reduction in sICH, an important safety endpoint, undermines the argument that JX10 is substantially safer than existing thrombolytics.

Furthermore, while vessel patency at 24 hours was reportedly improved in patients receiving JX10, the difference between the groups (58.3% vs. 26.7%) was modest at best. The odds ratio of 4.23, while statistically significant, is misleading without further context. The actual clinical significance of such a finding remains uncertain, as vessel reopening does not necessarily equate to improved functional outcomes. The secondary endpoint of modified Rankin Scale scores also demonstrates a modest benefit for JX10, with 40.4% of patients achieving a score of 0-1 versus 18.4% for placebo. While statistically significant, the clinical impact of this difference is questionable given the early nature of stroke treatment, the small sample size, and the inherent variability in patient recovery.

One of the more concerning aspects of the study is the lack of long-term follow-up. Stroke patients who receive thrombolytic treatment face a range of risks, and it is essential to understand the longer-term outcomes of therapies like JX10, including mortality, disability, and quality of life. The absence of these critical data points further weakens the study’s conclusions, as it provides a limited snapshot of the therapy’s true impact.

Finally, the novel mechanism of action for JX10, which involves modulating plasminogen conformation and inhibiting soluble epoxide hydrolase, remains speculative. The proposed benefits of enhanced endogenous fibrinolysis and anti-inflammatory properties are interesting, but there is insufficient evidence to support their clinical relevance in the context of acute ischemic stroke. The mechanism may sound promising in theory, but without more robust data from larger studies, these claims remain unsubstantiated.

In conclusion, while JX10 has shown some potential in expanding the therapeutic window for acute ischemic stroke treatment, the current clinical evidence does not justify the enthusiasm surrounding its future. The small sample size, the lack of meaningful safety and efficacy differences, and the absence of long-term data all point to the need for much more rigorous studies before this drug can be considered a viable treatment option. As it stands, JX10 remains an unproven, underdeveloped therapy with far too many unanswered questions to be hailed as the next generation of stroke treatment.

Endovascular Treatment of Patients With Acute Ischemic Stroke With Tandem Lesions Presenting With Low Alberta Stroke Program Early Computed Tomography Score

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The study “Endovascular Treatment of Patients With Acute Ischemic Stroke With Tandem Lesions Presenting With Low Alberta Stroke Program Early Computed Tomography Score” published in *J Am Heart Assoc* presents a retrospective analysis of endovascular thrombectomy (ET) in patients with acute ischemic stroke and tandem lesions. Despite its timely and relevant focus on a niche aspect of stroke treatment, the article suffers from several critical shortcomings that weaken its impact and utility in advancing clinical practice.

First, the methodology lacks rigor in several areas. While the authors employed inverse probability of treatment weighting (IPTW) to balance groups with different ASPECTS scores, this statistical approach is fraught with challenges. IPTW can only partially adjust for confounding variables and may still introduce biases that distort the relationship between treatment and outcomes. Additionally, the reliance on retrospective data from 16 centers raises concerns about the generalizability of the findings. The data, while extensive, are retrospective and not prospective, which significantly limits the strength of the conclusions.

Second, the outcomes presented, including symptomatic intracranial hemorrhage (sICH) and functional independence, are not analyzed in depth concerning potential confounders such as the timing of thrombectomy, variation in procedural expertise, and differences in patient management. Although the study finds that patients with low ASPECTS (0-5) have lower odds of functional recovery and higher odds of sICH, this oversimplification disregards the nuances that may impact outcomes in real-world clinical settings. The reported odds ratios (ORs) for functional recovery and sICH (0.48 and 3.78, respectively) do little to guide clinical decision-making, as they fail to explore the complexity of individual patient characteristics and treatment variables.

The suggestion that 30% of patients with low ASPECTS may still achieve functional independence should be viewed with caution. This result, while intriguing, is buried in a sea of statistical averages that gloss over the heterogeneity of stroke severity and treatment response. What does this functional independence mean in terms of quality of life for patients with low ASPECTS, and how does it compare to other treatment modalities or supportive care? These critical questions are left unaddressed.

Moreover, the paper glosses over the limitations of the study design, particularly the lack of standardization across the centers involved. Given the variability in treatment protocols and the experience of clinicians at each site, it’s difficult to draw definitive conclusions about the efficacy of ET in this cohort. The authors also fail to explore alternative explanations for the increased risk of sICH observed in the low ASPECTS group, such as the potential role of comorbidities or pre-existing vascular conditions.

The study’s conclusions also need more nuance. While it correctly notes that the low ASPECTS cohort faces worse outcomes, the implication that ET should be withheld from these patients due to “reduced odds of functional recovery” is problematic. Clinical decision-making in acute stroke care must consider the individual patient’s potential for recovery, comorbidities, and the risks associated with other interventions. A blanket recommendation against ET for low ASPECTS patients would be premature and overly simplistic, particularly in light of the 30% functional independence rate reported.

In summary, while the study addresses an important clinical question, its methodological flaws, lack of depth in analysis, and failure to consider confounding factors significantly diminish its value. The paper offers limited insight for clinicians faced with treating patients with low ASPECTS and tandem lesions, and its conclusions require careful interpretation before being applied in practice.

Mapping the global neurosurgical workforce

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Critical Review of: “Mapping the global neurosurgical workforce. 

The article “Mapping the global neurosurgery workforce. Part 1: Consultant neurosurgeon density,” published in *the Journal of Neurosurgery*, provides an ambitious attempt to quantify and map the global distribution of neurosurgeons. While the study sheds light on global disparities, it fails to deliver in multiple crucial areas, from methodological flaws to missed opportunities for impactful analysis and actionable solutions. Ultimately, the article’s findings feel shallow and underdeveloped, leaving significant gaps in understanding and addressing the real challenges in neurosurgery workforce expansion.

1. Lack of Rigorous Data Collection and Methodology

At the heart of any robust study lies the quality of the data collection process, and this is where the study falters. The authors relies heavily on “personal contacts” and “online searches” to identify survey participants. This non-rigorous, subjective approach to participant selection creates room for considerable bias. In a global study of this magnitude, using personal networks and unverified online sources compromises the reliability and representativeness of the data. For instance, countries with fewer or no strong neurosurgical networks could easily be overlooked, thus skewing the results. Moreover, the authors mention “electronic cross-sectional surveys” but do not provide a clear description of how non-respondents were handled, leading one to question whether the sample is truly reflective of the global workforce. The data gathered through such an ad hoc, unsystematic process cannot be trusted to form the foundation of a serious, scientific inquiry into global neurosurgery density.

2. Overemphasis on High-Income Countries (HICs)

While the study points out the disparities in neurosurgery workforce density between low-, middle-, and high-income countries, it spends far too much time reiterating what is already well known: that high-income countries have significantly more neurosurgeons per capita than low-income countries. At a time when the global health community is grappling with health inequalities, this basic observation does little to advance our understanding. The study highlights the numbers (e.g., 2.44 neurosurgeons per 100,000 people in HICs versus 0.12 in low-income countries) without digging deeper into the underlying causes of these disparities or offering substantial policy recommendations. The authors fail to explore how specific health system characteristics—such as political will, international aid, and government healthcare priorities—shape these disparities. Instead, they leave the reader with numbers and little context for how to address these gaps.

3. Superficial Analysis of Regional Disparities

While the paper acknowledges that the African and Southeast Asia regions have the lowest densities of neurosurgeons, it misses the opportunity to explore the social, political, and economic factors that contribute to this situation. The study simply mentions that “countries with higher income-level designations had more frequent access to resources,” without further dissection. What does “access to resources” really mean? How do governmental policies, international funding, and the prioritization of neurosurgery differ between these regions? How do factors such as local infrastructure, training capacity, and healthcare access play a role in shaping workforce densities? These are critical questions that go unanswered in the paper. The superficial analysis of these disparities gives the impression that the study is more focused on confirming preconceived notions than on uncovering the root causes of inequities in neurosurgery training and practice.

4. Lack of Actionable Recommendations

The study falls short of offering any substantial recommendations to address the glaring gaps in the global neurosurgery workforce. It mentions the correlation between the presence of a neurosurgery society and workforce growth, but this observation is left unexplored. What can be done to create or strengthen neurosurgical societies in underrepresented regions? What specific interventions could rapidly increase neurosurgeon training or resource allocation? The study does not offer concrete strategies for reducing the workforce disparities between high- and low-income countries or improving the infrastructure for neurosurgery in regions with significant gaps. This lack of actionable insights severely weakens the article’s potential impact. At best, it is a descriptive study; at worst, it is an academic exercise that fails to move the needle on the global neurosurgical crisis.

5. Inconsistent and Shallow Statistical Analysis

The study conducts a regression analysis to explore the factors associated with workforce growth, which is an admirable attempt to analyze correlations. However, the presentation of this analysis is shallow, and its implications are underexplored. For example, the authors identify that “increasing global development aid” is associated with neurosurgeon growth, yet they do not discuss how or why this aid contributes to workforce expansion. Is it due to targeted funding for education, infrastructure, or equipment? The lack of detailed interpretation of the regression results leaves the reader with a set of statistical relationships that are not fully explained or contextualized.

6. Missed Opportunity for Global Collaboration and Solutions

What is most disappointing about this study is its failure to leverage the potential for global collaboration to address the crisis. The authors briefly mentions the presence of national neurosurgery societies, but they do not explore how international partnerships, such as those between organizations like the World Federation of Neurosurgical Societies (WFNS) and local governments, could drive workforce expansion. They also miss a critical opportunity to discuss how global networks and knowledge-sharing platforms could be used to help bridge the training gaps. At a time when digital platforms, telemedicine, and international collaborations are increasingly seen as solutions to global health challenges, the study neglects to discuss these possibilities.

Conclusion

In conclusion, the study “Mapping the global neurosurgery workforce. Part 1: Consultant neurosurgeon density” provides an overview of the state of the neurosurgery workforce, but it fails to live up to its potential. The methodology is flawed, the analysis is superficial, and the lack of actionable recommendations makes the study feel like an academic exercise rather than a meaningful contribution to addressing the global neurosurgery crisis. The study’s narrow focus on high-income countries, combined with an insufficient examination of the root causes of regional disparities, leaves much to be desired. To truly make an impact, future research should go beyond the numbers, offering in-depth insights into the systemic barriers that contribute to the neurosurgery workforce gaps and proposing concrete, sustainable solutions for equitable workforce growth worldwide.

The article “Mapping the global neurosurgery workforce. Part 2: Trainee density,” published in *Journal of Neurosurgery*, offers a broad analysis of the distribution and density of neurosurgery trainees worldwide, using a dataset drawn from 187 countries and 25 additional territories, states, and disputed regions. Although the study provides a valuable overview of the global state of neurosurgical training, it suffers from significant limitations and shortcomings in its methodology, analysis, and impact.

1. Methodological Weaknesses

While the authors claim to have surveyed all 193 countries and 26 territories, the methodology for data collection raises concerns. The study’s reliance on “personal contacts” of coauthors and “bibliometric and search engine searches” to identify participants undermines its credibility. The absence of a clear, systematic, or independent verification process for participant inclusion could introduce bias, leading to the exclusion of underrepresented regions or training programs that may not have direct links to prominent neurosurgical societies. This potential sampling bias compromises the validity of the data, especially when making conclusions about global neurosurgical training.

2. Disproportionate Focus on High-Income Countries (HICs)

The study’s findings reveal a striking disparity in trainee density, with high-income countries (HICs) dominating the global landscape of neurosurgery training. While the data from these regions may seem compelling, the disproportionate focus on HICs (with a density of 0.48 trainees per 100,000 people) fails to address the systemic barriers that exist in low-income countries (LICs) and middle-income countries (MICs). The authors provide an extensive comparison of regions but fail to fully explore the reasons behind these disparities. More emphasis should have been placed on why LICs have such limited access to training resources like cadaver laboratories and subspecialty training. By glossing over these issues, the article misses an opportunity to spark deeper discussions on the global inequities in neurosurgery training.

3. Lack of Depth in Analysis of Accreditation and Training Standards

Another critical flaw in the article is its cursory treatment of accreditation processes. While the authors mention that accreditation is more common in HICs than in LICs and MICs, they do not provide enough context on how accreditation impacts training quality. For instance, how do variations in accreditation standards between countries influence the readiness and competence of neurosurgeons entering the workforce? Without a more nuanced analysis of the accreditation systems, including the role of international bodies like the WFNS and EANS, the study misses an important aspect of quality assurance in neurosurgical education.

4. Limited Discussion on Sustainable Solutions

The study rightly identifies disparities in trainee density and resource availability between regions. However, the authors fail to offer substantial recommendations or solutions to address these inequities. Given the critical importance of sustainable neurosurgical education in improving patient outcomes, the article would have benefited from a more robust exploration of global initiatives, partnerships, and funding mechanisms that could help address these gaps. Merely presenting the data without a forward-thinking approach to solving the challenges does little to drive the field of global neurosurgery forward.

5. Failure to Address the Broader Context

While the study provides a valuable snapshot of trainee density, it lacks any significant engagement with the broader socioeconomic, political, and cultural factors that influence neurosurgery training worldwide. For example, in LICs, the availability of neurosurgery training is not just a question of resources but also political will, governance, and the overall health system infrastructure. This oversight makes the conclusions feel somewhat superficial, as the authors do not sufficiently interrogate the broader structural determinants of the observed disparities.

Conclusion

In summary, while *J Neurosurg*’s study offers a broad overview of neurosurgery trainee density globally, it falls short in several critical areas. Its methodology suffers from potential biases, its analysis of global disparities lacks depth, and its conclusions do little to suggest actionable solutions to the pressing issues it highlights. As a result, while the article provides some useful information, it ultimately fails to live up to the importance of the topic it tackles. More rigorous, nuanced, and solution-oriented work is needed to effectively map and address the challenges in global neurosurgical training.

Preoperative embolization of intracranial meningioma

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Preoperative embolization of intracranial meningioma

Preoperative embolization(POE) of intracranial meningioma is performed worldwide. Although clear evidence of the effectiveness of POE has not been reported in the literature, the technique plays an important role in open surgery, especially for large or skull base meningiomas. The purposes of embolization include: 1)induction of tumor necrosis, resulting in a safer operation, 2)reduction in intraoperative bleeding, and 3)decrease in operative time. Knowledge of the functional vascular anatomy, embolic materials, and endovascular techniques is paramount to ensure safe embolization.

Indication

Tumor vascularity can now be determined using arterial spin labeling and Dynamic Susceptibility Weighted Contrast-Enhanced Perfusion Imaging, allowing the neurosurgeon or neurointerventionalist to assess patient candidacy for Preoperative embolization of intracranial meningioma 1).

Tumor embolization may become an in-office treatment under certain conditions, such as in cases of poor general condition, multiple meningiomas, recurrent and refractory cases, difficult surgery and cases where re-irradiation is difficult after post-radiation therapy 2).

Procedure

The standard procedure is as follows: 1)embolization is performed several days before open surgery; 2)in cases with strong peritumoral edema, steroid administration or embolization may be performed immediately prior to surgery; 3)patients undergo the procedure under local anesthesia; 4)the microcatheter is inserted as close as possible to the tumor; 5)particulate emboli are the first-line material; 6)embolization is occasionally performed with N-butyl cyanoacrylate(NBCA)glue; and 7)if possible, additional proximal feeder occlusion with coils is performed. The JR-NET study previous showed the situation regarding intracranial tumor embolization in Japan. Endovascular neurosurgeons should fully discuss the indications and strategies for POE with tumor neurosurgeons to ensure safe and effective procedures 3).

The superiority and usefulness of liquid material over particles for embolization have been a topic of debate due to differences in materials and techniques. The use of particles in embolization may reduce intraoperative bleeding, but not in all cases can it be used safely. Therefore, a thorough understanding of the characteristics of both approaches and their relative advantages in clinical practice is essential to opt for the appropriate material according to the case 4)

Efficacy

There is no standardized system to assess the efficacy or extent of embolization during the embolization procedure. We sought to establish a purely angiographic grading system to facilitate consistent reporting of the outcome of meningioma embolization and to characterize the anatomic and other features of meningiomas that predict the degree of devascularization achieved through preoperative embolization.

Matsoukas et al. identified patients with meningiomas who underwent preoperative cerebral angiography and subsequent resection between 2015 and 2021. Demographic, clinical, and imaging data were collected in a research registry. We defined an angiographic devascularization grading scale as follows: grade 0 for no embolization, 1 for partial embolization, 2 for majority embolization, 3 for complete external carotid artery embolization, and 4 for complete embolization.

Eighty consecutive patients were included, 60 of whom underwent preoperative tumor embolization (20 underwent angiography with an intention to treat but ultimately not embolization). Embolized tumors were larger (59.0 vs 35.9 cc; P = .03). Gross total resection, length of stay, and complication rates did not differ among groups. The distribution of arterial feeders differed significantly across tumors in a location-specific manner. Both the tumor location and the identity of arterial feeders were predictive of the extent of embolization. Anterior midline meningiomas were associated with internal carotid (ophthalmic, ethmoidal) supply and lower devascularization grades (P = .03). Tumors fed by meningeal feeders (convexity, falcine, lateral sphenoid wing) were associated with higher devascularization grades (P < .01). The procedural complication rate for tumor embolization was 2.5%.

Angiographic outcomes can be graded to indicate the extent of tumor embolization. This system may facilitate consistency of reported angiographic results. In addition, arterial feeders vary in a manner predicted by tumor location, and these patterns correlate with typical degrees of devascularization achieved in those tumor locations 5)

Complications

Hemorrhage (intratumoral and SAH), cranial nerve deficits (usually transient), stroke from embolization through ICA or VA anastomoses, scalp necrosis, retinal embolus, and potentially dangerous tumor swelling. Some meningiomas (e.g. olfactory groove) are less amenable to embolization.

Preoperative embolization has been an option for adjunctive treatment of intracranial meningiomas, but it remains used in only a minority of cases 6).

Systematic review and meta-analysis

In 2021 a systematic review and meta-analysis aimed to evaluate the safety profile of the procedure and to compare outcomes in embolized versus non-embolized meningiomas. PubMed was queried for studies after January 1990 reporting outcomes of Preoperative embolization. Pertinent variables were extracted and synthesized from eligible articles. Heterogeneity was assessed using I2, and a random-effects model was employed to calculate pooled 95% CI effect sizes. Publication bias was assessed using funnel plots and Harbord’s and Begg’s tests. Meta-analyses were used to assess estimated blood loss and operative duration (mean difference; MD), gross-total resection (odds ratio; OR), and postsurgical complications and postsurgical mortality (risk difference; RD). Thirty-four studies encompassing 1782 preoperatively embolized meningiomas were captured. The pooled immediate complication rate following embolization was 4.3% (34 studies, n = 1782). Although heterogeneity was moderate to high (I2 = 35-86%), meta-analyses showed no statistically significant differences in estimated blood loss (8 studies, n = 1050, MD = 13.9 cc, 95% CI = -101.3 to 129.1), operative duration (11 studies, n = 1887, MD = 2.4 min, 95% CI = -35.5 to 30.8), gross-total resection (6 studies, n = 1608, OR = 1.07, 95% CI = 0.8-1.5), postsurgical complications (12 studies, n = 2060, RD = 0.01, 95% CI = -0.04 to 0.07), and post-surgical mortality (12 studies, n = 2060, RD = 0.01, 95% CI = 0-0.01). Although POE is relatively safe, no clear benefit was observed in operative and postoperative outcomes. However, results must be interpreted with caution due to heterogeneity and selection bias between studies. Well-controlled future investigations are needed to define the patient population most likely to benefit from the procedure 7).

Shah et al. analyzed new therapeutic options for the embolization of intracranial meningiomas, as well as the future of meningioma treatment through recent relevant cohorts and articles. They investigate various embolic materials, types of meningiomas amenable to embolization, imaging techniques, and potential imaging biomarkers that could aid in the delivery of embolic materials. They also analyze perfusion status, complications, and new technical aspects of endovascular preoperative embolization of meningiomas. A literature search was performed in PubMed using the terms “meningioma” and “embolization” to investigate recent therapeutic options involving embolization in the treatment of meningioma. They looked at various cohorts, complications, materials, and timings of meningioma treatment. Liquid embolic materials are preferable to particle agents because particle embolization carries a higher risk of hemorrhage. Liquid agents maximize the effect of devascularization because of deeper penetration into the trunk and distal tumor vessels. The 3 main imaging techniques, MRI, CT, and angiography, can all be used in a complementary fashion to aid in analyzing and treating meningiomas. Intraarterial perfusion MRI and a new imaging modality for identifying biomarkers, susceptibility-weighted principles of echo shifting with a train of observations (SW-PRESTO), can relay information about perfusion status and degrees of ischemia in embolized meningiomas, and they could be very useful in the realm of therapeutics with embolic material delivery. Direct puncture is yet another therapeutic technique that would allow for more accurate embolization and less blood loss during resection 8).

Preoperative embolization of skull base meningioma

Preoperative embolization of skull base meningioma

Case series

Akimoto et al. retrospectively reviewed the medical records of 186 patients with WHO grade I meningiomas who underwent surgical treatment at our hospital between January 2010 and December 2020. We used propensity score matching to generate embolization and no-embolization groups (42 patients each) to examine embolization effects.

Results: Preoperative embolization was performed in 71 patients (38.2%). In the propensity-matched analysis, the embolization group showed favorable recurrence-free survival (RFS) (mean 49.4 vs 24.1 months; Wilcoxon p=0.049). The embolization group had significantly less intraoperative blood loss (178±203 mL vs 221±165 mL; p=0.009) and shorter operation time (5.6±2.0 hours vs 6.8±2.8 hours; p=0.036). There were no significant differences in Simpson grade IV resection (33.3% vs 28.6%; p=0.637) or overall perioperative complications (21.4% vs 11.9%; p=0.241). Tumor embolization prolonged RFS in a subanalysis of cases who experienced recurrence (n=39) among the overall cases before variable control (mean RFS 33.2 vs 16.0 months; log-rank p=0.003).

Conclusions: After controlling for variables, preoperative embolization for meningioma did not improve the Simpson grade or patient outcomes. However, it might have effects outside of surgical outcomes by prolonging RFS without increasing complications 9)

Rapper et al. performed a retrospective review of patients undergoing intracranial meningioma resection between (March 2001 to December 2012). Comparisons were made between embolized and nonembolized patients, including patient and tumor characteristics, embolization method, operative blood loss, complications, and extent of resection. Logistic regression analyses were used to identify factors predictive of operative blood loss and extent of resection.

Results: Preoperatively, 224 patients were referred for embolization, of which 177 received embolization. No complications were seen in 97.1%. There were no significant differences in operative duration, extent of resection, or complications. Estimated blood loss was higher in the embolized group (410 versus 315 mL, P=.0074), but history of embolization was not a predictor of blood loss in multivariate analysis. Independent predictors of blood loss included decreasing degree of tumor embolization (P=.037), skull base location (P=.005), and male sex (P=.034). Embolization was not an independent predictor of gross total resection.

Conclusions: Preoperative embolization is a safe option for selected meningiomas. In our series, embolization did not alter the operative duration, complications, or degree of resection, but the degree of embolization was an independent predictor of decreased operative blood loss 10)

This study is based on personal experience with about 100 embolized meningiomas and on the experience of others. Embolization is performed during the same session as diagnostic angiography. The appropriate embolic materials (absorbable or nonabsorbable) are chosen according to the location of the tumor, the size of the feeding arteries, the blood flow, and the presence of any potentially dangerous vessels (dangerous anastomoses between external carotid artery and internal carotid or vertebral arteries, arteries supplying the cranial nerves). Preoperative embolization appeared to be very useful in large tumors with pure or predominant external carotid artery supply (convexity meningiomas), in skull-base meningiomas, and in middle fossa and paracavernous meningiomas. It was also useful in falx and parasagittal meningiomas receiving blood supply from the opposite side and in posterior fossa meningiomas. CT low densities demonstrated after embolization did not always correlate with necrosis on microscopic examination, and large areas of infarction could be found despite normal CT. Embolic material was found on pathologic examination in 10%-30% of cases; fresh or recent ischemic and/or hemorrhagic necrosis consistent with technically successful embolization was demonstrated in 40%-60% of cases. With careful technique complications are rare 11)

Case reports

A case of hemorrhage in a parasellar meningioma shortly after embolization of the dural cavernous carotid artery branches supplying the tumor. This represents the first report of hemorrhage within a meningioma resulting from embolization with small (50 to 150-microns) polyvinyl alcohol particles, as well as the first reported case of hemorrhage complicating meningioma embolization from internal rather than external carotid artery branch embolization. We also review previously reported cases of postembolization hemorrhage from meningiomas 12).

1)

Beutler BD, Lee J, Edminster S, Rajagopalan P, Clifford TG, Maw J, Zada G, Mathew AJ, Hurth KM, Artrip D, Miller AT, Assadsangabi R. Intracranial meningioma: A review of recent and emerging data on the utility of preoperative imaging for management. J Neuroimaging. 2024 Aug 7. doi: 10.1111/jon.13227. Epub ahead of print. PMID: 39113129.
2)

Akimoto T, Nakai Y. [Preoperative Embolization Performed Before Meningioma Resection Might Inhibit Tumor Recurrence]. No Shinkei Geka. 2024 Jul;52(4):846-850. Japanese. doi: 10.11477/mf.1436204983. PMID: 39034522.
3)

Soutome Y, Sugiu K, Hiramatsu M, Haruma J, Ebisudani Y, Kimura R, Edaki H, Kawakami M, Fujita J, Tanaka S. [Preoperative Embolization of Intracranial Meningioma]. No Shinkei Geka. 2024 Jul;52(4):794-804. Japanese. doi: 10.11477/mf.1436204978. PMID: 39034517.
4)

Iida Y, Akimoto T, Miyake S, Suzuki R, Shimohigoshi W, Hori S, Suenaga J, Nakai Y, Sakata K, Yamamoto T. Differences and Advantages of Particles versus Liquid Material for Preoperative Intracranial Tumor Embolization: A Retrospective Multicenter Study. J Neuroendovasc Ther. 2024;18(4):110-118. doi: 10.5797/jnet.oa.2023-0083. Epub 2024 Feb 20. PMID: 38721619; PMCID: PMC11076144.
5)

Matsoukas S, Feng R, Faulkner DE, Odland IC, Durbin J, Tabani H, Schlachter L, Gutzwiller E, Kellner CP, Shigematsu T, Shoirah H, Majidi S, De Leacy R, Berenstein A, Mocco J, Fifi JT, Bederson JB, Shrivastava RK, Rapoport BI. Angiographic Features of Meningiomas Predicting Extent of Preoperative Embolization. Neurosurgery. 2024 Aug 1. doi: 10.1227/neu.0000000000003054. Epub ahead of print. PMID: 39087784.
6)

Shah AH, Patel N, Raper DM, et al. The role of preoperative embolization for intracranial meningiomas. J Neurosurg 2013;119: 364 –72
7)

Jumah F, AbuRmilah A, Raju B, Jaber S, Adeeb N, Narayan V, Sun H, Cuellar H, Gupta G, Nanda A. Does preoperative embolization improve outcomes of meningioma resection? A systematic review and meta-analysis. Neurosurg Rev. 2021 Mar 16. doi: 10.1007/s10143-021-01519-z. Epub ahead of print. PMID: 33723970.
8)

Shah A, Choudhri O, Jung H, Li G. Preoperative endovascular embolization of meningiomas: update on therapeutic options. Neurosurg Focus. 2015 Mar;38(3):E7. doi: 10.3171/2014.12.FOCUS14728. PubMed PMID: 25727229.
9)

Akimoto T, Ohtake M, Miyake S, Suzuki R, Iida Y, Shimohigoshi W, Higashijima T, Nakamura T, Shimizu N, Kawasaki T, Sakata K, Yamamoto T. Preoperative tumor embolization prolongs time to recurrence of meningiomas: a retrospective propensity-matched analysis. J Neurointerv Surg. 2022 Jul 8:neurintsurg-2022-019080. doi: 10.1136/neurintsurg-2022-019080. Epub ahead of print. PMID: 35803729.
10)

Raper DM, Starke RM, Henderson F Jr, Ding D, Simon S, Evans AJ, Jane JA Sr, Liu KC. Preoperative embolization of intracranial meningiomas: efficacy, technical considerations, and complications. AJNR Am J Neuroradiol. 2014 Sep;35(9):1798-804. doi: 10.3174/ajnr.A3919. Epub 2014 Apr 10. PMID: 24722303; PMCID: PMC7966288.
11)

Manelfe C, Lasjaunias P, Ruscalleda J. Preoperative embolization of intracranial meningiomas. AJNR Am J Neuroradiol. 1986 Sep-Oct;7(5):963-72. PMID: 3096121; PMCID: PMC8331988.
12)

Kallmes DF, Evans AJ, Kaptain GJ, Mathis JM, Jensen ME, Jane JA, Dion JE. Hemorrhagic complications in embolization of a meningioma: case report and review of the literature. Neuroradiology. 1997 Dec;39(12):877-80. Review. PubMed PMID: 9457715.

Neurosurgery

by

Definition

Neurosurgery is a surgical specialty focused on the diagnosis, treatment, and management of disorders affecting the nervous system, including the brain, spinal cord, and peripheral nerves.

It is a highly specialized field within medicine, and these procedures are typically performed by neurosurgeons who have extensive training and expertise in the diagnosis and treatment of neurological disorders.

Neurosurgeons

see Neurosurgeons.

Neurosurgical Diseases

Neurosurgical diseases.

Neurosurgical Procedure

Neurosurgical Procedure.

Neurosurgical Education

Neurosurgical Education.

Neurosurgical Training

Neurosurgical Training.

Technology and Innovation: Neurosurgery has seen significant advancements in recent years, thanks to the development of minimally invasive techniques, computer-assisted navigation, and neuroimaging technologies like MRI and CT scans. These innovations have improved the precision and safety of neurosurgical procedures.

Collaboration.

Subspecialties: Within neurosurgery, some subspecialties focus on specific areas, such as pediatric neurosurgery, functional neurosurgery (treating conditions like Parkinson’s disease), and neuro-oncology (treating brain and spinal cord tumors).

Neurosurgery (or neurological surgery), constitutes a medical discipline and surgical specialty that provides care for adult and pediatric patients in the treatment of pain or pathological processes that may modify the function or activity of the central nervous system (e.g. brain, hypophysis, and spinal cord), the peripheral nervous system (e.g. cranial, spinal, and peripheral nerves), the autonomic nervous system, the supporting structures of these systems (e.g. meninges, skull & skull base, and vertebral column), and their vascular supply (e.g. intracranial, extracranial, and spinal vasculature).

Treatment encompasses both non-operative management (e.g. prevention, diagnosis – including image interpretation – and treatments such as but not limited to neurocritical intensive care and rehabilitation) and operative management with its associated image use and interpretation (e.g. endovascular surgery, functional and restorative surgery, stereotactic radiosurgery, and spinal fusion – including its instrumentation.

They require precise and dexterous manipulation of a surgical suture in narrow and deep spaces in the brain. This is necessary for surgical tasks such as the anastomosis of microscopic blood vessels and dura mater suturing.

Neurosurgical procedures lead to great psychological stress. In the past decade, several strategies and techniques have been implemented to minimize the patient’s emotional stress 1) 2).

The esthetic aspect, not considered so important in the past, is now an important feature in the recovery and the quality of life in the postoperative period 3)

Today, neurosurgery is part of the portfolio of all university hospitals. It is a highly specialized service that, because of high costs, is often centralized.

Neurosurgery is one of the fastest-developing medical specialties, and results are continuously improving through the introduction of new treatment methods. Recent major advancements in neurosurgery include the application of microsurgery, the advancements in Imaging techniques, and the high quality and increased amount of a intensive care unit.

To improve the cost transparency of the local health care system, treatment cost was recently referenced to disease related groups (DRG). To define a valid case mix index (CMI), patient status at admission must be well documented. Concurrently, treatment quality must be closely monitored to provide transparency between health care providers concerning the clinical outcome and the complications during the treatment process 4) 5) 6).

Subspecialties

Neurosurgery Subspecialties.

History

see Neurosurgery History.

Books

see Books.

Journal

Neurosurgery Journal

see Neurosurgery Journal

Impact factor: 4.605 (2018)

Future

Globally, the lack of access to basic surgical care causes 3 times as many deaths as HIV/AIDS, tuberculosis, and malaria combined. The magnitude of this unmet need has been described recently, and the numbers are startling. Major shifts in the global health agenda have highlighted access to essential and emergency surgery as a high priority. A broad examination of the current global neurosurgical efforts to improve access has revealed some strengths, particularly in the realm of training; however, the demand grossly outstrips the supply; Most people in low-income countries do not have access to basic surgical care, either due to lack of availability or affordability. Projects that help create a robust and resilient health system within low- and middle-income countries require urgent implementation. In this context, concurrent scale-up of human resources, investments in capacity building, local data collection, and analysis for accurate assessment are essential. In addition, through the process of collaboration and consensus building within the neurosurgical community, a unified voice of neurosurgery is necessary to effectively advocate for all those who need neurosurgical care wherever, whenever 7).

1) 

Angelini GD, Butchart EG, Armistead SH, Breckenridge IM. Comparative study of leg wound skin closure in coronary artery bypass graft operations. Thorax. 1984;39:942–5.

2) 

Bekar A, Korfali E, Dogan S, Yilmazlar S, Baskan Z, Aksoy K. The effect of hair on infection after cranial surgery. Acta Neurochir (Wien) 2001;143:533–6. discussion 537.

3) 

Cho J, Harrop J, Veznaedaroglu E, Andrews DW. Concomitant use of computer image guidance, linear or sigmoid incisions after minimal shave, and liquid wound dressing with 2-octyl cyanoacrylate for tumor craniotomy or craniectomy: Analysis of 225 consecutive surgical cases with antecedent historical control at one institution. Neurosurgery. 2003;52:832–40. discussion 840-1.

4) 

Clark JC, Spetzler RF. Creating a Brave New World for Neurosurgery. World Neurosurgery. 2011; 75 (5):608–9. doi: 10.1016/j.wneu.2010.12.032

5) 

Scho¨b O, Kocher T, Langer I. Fu¨nf Fragen an die Medizinische Qualita¨tssicherung: Die Selbststeuerung erhalten. Bulletin des me´decins suisses. 2014; 95(39):1446–8.

6) 

OECD/WHO. OECD Reviews of Health Systems: Switzerland 2011.

7) 

Park KB, Johnson WD, Dempsey RJ. Global Neurosurgery: The Unmet Need. World Neurosurg. 2016 Apr;88:32-5. doi: 10.1016/j.wneu.2015.12.048. Epub 2015 Dec 28. PubMed PMID: 26732963.