Classifying glioma via liquid biopsy--progress towards an unmet clinical need

The diagnosis and classification of glioma by liquid biopsy represents a critical unmet need in neuro oncology. A recent study demonstrates targeted next generation sequencing (NGS) of cell-free DNA (cfDNA) from cerebrospinal fluid (CSF) as an evolving option for liquid biopsy in patients with glioma.

Matched three-dimensional organoids and two-dimensional cell lines of melanoma brain metastases mirror response to targeted molecular therapy

Purpose

Despite significant advances in the treatment paradigm for patients with metastatic melanoma, melanoma brain metastasis (MBM) continues to represent a significant treatment challenge. The study of MBM is limited, in part, by shortcomings in existing preclinical models. Surgically eXplanted Organoids (SXOs) are ex vivo, three-dimensional cultures prepared from primary tissue samples with minimal processing that recapitulate genotypic and phenotypic features of parent tumors and are grown without artificial extracellular scaffolding. We aimed to develop the first matched patient-derived SXO and cell line models of MBM to investigate responses to targeted therapy.

Methods

MBM SXOs were created by a novel protocol incorporating techniques for establishing glioma and cutaneous melanoma organoids. A BRAFV600K-mutant and BRAF-wildtype MBM sample were collected directly from the operating room for downstream experiments. Organoids were cultured in an optimized culture medium without an artificial extracellular scaffold. Concurrently, matched patient-derived cell lines were created. Drug screens were conducted to assess treatment response in SXOs and cell lines.

Results

Organoid growth was observed within 3-4 weeks, and MBM SXOs retained histological features of the parent tissue, including pleomorphic epithelioid cells with abundant cytoplasm, large nuclei, focal melanin accumulation, and strong SOX10 positivity. After sufficient growth, organoids could be manually parcellated to increase the number of replicates. Matched SXOs and cell lines demonstrated sensitivity to BRAF and MEK inhibitors.

Conclusion

Here, we describe the creation of a scaffold-free organoid model of MBM. Further study using SXOs may improve the translational relevance of preclinical studies and enable the study of the metastatic melanoma tumor microenvironment.

An ERK5-PFKFB3 axis regulates glycolysis and represents a therapeutic vulnerability in pediatric diffuse midline glioma

Metabolic reprogramming in pediatric diffuse midline glioma is driven by gene expression changes induced by the hallmark histone mutation H3K27M, which results in aberrantly permissive activation of oncogenic signaling pathways. Previous studies of diffuse midline glioma with altered H3K27 (DMG-H3K27a) have shown that the RAS pathway, specifically through its downstream kinase, extracellular-signal-related kinase 5 (ERK5), is critical for tumor growth. Further downstream effectors of ERK5 and their role in DMG-H3K27a metabolic reprogramming have not been explored. We establish that ERK5 is a critical regulator of cell proliferation and glycolysis in DMG-H3K27a. We demonstrate that ERK5 mediates glycolysis through activation of transcription factor MEF2A, which subsequently modulates expression of glycolytic enzyme PFKFB3. We show that in vitro and mouse models of DMG-H3K27a are sensitive to the loss of PFKFB3. Multi-targeted drug therapy against the ERK5-PFKFB3 axis, such as with small-molecule inhibitors, may represent a promising therapeutic approach in patients with pediatric diffuse midline glioma.

Emerging roles of nucleotide metabolism in cancer

Nucleotides are substrates for multiple anabolic pathways, most notably DNA and RNA synthesis. Since nucleotide synthesis inhibitors began to be used for cancer therapy in the 1950s, our understanding of how nucleotides function in tumor cells has evolved, prompting a resurgence of interest in targeting nucleotide metabolism for cancer therapy. In this review, we discuss recent advances that challenge the idea that nucleotides are mere building blocks for the genome and transcriptome and highlight ways that these metabolites support oncogenic signaling, stress resistance, and energy homeostasis in tumor cells. These findings point to a rich network of processes sustained by aberrant nucleotide metabolism in cancer and reveal new therapeutic opportunities.

Human plasma-like medium facilitates metabolic tracing and enables upregulation of immune signaling pathways in glioblastoma explants

Purpose

Metabolism within the tumor microenvironment (TME) represents an increasing area of interest to understand glioma initiation and progression. Stable isotope tracing is a technique critical to the study of tumor metabolism. Cell culture models of this disease are not routinely cultured under physiologically relevant nutrient conditions and do not retain cellular heterogeneity present in the parental TME. Moreover, in vivo, stable isotope tracing in intracranial glioma xenografts, the gold standard for metabolic investigation, is time consuming and technically challenging. To provide insights into glioma metabolism in the presence of an intact TME, we performed stable isotope tracing analysis of patient-derived, heterocellular Surgically eXplanted Organoid (SXO) glioma models in human plasma-like medium (HPLM).

Methods

Glioma SXOs were established and cultured in conventional media or transitioned to HPLM. We evaluated SXO cytoarchitecture and histology, then performed spatial transcriptomic profiling to identify cellular populations and differential gene expression patterns. We performed stable isotope tracing with 15N2-glutamine to evaluate intracellular metabolite labeling patterns.

Results

Glioma SXOs cultured in HPLM retain cytoarchitecture and cellular constituents. Immune cells in HPLM-cultured SXOs demonstrated increased transcription of immune-related signatures, including innate immune, adaptive immune, and cytokine signaling programs. 15N isotope enrichment from glutamine was observed in metabolites from diverse pathways, and labeling patterns were stable over time.

Conclusion

To enable ex vivo, tractable investigations of whole tumor metabolism, we developed an approach to conduct stable isotope tracing in glioma SXOs cultured under physiologically relevant nutrient conditions. Under these conditions, SXOs maintained viability, composition, and metabolic activity while exhibiting increased immune-related transcriptional programs.

DNA damage in IDH-mutant gliomas: mechanisms and clinical implications

PURPOSE

Since the discovery of IDH mutations in glioma over a decade ago, significant progress has been made in determining how these mutations affect epigenetic, transcriptomic, and metabolic programs in brain tumor cells. In this article, we summarize current understanding of how IDH mutations influence DNA damage in glioma and discuss clinical implications of these findings.

METHODS

We performed a thorough review of peer-reviewed publications and provide an overview of key mechanisms by which IDH mutations impact response to DNA damage in gliomas, with an emphasis on clinical implications.

RESULTS

The effects of mutant IDH on DNA damage largely fall into four overarching categories: Gene Expression, Sensitivity to Alkylating Agents, Homologous Recombination, and Oxidative Stress. From a mechanistic standpoint, we discuss how mutant IDH and the oncometabolite (R)-2HG affect each of these categories of DNA damage. We also contextualize these mechanisms with respect to ongoing clinical trials. Studies are underway that incorporate current standard-of-care therapies, including radiation and alkylating agents, in addition to novel therapeutic agents that exert genotoxic stress specifically in IDH-mutant gliomas. Lastly, we discuss key unanswered questions and emerging data in this field that have important implications for our understanding of glioma biology and for the development of new brain tumor therapies.

CONCLUSION

Mounting preclinical and clinical data suggest that IDH mutations alter DNA damage sensing and repair pathways through distinct mechanisms. Future studies are needed to deepen our understanding of these processes and provide additional mechanistic insights that can be leveraged for therapeutic benefit.

Lysine catabolism reprograms tumour immunity through histone crotonylation

Cancer cells rewire metabolism to favour the generation of specialized metabolites that support tumour growth and reshape the tumour microenvironment1,2. Lysine functions as a biosynthetic molecule, energy source and antioxidant3-5, but little is known about its pathological role in cancer. Here we show that glioblastoma stem cells (GSCs) reprogram lysine catabolism through the upregulation of lysine transporter SLC7A2 and crotonyl-coenzyme A (crotonyl-CoA)-producing enzyme glutaryl-CoA dehydrogenase (GCDH) with downregulation of the crotonyl-CoA hydratase enoyl-CoA hydratase short chain 1 (ECHS1), leading to accumulation of intracellular crotonyl-CoA and histone H4 lysine crotonylation. A reduction in histone lysine crotonylation by either genetic manipulation or lysine restriction impaired tumour growth. In the nucleus, GCDH interacts with the crotonyltransferase CBP to promote histone lysine crotonylation. Loss of histone lysine crotonylation promotes immunogenic cytosolic double-stranded RNA (dsRNA) and dsDNA generation through enhanced H3K27ac, which stimulates the RNA sensor MDA5 and DNA sensor cyclic GMP-AMP synthase (cGAS) to boost type I interferon signalling, leading to compromised GSC tumorigenic potential and elevated CD8+ T cell infiltration. A lysine-restricted diet synergized with MYC inhibition or anti-PD-1 therapy to slow tumour growth. Collectively, GSCs co-opt lysine uptake and degradation to shunt the production of crotonyl-CoA, remodelling the chromatin landscape to evade interferon-induced intrinsic effects on GSC maintenance and extrinsic effects on immune response.

Preclinical modeling of lower-grade gliomas

Models for human gliomas prove critical not only to advancing our understanding of glioma biology but also to facilitate the development of therapeutic modalities. Specifically, creating lower-grade glioma (LGG) models has been challenging, contributing to few investigations and the minimal progress in standard treatment over the past decade. In order to reliably predict and validate the efficacies of novel treatments, however, LGG models need to adhere to specific standards that recapitulate tumor genetic aberrations and micro-environment. This underscores the need to revisit existing models of LGG and explore prospective models that may bridge the gap between preclinical insights and clinical translation. This review first outlines a set of criteria aimed to address the current challenges hindering model development. We then evaluate the strengths and weaknesses of existing preclinical models of LGG with respect to these established standards. To conclude, the review discusses potential future directions for integrating existing models to maximize the exploration of disease mechanisms and therapeutics development.

Selective and brain-penetrant lanosterol synthase inhibitors target glioma stem-like cells by inducing 24(S),25-epoxycholesterol production

Glioblastoma (GBM) is an aggressive adult brain cancer with few treatment options due in part to the challenges of identifying brain-penetrant drugs. Here, we investigated the mechanism of MM0299, a tetracyclic dicarboximide with anti-glioblastoma activity. MM0299 inhibits lanosterol synthase (LSS) and diverts sterol flux away from cholesterol into a "shunt" pathway that culminates in 24(S),25-epoxycholesterol (EPC). EPC synthesis following MM0299 treatment is both necessary and sufficient to block the growth of mouse and human glioma stem-like cells by depleting cellular cholesterol. MM0299 exhibits superior selectivity for LSS over other sterol biosynthetic enzymes. Critical for its application in the brain, we report an MM0299 derivative that is orally bioavailable, brain-penetrant, and induces the production of EPC in orthotopic GBM tumors but not normal mouse brain. These studies have implications for the development of an LSS inhibitor to treat GBM or other neurologic indications.

Isocitrate dehydrogenase mutations in gliomas: A review of current understanding and trials

Isocitrate dehydrogenase (IDH) is a key enzyme in normal metabolism and homeostasis. However, mutant forms of IDH are also defining features of a subset of diffuse gliomas. In this review, we highlight current techniques targeting IDH-mutated gliomas and summarize current and completed clinical trials exploring these strategies. We discuss clinical data from peptide vaccines, mutant IDH (mIDH) inhibitors, and PARP inhibitors. Peptide vaccines have the unique advantage of targeting the specific epitope of a patient's tumor, inducing a highly tumor-specific CD4+ T-cell response. mIDH-inhibitors, on the other hand, specifically target mutant IDH proteins in cancer cell metabolism and thus help halt gliomagenesis. We also explore PARP inhibitors and their role in treating diffuse gliomas, which exploit IDH-mutant diffuse gliomas by allowing the persistence of unrepaired DNA complexes. We summarize various completed and current trials targeting IDH1 and IDH2 mutations in diffuse gliomas. Therapies targeting mutant IDH have significant promise in treating progressive or recurrent IDH-mutant gliomas and may significantly change treatment paradigms in the next decade.

Mismatch repair protein mutations in isocitrate dehydrogenase (IDH)-mutant astrocytoma and IDH-wild-type glioblastoma

BACKGROUND

Mutations in mismatch repair (MMR) genes (MSH2, MSH6, MLH1, and PMS2) are associated with microsatellite instability and a hypermutator phenotype in numerous systemic cancers, and germline MMR mutations have been implicated in multi-organ tumor syndromes. In gliomas, MMR mutations can function as an adaptive response to alkylating chemotherapy, although there are well-documented cases of germline and sporadic mutations, with detrimental effects on patient survival.

METHODS

The clinical, pathologic, and molecular features of 18 IDH-mutant astrocytomas and 20 IDH-wild-type glioblastomas with MMR mutations in the primary tumor were analyzed in comparison to 361 IDH-mutant and 906 IDH-wild-type tumors without MMR mutations. In addition, 12 IDH-mutant astrocytomas and 18 IDH-wild-type glioblastomas that developed MMR mutations between initial presentation and tumor recurrence were analyzed in comparison to 50 IDH-mutant and 104 IDH-wild-type cases that remained MMR-wild-type at recurrence.

RESULTS

In both IDH-mutant astrocytoma and IDH-wild-type glioblastoma cohorts, the presence of MMR mutation in primary tumors was associated with significantly higher tumor mutation burden (TMB) (P < .0001); however, MMR mutations only resulted in worse overall survival in the IDH-mutant astrocytomas (P = .0069). In addition, gain of MMR mutation between the primary and recurrent surgical specimen occurred more frequently with temozolomide therapy (P = .0073), and resulted in a substantial increase in TMB (P < .0001), higher grade (P = .0119), and worse post-recurrence survival (P = .0022) in the IDH-mutant astrocytoma cohort.

CONCLUSIONS

These results suggest that whether present initially or in response to therapy, MMR mutations significantly affect TMB but appear to only influence the clinical outcome in IDH-mutant astrocytoma subsets.

De novo pyrimidine synthesis is a targetable vulnerability in IDH mutant glioma

Mutations affecting isocitrate dehydrogenase (IDH) enzymes are prevalent in glioma, leukemia, and other cancers. Although mutant IDH inhibitors are effective against leukemia, they seem to be less active in aggressive glioma, underscoring the need for alternative treatment strategies. Through a chemical synthetic lethality screen, we discovered that IDH1-mutant glioma cells are hypersensitive to drugs targeting enzymes in the de novo pyrimidine nucleotide synthesis pathway, including dihydroorotate dehydrogenase (DHODH). We developed a genetically engineered mouse model of mutant IDH1-driven astrocytoma and used it and multiple patient-derived models to show that the brain-penetrant DHODH inhibitor BAY 2402234 displays monotherapy efficacy against IDH-mutant gliomas. Mechanistically, this reflects an obligate dependence of glioma cells on the de novo pyrimidine synthesis pathway and mutant IDH's ability to sensitize to DNA damage upon nucleotide pool imbalance. Our work outlines a tumor-selective, biomarker-guided therapeutic strategy that is poised for clinical translation.

Chromosomal instability in adult-type diffuse gliomas

Chromosomal instability (CIN) is a fundamental property of cancer and a key underlying mechanism of tumorigenesis and malignant progression, and has been documented in a wide variety of cancers, including colorectal carcinoma with mutations in genes such as APC. Recent reports have demonstrated that CIN, driven in part by mutations in genes maintaining overall genomic stability, is found in subsets of adult-type diffusely infiltrating gliomas of all histologic and molecular grades, with resulting elevated overall copy number burden, chromothripsis, and poor clinical outcome. Still, relatively few studies have examined the effect of this process, due in part to the difficulty of routinely measuring CIN clinically. Herein, we review the underlying mechanisms of CIN, the relationship between chromosomal instability and malignancy, the prognostic significance and treatment potential in various cancers, systemic disease, and more specifically, in diffusely infiltrating glioma subtypes. While still in the early stages of discovery compared to other solid tumor types in which CIN is a known driver of malignancy, the presence of CIN as an early factor in gliomas may in part explain the ability of these tumors to develop resistance to standard therapy, while also providing a potential molecular target for future therapies.

Surgical Management of a Massive Frontal Bone Hemangioma: Case Report

Intraosseous hemangiomas are rare, benign tumors that can arise from the calvarium. These lesions often invade the outer table of the skull, but typically spare the inner table and intracranial structures. En bloc surgical resection is the standard treatment for intraosseous hemangiomas. However, a piecemeal resection may be required to safely remove the tumor in cases involving the inner table to protect the underlying brain parenchyma and vascular structures. Proper reconstruction is critical to optimize the cosmetic outcome, and a staged procedure allowing implantation of a custom-made implant can be considered for large lesions involving the forehead. We present a case of a patient with a large frontal intraosseous hemangioma with intradural involvement to highlight the surgical nuances of resection and review the existing literature regarding optimal management of these patients.

Semi-Automated Computational Assessment of Cancer Organoid Viability Using Rapid Live-Cell Microscopy

The creation of patient-derived cancer organoids represents a key advance in preclinical modeling and has recently been applied to a variety of human solid tumor types. However, conventional methods used to assess in vivo tumor tissue treatment response are poorly suited for the evaluation of cancer organoids because they are time-intensive and involve tissue destruction. To address this issue, we established a suite of 3-dimensional patient-derived glioma organoids, treated them with chemoradiotherapy, stained organoids with non-toxic cell dyes, and imaged them using a rapid laser scanning confocal microscopy method termed "Apex Imaging." We then developed and tested a fragmentation algorithm to quantify heterogeneity in the topography of the organoids as a potential surrogate marker of viability. This algorithm, SSDquant, provides a 3-dimensional visual representation of the organoid surface and a numerical measurement of the sum-squared distance (SSD) from the derived mass center of the organoid. We tested whether SSD scores correlate with traditional immunohistochemistry-derived cell viability markers (cellularity and cleaved caspase 3 expression) and observed statistically significant associations between them using linear regression analysis. Our work describes a quantitative, non-invasive approach for the serial measurement of patient-derived cancer organoid viability, thus opening new avenues for the application of these models to studies of cancer biology and therapy.

Establishment of patient-derived organoid models of lower-grade glioma

BACKGROUND

Historically, creating patient-derived models of lower-grade glioma (LGG) has been challenging, contributing to few experimental platforms that support laboratory-based investigations of this disease. Although organoid modeling approaches have recently been employed to create in vitro models of high-grade glioma (HGG), it is unknown whether this approach can be successfully applied to LGG.

METHODS

In this study, we developed an optimized protocol for the establishment of organoids from LGG primary tissue samples by utilizing physiologic (5%) oxygenation conditions and employed it to produce the first known suite of these models. To assess their fidelity, we surveyed key biological features of patient-derived organoids using metabolic, genomic, histologic, and lineage marker gene expression assays.

RESULTS

Organoid models were created with a success rate of 91% (n = 20/22) from primary tumor samples across glioma histological subtypes and tumor grades (WHO Grades 1-4), and a success rate of 87% (13/15) for WHO Grade 1-3 tumors. Patient-derived organoids recapitulated stemness, proliferative, and tumor-stromal composition profiles of their respective parental tumor specimens. Cytoarchitectural, mutational, and metabolic traits of parental tumors were also conserved. Importantly, LGG organoids were maintained in vitro for weeks to months and reanimated after biobanking without loss of integrity.

CONCLUSIONS

We report an efficient method for producing faithful in vitro models of LGG. New experimental platforms generated through this approach are well positioned to support preclinical studies of this disease, particularly those related to tumor immunology, tumor-stroma interactions, identification of novel drug targets, and personalized assessments of treatment response profiles.

Global DNA methylation profiling reveals chromosomal instability in IDH-mutant astrocytomas

Diffusely infiltrating gliomas are among the most common central nervous system tumors in adults. Over the past decade, the subcategorization of these tumors has changed to include both traditional histologic features and more recently identified molecular factors. However, one molecular feature that has yet to be integrated is the presence/absence of chromosomal instability (CIN). Herein, we use global methylation profiling to evaluate a reference cohort of IDH-mutant astrocytomas with and without prior evidence of CIN (n = 42), and apply the resulting methylation-based characteristics to a larger test cohort of publicly-available IDH-mutant astrocytomas (n = 245). We demonstrate that IDH-mutant astrocytomas with evidence of CIN cluster separately from their chromosomally-stable counterparts. CIN cases were associated with higher initial histologic grade, altered expression patterns of genes related to CIN in other cancers, elevated initial total copy number burden, and significantly worse progression-free and overall survival. In addition, in a grade-for-grade analysis, patients with CIN-positive WHO grade 2 and 3 tumors had significantly worse survival. These results suggest that global methylation profiling can be used to discriminate between chromosomally stable and unstable IDH-mutant astrocytomas, and may therefore provide a reliable and cost-effective method for identifying gliomas with chromosomal instability and resultant poor clinical outcome.

Large Animal Models of Glioma: Current Status and Future Prospects

Enhanced understanding of the molecular features of glioma has led to an expansion of murine glioma models and successful preclinical studies. However, clinical trials continue to have a high cost, extended production time, and low proportion of success. Studies in large-animal models of various cancer types have emerged to bridge the translational gap between in vitro and in vivo animal studies and human clinical trials. The anatomy and physiology of large animals are of more direct relevance to human disease, allowing for more rigorous testing of treatments such as surgical resection and adjuvant therapy in glioma. The recent generation of multiple porcine glioma models supports their use in high-throughput preclinical studies. The demonstration of spontaneous glioblastoma formation in canines further provides a unique avenue for the study of de novo glioma. The aim of this review was to outline the current status of large animal models of glioma and their value as a transitional step between rodent models and human clinical trials.

Primary peripheral T-cell central nervous system lymphoma

BACKGROUND

Primary peripheral T-cell central nervous system lymphoma (PCNSL) is a rare, aggressive tumor that arises in the craniospinal axis and has an increased risk in individuals who are immunocompromised. This lesion often mimics other benign and malignant processes on radiographic imaging, leading to misdiagnosis and delays in treatment. We present a case of a patient with a history of Sjögren's syndrome and progressive neurologic symptoms who underwent craniotomy for diagnosis.

CASE DESCRIPTION

A 61-year-old woman with a history of Sjögren's syndrome, progressive aphasia, left facial droop, and right-sided paresthesias for 4 months presented for evaluation and management. An enhancing, infiltrative lesion in the left frontal lobe with underlying vasogenic edema was appreciated and suggestive of a primary or metastatic neoplasm. The patient underwent an open biopsy for further evaluation of the lesion. Extensive histopathologic evaluation revealed a diagnosis of T-cell PCNSL. The patient was started on induction methotrexate and temozolomide followed by consolidative radiotherapy.

CONCLUSION

Autoimmune conditions are a risk factor for T-cell PCNSL development. T-cell PCNSL has radiographic and gross histologic features that are consistent with a broad differential, including gliomas and inflammatory processes. Prompt diagnosis and extensive histopathological evaluation is essential to ensure appropriate treatment.

Near-Infrared Imaging with Second-Window Indocyanine Green in Newly Diagnosed High-Grade Gliomas Predicts Gadolinium Enhancement on Postoperative Magnetic Resonance Imaging

PURPOSE

Intraoperative molecular imaging with tumor-targeting fluorophores offers real-time detection of neoplastic tissue. The second window indocyanine green (SWIG) technique relies on passive accumulation of indocyanine green (ICG), a near-infrared fluorophore, in neoplastic tissues. In this study, we explore the ability of SWIG to detect neoplastic tissue and to predict postoperative magnetic resonance imaging (MRI) findings intraoperatively.

PROCEDURES

Retrospective data were collected from 36 patients with primary high-grade gliomas (HGG) enrolled as part of a larger trial between October 2014 and October 2018. Patients received systemic ICG infusions at 2.5-5 mg/kg 24 h preoperatively. Near-infrared fluorescence was recorded throughout the case and from biopsy specimens. The presence/location of residual SWIG signal after resection was compared to the presence/location of residual gadolinium enhancement on postoperative MRI. The extent of resection was not changed based on near-infrared imaging.

RESULTS

All 36 lesions demonstrated strong near-infrared fluorescence (signal-to-background = 6.8 ± 2.2) and 100 % of tumors reaching the cortex were visualized before durotomy. In 78 biopsy specimens, near-infrared imaging demonstrated higher sensitivity and accuracy than white light for diagnosing neoplastic tissue intraoperatively. Furthermore, near-infrared imaging predicted gadolinium enhancement on postoperative MRI with 91 % accuracy, with visualization of residual enhancement as small as 0.3 cm³. Patients with no residual near-infrared signal after resection were significantly more likely to have complete resection on postoperative MRI (p value < 0.0001).

CONCLUSIONS

Intraoperative imaging with SWIG demonstrates highly sensitive detection of HGG tissue in real time. Furthermore, post-resection near-infrared imaging correlates with postoperative MRI. Overall, our findings suggest that SWIG can provide surgeons with MRI-like results in real time, potentially increasing resection rates.

RADI-14. Bevacizumab vs Laser Interstitial Thermal Therapy in radiation necrosis from brain metastases: a systematic review and meta-analysis

Objective

Radiation necrosis (RN) represents a serious post-radiotherapy complication in patients with brain metastases. Bevacizumab and laser interstitial thermal therapy (LITT) are viable treatment options, but direct comparative data is scarce. We reviewed the literature to compare the two treatment strategies.

Methods

PubMed, EMBASE, Scopus, and Cochrane databases were searched. All studies of patients with RN from brain metastases treated with bevacizumab or LITT were included. Treatment outcomes were analyzed using indirect meta-analysis with random-effect modeling.

Results

Among the 18 studies included, 143 patients received bevacizumab and 148 underwent LITT. Both strategies were equally effective in providing post-treatment symptomatic improvement (P=0.187, I2=54.8%), weaning off steroids (P=0.614, I2=25.5%), and local lesion control (P=0.5, I2=0%). The mean number of lesions per patient was not statistically significant among groups (P=0.624). Similarly, mean T1-contrast-enhancing pre-treatment volumes were not statistically different (P=0.582). Patterns of radiological responses differed at 6-month follow-ups, with rates of partial regression significantly higher in the bevacizumab group (P=0.001, I2=88.9%), and stable disease significantly higher in the LITT group (P=0.002, I2=81.9%). Survival rates were superior in the LITT cohort, and statistical significance was reached at 18 months (P=0.038, I2=73.7%). Low rates of adverse events were reported in both groups (14.7% for bevacizumab and 12.2% for LITT).

Conclusion

Bevacizumab and LITT can be safe and effective treatments for RN from brain metastases. Clinical and radiological outcomes are mostly comparable, but LITT may relate to superior survival benefits in select patients. Further studies are required to identify the best patient candidates for each treatment group.

Bevacizumab vs laser interstitial thermal therapy in cerebral radiation necrosis from brain metastases: a systematic review and meta-analysis

PURPOSE

Radiation necrosis (RN) represents a serious post-radiotherapy complication in patients with brain metastases. Bevacizumab and laser interstitial thermal therapy (LITT) are viable treatment options, but direct comparative data is scarce. We reviewed the literature to compare the two treatment strategies.

METHODS

PubMed, EMBASE, Scopus, and Cochrane databases were searched. All studies of patients with RN from brain metastases treated with bevacizumab or LITT were included. Treatment outcomes were analyzed using indirect meta-analysis with random-effect modeling.

RESULTS

Among the 18 studies included, 143 patients received bevacizumab and 148 underwent LITT. Both strategies were equally effective in providing post-treatment symptomatic improvement (P = 0.187, I² = 54.8%), weaning off steroids (P = 0.614, I² = 25.5%), and local lesion control (P = 0.5, I² = 0%). Mean number of lesions per patient was not statistically significant among groups (P = 0.624). Similarly, mean T1-contrast-enhancing pre-treatment volumes were not statistically different (P = 0.582). Patterns of radiological responses differed at 6-month follow-ups, with rates of partial regression significantly higher in the bevacizumab group (P = 0.001, I² = 88.9%), and stable disease significantly higher in the LITT group (P = 0.002, I² = 81.9%). Survival rates were superior in the LITT cohort, and statistical significance was reached at 18 months (P = 0.038, I² = 73.7%). Low rates of adverse events were reported in both groups (14.7% for bevacizumab and 12.2% for LITT).

CONCLUSION

Bevacizumab and LITT can be safe and effective treatments for RN from brain metastases. Clinical and radiological outcomes are mostly comparable, but LITT may relate with superior survival benefits in select patients. Further studies are required to identify the best patient candidates for each treatment group.

Patient-Derived Cancer Organoids for Precision Oncology Treatment

The emergence of three-dimensional human organoids has opened the door for the development of patient-derived cancer organoid (PDO) models, which closely recapitulate parental tumor tissue. The mainstays of preclinical cancer modeling include in vitro cell lines and patient-derived xenografts, but these models lack the cellular heterogeneity seen in human tumors. Moreover, xenograft establishment is resource and time intensive, rendering these models difficult to use to inform clinical trials and decisions. PDOs, however, can be created efficiently and retain tumor-specific properties such as cellular heterogeneity, cell-cell and cell-stroma interactions, the tumor microenvironment, and therapeutic responsiveness. PDO models and drug-screening protocols have been described for several solid tumors and, more recently, for gliomas. Since PDOs can be developed in clinically relevant time frames and share many characteristics of parent tumors, they may enhance the ability to provide precision oncologic care for patients. This review explores the current literature on cancer organoids, highlighting the history of PDO development, organoid models of glioma, and potential clinical applications of PDOs.

DDRE-29. DE NOVO PYRIMIDINE SYNTHESIS IS A TARGETABLE VULNERABILITY IN IDH-MUTANT GLIOMA

70–90% of lower-grade gliomas and secondary glioblastomas harbor gain-of-function mutations in isocitrate dehydrogenase 1 (IDH1), causing overproduction of the oncometabolite (R)-2-hydroxyglutarate [(R)-2HG]. Although inhibitors of mutant IDH enzymes are effective in other cancers, including leukemia, they have shown guarded efficacy in preclinical and clinical brain tumor studies, thus underscoring the need to identify additional therapeutic targets in IDH mutant glioma. We sought to identify tumor-specific metabolic vulnerabilities induced by IDH1 mutations that could be exploited therapeutically. To uncover such vulnerabilities, we conducted a chemical synthetic lethality screen using isogenic IDH1 mutant and IDH1 wild-type (WT) glioma cell lines and a novel metabolic inhibitor screening platform. We discovered that IDH1 mutant cells are hypersensitive to drugs targeting enzymes in the de novo pyrimidine nucleotide synthesis pathway, including dihydroorotate dehydrogenase (DHODH). This vulnerability is specific because inhibitors of purine nucleotide metabolism did not score in our screen. We validated that the cytotoxicity of pyrimidine synthesis inhibitors is on-target and showed that IDH1 mutant patient-derived glioma stem-like cell lines are also hyperdependent on de novo pyrimidine nucleotide synthesis compared to IDH1 WT lines. To test pyrimidine synthesis dependence of IDH1 mutant gliomas in vivo, we used a brain-penetrent DHODH inhibitor currently undergoing evaluation in leukemia patients, BAY 2402234. We found that BAY 2402234 displays monotherapy activity against gliomas in an orthotopic xenograft model of IDH1 mutant glioma, with an effect size that compared favorably with radiotherapy. We also developed novel genetically engineered and allograft mouse models of mutant IDH1-driven anaplastic astrocytoma and showed that BAY 2402234 blocked growth of orthotopic astrocytoma allografts. Our findings bolster rationale to target DHODH in glioma, highlight BAY 2402234 as a clinical-stage drug that can be used to inhibit DHODH in brain tumors, and establish IDH1 mutations as predictive biomarkers of DHODH inhibitor efficacy.

Contemporary Mouse Models in Glioma Research

Despite advances in understanding of the molecular pathogenesis of glioma, outcomes remain dismal. Developing successful treatments for glioma requires faithful in vivo disease modeling and rigorous preclinical testing. Murine models, including xenograft, syngeneic, and genetically engineered models, are used to study glioma-genesis, identify methods of tumor progression, and test novel treatment strategies. Since the discovery of highly recurrent isocitrate dehydrogenase (IDH) mutations in lower-grade gliomas, there is increasing emphasis on effective modeling of IDH mutant brain tumors. Improvements in preclinical models that capture the phenotypic and molecular heterogeneity of gliomas are critical for the development of effective new therapies. Herein, we explore the current status, advancements, and challenges with contemporary murine glioma models.

Molecular Signatures of Chromosomal Instability Correlate With Copy Number Variation Patterns and Patient Outcome in IDH-Mutant and IDH-Wildtype Astrocytomas

Chromosomal instability due to mutations in genes guarding the stability of the genome is a well-known mechanism underlying tumorigenesis and malignant progression in numerous cancers. The effect of this process in gliomas is mostly unknown with relatively little research examining the effects of chromosomal instability on patient outcome and therapeutic efficacy, although studies have shown that overall/total copy number variation (CNV) is elevated in higher histologic grades and in cases with more rapid progression and shorter patient survival. Herein, we examine a 70-gene mRNA expression signature (CIN70), which has been previously shown to correlate tightly with chromosomal instability, in 2 independent cohorts of IDH-mutant astrocytomas (total n = 241), IDH-wildtype astrocytomas (n = 228), and oligodendrogliomas (n = 128). Our results show that CIN70 expression levels correlate with total CNV, as well as higher grade, progression-free survival, and overall survival in both IDH-mutant and IDH-wildtype astrocytomas. In oligodendrogliomas, these mRNA signatures correlate with total CNV but not consistently with clinical outcome. These data suggest that chromosomal instability is an underlying factor in aggressive behavior and progression of a subset of diffuse astrocytomas. In addition, chromosomal instability may in part explain the poor response of diffuse gliomas to treatment and may serve as a future therapeutic target.

Molecular Correlates of Long Survival in IDH-Wildtype Glioblastoma Cohorts

IDH-wildtype glioblastoma is a relatively common malignant brain tumor in adults. These patients generally have dismal prognoses, although outliers with long survival have been noted in the literature. Recently, it has been reported that many histologically lower-grade IDH-wildtype astrocytomas have a similar clinical outcome to grade IV tumors, suggesting they may represent early or undersampled glioblastomas. cIMPACT-NOW 3 guidelines now recommend upgrading IDH-wildtype astrocytomas with certain molecular criteria (EGFR amplifications, chromosome 7 gain/10 loss, and/or TERT promoter mutations), establishing the concept of a "molecular grade IV" astrocytoma. In this report, we apply these cIMPACT-NOW 3 criteria to 2 independent glioblastoma cohorts, totaling 393 public database and institutional glioblastoma cases: 89 cases without any of the cIMPACT-NOW 3 criteria (GBM-C0) and 304 cases with one or more criteria (GBM-C1-3). In the GBM-C0 groups, there was a trend toward longer recurrence-free survival (median 12-17 vs 6-10 months), significantly longer overall survival (median 32-41 vs 15-18 months), younger age at initial diagnosis, and lower overall mutation burden compared to the GBM-C1-3 cohorts. These data suggest that while histologic features may not be ideal indicators of patient survival in IDH-wildtype astrocytomas, these 3 molecular features may also be important prognostic factors in IDH-wildtype glioblastoma.

Molecular and Metabolic Mechanisms Underlying Selective 5-Aminolevulinic Acid-Induced Fluorescence in Gliomas

Simple Summary

5-aminolevulinic acid (5-ALA) is a medication that produces fluorescence in certain cancers, which enables surgeons to visualize tumor margins during surgery. Gliomas are brain tumors that can be difficult to fully resect due to their infiltrative nature. In this review we explored what is known about the mechanism of 5-ALA, recent discoveries that increase our understanding of that mechanism, and potential targets to increase fluorescence in lower grade gliomas.

Abstract

5-aminolevulinic acid (5-ALA) is a porphyrin precursor in the heme synthesis pathway. When supplied exogenously, certain cancers consume 5-ALA and convert it to the fluorogenic metabolite protoporphyrin IX (PpIX), causing tumor-specific tissue fluorescence. Preoperative administration of 5-ALA is used to aid neurosurgical resection of high-grade gliomas such as glioblastoma, allowing for increased extent of resection and progression free survival for these patients. A subset of gliomas, especially low-grade tumors, do not accumulate PpIX intracellularly or readily fluoresce upon 5-ALA administration, making gross total resection difficult to achieve in diffuse lesions. We review existing literature on 5-ALA metabolism and PpIX accumulation to explore potential mechanisms of 5-ALA-induced glioma tissue fluorescence. Targeting the heme synthesis pathway and understanding its dysregulation in malignant tissues could aid the development of adjunct therapies to increase intraoperative fluorescence after 5-ALA treatment.

Patient-specific prediction model for clinical and quality-of-life outcomes after lumbar spine surgery

OBJECTIVE

Patient demographics, comorbidities, and baseline quality of life (QOL) are major contributors to postoperative outcomes. The frequency and cost of lumbar spine surgery has been increasing, with controversy revolving around optimal management strategies and outcome predictors. The goal of this study was to generate predictive nomograms and a clinical calculator for postoperative clinical and QOL outcomes following lumbar spine surgery for degenerative disease.

METHODS

Patients undergoing lumbar spine surgery for degenerative disease at a single tertiary care institution between June 2009 and December 2012 were retrospectively reviewed. Nomograms and an online calculator were modeled based on patient demographics, comorbidities, presenting symptoms and duration of symptoms, indication for surgery, type and levels of surgery, and baseline preoperative QOL scores. Outcomes included postoperative emergency department (ED) visit or readmission within 30 days, reoperation within 90 days, and 1-year changes in the EuroQOL-5D (EQ-5D) score. Bootstrapping was used for internal validation.

RESULTS

A total of 2996 lumbar surgeries were identified. Thirty-day ED visits were seen in 7%, 30-day readmission in 12%, 90-day reoperation in 3%, and improvement in EQ-5D at 1 year that exceeded the minimum clinically important difference in 56%. Concordance indices for the models predicting ED visits, readmission, reoperation, and dichotomous 1-year improvement in EQ-5D were 0.63, 0.66, 0.73, and 0.84, respectively. Important predictors of clinical outcomes included age, body mass index, Charlson Comorbidity Index, indication for surgery, preoperative duration of symptoms, and the type (and number of levels) of surgery. A web-based calculator was created, which can be accessed here: https://riskcalc.org/PatientsEligibleForLumbarSpineSurgery/.

CONCLUSIONS

The prediction tools derived from this study constitute important adjuncts to clinical decision-making that can offer patients undergoing lumbar spine surgery realistic and personalized expectations of postoperative outcome. They may also aid physicians in surgical planning, referrals, and counseling to ultimately lead to improved patient experience and outcomes.

Tractography and the connectome in neurosurgical treatment of gliomas: the premise, the progress, and the potential

The ability of diffusion tensor MRI to detect the preferential diffusion of water in cerebral white matter tracts enables neurosurgeons to noninvasively visualize the relationship of lesions to functional neural pathways. Although viewed as a research tool in its infancy, diffusion tractography has evolved into a neurosurgical tool with applications in glioma surgery that are enhanced by evolutions in crossing fiber visualization, edema correction, and automated tract identification. In this paper the current literature supporting the use of tractography in brain tumor surgery is summarized, highlighting important clinical studies on the application of diffusion tensor imaging (DTI) for preoperative planning of glioma resection, and risk assessment to analyze postoperative outcomes. The key methods of tractography in current practice and crucial white matter fiber bundles are summarized. After a review of the physical basis of DTI and post-DTI tractography, the authors discuss the methodologies with which to adapt DT image processing for surgical planning, as well as the potential of connectomic imaging to facilitate a network approach to oncofunctional optimization in glioma surgery.

Economic implications of the modern treatment paradigm of glioblastoma: an analysis of global cost estimates and their utility for cost assessment

INTRODUCTION

Glioblastoma is the most common primary brain tumor in adults. Standard of care includes maximal surgical resection of the tumor followed by concurrent chemotherapy and radiation. The treatment of glioblastoma must account for an increased disease severity and treatment intensity compared to other cancers which place a significant cost burden on the patient and health system. Cost assessments of glioblastoma treatment have been sparse in comparison to other solid cancer subtypes. This study evaluates all currently available cost literature with an emphasis on the modern treatment paradigm to properly assess the economic implications of this disease.

METHODS

A critical review of 21 studies from 13 different countries measuring direct costs related to glioblastoma management was performed. Evaluated data included itemized costs, total costs of treatment regimens from diagnosis until death, the cost of second-line care after recurrence, and the incremental costs and cost-effectiveness of emerging therapies.

RESULTS

The average cost of a craniotomy was $10,042 across studies. Imaging for the duration of glioblastoma care had a mean cost of $2,788 ± 3,719. Studies examined different combinations of treatment modalities. Utilization of the modern treatment paradigm led to survival of 16.3 months across studies and had a mean cost of $62,602. Surgery for the recurrent disease had an average cost of $27,442 ± 18,992.

LIMITATIONS AND CONCLUSIONS

Direct cost estimates for glioblastoma varied substantially between institutions and countries and often failed to uniformly describe direct cost estimates associated with care for glioblastoma. The limitations of these studies make a true economic assessment of standards of care, costs of recurrence, and incremental costs associated with adjunctive therapy uncertain.

Endoscopic Paramedian Sitting Craniotomy for Resection of a Dorsal Midbrain Cavernous Malformation: 2-Dimensional Operative Video

This case video demonstrates the surgical technique for resection of a cavernous malformation in the right dorsal midbrain. This video was deemed exempt by the University of Pennsylvania Institutional Review Board (IRB), as it is considered a case report, which does not require IRB approval or patient consent. The patient was a 57-yr-old male with cerebral cavernous malformation syndrome with multiple intracranial cavernomas. He was noticed to have progressively slowed speech with worsening confusion and drowsiness. On exam, the patient exhibited worsening in swallowing and upward gaze paresis, secondary to Parinaud phenomena. The patient was treated with microsurgical resection, utilizing stereotactic navigation and intraoperative neurophysiologic monitoring. Intraoperative view provided in the video was captured using a Karl Storz Endoscope (Karl Storz SE & Co KG, Tuttlingen, Germany). Postoperatively, the patient had worsening double vision, which improved on follow-up, in addition to improvement in sensorium and swallowing.

An additive score optimized by a genetic learning algorithm predicts readmission risk after glioblastoma resection

Thirty-day readmission following glioblastoma (GBM) resection is not only correlated with decreased overall survival but also increasingly tied to quality metrics and reimbursement. This study aimed to determine factors linked with 30-day readmission to develop a simple risk stratification score. From 2005 to 2016, 666 unique resections (467 patients) of primary/recurrent tissue-confirmed glioblastoma were retrospectively identified. We recorded patient demographics and medical history, tumor characteristics, post-operative complications and 30-day readmission. Univariate and multivariate logistic regression, optimized using a genetic learning algorithm, were used to determine factors associated with readmission. The multivariate model was converted to a simple additive score. The 30-day readmission rate was 20.3% in our cohort of 666 unique resections (60.7% first resection). Lower pre/post-operative KPS, recurrent resection, surgical-site infection, post-operative VTE, post-operative VPS, and discharge to a rehabilitation facility were significantly associated with an increased readmission risk (p < 0.05). MGMT methylation and chemoradiation were associated with decreased readmission risk (p < 0.05). Medical co-morbidities and past medical history, location of tumor in eloquent areas of the brain, and length of ICU/hospital stay did not predict readmission. The Glioblastoma Readmission Risk Score, developed from the multivariate model, accounts for increased BMI, decreased pre-operative KPS, current smoking, post-operative complications, MGMT methylation, and post-operative radiation. This risk score can be routinely used to stratify risk and assist in clinical decision making and outcome analyses.

Amplifying the Noise: Oncometabolites Mask an Epigenetic Signal of DNA Damage

A recent study (Sulkowski et al., 2020) reveals that oncometabolites, which are produced by metabolic gene mutations in many cancers, sensitize cells to PARP inhibition by antagonizing histone demethylation and obscuring epigenetic marks that are necessary for efficient DNA repair.

Review of Audiovestibular Symptoms Following Exposure to Acoustic and Electromagnetic Energy Outside Conventional Human Hearing

Objective: We aim to examine the existing literature on, and identify knowledge gaps in, the study of adverse animal and human audiovestibular effects from exposure to acoustic or electromagnetic waves that are outside of conventional human hearing. Design/Setting/Participants: A review was performed, which included searches of relevant MeSH terms using PubMed, Embase, and Scopus. Primary outcomes included documented auditory and/or vestibular signs or symptoms in animals or humans exposed to infrasound, ultrasound, radiofrequency, and magnetic resonance imaging. The references of these articles were then reviewed in order to identify primary sources and literature not captured by electronic search databases. Results: Infrasound and ultrasound acoustic waves have been described in the literature to result in audiovestibular symptomology following exposure. Technology emitting infrasound such as wind turbines and rocket engines have produced isolated reports of vestibular symptoms, including dizziness and nausea and auditory complaints, such as tinnitus following exposure. Occupational exposure to both low frequency and high frequency ultrasound has resulted in reports of wide-ranging audiovestibular symptoms, with less robust evidence of symptomology following modern-day exposure via new technology such as remote controls, automated door openers, and wireless phone chargers. Radiofrequency exposure has been linked to both auditory and vestibular dysfunction in animal models, with additional historical evidence of human audiovestibular disturbance following unquantifiable exposure. While several theories, such as the cavitation theory, have been postulated as a cause for symptomology, there is extremely limited knowledge of the pathophysiology behind the adverse effects that particular exposure frequencies, intensities, and durations have on animals and humans. This has created a knowledge gap in which much of our understanding is derived from retrospective examination of patients who develop symptoms after postulated exposures. Conclusion and Relevance: Evidence for adverse human audiovestibular symptomology following exposure to acoustic waves and electromagnetic energy outside the spectrum of human hearing is largely rooted in case series or small cohort studies. Further research on the pathogenesis of audiovestibular dysfunction following acoustic exposure to these frequencies is critical to understand reported symptoms.

A Retrospective Propensity Score-Matched Early Thromboembolic Event Analysis of Prothrombin Complex Concentrate vs Fresh Frozen Plasma for Warfarin Reversal Prior to Emergency Neurosurgical Procedures

BACKGROUND

Reversal of therapeutic anticoagulation prior to emergency neurosurgical procedures is required in the setting of intracranial hemorrhage. Multifactor prothrombin complex concentrate (PCC) promises rapid efficacy but may increase the probability of thrombotic complications compared to fresh frozen plasma (FFP).

OBJECTIVE

To compare the rate of thrombotic complications in patients treated with PCC or FFP to reverse therapeutic anticoagulation prior to emergency neurosurgical procedures in the setting of intracranial hemorrhage at a level I trauma center.

METHODS

Sixty-three consecutive patients on warfarin therapy presenting with intracranial hemorrhage who received anticoagulation reversal prior to emergency neurosurgical procedures were retrospectively identified between 2007 and 2016. They were divided into 2 cohorts based on reversal agent, either PCC (n = 28) or FFP (n = 35). The thrombotic complications rates within 72 h of reversal were compared using the χ2 test. A multivariate propensity score matching analysis was used to limit the threat to interval validity from selection bias arising from differences in demographics, laboratory values, history, and clinical status.

RESULTS

Thrombotic complications were uncommon in this neurosurgical population, occurring in 1.59% (1/63) of treated patients. There was no significant difference in the thrombotic complication rate between groups, 3.57% (1/28; PCC group) vs 0% (0/35; FFP group). Propensity score matching analysis validated this finding after controlling for any selection bias.

CONCLUSION

In this limited sample, thrombotic complication rates were similar between use of PCC and FFP for anticoagulation reversal in the management of intracranial hemorrhage prior to emergency neurosurgical procedures.

Is There Socrates without Plato?

Not applicable.

Evaluating the Association Between the Extent of Resection and Survival in Gliosarcoma

Introduction: Gliosarcoma (GS) is a rare, malignant mixed tumor of the central nervous system with a median survival of approximately 13 months across multiple studies. Although the value of the extent of resection (EOR) has been confirmed as a prognostic survival factor in glioblastoma, no such association has been defined for GS. The goal of this study was to establish an association between EOR and survival and to determine if a threshold of resection exists for which a survival benefit is conferred in GS.

Methods: The authors identified 11 patients with histologically confirmed GS between January 2005 and January 2015, treated at the Hospital of the University of Pennsylvania. Clinical, radiographic, and outcome data were retrospectively reviewed. Volumetric analysis was completed using semi-automated segmentation to measure the change in contrast-enhancing material based on preoperative T1-contrast (T1c) and postoperative T1 & T1c magnetic resonance imaging (MRI) scans. A log-rank test was completed to confirm an association between EOR and survival, and a series of Kaplan-Meier curves were constructed to determine an EOR threshold. Univariate Cox proportional hazards model (CPHM) followed by multivariate CPHM was also completed to evaluate associations between the prognostic clinical and immunohistochemistry variables under consideration.

Results: Extent of resection categories were defined as gross total resection (GTR >95%), subtotal resection (STR 90%-95%), and partial resection (PR <90%). The median overall survival for the groups were as follows: GTR-17.3 months (n=4), STR-12.6 months (n=5), PR-4.3 months (n=2). A statistically significant association (p=05 level) was found between survival and the PR group with the GTR group as reference. Multivariate CPHM confirmed a statistically significant association between increased survival and age, preoperative Karnofsky Performance Status (KPS) scores, postoperative KPS scores, and KI-67 index. Serial Kaplan-Meier curves suggest a survival benefit with an EOR threshold of 94%.

Conclusion: This study agrees with previous correlations in glioblastoma EOR and prolonged survival. For patients undergoing surgical resection for GS, maximal surgical removal, when safely possible, should be attempted as it appears to translate to longer survival times.

High Resolution Computed Tomography Atlas of the Porcine Temporal Bone and Skull Base: Anatomical Correlates for Traumatic Brain Injury Research

Brain injuries are a significant cause of morbidity and mortality worldwide. Auditory and vestibular dysfunction may occur following trauma to the temporal bone (TB), including the lateral skull base. The porcine model is a commonly used large animal model for investigating brain injury. Reports detailing porcine TB anatomy based on high resolution computed tomography (HRCT) imaging, however, are limited. Herein, we employ HRCT to evaluate and describe the bony anatomy of the porcine TB and lateral skull base. High-resolution multi-detector and cone beam CT were used to image porcine TBs (n = 16). TBs were analyzed for major anatomical structures and compared to human species. Porcine temporal bone anatomy was readily identifiable by HRCT. Although some variability exists, the ossicular chain, vestibule, cochlea, course of the facial nerve, and skull base are similar to those of humans. Major differences included position of the external auditory canal and mastoid, as well as presence of the petrous carotid canal. Study findings may serve as an atlas to evaluate the porcine middle and inner ear, as well as lateral skull base injuries for future porcine brain injury models or other studies that require CT-based analysis.

Liver disease is an independent predictor of poor 30-day outcomes following surgery for degenerative disease of the cervical spine

BACKGROUND AND CONTEXT

The impact of underlying liver disease on surgical outcomes has been recognized in a wide variety of surgical disciplines. However, less empiric data are available about the importance of liver disease in spinal surgery.

PURPOSE

To measure the independent impact of underlying liver disease on 30-day outcomes following surgery for the degenerative cervical spine.

STUDY DESIGN

Retrospective comparative study.

PATIENT SAMPLE

A cohort of 21,207 patients undergoing elective surgery for degenerative disease of the cervical spine from the American College of Surgeons National Surgical Quality Improvement Program.

OUTCOME MEASURES

Outcome measures included mortality, hospital length of stay, and postoperative complications within 30 days of surgery.

METHODS

The NSQIP dataset was queried for patients undergoing surgery for degenerative disease of the cervical spine from 2006 to 2015. Assessment of underlying liver disease was based on aspartate aminotransferase-to-platelet ratio index and Model of End-Stage Liver Disease-Sodium scores, computed from preoperative laboratory data. The effect of liver disease on outcomes was assessed by bivariate and multivariate analyses, in comparison with 16 other preoperative and operative factors.

RESULTS

Liver disease could be assessed in 21,207 patients based on preoperative laboratory values. Mild liver disease was identified in 2.2% of patients, and advanced liver disease was identified in 1.6% of patients. The 30-day mortality rates were 1.7% and 5.1% in mild and advanced liver diseases, respectively, compared with 0.6% in patients with healthy livers. The 30-day complication rates were 11.8% and 31.5% in these patients, respectively, compared with 8.8% in patients with healthy livers. In multivariate analysis, the presence of any liver disease (mild or advanced) was independently associated with an increased risk of mortality (OR=2.00, 95% CI=1.12-3.55, p=.019), morbidity (OR=1.35, 95% CI=1.07-1.70, p=.012), and length of hospital stay longer than 7 days (OR=1.73, 95% CI=1.40-2.13, p<.001), when compared with 18 other preoperative and operative factors. Liver disease was also independently associated with perioperative respiratory failure (OR=1.80, 95% CI=1.21-2.68, p=.004), bleeding requiring transfusion (OR=1.43, 95% CI=1.01-2.02, p=.044), wound disruption (OR=2.82, 95% CI=1.04-7.66, p=.042), and unplanned reoperation (OR=1.49, 95% CI=1.05-2.11, p=.025).

CONCLUSIONS

Liver disease independently predicts poor perioperative outcome following surgery for degenerative disease of the cervical spine. Based on these findings, careful consideration of a patient's underlying liver function before surgery may prove valuable in surgical decision-making, preoperative patient counseling, and postoperative patient care.

Patient-reported Allergies are Associated With Preoperative Psychological Distress and Less Satisfying Patient Experience in a Lumbar Spine Surgery Population

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The main objectives of this study were: (1) to determine whether patient-reported allergies (PRAs) are associated with patient satisfaction scores, and (2) to clarify the association between PRAs and preoperative anxiety and depression in a lumbar spine surgery population.

SUMMARY OF BACKGROUND DATA

Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) survey is currently used to measure the patient experience and there is concern that psychosocial factors are unaccounted for. Interestingly, PRAs have been linked to concurrent mood and other psychiatric disorders, as well as poor clinical outcomes in the orthopedic surgery setting.

METHODS

HCAHPS survey data, patient demographics, surgical characteristics, and preoperative health status were obtained for each patient. Allergies were categorized as medical (ie, medications) and environmental (ie, food, animals). Univariable and multivariable logistic regression models were used to determine whether the number of medical and environmental PRAs are associated with HCAHPS scores. In addition, multivariable logistic regression was used to analyze the association between PRAs and psychological distress.

RESULTS

In 421 patients included, PRAs were associated with lower HCAHPS scores under several dimensions of the patient experience of care, including: nursing communication, pain management, communication about medicines, and transition of care. Medical PRAs was an independent predictor of low satisfaction with communication about a medication's side effects [odds ratio (OR), 0.88; P=0.03] and understanding the purpose for new medications (OR, 0.90; P=0.03). Environmental PRAs was an independent predictor of low satisfaction with both communication about a medication's side effects (OR, 0.68; P=0.03), and pain control (OR, 0.67; P=0.01). Moreover, having a PRA (OR, 1.64; P=0.04) was associated with EuroQol-5 Dimensions anxiety/depression and having an environmental PRA (OR, 2.13; P=0.03) was associated with depression.

CONCLUSIONS

These findings highlight the potential utility of PRAs to help identify patients with psychological distress who are at risk for a poor experience of lumbar spine surgery.

Otogenic brain abscesses: A systematic review

Objective

Otogenic brain abscesses are one of the most significant life-threatening complications of otologic infections. Given their low prevalence, otogenic brain abscesses require a high index of suspicion for diagnosis. In this systematic review, we aim to provide an analysis of otogenic brain abscesses and describe common clinical signs and symptoms, bacteriology, location, treatment options, morbidity, and mortality.

Data Sources

PubMed, Cochrane CENTRAL database, Google Scholar, and Scopus.

Methods

A systematic review of literature was performed using the Preferred Reporting Items for Systematic Reviews and Meta-analyses recommendations. Variables assessed included clinical signs and symptoms, bacteriology, location, treatment, morbidity, and mortality.

Results

Twenty-nine studies met inclusion and exclusion criteria, corresponding to a total of 1307 otogenic abscess cases for review. Fifty-five percent of abscesses were found in the temporal lobe and 28% in the cerebellum. Most patients (88.3%) had a history of suppurative chronic otitis media. The most common symptoms were headache, altered mental status, papilledema, and meningeal irritation. Fever, nausea, and vomiting affected about 40% of patients. The most commonly cultured bacterial species was Proteus mirabilis. In addition to antibiotics, most otogenic brain abscesses were treated by burr hole aspiration. Average mortality following advent of computed tomography was 8.11%.

Conclusion

Although rare, otogenic brain abscesses may occur as a complication of suppurative otitis media and require a high index of suspicion. Appropriate imaging studies and multidisciplinary expertise are crucial in the diagnosis and management.

Level of Evidence

4.

Outcomes and Prognostic Factors in Pediatric Oligodendroglioma: A Population-Based Study

BACKGROUND/AIMS

Pediatric oligodendroglioma (pODG) is a rare primary brain tumor that remains poorly understood. Demographics, outcomes, and prognostic factors were analyzed in 346 pODG cases from the Surveillance, Epidemiology, and End Results database.

METHODS

Gender, race, age, tumor location, tumor size, tumor grade, extent of resection, and use of radiotherapy were evaluated with respect to overall survival (OS) by univariate and multivariate analysis. These factors were assessed in the pediatric cohort and 5,753 adult oligodendroglioma cases for comparison.

RESULTS

The mean OS in pODG was 199.6 months. Five- and 10-year survival rates were 85 and 81%. pODG arose less frequently in the frontal lobe than adult tumors (53 vs. 22%) but was more common in the temporal lobe (32 vs. 18%) and extracortical regions (19 vs. 5%, p < 0.0001). pODG presented with smaller size (55 vs. 24%, p < 0.0001) and lower grade (72 vs. 54%, p < 0.0001) than adult tumors. Tumor location, size, grade, use of radiotherapy, and extent of resection were significant prognostic factors. Size and grade were much stronger prognostic factors in children than adults. While children with oligodendroglioma survive much longer than adults on the whole, there was no difference in outcome between children with high-grade tumors and adults with high-grade tumors.

CONCLUSION

pODG differs significantly from adult oligodendroglioma along a number of demographic and tumor factors at a population level, and key prognostic factors influence survival differently in pODG than in adult disease.

Topical Vancomycin Reduces Surgical-Site Infections After Craniotomy: A Prospective, Controlled Study

BACKGROUND

Surgical-site infections (SSIs) are an important cause of morbidity and mortality in neurosurgical patients. Topical antibiotics are one potential method to reduce the incidence of these infections.

OBJECTIVE

To examine the efficacy of topical vancomycin applied within the wound during craniotomy in a large prospective cohort study at a major academic center.

METHODS

Three hundred fifty-five patients were studied prospectively in this cohort study; 205 patients received 1 g of topical vancomycin powder in the subgaleal space while 150 matched control patients did not. Patients otherwise received identical care. The primary outcome variable was SSI rate factored by cohort. Secondary analysis examined cost savings from vancomycin usage estimated from hospital costs associated with SSI in craniotomy patients.

RESULTS

The addition of topical vancomycin was associated with a significantly lower rate of SSI than standard of care alone (0.49% [1/205] vs 6% [9/150], P = .002). Based on the costs of revision surgery for infections, topical vancomycin usage was estimated to save $1367 446 per 1000 craniotomy patients. No adverse reactions occurred.

CONCLUSION

Topical vancomycin is a safe, effective, and cost-saving measure to prevent SSIs following craniotomy. These results have broad implications for standard of care in craniotomy.

Three-Dimensional Printed Modeling of Diffuse Low-Grade Gliomas and Associated White Matter Tract Anatomy

BACKGROUND

Diffuse low-grade gliomas (DLGGs) represent several pathological entities that infiltrate and invade cortical and subcortical structures in the brain.

OBJECTIVE

To describe methods for rapid prototyping of DLGGs and surgically relevant anatomy.

METHODS

Using high-definition imaging data and rapid prototyping technologies, we were able to generate 3 patient DLGGs to scale and represent the associated white matter tracts in 3 dimensions using advanced diffusion tensor imaging techniques.

RESULTS

This report represents a novel application of 3-dimensional (3-D) printing in neurosurgery and a means to model individualized tumors in 3-D space with respect to subcortical white matter tract anatomy. Faculty and resident evaluations of this technology were favorable at our institution.

CONCLUSION

Developing an understanding of the anatomic relationships existing within individuals is fundamental to successful neurosurgical therapy. Imaging-based rapid prototyping may improve on our ability to plan for and treat complex neuro-oncologic pathology.

Quality of Life Outcomes Following Resection of Adult Intramedullary Spinal Cord Tumors

BACKGROUND

Intramedullary spinal cord tumors are rare but clinically significant entities. Resection is critical to prevent permanent neurological deficits. However, no studies have investigated the quality of life (QOL) benefit of resection in adults.

OBJECTIVE

To investigate QOL outcomes after intramedullary spinal cord tumors resection.

METHODS

A consecutive retrospective review of all patients who underwent intramedullary spinal cord tumors resection at a single tertiary care institution between January 2008 and December 2013 was conducted. QOL was measured by the EuroQol 5-Dimensions (EQ-5D), Pain Disability Questionnaire (PDQ), and Patient Health Questionnaire-9 (PHQ-9). Multivariable regression was used to identify independent predictors of outcomes.

RESULTS

Among 45 patients, the most common pathology was ependymoma (60%). No significant changes between preoperative and postoperative EQ-5D, PDQ, or PHQ-9 were observed. Improvements exceeding the minimal clinically important difference occurred in 28% of patients in EQ-5D, 28% in PDQ, and 16% in PHQ-9. Worse preoperative neurological status predicted worsened EQ-5D (β = -0.09, P = .04) and PDQ (β = 20.77, P < .01), while ependymomas predicted QOL improvement exceeding the minimal clinically important difference in PDQ (OR 14.98, P = .04) and approached significance in EQ-5D (OR 43.52, P = .06). Conversely, cervical tumors predicted worsened PDQ (β = 18.32, P < .01) and failure to achieve EQ-5D minimal clinically important difference (OR <0.01, 95% CI <0.01-0.65, P = .02). Postoperative complications, such as syrinx formation (β = -0.09, P = .04) and cerebrospinal fluid leak (β = 13.85, P = .04), predicted diminished improvement in EQ-5D and PDQ, respectively.

CONCLUSION

Although resection did not significantly improve QOL, it is likely necessary to arrest QOL deterioration. Patients with better preoperative neurological status or ependymoma experienced QOL improvement, while postoperative complications negatively impacted long-term QOL.

ABBREVIATIONS

EQ-5D, EuroQol 5-DimensionsGTR, gross total resectionIMSCT, intramedullary spinal cord tumorsMCID, minimal clinically important differenceMMS, Modified McCormick ScalePDQ, Pain Disability QuestionnairePHQ-9, Patient Health Questionnaire-9POD, plane of dissectionQOL, quality of lifeSSI, surgical site infection.