Adult glioblastoma multiforme (GBM) is the most common primary malignant brain tumour caused by multiple molecular factors. N-6-methyl-adenosine (m(6)A) is an abundant RNA modification that governs cellular RNA metabolism. We hypothesise that changes in m(6)A-modified RNA and regulatory machinery such as the writer proteins, Methyltransferase 3 (METTL3) and WT1-associating protein (WTAP), the demethyltransferase protein, and Alpha-ketoglutarate dependent dioxygenase (FTO), are driving factors of GBM development and treatment resistance. Here, we investigated m(6)A-RNA spatial and quantitative abundance and expression of m(6)A effector proteins directly in GBM tissue and patient-derived low-passage primary adult GBM and low-grade glioma (LGG) cells, and explored the consequences of m(6)A-RNA disruption on GBM invasive capabilities, self-renewal and responsiveness to temozolomide (TMZ). We observed that METTL3, WTAP and FTO transcript and protein expression were significantly increased in cells derived from invasive regions of GBM tumours, and elevated WTAP and FTO expression significantly correlated with poor GBM patient survival. We further found that the abundance of m(6)A-modified RNA in GBM tumours was significant higher in rim and invasive tissue, as well as significantly higher in patient-derived cells from GBM tumour invasive regions. Functional depletion of these effector proteins significantly altered m(6)A levels on and the expression of the pluripotency stem cell marker SOX2 while also impairing self-renewal and cell invasion behaviour and increasing sensitivity to TMZ. The targeting of RNA modification regulatory mechanisms reveals novel therapeutic strategies aimed at improving clinical outcomes for GBM patients.

Background: High grade glioma (HGG) is a devastating brain cancer with median survival of less than 18 months. The field of epitranscriptomics has emerged as a novel druggable target for multiple diseases, including cancers, with N6-methyladenosine (m6A) as the most prevalent mRNA modification. M6A levels are modified by ‘writers’ such as METTL3, METTL14 and WTAP and ‘erasers’ such as FTO and ALKBH5. The interplay between these two processes dynamically regulates the m6A modification. The fate of modified RNA is determined by the m6A-bound ‘readers’ such as YTHDF1 or YTHDF2 with rapid effects on translation and mRNA abundance. In the present study, we sought to investigate the functional importance of m6A RNA methylation in the pathogenesis and drug resistance of HGG. Methods: RT-qPCR and immunofluorescence for m6A modulators were undertaken in patient-derived HGG cell lines, paediatric HGG cells and human HGG tissues. The expression of these modulators was modified using siRNA knockdown and small molecules (such as a novel METTL3 inhibitor) to identify effects on key transcription factors in HGG. The effect of modification on stemness behaviours such as the ability to form neurospheres was also assessed. Developing chemotherapy-resistant cell lines, 3d cell culture and hypoxic cell culture were undertaken to assess associations between m6A RNA levels and the ability of HGG cells to adapt to environmental change. Measuring the level of m6A-modified transcripts were achieved by developing a MeRIP (methylated RNA immunoprecipitation) qPCR technique. An LC-MS/MS based protocol was developed to quantify m6A levels on poly-A+-enriched RNA. Results: We found that key m6A RNA methylation effectors such as METTL3, FTO and WTAP are expressed at significantly higher level in HGG cell lines and tissues than in control cells (astrocytes) at both gene and protein levels. LC-MS/MS and immunofluorescence showed an increase in the level of m6A in paediatric HGG compared with normal brain. Furthermore, knockdown of METTL3, FTO and WTAP affects the expression of key transcription factors in self-renewal, cell cycle regulation and tumorigenesis including FOXM1, nestin and SOX2. Depletion of m6A mediators also reduces the ability of cells to form neurospheres, increases apoptosis and suppresses invasion. Moreover, chemical inhibition of METTL3 and FTO was associated with a downregulation in the expression of oncogenes, reduction in neurosphere size and increase in apoptosis. Inhibitors of m6A effectors also sensitize HGG cell lines to the effect of chemotherapeutic agents such as temozolomide. LC-MS/MS data revealed dose-response change in m6A levels in cells treated with different concentrations of these inhibitors. Conclusion: These findings suggest a key role for RNA methylation in phenotypic plasticity in HGG, and could represent a new avenue for developing effective treatment strategies, with targeted inhibition of METTL3 showing promise. Citation Format: Masar Radhi, Jonathan Rowlinson, Nigel Halliday, Simon Deacon, Ella Collinson, Helen Knight, Dong-Hyun Kim, Stuart James Smith. m6A RNA methylation as a therapeutic target in high grade glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2234.

Molecular data integration plays a central role in central nervous system (CNS) tumor diagnostics but currently used assays pose limitations due to technical complexity, equipment and reagent costs, as well as lengthy turnaround times. We previously reported the development of Rapid-CNS2, an adaptive-sampling-based nanopore sequencing workflow. Here we comprehensively validated and further developed Rapid-CNS2 for intraoperative use. It now offers real-time methylation classification and DNA copy number information within a 30-min intraoperative window, followed by comprehensive molecular profiling within 24 h, covering the complete spectrum of diagnostically and therapeutically relevant information for the respective entity. We validated Rapid-CNS2 in a multicenter setting on 301 archival and prospective samples including 18 samples sequenced intraoperatively. To broaden the utility of methylation-based CNS tumor classification, we developed MNP-Flex, a platform-agnostic methylation classifier encompassing 184 classes. MNP-Flex achieved 99.6% accuracy for methylation families and 99.2% accuracy for methylation classes with clinically applicable thresholds across a global validation cohort of more than 78,000 frozen and formalin-fixed paraffin-embedded samples spanning five different technologies. Integration of these tools has the potential to advance CNS tumor diagnostics by providing broad access to rapid, actionable molecular insights crucial for personalized treatment strategies. Application of a nanopore sequencing workflow for real-time analysis of brain tumors results in molecular classification within a 30-minute intraoperative window, followed by comprehensive profiling within 24 hours.

Diffuse gliomas are the commonest malignant primary brain tumour in adults. Herein, we present analysis of the genomic landscape of adult glioma, by whole genome sequencing of 403 tumours (256 glioblastoma, 89 astrocytoma, 58 oligodendroglioma; 338 primary, 65 recurrence). We identify an extended catalogue of recurrent coding and non-coding genetic mutations that represents a source for future studies and provides a high-resolution map of structural variants, copy number changes and global genome features including telomere length, mutational signatures and extrachromosomal DNA. Finally, we relate these to clinical outcome. As well as identifying drug targets for treatment of glioma our findings offer the prospect of improving treatment allocation with established targeted therapies.

High grade glioma (HGG) is a devastating brain cancer. The field of epitranscriptome has emerged as a novel druggable target for multiple diseases. N6-methyladenosine (m6A) is the most prevalent mRNA modification. It is co-transcriptionally installed by a methylase complex called “writer” composed of METTL3, METTL14 and WTAP. The modification is reversible and erased by FTO and ALKBH5 which are called “eraser”. The fate of the modified RNA is determined by the m6A-bound “reader. Here, we sought to investigate the functional impor- tance of m6A RNA methylation in the pathogenesis and drug resistance of HGG. To identify the expression of key modulators of RNA methylation, RT-qPCR and immunofluorescence were un- dertaken HGG cells and tissues. The expression of these modulators was modified using siRNA knockdown and small molecules to identify their effects on key transcription factors. The consequences of m6A RNA methy- lation disruption on the invasive capabilities, self-renewal and sensitivity to temozolomide was also assessed. Measuring the level of m6A-modified transcripts were achieved by developing MeRIP (methylated RNA immuno- precipitation) qPCR technique and LC-MS/MS on poly-A+-enriched RNA. METTL3, WTAP and METTL14 are highly expressed in in HGG cells and tissues. LC-MS/MS and MeRIPqPCR showed an increase in the level of m6A in HGG. Furthermore, knockdown of m6A effectors affects the expression of key factors in self-renewal, cell cycle regulation and tumorigenesis including FOXM1, nestin and SOX2. It also reduces the ability of cells to form neurospheres, suppresses invasion and improves the sensitivity of HGG cells to temozolomide. Inhibiting the enzymatic activity of METTL3 using STM2457 and STM3006 reduces the ability of HGG cells to invade and form neutrospheres and also sensitizes the HGG cells to the effect of temozolomide. These findings suggest the role of RNA methylation in the pathogenesis of HGG, and therefore, could open a new avenue for developing effective treatment strategies.

Isocitrate dehydrogenase wild-type glioblastoma is an aggressive brain tumour with a poor prognosis and one of the highest recurrence rates despite multimodal treatment. The mechanisms underlying recurrence are not fully understood, but the tumour microenvironment is known to play a key role. Astrocytes, the most abundant glial cells in the brain, have been implicated in supporting tumour progression, yet their metabolic interactions with glioblastoma invasive margin cells remain poorly understood. This study aims to investigate these metabolic interactions using high resolution spatial metabolomics to identify pathways involved in tumour progression. We employed atmospheric pressure matrix-assisted laser desorption/ionisation (AP-MALDI) imaging mass spectrometry at 10 μm spatial resolution to investigate metabolic interactions between primary glioblastoma invasive margin (GIN) cells and human cortical astrocytes (HA) in a 2D co-culture model mimicking post-surgical residual disease. In addition, a 3D co-culture model was developed to better recapitulate the tumour microenvironment, enabling spatial comparative analysis. Metabolomic analysis revealed distinct pathway alterations in glioblastoma invasive margin cells and astrocytes in co-culture. Glioblastoma cells showed enrichment in purine metabolism and the pentose phosphate pathway, while astrocytes exhibited changes in pyrimidine, arginine, and serine-related pathways. Notably, both cell types showed involvement of tyrosine metabolism and phenylalanine, and tryptophan biosynthesis, with multiple contributing metabolites highlighting their potential importance in tumour–astrocyte metabolic communication. By mapping metabolite spatial distributions at high spatial resolution, this study provides novel insights into tumour–astrocyte metabolic interactions at the invasive margin, introducing methodology applicable to heterogeneous biopsy tissue from the glioblastoma infiltrative margin. The use of a 3D model revealed additional microenvironment-specific metabolic features, highlighting potential therapeutic targets to disrupt glioblastoma recurrence manifesting from residual disease.

Glioblastomas (GBMs) are the most aggressive and prevalent primary brain tumour. Their high adaptability and resistance to therapy make them exceptionally challenging to treat. One key factor in GBM aggressiveness is a reliance on glycolysis for energy production, which facilitates rapid biomass generation and tumour growth. The glycolytic byproduct, lactate, acidifies the tumour microenvironment, promoting polarisation of macrophages into a tumour-supportive phenotype. These alterations contribute to radioresistance, leading to tumour recurrence. In this study, we investigated the effects of FLASH radiotherapy (FLASH-RT), which delivers ultra-fast, high-dose radiation. We monitored GBM spheroid area before and after FLASH-RT and conventional radiotherapy (CONV-RT). Patient-derived GBM cells from infiltrative tumour margins were cultured as spheroids in Ultra-Low Attachment plates. Over three days of culture, spheroid area was measured using a live-cell imager. On day four, spheroids were exposed to either CONV-RT (0.1Gy/s) or FLASH-RT (5Gy per 3.5µs pulse, 300Hz repetition rate) at total doses of 0, 5, 10, 15, or 20Gy (n=4-8 per condition). Following irradiation, spheroid area change was monitored for 70 hours post-treatment. Spheroid area (µm²) varied with radiation dose (0-20 Gy) and demonstrated distinct patterns between CONV-RT and FLASH-RT. At 5Gy, both treatments showed high variability in the change in area of the spheroids; however, CONV-RT exhibited a wider range of values than FLASH-RT. Beyond 10Gy, spheroid areas under CONV-RT remained variable, with an average increase of 85,334µm². In contrast, FLASH-RT led to an average change in area of 29,663µm², with minimal variability and uniformly smaller spheroids. The superior control of FLASH-RT on spheroid area suggests that FLASH-RT may enhance tumour response while potentially reducing variability in treatment outcomes. Future work will investigate the combined effects of FLASH-RT with metabolic inhibition and macrophage co-culture to better understand its impact on metabolic pathways and immune modulation in GBM.

Abstract AIMS The 2021 WHO classification of CNS tumours necessitates the use of molecular testing in order to reach a confident diagnosis of many tumour types. At present, this is achieved using array-based technology delivered by a centralised model. This approach has inherent delays that mean it is often several weeks before the treating clinical team is informed of diagnosis, delaying the start of adjuvant therapy and causing significant distress for patients. As such, there is an urgent need to rethink this pathway and improve time to diagnosis. Nanopore longread sequencing technology has the potential to enable a paradigm shift in diagnostic and therapeutic pathways, offering rapid, comprehensive molecular diagnosis that can be performed in the intra-operative setting. We aimed to test the hypothesis that intra-operative methylation-based classification can be performed using nanopore sequencing and thereby expediently inform surgical and oncological decision-making. METHOD Oxford Nanopore Technology (ONT) is a native-strand, long-read sequencing platform that can perform copy- number profiling along with parallel single-gene methylation, structural variant, mutational and methylation analyses. Capital and consumable costs are relatively low, and testing can be performed in the local setting on single samples. We have optimised DNA extraction and library preparation for rapid tissue processing. We have developed a robust bioinformatic pipeline which is able to produce intraoperative classification within minutes of sequencing and full molecular profiling after 24 hours. RESULTS We demonstrate the feasibility of using ONT to deliver intra-operative methylation-based classification of CNS tumours in ‘realtime’ within an NHS hospital setting and will discuss the challenges of implementing this testing and the opportunities to inform neuro-oncological practice. CONCLUSION By giving a summary of our novel protocol of rapid DNA extraction, library preparation and bioinformatic analysis, we will show that this approach can revolutionise the diagnosis of brain tumours and has the potential for rapid adoption by non-expert laboratories.

Background Advances in our technological capacity to interrogate brain tumour biology has led to the ever-increasing use of genomic sequencing in routine diagnostic decision making. Presently, brain tumours are routinely classified based on their epigenetic signatures, leading to a paradigm shift in diagnostic pathways. Such testing can be performed so rapidly using nanopore sequencing that results can be provided intraoperatively. This information greatly improves upon the fidelity of smear diagnosis and can help surgeons tailor their approach, balancing the risks of surgery with the likely benefit. Nevertheless, full integrated diagnosis may require subsequent additional assays to detect pathognomonic somatic mutations and structural variants, thereby delaying the time to final diagnosis. Methods Here, we present ROBIN, a tool based upon PromethION nanopore sequencing technology that can provide both real-time, intraoperative methylome classification and next-day comprehensive molecular profiling within a single assay. ROBIN uniquely integrates three methylation classifiers to improve diagnostic performance in the intraoperative setting. Findings We demonstrate classifier performance on 50 prospective intraoperative cases, achieving a diagnostic turnaround time under 2 hours and generating robust tumour classifications within minutes of sequencing. Furthermore, ROBIN can detect single nucleotide variants (SNVs), copy number variants (CNVs) and structural variants (SVs) in real-time, and is able to inform a complete integrated diagnosis within 24 hours. Classifier performance demonstrated concordance with final integrated diagnosis in 90% of prospective cases. Interpretation Nanopore sequencing can greatly improve upon the turnaround times for standard of care diagnostic testing, including sequencing, and is furthermore able to reliably provide clinically actionable intraoperative tumour classification. Funding The Jean-Shanks Foundation, the Pathological Society of Great Britain and Ireland, the British Neuropathological Society, and the Wellcome Trust. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Jean-Shanks Foundation, the Pathological Society of Great Britain and Ireland, the British Neuropathological Society, and the Wellcome Trust. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The National Research Ethics Committee of the East Midlands gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes De-identified individual participant data that underlie the results reported in this article will be made available upon reasonable request. The ROBIN code used for the analysis is available at https://github.com/looselab/robin.

Although glioblastoma is the commonest primary brain tumour in adults, its location in the cerebellum is extremely rare. We present thirteen cases (3 female, 10 male; median age at presentation 56 [age range 21-77]) of surgically managed, histologically confirmed, primary cerebellar glioblastoma (cGB) over a 17 year period (2005-2022). Pre-operative radiological diagnosis was challenging given cGB rarity, although MRI demonstrated ring enhancement in all cases. Surgical management included posterior fossa craniectomy and debulking in 11 cases and burr hole biopsy in two. CSF diversion was necessary in four cases. No evidence of IDH or ATRX gene mutations was found when tested. Survival ranged from 1 to 22 months after diagnosis (mean 10.9 months). We also seek to understand why glioblastoma is rare in this location and discuss potential reasons for this. We hypothesise that increasing anatomical distance from germinal regions and decreased local endogenous neural stem cell activity (which has been associated with glioblastoma) may explain why glioblastoma is rare in the cerebellum. We hereby seek to add to the limited literature on cGB as this is the largest UK cGB series to date.

The impact of Covid-19 on surgical patients worldwide has been substantial. In the United Kingdom (UK) and the Republic of Ireland (RoI), the first wave of the pandemic occurred in March 2020. The aims of this study were to: (1) evaluate the volume of neurosurgical operative activity levels, Covid-19 infection rate and mortality rate in April 2020 with a retrospective cross-sectional cohort study conducted across 16 UK and RoI neurosurgical centres, and (2) compare patient outcomes in a single institution in April-June 2020 with a comparative cohort in 2019. Across the UK and RoI, 818 patients were included. There were 594 emergency and 224 elective operations. The incidence rate of Covid-19 infection was 2.6% (21/818). The overall mortality rate in patients with a Covid-19 infection was 28.6% (6/21). In the single centre cohort analysis, an overall reduction in neurosurgical operative activity by 65% was observed between 2020 (n = 304) and 2019 (n = 868). The current and future impact on UK neurosurgical operative activity has implications for service delivery and neurosurgical training.

Human land use can have lasting impacts on landscape characteristic, yet there remains a lack of information on how former land use affects plant communities in protected African grasslands. In this study, we investigated how land uses prior to the creation of Kitulo National Park, Tanzania, shaped the presence and abundance of the native shrub, Helichrysum species. We evaluated both plant species composition and soil properties across the park by dividing our sample into three different zones of historical land use based on participatory mapping. We divided the park into three former land uses: (1) livestock grazed and cultivated; (2) grazed only and (3) wild grazing with limited human impact. We observed that former grazed cultivated land use had five times higher Helichrysum abundance than former 'wild' land use. Soil pH, magnesium and phosphorus levels varied significantly across zones of historical land use but not between sites with and without Helichrysum species. Helichrysum splendidum was more abundant in soils with low soil phosphorus and magnesium concentrations. Our study demonstrates that historic grazing and cropping land uses through changes in soil nutrient properties can explain current Helichrysum species spread in protected areas. As such, conservation management plans would benefit from integrating mapping of former land uses to target interventions for problematic encroaching shrubs.

Abstract AIMS Despite multimodal treatment, 9/10 patients diagnosed with isocitrate dehydrogenase wild-type glioblastoma experience tumour recurrence within 5 years. Poor prognosis is in considerable part attributed to the ability of cancer cells to infiltrate healthy brain. We hypothesise that metabolic changes underpinning cellular crosstalk between astrocytes and glioblastoma invasive margin cells within a physiologically representative in-vitro tumour microenvironment, may reveal therapeutic targets to prevent or delay glioblastoma recurrence. An initial study aimed to establish baseline metabolomic profiles for glioblastoma invasive margin cells and healthy human frontal lobe astrocytes. METHOD We used human frontal lobe astrocytes (n=6) and transgenic glioblastoma invasive margin cells tagged with eGFP (n=18) to extract cellular metabolites using biphasic extraction method (methanol:water:chloroform). Liquid Chromatography – Mass Spectrometry (LC-MS) with a ZIC-pHILIC column, coupled to an Orbitrap Mass Spectrometer (Q-Exactive Orbitrap) was used to identify metabolites. Both multivariate and univariate statistical analyses were used to investigate significant alterations observed in the metabolic data. RESULTS The study uncovered distinct metabolic profiles differentiating glioblastoma invasive margin cells from astrocytes. Significant alterations were identified in the alanine, aspartate, and glutamate metabolism pathway, which is required for amino acid synthesis and neurotransmitter balance. Other metabolic pathways include glycine, serine, and threonine metabolism as well as glycerophospholipid metabolism. These preliminary findings lay the groundwork for further exploration into the cellular interactions in a postoperative tumour microenvironment model and elucidate mechanisms that may contribute to tumour recurrence. CONCLUSION Understanding the interactions between cancerous cells and astrocytes is crucial for developing new therapeutic approaches. Our subsequent research will integrate an advanced tumorsphere model composed of a scaffold combining PEGDA hydrogel and an extracellular matrix derived from a decellularized human autopsy brain. This model aims to replicate the postoperative tumour microenvironment more accurately to investigate astrocyte-glioblastoma cell interactions associated with tumour recurrence.

Local drug delivery systems (LDDSs) applied during neurosurgery offer a means of overcoming poor blood brain barrier (BBB) permeability and have been extensively investigated for the treatment of adult gliomas. To the best of our knowledge, they have not been investigated for the treatment of paediatric cerebellar tumours, including medulloblastoma group 3 (MB3) and atypical teratoid/rhabdoid tumours (ATRT), both of which are associated with poor prognoses. We prepared and characterised an injectable and biodegradable poly(ethyleneglycol)-poly(caprolactone)-poly(ethyleneglycol) (PECE) hydrogel, which has been investigated broadly throughout the literature with an array of therapeutic agents against numerous cancer types. Here, we loaded the PECE hydrogel with chemotherapeutics previously identified as being effective against primary MB3 and ATRT in vitro, but which do not cross the BBB in vivo, namely CHIR99021, ribavirin and PG545. Biocompatibility and cytotoxicity of drug loaded hydrogels was assessed in vitro. LDDSs safety and efficacy was evaluated using patient derived MB3 and ATRT intracranial xenograft resection models. The hydrogel was both biocompatible and effected cytotoxicity following drug release. In vivo efficacy experiments against MB3 indicated a comparable median survival in treatment arms receiving radiotherapy or CHIR99021 and PG545 loaded LDDS. However, combined radiotherapy and LDDS conferred a significant survival enhancement including long-term survivors. Against ATRT, the median survival of arms receiving radiotherapy was comparable to that of the CHIR99021 and ribavirin loaded LDDS, with long-term survivors observed only in the latter arm. The application of LDDSs against cerebellar brain tumours offers a promising novel therapeutic alternative. For MB3, the combination of radiotherapy and a LDDS significantly enhances survival compared to radiotherapy alone. For ATRT, the comparable survival of the LDDS and radiotherapy alone is encouraging and indicates the possibility of circumventing radiation-induced adverse effects for young children impacted by this disease.

Isocitrate dehydrogenase wild-type glioblastoma (GBM) is characterised by a heterogeneous genetic landscape resulting from dynamic competition between tumour subclones to survive selective pressures. Improvements in metabolite identification and metabolome coverage have led to increased interest in clinically relevant applications of metabolomics. Here, we use liquid chromatography-mass spectrometry and gene expression microarray to profile integrated intratumour metabolic heterogeneity, as a direct functional readout of adaptive responses of subclones to the tumour microenvironment. Multi-region surgical sampling was performed on five adult GBM patients based on pre-operative brain imaging and fluorescence-guided surgery. Polar and hydrophobic metabolites extracted from tumour fragments were assessed, followed by putative assignment of metabolite identifications based on retention times and molecular mass. Class discrimination between tumour regions through showed clear separation of tumour regions based on polar metabolite profiles. Metabolic pathway assignments revealed several significantly altered metabolites between the tumour core and invasive region to be associated with purine and pyrimidine metabolism. This proof-of-principle study assesses intratumour heterogeneity through mass spectrometry-based metabolite profiling of multi-region biopsies. Bioinformatic interpretation of the GBM metabolome has highlighted the invasive region to be biologically distinct compared to tumour core and revealed putative drug-targetable metabolic pathways associated with purine and pyrimidine metabolism.

In 1932, Harvey Cushing described peptic ulceration secondary to raised intracranial pressure and attributed this to vagal overactivity, causing excess gastric acid secretion. Cushing ulcer remains a cause of morbidity in patients, albeit one that is preventable. This narrative review evaluates the evidence pertaining to the pathophysiology of neurogenic peptic ulceration. Review of the literature suggests that the pathophysiology of Cushing ulcer may extend beyond vagal mechanisms for several reasons: (1) clinical and experimental studies have shown only a modest increase in gastric acid secretion in head-injured patients; (2) increased vagal tone is found in only a minority of cases of intracranial hypertension, most of which are related to catastrophic, nonsurvivable brain injury; (3) direct stimulation of the vagus nerve does not cause peptic ulceration, and; (4) Cushing ulcer can occur after acute ischemic stroke, but only a minority of strokes are associated with raised intracranial pressure and/or increased vagal tone. The 2005 Nobel Prize in Medicine honored the discovery that bacteria play key roles in the pathogenesis of peptic ulcer disease. Brain injury results in widespread changes in the gut microbiome in addition to gastrointestinal inflammation, including systemic upregulation of proinflammatory cytokines. Alternations in the gut microbiome in patients with severe traumatic brain injury include colonization with commensal flora associated with peptic ulceration. The brain-gut-microbiome axis integrates the central nervous system, the enteric nervous system, and the immune system. Following the review of the literature, we propose a novel hypothesis that neurogenic peptic ulcer may be associated with alterations in the gut microbiome, resulting in gastrointestinal inflammation leading to ulceration.

Background: Total intravenous anaesthesia (TIVA) is emerging as a preferred neuroanaesthetic agent compared with inhalational anaesthetic (IA) agents. We asked if TIVA with propofol and remifentanil was associated with shorter operative times compared to IA using sevoflurane in brain tumour surgery under GA. Methods: We performed a retrospective analysis of all patients undergoing surgery for glioblastoma (GBM). We assessed choice of GA agent (TIVA or IA) with total time patient was under GA (anaesthetic time), operative time and time taken to recover fully from GA (recovery time). Results: Over a two year period 263 patients underwent surgery under GA for their GBM including 188 craniotomy operations, 63 burr hole biopsy procedures and 12 open biopsy procedures. Of these, 79 operations took place under TIVA and 184 operations under IA. TIVA was associated with significantly reduced mean operative time including time taken to wake up in theatre (104 min with TIVA, 129 min with IA; p = 0.02). TIVA was also associated with trends toward shorter mean recovery time (118 min, versus 135 min with IA; p = 0.08) and shorter mean anaesthetic time (163 min, versus 181 min with IA; p = 0.07). There was no difference between TIVA and IA groups as regards duration of inpatient stay, readmission rates, complications or survival. Conclusions: TIVA with propofol and remifentanil may reduce anaesthetic, operative and recovery times in patients undergoing surgery for their GBM. These findings may be attributable to favourable effects on intracranial pressure and cerebral perfusion, as well as rapid recovery from GA. In addition to clinical advantages, there may be financial and logistical benefits.