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Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is characteristic for astrocytes and neural stem cells, and their malignant analogues in glioma. Since the discovery of the protein 50 years ago, multiple alternative splice variants of the GFAP gene have been discovered, leading to different GFAP isoforms. In this review, we will describe GFAP isoform expression from gene to protein to network, taking the canonical isoforms GFAPa and the main alternative variant GFAPd as the starting point. We will discuss the relevance of studying GFAP and its isoforms in disease, with a specific focus on diffuse gliomas. [ABSTRACT FROM AUTHOR]

Objective: Intraoperative electrocorticography (ioECoG) during neurosurgery is influenced by anesthetics. In our center we stop the propofol to enable interpretation of ioECoG. We reported our clinical experience and evaluated awareness and hemodynamic changes during the propofol-free periods (PFP)., Methods: We retrospectively included surgeries with paused propofol administration to record ioECoG (period: 2008-2019). Clinical reports were screened for symptoms of awareness. We compared mean arterial blood pressure (MAP; mmHg) and heart rate (HR;bpm) during PFP to baseline (ten minutes preceding PFP). An increase > 15% was defined as clinically relevant. The association between hemodynamic changes and clinical characteristics was analyzed using logistic regression models., Results: Propofol administration was paused 742 times in 352 surgeries (mean PFP duration 9 ± 5 min). No signs of awareness were reported. MAP and HR increased > 15% in 54 and six PFPs. Five PFPs showed both MAP and HR increases. Prolonged PFP was associated with having MAP and HR increase during surgery (OR=1.18, 95%CI [1.12-1.26])., Conclusions: Signs of inadequate sedation depth were rare. MAP and HR increases were related to the length of PFP., Significance: We summarize 10 years of clinical experience with pausing propofol administration during epilepsy surgery to record ioECoG without evidence of awareness., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

The ex vivo organotypic brain slice invasion model is commonly used to study the growth dynamics of gliomas, primary brain tumors that are known for their invasive behavior. Here, we describe a protocol where the ex vivo organotypic mouse brain slice invasion model is combined with whole-mount immunostaining, tissue clearing, and 3D reconstruction, to visualize and quantify the invasion of glioma cells. In addition, we describe an approach to determine the proliferation rate of the cells within this model. For complete details on the use and execution of this protocol, please refer to Uceda-Castro et al. (2022)., Competing Interests: Declaration of interests The authors declare no conflict of interest., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Liquid biopsies are promising diagnostic tools for glioma. In this quantitative systematic review, we investigate whether the detection of intermediate filaments (IF) in body fluids can be used as a tool for glioma diagnosis and prognosis., Materials and Methods: We included all studies in which IF-levels were determined in patients with glioma and healthy controls. Of the 28 identified eligible studies, 12 focussed on levels of GFAP in serum (sGFAP) and were included for metadata analysis., Results: In all studies combined, 62.7% of all grade-IV patients had detectable levels of sGFAP compared to 12.7% of healthy controls. sGFAP did not surpass the limit of detection in lower-grade patients or healthy controls, but sGFAP was significantly elevated in grade-IV glioma (0.12 ng/mL (0.06 - 0.18), P  < 0.001) and showed an average median difference of 0.15 ng/mL (0.04 - 0.25, P  < 0.01) compared to healthy controls. sGFAP levels were linked to tumour volume, but not to patient outcome., Conclusion: The presence of sGFAP is indicative of grade-IV glioma, but additional studies are necessary to fully determine the usefulness of GFAP in body fluids as a tool for grade-IV glioma diagnosis and follow-up.

Objective: High frequency oscillations (HFOs) in intraoperative electrocorticography (ioECoG) are thought to be generated by hyperexcitable neurons. Inflammation may promote neuronal hyperexcitability. We investigated the relation between HFOs and inflammation in tumor-related epilepsy., Methods: We identified HFOs (ripples 80-250 Hz, fast ripples 250-500 Hz) in the preresection ioECoG of 32 patients with low-grade tumors. Localization of recorded HFOs was classified based on magnetic resonance imaging reconstructions: in tumor, in resected non-tumorous area and outside the resected area. We tested if the following inflammatory markers in the tumor or peritumoral tissue were related to HFOs: activated microglia, cluster of differentiation 3 (CD3)-positive T-cells, interleukin 1-beta (IL1β), toll-like receptor 4 (TLR4) and high mobility group box 1 protein (HMGB1)., Results: Tumors that generated ripples were infiltrated by more CD3-positive cells than tumors without ripples. Ripple rate outside the resected area was positively correlated with IL1β/TLR4/HMGB1 pathway activity in peritumoral area. These two areas did not directly overlap., Conclusions: Ripple rates may be associated with inflammatory processes., Significance: Our findings support that ripple generation and spread might be associated with synchronized fast firing of hyperexcitable neurons due to certain inflammatory processes. This pilot study provides arguments for further investigations in HFOs and inflammation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Purpose: The aim of glioblastoma surgery is to maximize the extent of resection while preserving functional integrity, which depends on the location within the brain. A standard to compare these decisions is lacking. We present a volumetric voxel-wise method for direct comparison between two multidisciplinary teams of glioblastoma surgery decisions throughout the brain., Methods: Adults undergoing first-time glioblastoma surgery from 2012 to 2013 performed by two neuro-oncologic teams were included. Patients had had a diagnostic biopsy or resection. Preoperative tumors and postoperative residues were segmented on magnetic resonance imaging in three dimensions and registered to standard brain space. Voxel-wise probability maps of tumor location, biopsy, and resection were constructed for each team to compare patient referral bias, indication variation, and treatment variation. To evaluate the quality of care, subgroups of differentially resected brain regions were analyzed for survival and functional outcome., Results: One team included 101 patients, and the other included 174; 91 tumors were biopsied, and 181 were resected. Patient characteristics were largely comparable between teams. Distributions of tumor locations were dissimilar, suggesting referral bias. Distributions of biopsies were similar, suggesting absence of indication variation. Differentially resected regions were identified in the anterior limb of the right internal capsule and the right caudate nucleus, indicating treatment variation. Patients with (n = 12) and without (n = 6) surgical removal in these regions had similar overall survival and similar permanent neurologic deficits., Conclusion: Probability maps of tumor location, biopsy, and resection provide additional information that can inform surgical decision making across multidisciplinary teams for patients with glioblastoma.