Navigated intraoperative ultrasound in pediatric brain tumors.

PURPOSE: The aim of this study was to evaluate the diagnostic value and accuracy of navigated intraoperative ultrasound (iUS) in pediatric oncological neurosurgery as compared to intraoperative magnetic resonance imaging (iMRI). METHODS: A total of 24 pediatric patients undergoing tumor debulking surgery with iUS, iMRI, and neuronavigation were included in this study. Prospective acquisition of iUS images was done at two time points during the surgical procedure: (1) before resection for tumor visualization and (2) after resection for residual tumor assessment. Dice similarity coefficients (DSC), Hausdorff distances 95th percentiles (HD95) and volume differences, sensitivity, and specificity were calculated for iUS segmentations as compared to iMRI. RESULTS: A high correlation (R = 0.99) was found for volume estimation as measured on iUS and iMRI before resection. A good spatial accuracy was demonstrated with a median DSC of 0.72 (IQR 0.14) and a median HD95 percentile of 4.98 mm (IQR 2.22 mm). The assessment after resection demonstrated a sensitivity of 100% and a specificity of 84.6% for residual tumor detection with navigated iUS. A moderate accuracy was observed with a median DSC of 0.58 (IQR 0.27) and a median HD95 of 5.84 mm (IQR 4.04 mm) for residual tumor volumes. CONCLUSION: We found that iUS measurements of tumor volume before resection correlate well with those obtained from preoperative MRI. The accuracy of residual tumor detection was reliable as compared to iMRI, indicating the suitability of iUS for directing the surgeon's attention to areas suspect for residual tumor. Therefore, iUS is considered as a valuable addition to the neurosurgical armamentarium. TRIAL REGISTRATION NUMBER AND DATE: PMCLAB2023.476, February 12th 2024.

Protocol for investigating data quality and reporting outcomes of pediatric gliomas in population-based cancer registry research.

Cancer registry data on pediatric gliomas come with inherent limitations as inclusion criteria and registration practices of these tumors differ between registries due to specific guidelines that are lacking. These limitations can lead to biased estimates in incidence and survival outcomes. Here, we present a protocol to investigate data quality and comparability for retrospective population-based pediatric glioma studies. We describe steps for obtaining institutional permissions, dealing with data quality issues, regrouping tumors, and reporting tumors in a clinically relevant manner. For complete details on the use and execution of this protocol, please refer to Hoogendijk et al.1.

Taenia martis Neurocysticercosis-Like Lesion in Child, Associated with Local Source, the Netherlands.

A neurocysticercosis-like lesion in an 11-year-old boy in the Netherlands was determined to be caused by the zoonotic Taenia martis tapeworm. Subsequent testing revealed that 15% of wild martens tested in that region were infected with T. martis tapeworms with 100% genetic similarity; thus, the infection source was most likely local.

Improving advanced intraoperative MRI methods during pediatric neurosurgery.

Advanced intraoperative MR images (ioMRI) acquired during the resection of pediatric brain tumors could offer additional physiological information to preserve healthy tissue. With this work, we aimed to develop a protocol for ioMRI with increased sensitivity for arterial spin labeling (ASL) and diffusion MRI (dMRI), optimized for patient positioning regularly used in the pediatric neurosurgery setting. For ethical reasons, ASL images were acquired in healthy adult subjects that were imaged in the prone and supine position. After this, the ASL cerebral blood flow (CBF) was quantified and compared between both positions. To evaluate the impact of the RF coils setups on image quality, we compared different setups (two vs. four RF coils) by looking at T1-weighted (T1w) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), as well as undertaking a qualitative evaluation of T1w, T2w, ASL, and dMR images. Mean ASL CBF did not differ between the surgical prone and supine positions in any of the investigated regions of interest or the whole brain. T1w SNR (gray matter: p = 0.016, 34% increase; white matter: p = 0.016, 32% increase) and CNR were higher (p = 0.016) in the four versus two RF coils setups (18.0 ± 1.8 vs. 13.9 ± 1.8). Qualitative evaluation of T1w, T2w, ASL, and dMR images resulted in acceptable to good image quality and did not differ statistically significantly between setups. Only the nonweighted diffusion image maps and corticospinal tract reconstructions yielded higher image quality and reduced susceptibility artifacts with four RF coils. Advanced ioMRI metrics were more precise with four RF coils as the standard deviation decreased. Taken together, we have investigated the practical use of advanced ioMRI during pediatric neurosurgery. We conclude that ASL CBF quantification in the surgical prone position is valid and that ASL and dMRI acquisition with two RF coils can be performed adequately for clinical use. With four versus two RF coils, the SNR of the images increases, and the sensitivity to artifacts reduces.

Robotic alignment system Cirq (Brainlab) for navigated brain tumor biopsies in children.

INTRODUCTION: The Cirq robotic alignment system (Brainlab, Munich, Germany) is a manually adjustable electronic arm with a robotic alignment module on its distal end, enabling the neurosurgeon to automatically and accurately align surgical instruments to a preoperatively planned trajectory. In this study, we share our first experiences and results using Cirq for intracranial tumor biopsy in children. METHODS: From May 2021 until October 2022, all consecutive patients that underwent a brain tumor biopsy using Cirq were included and compared to a historical cohort of patients biopsied with the non-robotic system Varioguide (Brainlab, Munich, Germany). Patient-related data, tumor-related data, and surgery-related data were collected. Registration accuracy was calculated for different patient-to-image registration methods. Pre- and postoperative images were fused, and entry error, target error, and angulation error were calculated. RESULTS: Thirty-seven patients, aged 1-19 years, were included (14 with Cirq and 23 with Varioguide). An integrated histopathological and molecular diagnosis was acquired in all cases. Patient-to-image registration was significantly more accurate when based on bone screw fiducials combined with intraoperative CT, as compared to surface matching or skin fiducials. The target error (Euclidian distance) was 5.3 mm for Cirq as compared to 8.3 mm for Varioguide, but this was not statistically significant. Entry error and angulation error were also not significantly different between both groups. CONCLUSION: Intracranial biopsy with the Cirq robotic system is feasible and safe, and its accuracy does not differ from the Varioguide system.

Treatment and outcome of the Dutch Childhood Craniopharyngioma Cohort study: First results after centralization of care.

BACKGROUND: Childhood craniopharyngioma (cCP) has excellent survival, but quality of life may be severely hampered by hypothalamic dysfunction. We aimed to evaluate treatment and hypothalamic outcomes of a Dutch cCP cohort, and evaluate the effect of centralization of care. METHODS: A retrospective cohort study was performed, including cCP patients diagnosed between 2004 and 2021. Treatment characteristics and hypothalamic outcomes were evaluated and compared before and since centralization of care in May 2018. RESULTS: We included 87 cCP patients. Cyst drainage/fenestration was performed in 29.9%, limited resection in 27.6%, near-total resection in 16.1%, and gross total resection (GTR) in 25.4%. Radiotherapy was given in 46.0%. After a median follow-up of 6.5 years, hypothalamic obesity (HO) was present in 24.7% and panhypopituitarism with diabetes insipidus in 71.3%. Higher body mass index (BMI) SDS at diagnosis and Muller grade II at last magnetic resonance imaging of follow-up were associated with overweight/obesity. No association was found between extensiveness of resection and overweight/obesity at last follow-up. When comparing before and after centralization of care, rates of GTR remained similar, but BMI outcomes changed; mean ΔBMI SDS 1 year after diagnosis from 1.12 (SD 1.15) to 0.81 (SD 1.24), and HO after 1 year decreased from 33.3% to 12.0% (P = .067), and after 2 years from 28.6% to 6.7% (P = NS). CONCLUSIONS: In our nationwide cohort, GTR was performed in a relatively low percentage of patients and extensiveness of resection was no longer associated with HO at follow-up. A trend toward improvement of BMI is observed since centralization of care, which needs further exploration.

Safety of Growth Hormone Replacement Therapy in Childhood-Onset Craniopharyngioma: A Systematic Review and Cohort Study.

INTRODUCTION: Survival of childhood-onset craniopharyngioma (cCP) is excellent; however, many survivors suffer from hypothalamic-pituitary dysfunction. Growth hormone replacement therapy (GHRT) is of high importance for linear growth and metabolic outcome. Optimal timing for initiation of GHRT in cCP is on debate because of concerns regarding tumor progression or recurrence. METHODS: A systematic review and cohort studys were performed for the effect and timing of GHRT on overall mortality, tumor progression/recurrence, and secondary tumors in cCP. Within the cohort, cCP receiving GHRT ≤1 year after diagnosis were compared to those receiving GHRT >1 year after diagnosis. RESULTS: Evidence of 18 included studies, reporting on 6,603 cCP with GHRT, suggests that GHRT does not increase the risk for overall mortality, progression, or recurrent disease. One study evaluated timing of GHRT and progression/recurrence-free survival and found no increased risk with earlier initiation. One study reported a higher than expected prevalence of secondary intracranial tumors compared to a healthy population, possibly confounded by radiotherapy. In our cohort, 75 of 87 cCP (86.2%) received GHRT for median of 4.9 years [0.0-17.1]. No effect of timing of GHRT was found on mortality, progression/recurrence-free survival, or secondary tumors. CONCLUSION: Although the quality of the evidence is low, the available evidence suggests no effect of GHRT or its timing on mortality, tumor progression/recurrence, or secondary neoplasms in cCP. These results support early initiation of GHRT in cCP aiming to optimize linear growth and metabolic outcome. Prospective studies are needed to increase the level of evidence upon the optimal timing to start GHRT in cCP patients.

Advanced intraoperative MRI in pediatric brain tumor surgery.

Introduction: In the pediatric brain tumor surgery setting, intraoperative MRI (ioMRI) provides "real-time" imaging, allowing for evaluation of the extent of resection and detection of complications. The use of advanced MRI sequences could potentially provide additional physiological information that may aid in the preservation of healthy brain regions. This review aims to determine the added value of advanced imaging in ioMRI for pediatric brain tumor surgery compared to conventional imaging. Methods: Our systematic literature search identified relevant articles on PubMed using keywords associated with pediatrics, ioMRI, and brain tumors. The literature search was extended using the snowball technique to gather more information on advanced MRI techniques, their technical background, their use in adult ioMRI, and their use in routine pediatric brain tumor care. Results: The available literature was sparse and demonstrated that advanced sequences were used to reconstruct fibers to prevent damage to important structures, provide information on relative cerebral blood flow or abnormal metabolites, or to indicate the onset of hemorrhage or ischemic infarcts. The explorative literature search revealed developments within each advanced MRI field, such as multi-shell diffusion MRI, arterial spin labeling, and amide-proton transfer-weighted imaging, that have been studied in adult ioMRI but have not yet been applied in pediatrics. These techniques could have the potential to provide more accurate fiber tractography, information on intraoperative cerebral perfusion, and to match gadolinium-based T1w images without using a contrast agent. Conclusion: The potential added value of advanced MRI in the intraoperative setting for pediatric brain tumors is to prevent damage to important structures, to provide additional physiological or metabolic information, or to indicate the onset of postoperative changes. Current developments within various advanced ioMRI sequences are promising with regard to providing in-depth tissue information.

Atypical teratoid/rhabdoid tumoroids reveal subgroup-specific drug vulnerabilities.

Atypical teratoid/rhabdoid tumors (ATRTs) represent a rare, but aggressive pediatric brain tumor entity. They are genetically defined by alterations in the SWI/SNF chromatin remodeling complex members SMARCB1 or SMARCA4. ATRTs can be further classified in different molecular subgroups based on their epigenetic profiles. Although recent studies suggest that the different subgroups have distinct clinical features, subgroup-specific treatment regimens have not been developed thus far. This is hampered by the lack of pre-clinical in vitro models representative of the different molecular subgroups. Here, we describe the establishment of ATRT tumoroid models from the ATRT-MYC and ATRT-SHH subgroups. We demonstrate that ATRT tumoroids retain subgroup-specific epigenetic and gene expression profiles. High throughput drug screens on our ATRT tumoroids revealed distinct drug sensitivities between and within ATRT-MYC and ATRT-SHH subgroups. Whereas ATRT-MYC universally displayed high sensitivity to multi-targeted tyrosine kinase inhibitors, ATRT-SHH showed a more heterogeneous response with a subset showing high sensitivity to NOTCH inhibitors, which corresponded to high expression of NOTCH receptors. Our ATRT tumoroids represent the first pediatric brain tumor organoid model, providing a representative pre-clinical model which enables the development of subgroup-specific therapies.

Could deep brain stimulation be a possible solution for acquired hypothalamic obesity?

Objective: Hypothalamic dysfunction may result in morbid obesity as a consequence of decreased energy expenditure, decreased feelings of satiety, and increased fat storage. In patients with hypothalamic dysfunction, neurobehavioral dysfunction is also often present. Currently, no effective treatment has been found for hypothalamic obesity (HO). We hypothesize that deep brain stimulation (DBS) may be an effective treatment for patients with hypothalamic dysfunction, aiming to treat HO as well as the neurobehavioral dysfunction. Methods: A systematic search was conducted in the PubMed, EMBASE and Cochrane Library databases for studies published until May 2022 reporting on DBS for the treatment of HO. Results: Three studies met the predetermined inclusion criteria, with in total six patients treated with DBS for HO, of which five patients with Prader-Willi syndrome (PWS) and one patient with HO after treatment for craniopharyngioma (CP). Targets of DBS included the lateral hypothalamic area (LHA) and the nucleus accumbens (NAcc). In patients with PWS, LHA-DBS was associated with a mean increase of Body Mass Index (BMI) (+5.8%), with no change in hormonal levels, results of blood workup, sleep, or neuropsychological evaluation. In the patient with CP, NAcc-DBS was associated with a decrease in BMI (-8.7%) and a subjective increase in mental health, energy and willingness to act, and no feeling of increased appetite. No objective measurements on neurobehavioral function were reported. No severe adverse events were reported in these cases. Mild to moderate adverse events included hypomanic symptoms and infection. All patients with a described follow-up period (n = 5) were able to sustain the treatment for at least 6 months with few interruptions. Conclusion: There is limited research reporting on DBS for HO. The effectiveness differed across studies and the evidence is limited. Although there may be potential for DBS treatment in the severe-refractory condition of HO in patients with CP, more research is needed for target selection and evaluation of effectiveness.

Incisional CSF leakage after intradural cranial surgery in children: incidence, risk factors, and complications.

OBJECTIVE: The risk of cerebrospinal fluid (CSF) leakage after cranial surgery and its associated complications in children are unclear because of variable definitions and the lack of multicenter studies. In this study, the authors aimed to establish the incidence of CSF leakage after intradural cranial surgery in the pediatric population. In addition, they evaluated potential risk factors and complications related to CSF leakage in the pediatric population. METHODS: The authors performed an international multicenter retrospective cohort study in three tertiary neurosurgical referral centers. Included were all patients aged 18 years or younger who had undergone cranial surgery to reach the subdural space during the period between 2015 and 2021. Patients who died or were lost to follow-up within 6 weeks after surgery were excluded. The primary outcome measure was the incidence of CSF leakage, defined as leakage through the skin, within 6 weeks after surgery. Univariable and multivariable logistic regression analyses were performed to identify risk factors for and complications related to CSF leakage. RESULTS: In total, 759 procedures were identified, performed in 687 individual patients. The incidence of CSF leakage was 7.5% (95% CI 5.7%-9.6%). In the multivariate model, independent risk factors for CSF leakage were hydrocephalus (OR 4.5, 95% CI 2.2-8.9) and craniectomy (OR 7.6, 95% CI 3.0-19.5). Patients with CSF leakage had higher odds of pseudomeningocele (5.7, 95% CI 3.0-10.8), meningitis (21.1, 95% CI 9.5-46.8), and surgical site infection (7.4, 95% CI 2.6-20.8) than patients without leakage. CONCLUSIONS: CSF leakage risk in children after cranial surgery, which is comparable to the risk reported in adults, is an event of major concern and has a serious clinical impact.

Towards Standardisation of a Diffuse Midline Glioma Patient-Derived Xenograft Mouse Model Based on Suspension Matrices for Preclinical Research.

Diffuse midline glioma (DMG) is an aggressive brain tumour with high mortality and limited clinical therapeutic options. Although in vitro research has shown the effectiveness of medication, successful translation to the clinic remains elusive. A literature search highlighted the high variability and lack of standardisation in protocols applied for establishing the commonly used HSJD-DIPG-007 patient-derived xenograft (PDX) model, based on animal host, injection location, number of cells inoculated, volume, and suspension matrices. This study evaluated the HSJD-DIPG-007 PDX model with respect to its ability to mimic human disease progression for therapeutic testing in vivo. The mice received intracranial injections of HSJD-DIPG-007 cells suspended in either PBS or Matrigel. Survival, tumour growth, and metastases were assessed to evaluate differences in the suspension matrix used. After cell implantation, no severe side effects were observed. Additionally, no differences were detected in terms of survival or tumour growth between the two suspension groups. We observed delayed metastases in the Matrigel group, with a significant difference compared to mice with PBS-suspended cells. In conclusion, using Matrigel as a suspension matrix is a reliable method for establishing a DMG PDX mouse model, with delayed metastases formation and is a step forward to obtaining a standardised in vivo PDX model.

Cerebrospinal fluid leakage after intradural spinal surgery in children.

PURPOSE: This study aimed to establish the incidence of CSF leakage in children and associated complications after intradural spinal surgery in three tertiary neurosurgical referral centers and to describe the treatment strategies applied. METHODS: Patients of 18 years or younger who underwent intradural spinal surgery between 2015 and 2021 in three tertiary neurosurgical referral centers were included. Patients who died or were lost to follow-up within six weeks after surgery were excluded. The primary outcome measure was CSF leakage within six weeks after surgery, defined as leakage of CSF through the skin. Secondary outcome measures included the presence of pseudomeningocele (PMC), meningitis, and surgical site infection (SSI). RESULTS: We included a total of 75 procedures, representing 66 individual patients. The median age in this cohort was 5 (IQR = 0-13 years. CSF leakage occurred in 2.7% (2/75) of procedures. It occurred on days 3 and 21 after the index procedure, respectively. One patient was treated with a pressure bandage and an external lumbar drain on day 4 after diagnosis of the leak, and the other was treated with wound revision surgery on day 1 after the leak occurred. In total, 1 patient developed a PMC without a CSF leak which was treated with wound revision surgery. SSI occurred in 10.7%, which included both cases of CSF leak. CONCLUSIONS: CSF leakage after intradural spinal surgery in the pediatric population is relatively rare (2.7%). Nevertheless, the clinical consequences with respect to secondary complications such as infection and the necessity for invasive treatment are serious.

Implementation of paediatric precision oncology into clinical practice: The Individualized Therapies for Children with cancer program 'iTHER'.

iTHER is a Dutch prospective national precision oncology program aiming to define tumour molecular profiles in children and adolescents with primary very high-risk, relapsed, or refractory paediatric tumours. Between April 2017 and April 2021, 302 samples from 253 patients were included. Comprehensive molecular profiling including low-coverage whole genome sequencing (lcWGS), whole exome sequencing (WES), RNA sequencing (RNA-seq), Affymetrix, and/or 850k methylation profiling was successfully performed for 226 samples with at least 20% tumour content. Germline pathogenic variants were identified in 16% of patients (35/219), of which 22 variants were judged causative for a cancer predisposition syndrome. At least one somatic alteration was detected in 204 (90.3%), and 185 (81.9%) were considered druggable, with clinical priority very high (6.1%), high (21.3%), moderate (26.0%), intermediate (36.1%), and borderline (10.5%) priority. iTHER led to revision or refinement of diagnosis in 8 patients (3.5%). Temporal heterogeneity was observed in paired samples of 15 patients, indicating the value of sequential analyses. Of 137 patients with follow-up beyond twelve months, 21 molecularly matched treatments were applied in 19 patients (13.9%), with clinical benefit in few. Most relevant barriers to not applying targeted therapies included poor performance status, as well as limited access to drugs within clinical trial. iTHER demonstrates the feasibility of comprehensive molecular profiling across all ages, tumour types and stages in paediatric cancers, informing of diagnostic, prognostic, and targetable alterations as well as reportable germline variants. Therefore, WES and RNA-seq is nowadays standard clinical care at the Princess Máxima Center for all children with cancer, including patients at primary diagnosis. Improved access to innovative treatments within biology-driven combination trials is required to ultimately improve survival.

Radiologic Characteristics of Spinal Hemangioblastomas in von Hippel Lindau Disease as Guidance in Clinical Interventions.

OBJECTIVE: Hemangioblastomas in the central nervous system are the most common manifestation of von Hippel-Lindau (VHL) disease. Because the growth rate of hemangioblastomas is unpredictable, regular follow-up is mandatory, focusing on clinical symptoms and imaging of the central nervous system. However, clinical symptoms may be subtle and nonspecific, and data about the relationship between the radiologic findings and clinical symptoms are sparse. This study aims to evaluate if and how findings of magnetic resonance imaging (MRI) regarding spinal hemangioblastomas are associated with symptoms of VHL disease, with special attention to peritumoral edema and spinal cysts. METHODS: Serial spinal MRI scans of 43 genetically or clinically established VHL patients with at least 2 years of follow-up were reevaluated to examine the volume, growth rate, and location of spinal hemangioblastomas and the presence, size, and growth rate of peritumoral edema and cysts. Findings were compared with clinical symptoms using the Fisher exact test. RESULTS: We observed a total of 77 spinal hemangioblastomas in 28 patients. Eight of the 28 patients showed peritumoral edema and spinal cysts, and 1 patient showed peritumoral edema without cyst formation; 6 of these 9 patients showed clinical symptoms. Both peritumoral edema and spinal cysts were associated with clinical symptoms (P = 0.023 and P = 0.011, respectively). CONCLUSIONS: The presence of peritumoral edema and/or spinal cysts shown on MRI in VHL patients with spinal hemangioblastomas is associated with symptoms in more than half of the patients and may alert the clinician to intensify clinical and radiologic surveillance.

Ophthalmological Findings in Youths With a Newly Diagnosed Brain Tumor.

Importance: Visual impairment is an irreversible adverse effect in individuals who experienced a childhood brain tumor. Ophthalmological evaluation at diagnosis enables early detection of vision loss, decision-making about treatment, and when applicable, the timely use of visual interventions. However, awareness of visual impairment in clinical practice is suboptimal, and adherence to ophthalmological evaluation needs to be improved. Objective: To assess the prevalence and types of abnormal ophthalmological findings in youths with a newly diagnosed brain tumor. Design, Setting, and Participants: In this nationwide, prospective cohort study, youths aged 0 to 18 years with a newly diagnosed brain tumor between May 15, 2019, and August 11, 2021, were consecutively enrolled in 4 hospitals in the Netherlands, including the dedicated tertiary referral center for pediatric oncology care. Exposures: A standardized and comprehensive ophthalmological examination, including orthoptic evaluation, visual acuity testing, visual field examination, and ophthalmoscopy, was performed within 4 weeks from brain tumor diagnosis. Main Outcomes and Measures: The main outcomes were prevalence and types of visual symptoms and abnormal ophthalmological findings at brain tumor diagnosis. Results: Of 170 youths included in the study (96 [56.5%] male; median age, 8.3 years [range, 0.2-17.8 years]), 82 (48.2%) had infratentorial tumors; 53 (31.2%), supratentorial midline tumors; and 35 (20.6%), cerebral hemisphere tumors. A total of 161 patients (94.7%) underwent orthoptic evaluation (67 [41.6%] preoperatively; 94 [58.4%] postoperatively); 152 (89.4%), visual acuity testing (63 [41.4%] preoperatively; 89 [58.6%] postoperatively); 121 (71.2%), visual field examination (49 [40.4%] preoperatively; 72 [59.6%] postoperatively); and 164 (96.5%), ophthalmoscopy (82 [50.0%] preoperatively; 82 [50.0%] postoperatively). Overall, 101 youths (59.4%) presented with visual symptoms at diagnosis. Abnormal findings were found in 134 patients (78.8%) during ophthalmological examination. The most common abnormal findings were papilledema in 86 of 164 patients (52.4%) who underwent ophthalmoscopy, gaze deficits in 54 of 161 (33.5%) who underwent orthoptic evaluation, visual field defects in 32 of 114 (28.1%) with reliable visual field examination, nystagmus in 40 (24.8%) and strabismus in 32 (19.9%) of 161 who underwent orthoptic evaluation, and decreased visual acuity in 13 of 152 (8.6%) with reliable visual acuity testing. Forty-five of 69 youths (65.2%) without visual symptoms at diagnosis had ophthalmological abnormalities on examination. Conclusions and Relevance: The results of this study suggest that there is a high prevalence of abnormal ophthalmological findings in youths at brain tumor diagnosis regardless of the presence of visual symptoms. These findings support the need of standardized ophthalmological examination and the awareness of ophthalmologists and referring oncologists, neurologists, and neurosurgeons for ophthalmological abnormalities in this patient group.

Chromosomal Instability Characterizes Pediatric Medulloblastoma but Is Not Tolerated in the Developing Cerebellum.

Medulloblastoma is a pediatric brain malignancy that consists of four transcriptional subgroups. Structural and numerical aneuploidy are common in all subgroups, although they are particularly profound in Group 3 and Group 4 medulloblastoma and in a subtype of SHH medulloblastoma termed SHHα. This suggests that chromosomal instability (CIN), the process leading to aneuploidy, is an important player in medulloblastoma pathophysiology. However, it is not known if there is ongoing CIN in medulloblastoma or if CIN affects the developing cerebellum and promotes tumor formation. To investigate this, we performed karyotyping of single medulloblastoma cells and demonstrated the presence of distinct tumor cell clones harboring unique copy number alterations, which is suggestive of ongoing CIN. We also found enrichment for processes related to DNA replication, repair, and mitosis in both SHH medulloblastoma and in the highly proliferative compartment of the presumed tumor cell lineage-of-origin, the latter also being sensitive to genotoxic stress. However, when challenging these tumor cells-of-origin with genetic lesions inducing CIN using transgenic mouse modeling, we found no evidence for large chromosomal aberrations in the cerebellum or for medulloblastoma formation. We therefore conclude that without a background of specific genetic mutations, CIN is not tolerated in the developing cerebellum in vivo and, thus, by itself is not sufficient to initiate medulloblastoma.

Cerebrospinal Fluid Leak after Transsphenoidal Surgery: A Systematic Review and Meta-analysis.

Background Cerebrospinal fluid (CSF) leak is widely recognized as a challenging and commonly occurring postoperative complication of transsphenoidal surgery (TSS). The primary objective of this study is to benchmark the current prevalence of CSF leak after TSS in the adult population. Methods The authors followed the PRISMA guidelines. The PubMed, Embase, and Cochrane Library databases were searched for articles reporting CSF leak after TSS in the adult population. Meta-analysis was performed using the Untransformed Proportion metric in OpenMetaAnalyst. For two between-group comparisons a generalized linear mixed model was applied. Results We identified 2,408 articles through the database search, of which 70, published since 2015, were included in this systematic review. These studies yielded 24,979 patients who underwent a total of 25,034 transsphenoidal surgeries. The overall prevalence of postoperative CSF leak was 3.4% (95% confidence interval or CI 2.8-4.0%). The prevalence of CSF leak found in patients undergoing pituitary adenoma resection was 3.2% (95% CI 2.5-4.2%), whereas patients who underwent TSS for another indication had a CSF leak prevalence rate of 7.1% (95% CI 3.0-15.7%) (odds ratio [OR] 2.3, 95% CI 0.9-5.7). Patients with cavernous sinus invasion (OR 3.0, 95% CI 1.1-8.7) and intraoperative CSF leak (OR 5.9, 95% CI 3.8-9.0) have increased risk of postoperative CSF leak. Previous TSS and microscopic surgery are not significantly associated with postoperative CSF leak. Conclusion The overall recent prevalence of CSF leak after TSS in adults is 3.4%. Intraoperative CSF leak and cavernous sinus invasion appear to be significant risk factors for postoperative CSF leak.

Pediatric high-grade gliomas and the WHO CNS Tumor Classification-Perspectives of pediatric neuro-oncologists and neuropathologists in light of recent updates.

Background: The WHO Classification of Tumors of the Central Nervous System has undergone major restructuring. Molecularly defined diagnostic criteria were introduced in 2016 (revised 4th edition) and expanded in 2021 (5th edition) to incorporate further essential diagnostic molecular parameters. We investigated potential differences between specialists in perception of these molecularly defined subtypes for pediatric high-grade gliomas (pedHGG). Methods: We designed a 22-question survey studying the impact of the revised 4th edition of the WHO classification on pedHGG. Data were collected and statistically analyzed to examine the spectrum of viewpoints and possible differences between neuro-oncologists and neuropathologists. Results: 465 participants from 53 countries were included; 187 pediatric neuro-oncologists (40%), 160 neuropathologists (34%), and 118 additional experts (26%). Neuro-oncologists reported issues with the introduction of molecularly defined tumor types, as well as the abolishment or renaming of established tumor entities, while neuropathologists did not to the same extent. Both groups indicated less relevant or insufficient diagnostic definitions were available in 2016. Reported issues were classified and assessed in the 2021 WHO classification and a substantial improvement was perceived. However, issues of high clinical relevance remain to be addressed, including the definition of clinical phenotypes for diffuse intrinsic pontine glioma and gliomatosis cerebri. Conclusions: Within the WHO classification of pediatric brain tumors, such as pedHGG, rapid changes in molecular characterization have been introduced. This study highlights the ongoing need for cross talk between pathologist and oncologist to advance the classification of pedHGG subtypes and ensure biological relevance and clinical impact.

Generation of immunocompetent syngeneic allograft mouse models for pediatric diffuse midline glioma.

Background: Diffuse midline gliomas (DMG) are highly malignant incurable pediatric brain tumors. A lack of effective treatment options highlights the need to investigate novel therapeutic strategies. This includes the use of immunotherapy, which has shown promise in other hard-to-treat tumors. To facilitate preclinical immunotherapeutic research, immunocompetent mouse models that accurately reflect the unique genetic, anatomical, and histological features of DMG patients are warranted. Methods: We established cell cultures from primary DMG mouse models (C57BL/6) that were generated by brainstem targeted intra-uterine electroporation (IUE). We subsequently created allograft DMG mouse models by orthotopically implanting these tumor cells into syngeneic mice. Immunohistochemistry and -fluorescence, mass cytometry, and cell-viability assays were then used to verify that these murine tumors recapitulated human DMG. Results: We generated three genetically distinct allograft models representing histone 3 wildtype (H3WT) and K27M-mutant DMG (H3.3K27M and H3.1K27M). These allograft models recapitulated the histopathologic phenotype of their human counterparts, including their diffuse infiltrative growth and expression of DMG-associated antigens. These murine pontine tumors also exhibited an immune microenvironment similar to human DMG, characterized by considerable myeloid cell infiltration and a paucity of T-lymphocytes and NK cells. Finally, we show that these murine DMG cells display similar sensitivity to histone deacetylase (HDAC) inhibition as patient-derived DMG cells. Conclusions: We created and validated an accessible method to generate immunocompetent allograft models reflecting different subtypes of DMG. These models adequately recapitulated the histopathology, immune microenvironment, and therapeutic response of human DMG, providing useful tools for future preclinical studies.