Posterior Fossa Tumors In Children Research Articles

Comprehensive Review of Primary Posterior Fossa Tumors in Children

Comprehensive Review of Primary Posterior Fossa Tumors in Children

Posterior Fossa Tumors Special Edition. Celebrating 4 years!

Posterior fossa tumors account for approximately half of the central nervous system tumors in children. Major technological advances, mainly in the fields of molecular biology and neuroimaging, have modified their classification, leading to a more detailed description of these entities. Certain modifications in the general nomenclature introduced by the 2021 WHO classification of tumors of the CNS have an impact on how we approach the posterior fossa tumors described in this study. The focus of this annual special issue is posterior fossa tumors in children. There were several emerging technologies and approaches in the diagnosis and treatment of posterior fossa tumors in children. It's important to note that medical technology and research are continually evolving, so there may have been further advancements in this field since then. Here are some promising technologies and strategies that were being explored: Advanced Imaging Techniques: Functional MRI (fMRI): This technology helps in mapping the brain's functional areas, allowing surgeons to plan their approach more accurately and minimize damage to critical brain regions. Diffusion Tensor Imaging (DTI): DTI provides information on the brain's white matter tracts, aiding surgeons in preserving essential neural pathways during surgery. Spectroscopy: It helps in identifying tumor types and differentiating between tumor tissue and healthy brain tissue. Surgical Navigation Systems: The use of advanced navigation systems during surgery allows for precise tumor localization and safer tumor removal, minimizing damage to surrounding healthy tissue. Brain Ultrasound and iMRI: Some hospitals are equipped with iMRI suites that allow real-time imaging during surgery. Most common brain ultrasound helps a lot during the posterior fossa surgery and can use simultaneously with neuronavigation system. Minimally Invasive Techniques: Minimally invasive procedures, such as endoscopic surgery, are being explored for certain types of posterior fossa tumors. These techniques can reduce recovery times and complications. Intraoperative monitoring (IOM), also known as intraoperative neurophysiological monitoring (IONM), is a critical technique used during certain surgeries to monitor the nervous system's function in real-time. It helps surgeons and medical teams assess the integrity of neural structures, particularly the brain and spinal cord, during surgical procedures. Genomic and Molecular Analysis: Advances in genomic and molecular analysis of tumors can provide insights into the specific genetic mutations driving the tumor's growth. This information can help guide treatment decisions, including targeted therapies. Radiation Therapy Advancements: Techniques like proton therapy and stereotactic radiosurgery are being used to precisely target tumors while minimizing damage to surrounding healthy tissue, which is especially important in pediatric cases. Immunotherapy: Immunotherapy approaches, such as checkpoint inhibitors, are being investigated for their potential in treating certain types of posterior fossa tumors in children. These therapies aim to harness the body's immune system to fight the tumor. Personalized Medicine: Tailoring treatment plans to the individual characteristics of each patient's tumor is becoming increasingly important. This includes considering factors such as tumor genetics, location, and the child's overall health. Telemedicine and Remote Consultations: Telemedicine technologies enable pediatric neuro-oncologists to collaborate with experts worldwide, improving the quality of care, especially in regions with limited access to specialized healthcare. This special issue covers the different aspects of posterior fossa tumors surgery. We wish to thank all the authors for their tremendous contributions, and we hope that you will have the same interest and pleasure to read this special issue as we have had to edit it.

Posterior fossa tumor resection in children: a case report and the role of intraoperative neurophysiologic monitoring

Introduction/Background: Surgery plays a crucial role in the surgical management of posterior fossa tumors in children, but maximizing the resection while preserving function remains challenging. Along with other tools available to the surgeon, intraoperative neuromonitoring aims at improving safety during these complex interventions. This case report highlights the role of real-time intraoperative neuromonitoring during surgery and its impact on the surgeon's decision-making process. Case report: We present the case of a 10-year-old boy with a fourth ventricle medulloblastoma, who underwent microneurosurgical resection under intraoperative neuromonitoring. The use of neurophysiological monitoring yielded relevant information during the tumor dissection of the floor of the fourth ventricle, the most crucial step of surgery, thus helping the surgeon to change tactics to minimize long-term neurological deficits. Conclusion: In combination with meticulous microneurosurgery techniques, modern anesthetic regimens, and ultrasonic aspiration, intraoperative neuromonitoring adds up to the surgeon's armamentarium for increasing safety and improving outcomes following surgery for pediatric patients bearing posterior fossa tumors.

Posterior fossa tumors in children: current insights.

While in adults most intracranial tumors develop around the cerebral hemispheres, 45 to 60% of pediatric lesions are found in the posterior fossa, although this anatomical region represents only 10% of the intracranial volume. The latest edition of the WHO classification for CNS tumors presented some fundamental paradigm shifts that particularly affected the classification of pediatric tumors, also influencing those that affect posterior fossa. Molecular biomarkers play an important role in the diagnosis, prognosis, and treatment of childhood posterior fossa tumors and can be used to predict patient outcomes and response to treatment and monitor its effectiveness. Although genetic studies have identified several posterior fossa tumor types, differing in terms of their location, cell of origin, genetic mechanisms, and clinical behavior, recent management strategies still depend on uniform approaches, mainly based on the extent of resection. However, significant progress has been made in guiding therapy decisions with biological or molecular stratification criteria and utilizing molecularly targeted treatments that address specific tumor biological characteristics. The primary focus of this review is on the latest advances in the diagnosis and treatment of common subtypes of posterior fossa tumors in children, as well as potential therapeutic approaches in the future. Conclusion:Molecular biomarkers play a central role, not only in the diagnosis and prognosis of posterior fossa tumors in children but also in customizing treatment plans. They anticipate patient outcomes, measure treatment responses, and assess therapeutic effectiveness. Advances in neuroimaging and treatment have significantly enhanced outcomes for children with these tumors. What is Known: • Central nervous system tumors are the most common solid neoplasms in children and adolescents, with approximately 45 to 60% of them located in the posterior fossa. • Multimodal approaches that include neurosurgery, radiation therapy, and chemotherapy are typically used to manage childhood posterior fossa tumors What is New: • Notable progress has been achieved in the diagnosis, categorization and management of posterior fossa tumors in children, leading to improvement in survival and quality of life.

Analysis of Evolution of Hydrocephalus in Posterior Fossa Tumors and Validation Study of the Modified Canadian Preoperative Prediction Rule for Hydrocephalus in Children and Frankfurt Grading System for Prediction of Cerebrospinal Fluid Diversion in Adults with Posterior Fossa Tumors

We sought to analyze the evolution of hydrocephalus and enumerate its predictive factors in posterior fossa tumors in children and adults. We also validated the modified Canadian Preoperative Prediction Rule for Hydrocephalus (mCPPRH) and Frankfurt grading systems as tools to predict cerebrospinal fluid (CSF) diversion in children and adults, respectively. A retrospective review of patients with posterior fossa tumors operated between 2012 and 2019 was performed. Clinical, radiologic, and operative data were obtained. Validation was performed for both scores via receiver operating characteristic (ROC) curves and evaluation of the area under the curve (AUC). We included 116 children and 343 adults in the study. Of the adults, 141 patients had intraaxial tumors and 172 had extraaxial tumors. The insertion of external ventricular drain (EVD), its duration, papilledema was noted to have significant influence on the need for permanent CSF diversion (P < 0.05) in children. The ROC for mCPPRH score was 0.659 (0.501-0.816), Age- 0.496 (0.334-0.658) and Evans index- 0.788 (0.654-0.922). In adults- Intraaxial tumours Age, Frankfurt score, duration of EVD, Diagnosis, Extent of resection and periventricular capping significant predictors and ROC age AUC 0.300 (0.193-0.407), Evans index 0.939 (0.888-0.990), and Frankfurt score 0.908 (0.853-0.964) (P < 0.05), whereas in extraaxial tumors Frankfurt grading, sex, duration of EVD, presence of perilesional edema and extent of resection (P < 0.05) ROC age AUC 0.439 (0.344-0.534), Evans index 0.941 (0.906-0.977), and Frankfurt score 0.847 (0.782-0.912). This is the first external validation study for the 2 predictive systems in use. mCPPRH demonstrated poor predictive accuracy, and Frankfurt grading system demonstrated good accuracy. EVD insertion and its duration was significantly predictive of the need for permanent CSF diversion.

The outcome of using zolpidem for treatment of postoperative posterior fossa syndrome in children with brain tumor

Abstract Introduction: At present, there is no supporting evidence-based therapy of proven efficacy to treat posterior fossa syndrome (PFS) after surgical resection of posterior fossa tumors in children where only 22% of patients may experience a full recovery. However, zolpidem, a nonbenzodiazepine hypnotics drug, seems to be a possible treatment option for PFS symptoms. Methods and Materials: This was a retrospective chart review for all children with brain tumors younger than 15 years diagnosed with confirmed PFS after surgical resection at King Abdulaziz Medical City, Jeddah, and received zolpidem to alleviate the PFS symptoms between May 2016 and April 2019. Results: A total of 6 pediatric patients who experienced PFS symptoms (median of 4 days, range 1–7 days) were included. The most commonly observed symptoms were irritability, hypotonia, swallowing deficit, unsteady walking, and delayed speech. To alleviate the PFS symptoms, zolpidem was commenced 2–5 days postoperatively. The median duration of use was 13.5 days. During the hospital course, recovery of speech was observed after 2 weeks in most patients (50%) while 83.3% of patients recovered their normal speech in 4 months although not fully ambulated. No discontinuation of zolpidem use was reported because of adverse events. Conclusion: Most of our children (83.3%) who experienced PFS postresection responded to zolpidem trials which may represent a promising research field.

Pediatric posterior fossa tumors

Tumors of the posterior fossa account for about 50-55% of brain tumors in childhood. The most frequent tumor entities are medulloblastomas, pilocytic astrocytomas, ependymomas, diffuse midline gliomas and atypical teratoid-rhabdoid tumors. Neuroradiological differential diagnosis with magnetic resonance imaging (MRI) is of considerable importance for preoperative planning as well as planning of follow-up therapy. Most important findings for differential diagnosis of pediatric posterior fossa tumors are tumor location, patient age and the intratumoral apparent diffusion assessed by diffusion-weighted imaging. Advanced MR techniques like MRI perfusion and MR spectroscopy can be helpful both in the initial differential diagnosis and in tumor surveillance, but exceptional characteristics of certain tumor entities should be kept in mind. Standard clinical MRI sequences including diffusion-weighted imaging are the main diagnostic tool in evaluating posterior fossa tumors in children. Advanced imaging methods can be helpful, but should never be interpreted separately from conventional MRI sequences.

Characterizing Various Posterior Fossa Tumors in Children and Adults With Diffusion-Weighted Imaging and Spectroscopy.

Background Theposterior fossa is situated between thetentorium cerebelli above and the foramen magnum below. Vital structures like the cerebellum, the pons, and the medulla are situated within it; hence, tumors within the posterior fossa are considered one of the most critical brain lesions. Children are more likely to develop posterior fossa tumors than adults. Diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) sequences along with the conventional MRI helpin providing additional information in the characterization of the various posterior fossa tumors. We hereby present a series of 30 patients with clinically suspected posterior fossa masses who underwent preoperative MRI. Objectives This study aims to differentiate the neoplastic from non-neoplastic posterior fossa mass by evaluating the diffusion restriction pattern on DWI, quantifying the apparent diffusion coefficient (ADC) map in various posterior fossa tumors, and comparing the different metabolites of various posterior fossa tumors on MRS. Results Out of the 30 patients with posterior fossa lesions, 18 were males and 12 were females. Eight of them were in the pediatric age group, while twenty-two of them were adults. Metastasis was the most common posterior fossa lesionin our study sample and was found in six patients (20%), followed by vestibular schwannomas (17%) and arachnoid cysts (13%), meningiomas, medulloblastoma, and pilocytic astrocytoma (10% each) and epidermoid, ependymoma, and hemangioblastoma (7% each). The mean ADC value of benign tumors was higher than that of malignant tumors, and this difference was found to be significant (p = 0.012). The cut-off ADC value 1.21x 10-3mm2/s had a sensitivity of 81.82% and specificity of 80.47%. MRS metabolites played an additional role in differentiating benign from malignant tumors. Conclusion A combination of conventional MRI, DWI,ADC values, and MRS metabolites showed good diagnostic accuracy to differentiate between the various posterior fossa neoplastic tumors both in adults and children.

Posterior fossa tumors in children: An update and new concepts.

Posterior fossa tumors account for approximately half of the central nervous system tumors in children. Major technological advances, mainly in the fields of molecular biology and neuroimaging, have modified their classification, leading to a more detailed description of these entities. Into the classic taxonomy, used for many years, new concepts have been incorporated at times eliminating or modifying former ones. A literature search was conducted in PubMed using the medical subject headings involving the five most common pediatric posterior fossa tumors: diffuse midline glioma, medulloblastoma, ependymoma, atypical teratoid/rhabdoid tumor, and pilocytic astrocytoma. Only English published articles in the past 11 years that provided technological, neuroimaging, and molecular biology insight into posterior fossa tumors in children were considered. Substantial changes have been introduced in the nomenclature of pediatric posterior fossa tumors. Diffuse midline gliomas are named based on alterations in histone H3. Molecular rearrangements of medulloblastomas are more important in defining the prognosis than histological variants; therefore, these tumors are currently named based on their molecular subgroups. Posterior fossa ependymomas and atypical teratoid rhabdoid tumor classification have incorporated new groups based on different genetic profiles. Pilocytic astrocytoma has been placed in a new category that distinguishes circumscribed from diffuse entities. Advances in molecular biology and neuroimaging have substantially changed the way pediatric neoplasms are studied. The classical taxonomy has been modified leading to more accurate classifications that are based on the genetic alterations.

Role of MR Spectroscopy in Evaluation of Posterior Fossa Tumors in Children

Role of MR Spectroscopy in Evaluation of Posterior Fossa Tumors in Children

Application of Apparent Diffusion Coefficient Histogram Metrics for Differentiation of Pediatric Posterior Fossa Tumors : ALarge Retrospective Study and Brief Review of Literature.

This study aimed to evaluate the application of apparent diffusion coefficient (ADC) histogram analysis to differentiate posterior fossa tumors (PFTs) in children. A total of 175 pediatric patients with PFT, including 75pilocytic astrocytomas (PA), 59medulloblastomas, 16ependymomas, and 13atypical teratoid rhabdoid tumors (ATRT), were analyzed. Tumors were visually assessed using DWI trace and conventional MRI images and manually segmented and post-processed using parametric software (pMRI). Furthermore, tumor ADC values were normalized to the thalamus and cerebellar cortex. The following histogram metrics were obtained: entropy, minimum, 10th, and 90th percentiles, maximum, mean, median, skewness, and kurtosis to distinguish the different types of tumors. Kruskal Wallis and Mann-WhitneyU tests were used to evaluate the differences. Finally, receiver operating characteristic (ROC) curves were utilized to determine the optimal cut-off values for differentiating the various PFTs. Most ADC histogram metrics showed significant differences between PFTs (p < 0.001) except for entropy, skewness, and kurtosis. There were significant pairwise differences in ADC metrics for PA versus medulloblastoma, PA versus ependymoma, PA versus ATRT, medulloblastoma versus ependymoma, and ependymoma versus ATRT (all p < 0.05). Our results showed no significant differences between medulloblastoma and ATRT. Normalized ADC data showed similar results to the absolute ADC value analysis. ROC curve analysis for normalized ADCmedian values to thalamus showed 94.9% sensitivity (95% CI: 85-100%) and 93.3% specificity (95% CI: 87-100%) for differentiating medulloblastoma from ependymoma. ADC histogram metrics can be applied to differentiate most types of posterior fossa tumors in children.

IMG-02. Improved prediction of postoperative paediatric cerebellar mutism syndrome using an artificial neural network

Abstract BACKGROUND: Postoperative paediatric cerebellar mutism syndrome (pCMS) is a common but severe complication which may arise following the resection of posterior fossa tumours in children. Two previous studies have aimed to preoperatively predict pCMS, with varying results. In this work, we examine the generalisation of these models and determine if pCMS can be predicted more accurately using an artificial neural network (ANN). METHODS: An overview of reviews was performed to identify risk factors for pCMS, and a retrospective dataset collected as per these defined risk factors from children undergoing resection of primary posterior fossa tumours. The ANN was trained on this dataset and its performance evaluated in comparison to logistic regression and other predictive indices via analysis of receiver operator characteristic curves. Area under the curve (AUC) and accuracy were calculated and compared using a Wilcoxon signed rank test, with p&amp;lt;0.05 considered statistically significant. RESULTS: 204 children were included, of whom 80 developed pCMS. The performance of the ANN (AUC 0.949; accuracy 90.9%) exceeded that of logistic regression (p&amp;lt;0.05) and both external models (p&amp;lt;0.001). CONCLUSION: Using an ANN, we show improved prediction of pCMS in comparison to previous models and conventional methods.

Posterior Fossa Tumours in the First Year of Life: A Two-Centre Retrospective Study.

Posterior fossa tumours (PFTs) in infants are very rare, and information on these tumours is scarce in the literature. This retrospective study reports their pathological characteristics and describes surgical aspects and treatment outcomes. A two-centre cohort of infants with PFTs treated from 2007 to 2018 was retrospectively reviewed. Patient characteristics, clinical, and treatment data were reviewed. Survival curves for progression-free survival (PFS) and overall survival (OS) were generated. Thirty-three infants were retrieved. There were 11 low grade and 22 high-grade tumours. The most common presenting symptom was intracranial hypertension. Fifteen children out of thirty-three progressed. Five-year PFS was significantly lower in children with high-grade tumours (38.3%) than those with low-grade tumours (69.3%), p = 0.030. High-grade pathology was the only predictor of progression (HR 3.7, 95% CI 1.1–13.31), p = 0.045. Fourteen children with high-grade tumours died, with a 5-year OS of 55.25%. PFTs in children below one year of age still represent a unique challenge. Infants with high-grade tumours display the worst outcomes and the lowest survival, indicating that more effective strategies are needed.

Prevalence of Tumors in the Posterior Cerebral Fossa in Children and Adults, as well as their Histological Kinds: a Cross-Sectional Study

Aim: To determine the prevalence of posterior fossa tumors in children and adults, as well as their histological kinds. Study design: A cross-sectional study Place and duration: From February 2012 to January 2019, the Department of Neurosurgery at Riyadh Care Hospital Methodology: We undertook a descriptive analysis of patients with posterior fossa space-occupying lesions. The neurosurgical intervention was done in all of the instances due to the critical location. Specimens were sent for histological evaluation after surgery. The data from these patients, as well as histology reports, were examined. The data was analyzed using SPSS version 21. Results: Males made up 57.14 percent (n=48) of the 84 patients, while children made up 41.66 percent (n=35). The most common tumor was schwannoma, seen in 34.52 percent (n=29) of cases, 72.41 percent of adults, and 27.58 % of children. In 22.61 %, 15.47 %, and 14.28 % of cases, meningioma, pilocytic astrocytoma (PCA), and Meduloblastoma were found, respectively. Metastasis was only seen in adults, and malignant round blue cell tumors were only found in children. Astrocytoma and schwannoma were prevalent in adults. Children were more likely to develop Meduloblastoma, Pilocytic astrocytoma, and malignant round blue cell tumors. Conclusion: High-grade Astrocytoma and Schwannoma are dominantly present in adults. Malignant round blue cell tumor, Pilocytic astrocytoma Medulloblastoma is more prevalent in children. Metastasis was only observed in adults. Because of their location, risk of excision, and involvement of the brain stem structures and fourth ventricle, posterior fossa tumors are widely known for their significant morbidity and mortality. Early diagnosis is now possible due to modern diagnostic and therapy technologies, which help to lower mortality rates and improve postoperative prognosis. Keywords: posterior cerebral fossa tumors, children, adults

Common Histopathological spectrum of Posterior Fossa Tumors in Pediatric Age Group

Objective: To know about the common posterior fossa tumors in the pediatric age group on basis of Histopathology in Neurosurgery Department, Hayatabad Medical Complex Peshawar.&#x0D; Material and Methods: This descriptive cross-sectional study was conducted in the department of MTI Hayatabad medical complex Peshawar from January 2017 to January 2020. We included a total of 52 patients who operated for posterior fossa tumors and biopsy reports were observed to know the histological pattern of the tumor. We included all those patients who have posterior fossa tumors except those tumors which involved or arise from brain stem and infections. The data was collected and analyzed using SPSS version 21.&#x0D; Results: Our study shows that the mean age was 6 years with a standard deviation ± 2.81. Fifty-eight percent of children were male and 42% of children were female. Histopathologic patterns were analyzed as 48% of children had Medulloblastoma, 25% of children had Astrocytoma, 19% of children had Ependymoma, 8% of patients had other histopathologic patterns.&#x0D; Conclusion: Our study concludes that common histopathologic patterns of posterior fossa tumors in children were medulloblastoma (48%), Astrocytoma (25%), ependymoma (19%) respectively.

Improved prediction of postoperative pediatric cerebellar mutism syndrome using an artificial neural network.

BackgroundPostoperative pediatric cerebellar mutism syndrome (pCMS) is a common but severe complication that may arise following the resection of posterior fossa tumors in children. Two previous studies have aimed to preoperatively predict pCMS, with varying results. In this work, we examine the generalization of these models and determine if pCMS can be predicted more accurately using an artificial neural network (ANN).MethodsAn overview of reviews was performed to identify risk factors for pCMS, and a retrospective dataset was collected as per these defined risk factors from children undergoing resection of primary posterior fossa tumors. The ANN was trained on this dataset and its performance was evaluated in comparison to logistic regression and other predictive indices via analysis of receiver operator characteristic curves. The area under the curve (AUC) and accuracy were calculated and compared using a Wilcoxon signed-rank test, with P < .05 considered statistically significant.ResultsTwo hundred and four children were included, of whom 80 developed pCMS. The performance of the ANN (AUC 0.949; accuracy 90.9%) exceeded that of logistic regression (P < .05) and both external models (P < .001).ConclusionUsing an ANN, we show improved prediction of pCMS in comparison to previous models and conventional methods.

Post-operative meningeal thickening seen on magnetic resonance imaging

Posterior fossa tumors are relatively common in children, and the meningeal dissemination of these tumors is well established in the literature. Although leptomeningeal dissemination is more common in high-grade tumors, even low-grade tumors can generate meningeal metastases. In this case report, we would like to discuss the importance of leptomeningeal dissemination assessment of posterior fossa tumors in children, in the preoperative period, through the entire neuroaxis magnetic resonance imaging (MRI). This is important since transient meningeal thickening is very common in the postoperative periods of neurosurgical patients, and can be found for up to 5 or 6 years after surgery, causing these patients to undergo prolonged follow-ups and repeated MRIs and lumbar punctures.

Added value of magnetic resonance spectroscopy for diagnosing childhood cerebellar tumours.

1 H-magnetic resonance spectroscopy (MRS) provides noninvasive metabolite profiles with the potential to aid the diagnosis of brain tumours. Prospective studies of diagnostic accuracy and comparisons with conventional MRI are lacking. The aim of the current study was to evaluate, prospectively, the diagnostic accuracy of a previously established classifier for diagnosing the three major childhood cerebellar tumours, and to determine added value compared with standard reporting of conventional imaging. Single-voxel MRS (1.5 T, PRESS, TE 30 ms, TR 1500 ms, spectral resolution 1 Hz/point) was acquired prospectively on 39 consecutive cerebellar tumours with histopathological diagnoses of pilocytic astrocytoma, ependymoma or medulloblastoma. Spectra were analysed with LCModel and predefined quality control criteria were applied, leaving 33 cases in the analysis. The MRS diagnostic classifier was applied to this dataset. A retrospective analysis was subsequently undertaken by three radiologists, blind to histopathological diagnosis, to determine the change in diagnostic certainty when sequentially viewing conventional imaging, MRS and a decision support tool, based on the classifier. The overall classifier accuracy, evaluated prospectively, was 91%. Incorrectly classified cases, two anaplastic ependymomas, and a rare histological variant of medulloblastoma, were not well represented in the original training set. On retrospective review of conventional MRI, MRS and the classifier result, all radiologists showed a significant increase (Wilcoxon signed rank test, p < 0.001) in their certainty of the correct diagnosis, between viewing the conventional imaging and MRS with the decision support system. It was concluded that MRS can aid the noninvasive diagnosis of posterior fossa tumours in children, and that a decision support classifier helps in MRS interpretation.

Postoperative speech impairment and surgical approach to posterior fossa tumours in children: a prospective European multicentre cohort study

Brain tumours are the most common solid tumours in childhood. Half of these tumours occur in the posterior fossa, where surgical removal is complicated by the risk of cerebellar mutism syndrome, of which postoperative speech impairment (POSI) is a cardinal symptom, in up to 25% of patients. The surgical approach to midline tumours, mostly undertaken by transvermian or telovelar routes, has been proposed to influence the risk of POSI. We aimed to investigate the risk of developing POSI, the time course of its resolution, and its association with surgical approach and other clinical factors. In this observational prospective multicentre cohort study, we included children (aged <18 years) undergoing primary surgery for a posterior fossa tumour at 26 centres in nine European countries. Within 72 h of surgery, the operating neurosurgeon reported details on the tumour location, surgical approach used, duration of surgery, use of traction, and other predetermined factors, using a standardised surgical report form. At 2 weeks, 2 months, and 1 year after surgery, a follow-up questionnaire was filled out by a paediatrician or neurosurgeon, including neurological examination and assessment of speech. Speech was classified as mutism, reduced speech, or habitual speech. POSI was defined as either mutism or severely reduced speech. Ordinal logistic regression was used to analyse the risk of POSI. Between Aug 11, 2014, and Aug 24, 2020, we recruited 500 children. 426 (85%) patients underwent primary tumour surgery and had data available for further analysis. 192 (45%) patients were female, 234 (55%) patients were male, 81 (19%) patients were aged 0-2 years, 129 (30%) were aged 3-6 years, and 216 (51%) were aged 7-17 years. 0f 376 with known postoperative speech status, 112 (30%) developed POSI, 53 (14%) developed mutism (median 1 day [IQR 0-2]; range 0-10 days), and 59 (16%) developed reduced speech after surgery (0 days [0-1]; 0-4 days). Mutually adjusted analyses indicated that the independent risk factors for development of POSI were younger age (linear spline, p=0·0087), tumour location (four levels, p=0·0010), and tumour histology (five levels, p=0·0030); surgical approach (six levels) was not a significant risk factor (p=0·091). Tumour location outside the fourth ventricle and brainstem had a lower risk of POSI (with fourth ventricle as reference, odds ratio (OR) for cerebellar vermis 0·34 [95% CI 0·14-0·77] and OR for cerebellar hemispheres 0·23 [0·07-0·70]). Compared with pilocytic or pilomyxoid astrocytoma, a higher risk of POSI was seen for medulloblastoma (OR 2·85 [1·47-5·60]) and atypical teratoid rhabdoid tumour (10·30 [2·10-54·45]). We did not find an increased risk of POSI for transvermian surgical approach compared with telovelar (0·89 [0·46-1·73]). Probability of speech improvement from mutism reached 50% around 16 days after mutism onset. Our data suggest that a midline tumour location, younger age, and high-grade tumour histology all increase the risk of speech impairment after posterior fossa tumour surgery. We found no evidence to recommend a preference for telovelar over transvermian surgical approach in the management of posterior fossa tumours in children in relation to the risk of developing POSI. The Danish Childhood Cancer Foundation, the Swedish Childhood Cancer Foundation, the UK Brain Tumour Charity, the Danish Cancer Society, Det Kgl Kjøbenhavnske Skydeselskab og Danske Broderskab, the Danish Capitol Regions Research Fund, Dagmar Marshall Foundation, Rigshospitalet's Research Fund, and Brainstrust.

A Diagnostic Algorithm for Posterior Fossa Tumors in Children: A Validation Study.

Primary posterior fossa tumors comprise a large group of neoplasias with variable aggressiveness and short and long-term outcomes. This study aimed to validate the clinical usefulness of a radiologic decision flow chart based on previously published neuroradiologic knowledge for the diagnosis of posterior fossa tumors in children. A retrospective study was conducted (from January 2013 to October 2019) at 2 pediatric referral centers, Children's Hospital of Philadelphia, United States, and Great Ormond Street Hospital, United Kingdom. Inclusion criteria were younger than 18 years of age and histologically and molecularly confirmed posterior fossa tumors. Subjects with no available preoperative MR imaging and tumors located primarily in the brain stem were excluded. Imaging characteristics of the tumors were evaluated following a predesigned, step-by-step flow chart. Agreement between readers was tested with the Cohen κ, and each diagnosis was analyzed for accuracy. A total of 148 cases were included, with a median age of 3.4 years (interquartile range, 2.1-6.1 years), and a male/female ratio of 1.24. The predesigned flow chart facilitated identification of pilocytic astrocytoma, ependymoma, and medulloblastoma sonic hedgehog tumors with high sensitivity and specificity. On the basis of the results, the flow chart was adjusted so that it would also be able to better discriminate atypical teratoid/rhabdoid tumors and medulloblastoma groups 3 or 4 (sensitivity = 75%-79%; specificity = 92%-99%). Moreover, our adjusted flow chart was useful in ruling out ependymoma, pilocytic astrocytomas, and medulloblastoma sonic hedgehog tumors. The modified flow chart offers a structured tool to aid in the adjunct diagnosis of pediatric posterior fossa tumors. Our results also establish a useful starting point for prospective clinical studies and for the development of automated algorithms, which may provide precise and adequate diagnostic tools for these tumors in clinical practice.