Pediatric Posterior Fossa Tumors Research Articles

ROLE OF DIFFUSION WEIGHTED MRI IN DIFFERENTIAL DIAGNOSIS OF PAEDIATRIC POSTERIOR FOSSA TUMORS

Background: Infratentorial tumors accounts for 65% of all paediatric tumors, and most common infratentorial tumors in children include juvenile pilocytic astrocytoma (JPA), medulloblastoma, ependymoma and brainstem glioma. An accurate diagnosis has important clinical implications related to treatment and prognosis. DWI and ADC maps provide information regarding the cellularity of tumors and have an important role in the preoperative differentiation of different tumor types.
 Aim: To evaluate the role of DWI and ADC measurement in distinguishing between the most common pediatric posterior fossa tumors.
 Methods: In this study, we evaluated 25 paediatric patients aged between 1 to 15 years suspected to have posterior fossa mass on the CT referred from neurosurgery department to our department for MRI brain. All these patients subjected to conventional MRI followed by diffusion MR imaging and calculation of the ADC values. Written consent was taken from the guardians.
 Results: In juvenile pilocytic astrocytoma ( n = 10), ADC values ranged between 1.3 and 1.9 × 10?3 mm2/s, ependymoma (n = 8), ADC values ranged between 1.1 and 1.5 × 10?3 mm2/s and medulloblastoma (n = 7), ADC values ranged between 0.45 and 0.9 × 10?3 mm2/s. Statistically significant difference in ADC value was detected between JPA, ependymomas and medulloblastomas, while no statistically significant difference was detected between JPA and ependymomas.
 Conclusion: Diffusion Imaging plays an important role in demonstrating the features of posterior fossa brain tumours for appropriate diagnosis of medulloblastomas, ependymomas, and pilocytic astrocytoma.
 Keywords: DWI, MRI, Posterior fossa

Posterior fossa tumors in children, Histopathology &extent of excision as prognostic factors

The Posterior fossa is the commonest site of primary intracranial tumors in children, for the last two decades the over-all survival and 5-years progression-free survival of children with posterior fossa tumors (PFT) like Medulloblastoma& Ependymomas has been doubled due to the improvement in the diagnostic tools and the advances in the surgical techniques approaching total or near total resection. The aim of the study is to find the relation of histopathology and the extent of excision with mortality and survival. A total of twenty eight cases with Histologically (26 cases) and two cases radiologically (CT-scan and MRI) confirmed pediatric posterior fossa tumors treated in Erbil Teaching Hospital between ,Jan.2013 and Dec.2015 were included in the study As a result the twenty-eight pediatric patients were included in the study, mean age was (8 years),16 boys and 12 girls, mean follow-up period was 14 months,11 cases had Medulloblastoma (39%), 5 cases had Ependymoma (18%), 9 cases had Astrocytoma(32%) , 2 cases had Brainstem mass (7%) and one case had Choroid plexus papilloma (4%).Tumor resection was performed in 26 patients, Twenty cases had total resection (77%), and six Pts .had subtotal resection (23%), two cases without surgery During the follow-up period out of the 20 cases that had total resection nineteen are still alive(95%) and only one died (5%),six cases that had Subtotal resection; four of them are dead (67%) and only two cases are still alive(33%). Two cases that had no surgery both of them are dead (100%).Eleven cases of Medulloblastoma 8 of them had gross total resection and three of them had subtotal resection, 9 of them still alive (82%) and two are dead (18%). Nine Pts of Astrocytoma, 8 of them had total resection and one subtotal; eight of them are still .(alive (89%) and only one died (11%Five pts with Ependymoma, three had total resection and two had subtotal resection, three are still alive (60%) and two dead (40%). Two cases of Brainstem mass not operated and both are dead, One case of Choroid papilloma totally resected & still alive. In conclusion treatment of posterior fossa tumors in children with surgery yields long survival rates, children with gross total resection or a near total resection had better outcome. Histopathology subtypes of the tumors were associated with a favorable outcome for Astrocytoma which has less mortality and better survival rate than others

Comparison between MRI Findings and Histopathological Diagnosis in the Evaluation of Posterior Fossa Tumors in Pediatric Patients

Background: Conventional radiography and CT scan failed to reveal the posterior fossa tumors which not accurately show tumors behind bone. MRI is currently recognized as the optimal screening technique for detection of posterior fossa tumors. We tried to compare the MRI findings with the histopathological findings of different types of posterior fossa tumors in pediatric patients. Histopathological reports were regarded as the gold standard.
 Objective: To assess the diagnostic effectiveness of MRI in detection of posterior cranial fossa tumors in pediatric patients.
 Methods: This cross sectional study was carried out in the department of Neurosurgery, DMCH, NINS and some private hospitals in Dhaka from March, 2012 to November, 2013. Purposive sampling technique was applied and 34 cases were included in the study. Data were collected by specially designed questionnaire and analysed by SPSS.
 Results: Out of 34 cases, MRI failed to match with the histopathological diagnosis only in 2 cases. One case was diagnosed as cerebellar astrocytoma by MRI, histopathology proved it brain abscess. In another case, MRI diagnosed as ependymoma but histopathology revealed medulloblastoma.
 Conclusion: It can be concluded That MRI is accepted as the most effective imaging modality in the diagnosis of paediatric posterior fossa tumors. T1WI, T2WI, FLAIR, axial, sagittal, coronal and T1WI post contrast sequences permit confident diagnosis and localization of the pediatric posterior fossa tumor.
 Bang. J Neurosurgery 2020; 10(1): 62-66

Pediatric posterior fossa tumors outcomes: Experience in a tertiary care center in the Middle East

BackgroundAmong all childhood cancers, brain tumors are second only to leukemia in incidence and are the most common solid pediatric tumors. More than 60 % of pediatric brain tumors are infra-tentorial. The first-line treatment for most infra-tentorial tumors in pediatric patients is surgical resection, with the goal of gross-total resection, relief of symptoms and hydrocephalus, and increased survival. The proximity to the fourth ventricle, and therefore, the cerebrospinal fluid (CSF) pathways, predisposes children with posterior fossa tumors to the development of obstructive hydrocephalus and multiple other co-morbidities pre and post-surgery. ObjectivesThis study aims to present our series of pediatric posterior fossa tumor surgeries in the Neurosurgical Department at the American University of Beirut Medical Center(AUBMC) and perform internal quality control for our single-institution consecutive series as one of the largest referral and tertiary care centers in the region. The second purpose of this retrospective study is to weigh the risks of surgery against the presumed advantages and to have specific knowledge about the complication rates, especially those related to the CSF pathway, comparing our results to those in the literature. MethodsAll pediatric patients (< 18 years of age), referred to our center from different regions in the middle east, and surgically treated for a posterior fossa tumor from June 2006 to June 2018 at the American University of Beirut Medical Center were included. A thorough review of all medical charts was performed to validate all the database records. ResultsThe patient sample consisted of 64 patients having a mean age of 6.19 ± 4.42 years and 59.37 % of whom were males. The most common tumor pathology was pilocytic astrocytoma (40.62 %) followed by medulloblastoma (35.93 %) and ependymoma. The most common type of tumor that was seen in patients that developed mutism postoperatively (n = 6, 9.37 %) was medulloblastoma (n = 4, 66.66 %). In this patient sample, 12.28 % (n = 7) of the patients developed hydrocephalus postoperatively.Midline tumors were more associated with the development of mutism(OR = 4.632, p = 0.306) and hydrocephalus (OR = 5.056, p = 0.135) postoperatively, albeit not statistically significantly.The presence of a preoperative shunt was shown to be protective against the development of CSF leak (OR = 0.636, p = 0.767), as none of the patients that came in with CSF diversion developed a CSF leak after their surgery. ConclusionThis study from a single center experience accompanied by a thorough literature review sheds light on the complications frequently encountered after posterior fossa tumor surgery in children. These included transient cerebellar mutism, CSF leak, and hydrocephalus as seen in some of our patients. Our findings highlight the need for prospective studies with well-defined protocols directed at assessing novel ways and approaches to minimize the risk of these complications.

Deep Learning for Pediatric Posterior Fossa Tumor Detection and Classification: A Multi-Institutional Study.

Posterior fossa tumors are the most common pediatric brain tumors. MR imaging is key to tumor detection, diagnosis, and therapy guidance. We sought to develop an MR imaging-based deep learning model for posterior fossa tumor detection and tumor pathology classification. The study cohort comprised 617 children (median age, 92 months; 56% males) from 5 pediatric institutions with posterior fossa tumors: diffuse midline glioma of the pons (n = 122), medulloblastoma (n = 272), pilocytic astrocytoma (n = 135), and ependymoma (n = 88). There were 199 controls. Tumor histology served as ground truth except for diffuse midline glioma of the pons, which was primarily diagnosed by MR imaging. A modified ResNeXt-50-32x4d architecture served as the backbone for a multitask classifier model, using T2-weighted MRIs as input to detect the presence of tumor and predict tumor class. Deep learning model performance was compared against that of 4 radiologists. Model tumor detection accuracy exceeded an AUROC of 0.99 and was similar to that of 4 radiologists. Model tumor classification accuracy was 92% with an F1 score of 0.80. The model was most accurate at predicting diffuse midline glioma of the pons, followed by pilocytic astrocytoma and medulloblastoma. Ependymoma prediction was the least accurate. Tumor type classification accuracy and F1 score were higher than those of 2 of the 4 radiologists. We present a multi-institutional deep learning model for pediatric posterior fossa tumor detection and classification with the potential to augment and improve the accuracy of radiologic diagnosis.

Automatic Machine Learning to Differentiate Pediatric Posterior Fossa Tumors on Routine MR Imaging.

Differentiating the types of pediatric posterior fossa tumors on routine imaging may help in preoperative evaluation and guide surgical resection planning. However, qualitative radiologic MR imaging review has limited performance. This study aimed to compare different machine learning approaches to classify pediatric posterior fossa tumors on routine MR imaging. This retrospective study included preoperative MR imaging of 288 patients with pediatric posterior fossa tumors, including medulloblastoma (n = 111), ependymoma (n = 70), and pilocytic astrocytoma (n = 107). Radiomics features were extracted from T2-weighted images, contrast-enhanced T1-weighted images, and ADC maps. Models generated by standard manual optimization by a machine learning expert were compared with automatic machine learning via the Tree-Based Pipeline Optimization Tool for performance evaluation. For 3-way classification, the radiomics model by automatic machine learning with the Tree-Based Pipeline Optimization Tool achieved a test micro-averaged area under the curve of 0.91 with an accuracy of 0.83, while the most optimized model based on the feature-selection method χ2 score and the Generalized Linear Model classifier achieved a test micro-averaged area under the curve of 0.92 with an accuracy of 0.74. Tree-Based Pipeline Optimization Tool models achieved significantly higher accuracy than average qualitative expert MR imaging review (0.83 versus 0.54, P < .001). For binary classification, Tree-Based Pipeline Optimization Tool models achieved an area under the curve of 0.94 with an accuracy of 0.85 for medulloblastoma versus nonmedulloblastoma, an area under the curve of 0.84 with an accuracy of 0.80 for ependymoma versus nonependymoma, and an area under the curve of 0.94 with an accuracy of 0.88 for pilocytic astrocytoma versus non-pilocytic astrocytoma. Automatic machine learning based on routine MR imaging classified pediatric posterior fossa tumors with high accuracy compared with manual expert pipeline optimization and qualitative expert MR imaging review.

Diagnostic accuracy of apparent diffusion coefficient ratio in distinguishing common pediatric CNS posterior fossa tumors

BackgroundPilocytic astrocytoma, medulloblastoma, and ependymoma are the most common pediatric CNS tumors seen at posterior cranial fossa and final diagnosis obtained by histopathology after surgical excision. Routine MRI study gives an idea about site and extension of the tumors but provide a little information about type and grade of tumors. ADC ratio had high sensitivity and specificity in differentiation between these tumors as regard type and grade according to tumor cellularity.Patients and methodsProspective study conducted on thirty pediatric patients (11 males and 19 females) with CNS posterior fossa masses, their ages ranged from 2 to 17 years (mean age of 8.7 years), conventional MRI, DWI, ADC value, and ADC ratio were done for all patients.ResultsADC values were significantly different between pilocytic astrocytomas (1.43 ± 0.28 × 10−3) and medulloblastomas (0.71 ± 0. 21 × 10−3) with a P value < 0.001, also there was a significant difference when comparing medulloblastomas (0.71 ± 0.21 × 10−3) with ependymomas (1.04 × 10−3 ± 0.21) with a P value < 0.001. ADC ratio at a cutoff > 1.7 showed significant good power of discrimination of astrocytoma (AUC = 0.85) from ependymoma with 87.5% sensitivity and 93.3% specificity. Similarly, at cutoff ≤ 1.6-> 1.2 was a significant good predictor of ependymoma (AUC = 0.85) with 87.8% sensitivity and 99.5% specificity. While, ADC ratio ≤ 1.2 was significant excellent discriminator of medulloblastoma (AUC = 0.99) with 100% sensitivity and 90% specificity.ConclusionADC ratio is a simple way used in distinguishing juvenile pilocytic astrocytoma, ependymoma, and medulloblastoma, which are the most frequent pediatric posterior fossa tumors. Cutoff ADC ratio of more than 1.7 characteristic of JPA with 87.5% sensitivity and 93.3% specificity, ADC ratio less than 1.1 characteristic of medulloblastoma with 100% sensitivity and 90% specificity. ADC ratios more than 1.1 and less than 1.7 characteristic of ependymoma with 87.8% sensitivity and 99.5% specificity. We recommended ADC ratio as a routine study in evaluation of pediatric CNS posterior fossa tumors.

Ependymoma and pilocytic astrocytoma: Differentiation using radiomics approach based on machine learning

Mandatory accurate and specific diagnosis demands have brought about increased challenges for radiologists in pediatric posterior fossa tumor prediction and prognosis. With the development of high-performance computing and machine learning technologies, radiomics provides increasing opportunities for clinical decision-making. Several studies have applied radiomics as a decision support tool in intracranial tumors differentiation. Here we seek to achieve preoperative differentiation between ependymoma (EP) and pilocytic astrocytoma (PA) using radiomics analysis method based on machine learning. A total of 135 Magnetic Resonance Imaging (MRI) slices are divided into training sets and validation sets. Three kinds of radiomics features, including Gabor transform, texture and wavelet transform based ones are used to obtain 300 multimodal features. Kruskal–Wallis test score (KWT) and support vector machines (SVM) are applied for feature selection and tumor differentiation. The performance is investigated via accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) analysis. Results show that the accuracy, sensitivity, specificity, and AUC of the selected feature set are 0.8775, 0.9292, 0.8000, and 0.8646 respectively, having no significantdifferencescomparedwiththe overall feature set. For different types of features, texture features yield the best differentiation performance and the significance analysis results are consistent with this. Our study demonstrates texture features perform better than the other features. The radiomics approach based on machine learning is efficient for pediatric posterior fossa tumors differentiation and could enhance the application of radiomics methods for assisted clinical diagnosis.

Does pre-resection endoscopic third ventriculostomy prevent the need for post-resection CSF diversion after pediatric posterior fossa tumor excision? A historical cohort study and review of the literature.

Children with posterior fossa tumors (PFTs) may present with hydrocephalus. Persistent (or new) hydrocephalus is common after PFT resection. Endoscopic third ventriculostomy (ETV) is sometimes performed prior to resection to 1) temporize hydrocephalus prior to resection and 2) prophylactically treat post-resection hydrocephalus. The objective of this study was to establish, in a historical cohort study of pediatric patients who underwent primary craniotomy for PFT resection, whether or not pre-resection ETV prevents the need for post-resection CSF diversion to manage hydrocephalus. The authors interrogated their prospectively maintained surgical neuro-oncology database to find all primary PFT resections from a single tertiary pediatric neurosurgery unit. These data were reviewed and supplemented with data from case notes and radiological review. The modified Canadian Preoperative Prediction Rule for Hydrocephalus (mCPPRH) score was retrospectively calculated for all patients. The primary outcome was the need for any form of postoperative CSF diversion within 6 months of PFT resection (including ventriculoperitoneal shunting, ETV, external ventricular drainage [EVD], and lumbar drainage [LD]). This was considered an ETV failure in the ETV group. The secondary outcomes were time to CSF diversion, shunt dependence at 6 months, and complications of ETV. Statistical analysis was done in RStudio, with significance defined as p < 0.05. A total of 95 patients were included in the study. There were 28 patients in the ETV group and 67 in the non-ETV group. Patients in the ETV group were younger (median age 5 vs 7 years, p = 0.04) and had more severe preoperative hydrocephalus (mean frontal-occipital horn ratio 0.45 vs 0.41 in the non-ETV group, p = 0.003) and higher mCPPRH scores (mean 4.42 vs 2.66, p < 0.001). The groups were similar in terms of sex and tumor histology. The overall rate of post-resection CSF diversion of any kind (shunt, repeat ETV, LD, or EVD) in the entire cohort was 25.26%. Post-resection CSF diversion was needed in 32% of patients in the ETV group and in 22% of the patients in the non-ETV group (p > 0.05). Shunt dependence at 6 months was seen in 21% of the ETV group and 16% of the non-ETV group (p > 0.05). The median time to ETV failure was 9 days. ETV failure correlated with patients with ependymoma (p = 0.02). Children who had ETV failure had higher mCPPRH scores than the ETV success group (5.67 vs 3.84, p = 0.04). Pre-resection ETV did not reliably prevent the need for post-resection CSF diversion. ETV was more likely to fail in children with ependymoma and those with higher mCPPRH scores. Based on the findings of this study, the authors will change the practice at their institution; pre-resection ETV will now be performed based on a newly defined protocol.

Role of magnetic resonance imaging in diagnosis of pediatric posterior fossa tumors

Objective The aim was to study the role of MRI in diagnosis of pediatric posterior fossa tumors. Background Brain tumors represent the most common solid neoplasms in children and the second most common pediatric malignancy following leukemia. Patients and methods A retrospective study was conducted on 25 pediatric patients with known brain posterior fossa masses, who ranged in age from 1 to 15 years and had suspected posterior fossa tumor by computed tomography. All participants attended the MR unit of Radiology Department, Menoufia University, Menoufia Governorate, during the period from October 2016 to November 2017. Complete history taking, clinical examination, and MR data were compared with histopathology obtained from all patients. Results The mean age of the cases was 7.2 ± 3.9 years. The most common tumors were medulloblastoma (MB) and pilocytic astrocytoma. MB showed restricted diffusion with low apparent diffusion coefficient value, and pilocytic astrocytoma showed free diffusion with higher apparent diffusion coefficient value. High-grade tumors such as MB and brain stem glioma showed elevated choline and reduced N-acetyl aspartate in magnetic resonance spectroscopy curve. Low-grade tumors such as low-grade glioma showed mild rise of choline and mild reduction of creatine in magnetic resonance spectroscopy curve. Conclusion Conventional MRI provided limited information regarding tumor type and grade, falling short as a definitive diagnostic examination. Advanced brain MRI techniques provided incremental diagnostic value over conventional MRI. However, no single advanced technique was perfect, but different techniques typically complement one another.

Postural balance in pediatric posterior fossa tumor survivors: Through impairments to rehabilitation possibilities

BackgroundThe rehabilitation after pediatric brain tumors is a pressing issue in current neuro-oncology. The purpose of this study was to reveal the peculiarities of postural stability in pediatric posterior fossa tumor survivors as compared to the healthy controls. Additionally, we aimed to determine the feasibility of the balance biofeedback training for these patients. MethodsWe measured 6 postural stability parameters with the eyes opened and closed in 35 patients and 25 healthy controls aged 7–17. Further, the patients were divided into two groups: the intervention and waitlist. The intervention group was the first to undergo a 2-week biofeedback training designed to enhance balance control, while the waitlist group performed only the usual exercises. Then the groups were interchanged. Pre- and post-stability scores were measured in each condition. FindingsThe current results suggest the pronounced deficiency of stability in the patients. Their results in both opened and closed eyes conditions were similar. The post-training measurements revealed that some stability parameters were improved: ellipse square and mean root square oscillations in the frontal and sagittal planes. InterpretationThe patients predictably demonstrated the significantly worse stability measurements as compared to the healthy controls. Moreover, they were shown not to use visual information to correct postural balance thus prompting us to assume severe deficits of the eye movements control due to the cerebellar pathology. This specificity, as well as the post-training significant improvement, emphasizes the clinical necessity to consider them when designing the rehabilitation protocols for posterior fossa tumor survivors.

Surgical Management of Tumors Involving the Cerebello-Medullary Angle: Anatomical Classification, Technique and Retrospective Analysis of 90 Pediatric Patients

Abstract INTRODUCTION Extent of resection (EOR) remains the most crucial factor in determining long-term and progression-free survivals for most pediatric posterior fossa tumors. The lateral cerebello-medullary region harbors complex anatomical relationships, making radical resection challenging. Indeed, the cerebella-medullary angle (CMA) was found to be a common area for residual disease in ependymomas and medulloblastomas. We examine a series of pediatric tumors in the region, and classify them anatomically regardless of their pathological diagnosis. METHODS We reviewed preoperative MRI scans of 347 elective posterior fossa craniotomies performed at Le Bonheur Children's Hospital between January 2010 and June 2018. We defined the lateral cerebellomedullary angle (CMA) as the region involving the foramen of Luschka (FL) and/or the cerebellomedullary cistern (CMC). Tumors in that area were classified according to their extension: type 1 (FL), 2 (CMC), 3A (premedullary cistern), 3B (cerebellopontine angle), and 3C (all compartments). Demographic, preoperative, intraoperative, and postoperative data were recorded. The primary endpoints were EOR and any resultant surgical complications. RESULTS A total of 90 patients met inclusion criteria, of which 37 (41%) had prior surgery with residual disease. Ependymomas (45%) and medulloblastomas (27%) formed the majority of tumors. There were 25 type 1 tumors, 23 type 2, and 42 patients type 3 tumors. Cerebella-Medullary fissure dissection was necessary in all cases, but type 2 and 3 tumors were more likely to be treated using an extended or a lateral sub occipital approach (P = .04). Residual disease on intraoperative and immediate postoperative MRI requiring re-exploration was consistent with the anatomical type, and occurred more frequently in type 3 (P = .043). However, gross-total or near-total resection was achieved in 81% of cases, with no intergroup difference. Group 3 had more postoperative cranial nerve (CN) deficits (P = .0003) with longer ICU stays (P = .01). CONCLUSION Although modern research is shifting towards molecular and genomic subtyping, anatomical factors remain the most crucial determinant of EOR. Lateral tumors can exhibit different genetic, anatomic and clinical characteristics compared to median tumors, but may be sub-classified further based on their anatomical extension. Such sub-classification has implications on residual disease in predictable anatomical blind spots, approach selection, and expected postoperative deficits.

Predictors of Posterior Fossa Syndrome: Results From an International Multicenter Cohort Study of Molecularly Characterized Medulloblastoma Patients

Abstract INTRODUCTION Posterior Fossa Syndrome (PFS) is a common complication following surgical resection of pediatric posterior fossa tumors. PFS is characterized by a combination of mutism, ataxia, and other behavioral symptoms that typically improves within weeks to months. Medulloblastoma histology, midline location, and brainstem invasion increase risk for PFS. Medulloblastoma subgroups have historically been treated as a single entity when assessing PFS risk, however, recent studies highlighting their clinical heterogeneity suggest the need for a subgroup-specific analysis of PFS risk. Here, we examine a large international multicenter cohort of molecularly characterized medulloblastoma patients to assess predictors of PFS. METHODS We assembled a cohort of 270 medulloblastoma patients from 4 sites including Christian Medical College and Hospital (n = 87), Great Ormond Street Hospital (n = 25), Hospital for Sick Kids (n = 111), and Stanford University Medical Center (n = 47), who underwent surgical treatment of medulloblastoma and had molecular subgrouping of their tumors. Patient age at diagnosis, gender, tumor volume, and PFS status were assessed in addition to molecular subgroup. RESULTS Overall, 25.9% of our cohort developed PFS. PFS patients were younger (mean difference −2.73 yr ± 0.8, P = .0009) and had larger tumors (mean difference 16.99 cm3 ± 5.287, P = .0015) that were more midline (OR = 20.03, P &lt; .0001). On multivariate analysis adjusting for age, sex, midline location, and tumor volume, WNT (adjusted OR = 5.19, P = .022) and Group 4 (adjusted OR = 7.15, P = .004) tumors were found to be independently associated with higher risk of PFS as compared to SHH tumors. CONCLUSION Here, we present the largest molecularly characterized cohort of medulloblastoma patients in the context of PFS development. In combination with recent data showing that WNT and Group 4 tumors have a longer pre-diagnostic interval our results support the hypothesis that large midline tumors that grow slowly have a higher risk of PFS.

Machine learning methods for MRI biomarkers analysis of pediatric posterior fossa tumors

Medical imaging technologies provide an increasing number of opportunities for disease prediction and prognosis. Specifically, imaging biomarkers can quantify the entire tumor phenotypes to enhance the prediction. Machine learning technology can be explored to mine and analyze these biomarkers and to establish predictive models for the clinical applications. Several studies have applied various machine learning methods to imaging biomarkers based clinical predictions of different diseases. Here we seek to evaluate different machine learning methods in pediatric posterior fossa tumor prediction. We present a machine learning based magnetic resonance imaging biomarkers analysis framework for two kinds of pediatric posterior fossa tumors. In details, three feature extraction methods are used to obtain 300 imaging biomarkers. 10 feature selection methods and 11 classifiers are evaluated by the quantified predictive performance and stability, and importance consistency of features and the influence of the experimental factors are also analyzed. Our results demonstrate that the CFS feature selection method (accuracy: 83.85±5.51%, stability: [0.84, 0.06]) and SVM classifier (accuracy: 85.38±3.47%, RSD: 4.77%) show relatively better performance than others and should be preferred. Among all the biomarkers, 17 texture features seem to be more important. Multifactor analysis results indicate the choice of classifier accounts for the most contribution to the variability in performance (37.25%). The machine learning based framework is efficient for pediatric posterior fossa tumors biomarkers analysis and could provide valuable references and decision support for assisted clinical diagnosis.

EFFECTIVENESS OF DIFFUSION WEIGHTED MRI DERIVED METRICS IN DIFFERENTIATION OF PEDIATRIC POSTERIOR FOSSA TUMORS

Background: The value of diffusion weighted imaging (DWI) in differentiation of pediatric posterior fossa tumors (PFTs)has been established previously, however most studies were limited only to the most common types of PFTs and their results were contradictory.. Aim of work: The aim of this study was to investigate the effectiveness of DWI in differentiation of PFTs taking care to include the less frequent types, and to clarify previously reported debatable findings. Patients and methods: We retrospectively analyzed 13 embryonal tumors (EMBTs), 4 ependymomas (EPNs),8 low grade gliomas (LGGs),2 mixed neuronal glial tumors (MNGTs), and 5 diffuse intrinsic pontine gliomas (DIPGs) . For all tumors, absolutemean ADC of the non necrotic enhancing portions of the tumor and ADC ratios of the solid enhancing region of the tumor to the ADC of normal appearing cerebellum were generated. The ADC metrics of the various groups (designated according to histological subtype and WHO grade) were compared using the kruskal – wallis and student-ttests. Receiver operating characteristic (ROC) curve analysis was used to generate cutoff absolute ADC values and ADC ratios for differentiation of different types of PFTs Results: Mean ADC values and ADC ratios were significantly lower in high than in low grade tumors (P 1.108× 10−3 (100% sensitivity and 92.3% specificity)but not with mean ADC values and from LGGs using a cutoff mean ADC value of ≤ 1.333 (100% sensitivity and specificity). No statistically significant difference (P >0.05) was seen between the mean ADC values of MNGTs (1.5+/-0.02) and LGGs (1.71+/-0.13) with wide overlap in their range of ADC values and ratios.Conclusion: Apart from a few exceptions, absolute ADC values and ratios go a long way in enabling pre-operative differentiation of different types of PFTs.

P.095 Novel use of fluorescein sodium in the resection of a pediatric posterior fossa tumor

Background: Gross total resection of pediatric posterior fossa tumors is paramount towards improving progression-free survival.Fluorescein accumulates in tumoral tissue, where the blood-brain barrier is disrupted. It can therefore potentially aid in differentiating tumoral versus normal tissue. We aimed to evaluate the efficacy of fluorescent-guidance (using fluorescein) towards the resection of a pediatric cerebellar tumor, as the index case at our institution using this technique. Methods: 5 mg/kg of IV fluorescein sodium was injected upon induction of general anesthesia. During tumor resection, a yellow 560-nm filter (Kinevo microscope, Zeiss) was employed for fluorescent-guidance. The extent of resection was assessed via post-operative MRI. Results: There were no adverse side effects experienced by the patient. Tumoral material was clearly visualized under the yellow 560-nm filter, allowing for satisfactory gross total resection of the lesion (confirmed on post-operative MRI). Preliminary pathology was consistent with medulloblastoma. Conclusions: Fluorescent-guided resection of pediatric posterior fossa tumors appears to be a safe and useful adjunct for gross total resection of these lesions. To the best of our knowledge, this is the first reported case in Canada wherein IV fluorescein was used under a yellow 560-nm filter for resection of a posterior fossa medulloblastoma in a child.

Cognitive and Motor Training in Pediatric Posterior Fossa Tumor Survivors

Cognitive and Motor Training in Pediatric Posterior Fossa Tumor Survivors

Endoscopic third ventriculostomy prior to resection of posterior fossa tumors in children.

Hydrocephalus is a common presenting symptom of pediatric posterior fossa tumors and often requires permanent cerebrospinal fluid diversion even after resection. Endoscopic third ventriculostomy (ETV) is a well-established treatment of obstructive hydrocephalus in children. The objective of this study is to demonstrate that ETV prior to posterior fossa tumor resection decreases the rate of postoperative ventriculoperitonal shunt (VPS) placement. We performed a retrospective analysis of patients who presented with hydrocephalus and underwent posterior fossa tumor resection between 2005 and 2016 excluding pineal and tectal tumors. The rate of postoperative VPS placement was compared in patients who underwent resection and had a VPS placed perioperatively (historical controls) with patients who underwent ETV prior to resection. The two groups were matched for demographics, tumor histology, and tumor location. We also performed a literature review of prior studies that examined the role of ETV in pediatric posterior fossa tumors. Thirty-six patients in the control group were compared to 38 patients in our study. The patients were matched across all variables (age, gender, tumor histology, and tumor locations). The rate of postoperative VPS placement was 31% in the control group compared to 16% in the ETV group. No complications were encountered during ETV. Endoscopic third ventriculostomy prior to posterior fossa tumor resection in children appears to decrease the rate of postoperative VPS placement. Given its efficacy and safety, ETV should be considered prior to tumor resection in these patients.

A case of pediatric infratentorial oligodendroglioma

Pediatric posterior fossa tumors most commonly are pilocytic astrocytomas (PA), ependymomas, medulloblastomas, and atypical teratoid rhabdoid tumor (ATRT). MRI has some special radiological findings which can be used in the differential diagnosis. We report on the radiologic images and the clinical course of a 3 year-old-girl with oligodendroglial tumor arising from the cerebellum. There were no focal deficits in the neurological examination. MRI revealed a left cerebellar lesion extending into the left cerebellopontine region causing a pressure and shift in the fourth ventricle, pons and mesencephalon. She underwent a left occipital craniectomy and total tumor decompression. In the pathological examination, mainly oligodendroglial cells were seen in the tumor and they had round nucleus and perinuclear halos. No recurrence was detected at MRI and CT at 6 months postoperatively. Except for the following most common tumors as PA, ependymoma, medulloblastoma and AT/RT in the posterior fossa, the oligodendroglioma must be considered in the differential diagnosis.

Visual Complications of Pediatric Posterior Fossa Tumors: Analysis of Outcomes

ObjectiveVisual abnormalities are common among children with posterior fossa tumors, resulting from disruption of ocular afferent and efferent systems due to the tumor or surgery. This study describes the visual complications and outcomes associated with these tumors. MethodsClinical and radiographic data of patients who underwent index surgery for resection of posterior fossa tumor from 2007 to 2016 were reviewed. Descriptive statistics, univariate, and multivariate regression were performed to assess factors contributing to visual acuity and postoperative strabismus. ResultsThere were 182 patients who underwent posterior fossa craniotomy for neoplasm were included. Ophthalmologic symptoms were the fourth most common presenting complaint; initial ophthalmologic examination was abnormal in 40% of patients. Evaluation of visual acuity demonstrated a good outcome in 88% of patients following treatment. The most common postoperative oculomotor finding was esotropia (29%) which resolved spontaneously in more than half of patients. A good outcome was obtained in all patients who underwent surgery for esotropia. Hypertropia was noted in 14% of the cohort and less than half resolved spontaneously; less than half undergoing strabismus surgery for hypertropia had a good outcome. Multivariate analysis confirmed the association between cerebellar mutism and postoperative esotropia and hypertropia. Clinically significant pathological nystagmus was seen in 8% of the cohort. ConclusionsOur results indicate a good visual outcome in the majority of pediatric patients undergoing resection of posterior fossa tumors. Ophthalmologic complications should be appropriately evaluated and addressed to allow for the best possible vision to survivors of posterior fossa tumors.