CT and MR imaging findings in adults with cerebellar medulloblastoma: comparison with findings in children

Extra-axial desmoplastic/nodular medulloblastoma in adult mimicking cerebellar metastasis: reappraisal of this rare presentation with literature review

Introduction and importance

Medulloblastomas are the most common malignant intra-axial brain tumour in paediatric patients and represent 35-40% of posterior fossa tumour types in children between 3 and 9 years of age. Medulloblastomas may also be found in adulthood. These tumours are classified into two groups according to its molecular characteristics and histological type. The desmoplastic/nodular subtype is the second common subtype after the classic one. Only three cases of desmoplastic/nodular extra-axial medelloblastoma have been previously reported in the literature originating from to the cerebellopontine angle.

Case presentation

The authors report a new case of an extra-axial desmoplastic/nodular cerebellar medulloblastoma originating outside the cerebellopontine angle and mimicking a solitary cerebellar metastasis in a 49-year-old female patient who presented for a raised intracranial pressure and cerebellar syndrome.

Clinical discussion

Medulloblastoma is a malignant embryonal intra-axial tumour of the cerebellum or posterior brain stem that occurs mainly in children. Medulloblastomas may also be found in adulthood. Desmoplastic/nodular medulloblastoma is the second most common type of all medulloblastomas. The intra-axial form is always predominant. Only three cases of extra-axial desmoplastic/nodular medulloblastoma have been reported in the literature. The authors will go through the literature to dissect this rare entity.

Conclusion

Although considered a common paediatric intra-axial tumour, there are increasing numbers of solitary cases reporting an extra-axial presentation in different locations of the posterior cerebral fossa even in adulthood. These rare and unusual presentations and locations may mislead the correct diagnosis and delay treatment.

Adult Medulloblastoma: Updates on Current Management and Future Perspectives

Medulloblastoma (MB) is a malignant embryonal tumor of the posterior fossa belonging to the family of primitive neuro-ectodermic tumors (PNET). MB generally occurs in pediatric age, but in 14–30% of cases, it affects the adults, mostly below the age of 40, with an incidence of 0.6 per million per year, representing about 0.4–1% of tumors of the nervous system in adults. Unlike pediatric MB, robust prospective trials are scarce for the post-puberal population, due to the low incidence of MB in adolescent and young adults. Thus, current MB treatments for older patients are largely extrapolated from the pediatric experience, but the transferability and applicability of these paradigms to adults remain an open question. Adult MB is distinct from MB in children from a molecular and clinical perspective. Here, we review the management of adult MB, reporting the recent published literature focusing on the effectiveness of upfront chemotherapy, the development of targeted therapies, and the potential role of a reduced dose of radiotherapy in treating this disease.

The Current State of Radiotherapy for Pediatric Brain Tumors: An Overview of Post-Radiotherapy Neurocognitive Decline and Outcomes

Tumors of the central nervous system are the most common solid malignancies diagnosed in children. While common, they are also found to have some of the lowest survival rates of all malignancies. Treatment of childhood brain tumors often consists of operative gross total resection with adjuvant chemotherapy or radiotherapy. The current body of literature is largely inconclusive regarding the overall benefit of adjuvant chemo- or radiotherapy. However, it is known that both are associated with conditions that lower the quality of life in children who undergo those treatments. Chemotherapy is often associated with nausea, emesis, significant fatigue, immunosuppression, and alopecia. While radiotherapy can be effective for achieving local control, it is associated with late effects such as endocrine dysfunction, secondary malignancy, and neurocognitive decline. Advancements in radiotherapy grant both an increase in lifetime survival and an increased lifetime for survivors to contend with these late effects. In this review, the authors examined all the published literature, analyzing the results of clinical trials, case series, and technical notes on patients undergoing radiotherapy for the treatment of tumors of the central nervous system with a focus on neurocognitive decline and survival outcomes.

New Developments in the Pathogenesis, Therapeutic Targeting, and Treatment of Pediatric Medulloblastoma

Pediatric medulloblastoma (MB) is the most common pediatric brain tumor with varying prognoses depending on the distinct molecular subtype. The four consensus subgroups are WNT, Sonic hedgehog (SHH), Group 3, and Group 4, which underpin the current 2021 WHO classification of MB. While the field of knowledge for treating this disease has significantly advanced over the past decade, a deeper understanding is still required to improve the clinical outcomes for pediatric patients, who are often vulnerable in ways that adult patients are not. Here, we discuss how recent insights into the pathogenesis of pediatric medulloblastoma have directed current and future research. This review highlights new developments in understanding the four molecular subtypes’ pathophysiology, epigenetics, and therapeutic targeting. In addition, we provide a focused discussion of recent developments in imaging, and in the surgery, chemotherapy, and radiotherapy of pediatric medulloblastoma. The article includes a brief explanation of healthcare costs associated with medulloblastoma treatment.

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

BACKGROUND

Among 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.

OBJECTIVES

This 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.

METHODS

All 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.

RESULTS

The 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.

CONCLUSION

This 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.

Magnetic resonance spectroscopy in posterior fossa tumours: the tumour spectroscopic signature may improve discrimination in adults among haemangioblastoma, ependymal tumours, medulloblastoma, and metastasis

OBJECTIVES

Assessing a posterior fossa tumour in an adult can be challenging. Metastasis, haemangioblastoma, ependymal tumours, and medulloblastoma are the most common diagnostic possibilities. Our aim was to evaluate the contribution of magnetic resonance spectroscopy (MRS) in the diagnosis of these entities.

METHODS

We retrospectively evaluated 56 consecutive patients with a posterior fossa tumour and histological diagnosis of ependymal tumour, medulloblastoma, haemangioblastoma, and metastasis in which good-quality spectra at short (TE 30 ms) or/and intermediate (TE, 136 ms) TE were available. Spectra were compared using the Mann-Whitney U non-parametric test in order to select the spectral datapoints and the intensity ratios that showed significant differences between groups of lesions. Performance of these datapoints and their ratios were assessed with ROC curves.

RESULTS

The most characteristic signatures on spectroscopy were high choline (Cho) in medulloblastoma (p < 0.001), high myoinositol (mIns) in ependymal tumours (p < 0.05), and high lipids (LIP) in haemangioblastoma (p < 0.01) and metastasis (p < 0.01). Selected ratios between normalised intensity signals of resonances provided accuracy values between 79 and 95% for pairwise comparisons. Intensity ratio NI_{3.21ppm/3.55ppm} provided satisfactory discrimination between medulloblastoma and ependymal tumours (accuracy, 92%), ratio NI_{2.11ppm/1.10ppm} discriminated ependymal tumours from haemangioblastoma (accuracy, 94%), ratio NI_{3.21ppm/1.13ppm} discriminated haemangioblastoma from medulloblastoma (accuracy, 95%), and ratio NI_{1.28ppm/2.02pmm} discriminated haemangioblastoma from metastasis (accuracy, 83%).

CONCLUSIONS

MRS may improve the non-invasive diagnosis of posterior fossa tumours in adults.

KEY POINTS

• High choline suggests a medulloblastoma in a posterior fossa tumour. • High myoinositol suggests an ependymal lesion in a posterior fossa tumour. • High lipids suggest a metastasis or a haemangioblastoma in a posterior fossa tumour.

Imaging features of medulloblastoma: Conventional imaging, diffusion-weighted imaging, perfusion-weighted imaging, and spectroscopy: From general features to subtypes and characteristics

Medulloblastoma is a frequent high-grade neoplasm among pediatric brain tumours. Its classical imaging features are a midline tumour growing into the fourth ventricle, hyperdense on CT-scan, displaying a hypersignal when using diffusion-weighted imaging, with a variable contrast enhancement. Nevertheless, atypical imaging features have been widely reported, varying according to the age of the patient, and histopathological subtype. In this study, we review the classical and atypical imaging features of medulloblastomas, with emphasis on advanced MRI techniques, histopathological and molecular subtypes and characteristics, and follow-up modalities.

Imaging Biomarkers for Adult Medulloblastomas: Genetic Entities May Be Identified by Their MR Imaging Radiophenotype

BACKGROUND AND PURPOSE

The occurrence of medulloblastomas in adults is rare; nevertheless, these tumors can be subdivided into genetic and histologic entities each having distinct prognoses. This study aimed to identify MR imaging biomarkers to classify these entities and to uncover differences in MR imaging biomarkers identified in pediatric medulloblastomas.

MATERIALS AND METHODS

Eligible preoperative MRIs from 28 patients (11 women; 22-53 years of age) of the Multicenter Pilot-study for the Therapy of Medulloblastoma of Adults (NOA-7) cohort were assessed by 3 experienced neuroradiologists. Lesions and perifocal edema were volumetrized and multiparametrically evaluated for classic morphologic characteristics, location, hydrocephalus, and Chang criteria. To identify MR imaging biomarkers, we correlated genetic entities sonic hedgehog (SHH) TP53 wild type, wingless (WNT), and non-WNT/non-SHH medulloblastomas (in adults, Group 4), and histologic entities were correlated with the imaging criteria. These MR imaging biomarkers were compared with corresponding data from a pediatric study.

RESULTS

There were 19 SHH TP53 wild type (69%), 4 WNT-activated (14%), and 5 Group 4 (17%) medulloblastomas. Six potential MR imaging biomarkers were identified, 3 of which, hydrocephalus (P = .03), intraventricular macrometastases (P = .02), and hemorrhage (P = .04), when combined, could identify WNT medulloblastoma with 100% sensitivity and 88.3% specificity (95% CI, 39.8%-100.0% and 62.6%-95.3%). WNT-activated nuclear β-catenin accumulating medulloblastomas were smaller than the other entities (95% CI, 5.2-22.3 cm³ versus 35.1-47.6 cm³; P = .03). Hemorrhage was exclusively present in non-WNT/non-SHH medulloblastomas (P = .04; n = 2/5). MR imaging biomarkers were all discordant from those identified in the pediatric cohort. Desmoplastic/nodular medulloblastomas were more rarely in contact with the fourth ventricle (4/15 versus 7/13; P = .04).

CONCLUSIONS

MR imaging biomarkers can help distinguish histologic and genetic medulloblastoma entities in adults and appear to be different from those identified in children.

Distinctive localization and MRI features correlate of molecular subgroups in adult medulloblastoma

Medulloblastoma (MB) is recognized as comprising four molecular subgroups with distinct transcriptional profiles, clinical features, and outcomes. Previous studies demonstrate that pediatric MBs present with subgroup-specific MRI manifestations. We hypothesized that combination of anatomical localization and conventional features based on MR imaging can predict these subgroups in adult MBs. MR Imaging manifestations of 125 adult patients with MB were analyzed retrospectively based on pre-operative MRI scans. MB molecular subgroups were evaluated by the expression profiling array and immunohistochemistry. A pediatric MB cohort of 60 patients were analyzed for comparison with data of adult patients. Multiple logistic regression analysis revealed that tumor location (P < 0.0001) and pattern of enhancement (P = 0.0048) were significantly correlated with molecular subgroups in adult MBs. Ninety-two percent of adult MBs were correctly predicted by using logistic regression model based on the anatomical localization patterns and pattern of enhancement. Exclusively intra-cerebellar growth, localization in the rostral cerebellum, and no brainstem contact were specific to adult SHH-MBs. Group 4-MBs in adult were characterized by minimal/no enhancement compared with other two subgroups. Infant SHH-MBs represented significant different localization patterns compared with SHH tumors in children and adults. We identified that molecular subgroups of adult MBs could be well predicted by tumor localization patterns and enhancement pattern. Our study also provided important evidence that MB subgroups in adult possibly derived from different cellular origins.

Adult Brain Tumors: Clinical Applications of Magnetic Resonance Spectroscopy

Proton magnetic resonance spectroscopy (H-MRS) may be helpful in suggesting tumor histology and tumor grade and may better define tumor extension and the ideal site for biopsy compared with conventional magnetic resonance (MR) imaging. A multifunctional approach with diffusion-weighted imaging, perfusion-weighted imaging, and permeability maps, along with H-MRS, may enhance the accuracy of the diagnosis and characterization of brain tumors and estimation of therapeutic response. Integration of advanced imaging techniques with conventional MR imaging and the clinical history help to improve the accuracy, sensitivity, and specificity in differentiating tumors and nonneoplastic lesions.

Posterior Fossa Tumors

Pediatric brain tumors are the leading cause of death from solid tumors in childhood. The most common posterior fossa tumors in children are medulloblastoma, atypical teratoid/rhabdoid tumor, cerebellar pilocytic astrocytoma, ependymoma, and brainstem glioma. Location, and imaging findings on computed tomography (CT) and conventional MR (cMR) imaging may provide important clues to the most likely diagnosis. Moreover, information obtained from advanced MR imaging techniques increase diagnostic confidence and help distinguish between different histologic tumor types. Here we discuss the most common posterior fossa tumors in children, including typical imaging findings on CT, cMR imaging, and advanced MR imaging studies.

Adult medulloblastoma: A rare case report and literature review

Background:

Medulloblastoma is a highly malignant embryonal tumor which commonly arises in the cerebellum. It is relatively rare and accounts for less than 2% of all primary brain tumors. The tumor primarily occurs in childhood; however, rarely, it may be found in adult population. In addition, medulloblastoma in adult population shows features which are quite distinct from the pediatric group.

Case Description:

We report the case of a 33-year-old man who presented to our institution with a history of blurred vision of both eyes for 5 months preceded by intermittent headache since the previous year. Preoperative investigation suggested a posterior fossa mass and we suspected an ependymoma. The patient underwent ventriculoperitoneal shunt and craniotomy tumor removal, followed by radiotherapy. Histopathological and immunohistochemical examination were performed, and the results showed a diagnosis of medulloblastoma.

Conclusion:

This case is exceptional because adult medulloblastoma occurrence in our center is extremely rare, and the diagnosis can only be established through histopathological and immunohistochemical studies.

The Neuroradiological Spectra of Adult and Pediatric Medulloblastoma Differ : Results from a Literature-based Meta-analysis

PURPOSE

Current knowledge on the spectrum of the neuroradiological appearance of adult medulloblastoma is sparse. Due to the rarity of the disease, adult patients were generally diagnosed and treated similar to children; however, pediatric and adult medulloblastomas display substantial molecular differences that may influence the neuroradiological phenotype. This study therefore aimed at assessment of the neuroradiological spectrum of adult medulloblastoma in comparison to pediatric tumors.

METHODS

All available publications on adult medulloblastoma published until June 2013 were screened for imaging data on single patients. A total of 109 patients were identified and compared to 118 pediatric patients described in 4 cohorts.

RESULTS

The average age of the adult patients was 34.3 years. Most adult medulloblastomas (57.6 %) were localized laterally (vs. 14.4 % in pediatric patients). On T1-weighted sequences, only 41.1 % of all adult medulloblastomas appeared hypointense (vs. 89.3 %) and 69.6 % were hyperintense on T2 sequences (vs. 83 %). In contrast to pediatric patients only 53.3 % showed strong contrast enhancement (pediatric patients 77.1 %), while the contrast uptake of the remainder was described as subtle, moderate or lacking. Contrast enhancement was more often described as inhomogeneous in adults (35.5 % as compared to 15.2 % in children) and 26.4 % had cysts.

CONCLUSION

Although the neuroradiological spectrum of medulloblastoma in adults was similar to children, an atypical presentation with inhomogeneous contrast enhancement, more hyperintense signal on T1 and a more hypointense signal on T2-weighted sequences was common. Given the rarity of the tumor, awareness of these differences constitutes a prerequisite to avoid delays in diagnostics.

Fatal cerebellar hemorrhage as an initial presentation of medulloblastoma in a child

Children with medulloblastomas most commonly present with signs and symptoms of elevated intracranial pressure due to obstructive hydrocephalus, especially headaches and vomiting. However, some pediatric patients present with sudden neurological deterioration due to intracerebellar hemorrhage associated with medulloblastoma, although very few reports exist that document this phenomenon. An 8-year-old girl was admitted to our emergency department who presented with sudden loss of consciousness, vomiting, and bradycardia. The neuroradiological evaluation revealed a hemorrhagic mass lesion in the posterior fossa. Urgent evacuation of the hematoma was performed. The postoperative course was uneventful, and the postoperative histopathological examination revealed the lesion to be a medulloblastoma. This report presents an unusual case of a medulloblastoma presenting with fatal intracranial hemorrhage in a child. The clinical features and intraoperative and pathologic findings of the case are discussed.

Clinical, radiological, and pathological features in 43 cases of intracranial subependymoma

OBJECT

Intracranial subependymomas are rarely reported due to their extremely low incidence. Knowledge about subependymomas is therefore poor. This study aimed to analyze the incidence and clinical, radiological, and pathological features of intracranial subependymomas.

METHODS

Approximately 60,000 intracranial tumors were surgically treated at Beijing Tiantan Hospital between 2003 and 2013. The authors identified all cases in which patients underwent resection of an intracranial tumor that was found to be pathological examination demonstrated to be subependymoma and analyzed the data from these cases.

RESULTS

Forty-three cases of pathologically confirmed, surgically treated intracranial subependymoma were identified. Thus in this patient population, subependymomas accounted for approximately 0.07% of intracranial tumors (43 of an estimated 60,000). Radiologically, 79.1% (34/43) of intracranial subependymomas were misdiagnosed as other diseases. Pathologically, 34 were confirmed as pure subependymomas, 8 were mixed with ependymoma, and 1 was mixed with astrocytoma. Thirty-five patients were followed up for 3.0 to 120 months after surgery. Three of these patients experienced tumor recurrence, and one died of tumor recurrence. Univariate analysis revealed that shorter progression-free survival (PFS) was significantly associated with poorly defined borders. The association between shorter PFS and age < 14 years was almost significant (p = 0.51), and this variable was also included in the multivariate analysis. However, multivariate analysis showed showed only poorly defined borders to be an independent prognostic factor for shorter PFS (RR 18.655, 95% CI 1.141–304.884, p = 0.040). In patients 14 years of age or older, the lesions tended to be pure subependymomas located in the unilateral supratentorial area, total removal tended to be easier, and PFS tended to be longer. In comparison, in younger patients subependymomas tended to be mixed tumors involving the bilateral infratentorial area, with a lower total removal rate and shorter PFS.

CONCLUSIONS

Intracranial subependymoma is a rare benign intracranial tumor with definite radiological features. Long-term survival can be expected, although poorly defined borders are an independent predictor of shorter PFS. All the features that differ between tumors in younger and older patients suggest that they might have different origins, biological behaviors, and prognoses.

An adult multifocal medulloblastoma with diffuse acute postoperative cerebellar swelling: immunohistochemical and molecular genetics analysis

Medulloblastoma (MB), the most common malignant tumor typically affecting children, occurs only exceptionally in adults. Multifocal presentation of this malignancy in adulthood is even much rarer—only four cases with favorable postoperative course have been reported, so far. The study illustrates a very rare rapid postoperative clinical deterioration due to diffuse cerebellar swelling (DCS) in an adult multifocal MB (MMB). To the best of their knowledge, authors for the first time performed genetic analysis of MMB and demonstrated expression patterns of selected markers that put the patient within the sonic hedgehog (SHH) molecular subgroup and at least partially explain her unsatisfactory clinical course. Herein, authors summarized the relevant literature concerning this issue with the aim to determine features that would facilitate diagnosis and therapy of such a scarce clinical entity.

MRI surrogates for molecular subgroups of medulloblastoma

BACKGROUND AND PURPOSE

Recently identified molecular subgroups of medulloblastoma have shown potential for improved risk stratification. We hypothesized that distinct MR imaging features can predict these subgroups.

MATERIALS AND METHODS

All patients with a diagnosis of medulloblastoma at one institution, with both pretherapy MR imaging and surgical tissue, served as the discovery cohort (n = 47). MR imaging features were assessed by 3 blinded neuroradiologists. NanoString-based assay of tumor tissues was conducted to classify the tumors into the 4 established molecular subgroups (wingless, sonic hedgehog, group 3, and group 4). A second pediatric medulloblastoma cohort (n = 52) from an independent institution was used for validation of the MR imaging features predictive of the molecular subtypes.

RESULTS

Logistic regression analysis within the discovery cohort revealed tumor location (P < .001) and enhancement pattern (P = .001) to be significant predictors of medulloblastoma subgroups. Stereospecific computational analyses confirmed that group 3 and 4 tumors predominated within the midline fourth ventricle (100%, P = .007), wingless tumors were localized to the cerebellar peduncle/cerebellopontine angle cistern with a positive predictive value of 100% (95% CI, 30%-100%), and sonic hedgehog tumors arose in the cerebellar hemispheres with a positive predictive value of 100% (95% CI, 59%-100%). Midline group 4 tumors presented with minimal/no enhancement with a positive predictive value of 91% (95% CI, 59%-98%). When we used the MR imaging feature-based regression model, 66% of medulloblastomas were correctly predicted in the discovery cohort, and 65%, in the validation cohort.

CONCLUSIONS

Tumor location and enhancement pattern were predictive of molecular subgroups of pediatric medulloblastoma and may potentially serve as a surrogate for genomic testing.

Pediatric brain tumors

Pediatric brain tumors are the most common solid tumor of childhood. This article focuses on the metabolic signature of common pediatric brain tumors using MR spectroscopic analyses.

Choroid plexus tumours: classification, MR imaging findings and pathological correlation

INTRODUCTION

Choroid plexus tumours (CPTs) are extremely rare intraventricular neoplasms and are prone to bleeding during surgery. The purpose of this study was to summarise the MR imaging characteristics of 13 CPT cases.

METHODS

Magnetic resonance images of 13 patients (six men and seven women; mean age 21.1 years) with pathologically proved CPTs were retrospectively reviewed. MR findings of the tumours were evaluated, with emphasis on their location, size, shape, internal architecture, margin and pattern and degree of enhancement. Differences in signal intensity characteristics were also investigated on MR images and analysed according to histological subtypes.

RESULTS

Lesions were in the lateral ventricles (n = 7), fourth ventricle (n = 5) and cisterna magna (n = 1), with a mean size of 5.0 cm (range 2.0-7.9 cm). The tumour parenchyma was a mixture of nodular or patchy areas of inhomogeneous isointense to slightly hyperintense signal on T2-weighted images. On postcontrast MR images, all lesions, except for one, had moderate to marked contrast enhancement. Multiple tortuous areas of 'flow void' signal extended through all the tumours except for two. A thin capsule could be seen in six cases.

CONCLUSION

Observation of large intraventricular tumours with inhomogeneity on T2-weighted images and flow void is suggestive of CPTs. Checking for signs of a thin capsule, extensive peritumoural oedema and necrosis may be useful when classifying CPTs.

Primary fourth ventricular meningioma: a case report of an adult male

Primary fourth ventricular meningiomas are extremely rare and often misdiagnosed as other tumors. They have no characteristic imaging appearance on computed tomography and magnetic resonance imaging. Therefore, differentiating the lesion from common lesions in the fourth ventricle can be diagnostically challenging. In this report, we present a 25-year-old man with fourth ventricular meningioma and refer to the usefulness of diffusion-weighted imaging and apparent diffusion coefficient measurements for the differential diagnosis of fourth ventricular tumors.

Magnetic resonance spectroscopy findings in non-enhancing desmoplastic medulloblastoma

Medulloblasoma is a common posterior fossa tumor seen in children and presents with some typical features like midline vermian location and fairly homogeneous enhancment. Desmoplastic variety of medulloblastoma is usually seen in the adults and is known to show some atypical features like lateral cerebellar location, variable enhancement, and early meningeal infilteration. Therefore medulloblastoma should always be considered in differential diagnosis of posterior fossa mass in adults even when typical imaging findings are not that of medulloblastoma. Enhancement pattern can be variable in these tumors varying from mild to striking. Occasionally, totally non-enhancing tumors are encountered, which can cause further diagnostic confusion. We describe the magnetic resonance (MR) and MR spectroscopy findings in a case of midline vermian mass, which did not show any enhancement on post-contrast images, and was subsequently proven to be desmoplastic medulloblastoma. On MR spectroscopy, the mass showed elevated choline peak consistent with mitotic lesion. No significant lipid lactate leak was seen, which is also consistent with the ususally homogeneous nature of these tumors. Moreover, it displayed taurine peak at 3.4 ppm which is considered fairly specific for medulloblastoma. Therefore, MR spectroscopy findings can be helpful in the diagnosis of medulloblastoma in adults when MR imaging findings can be nonspecific.

Imaging tumors of the pediatric central nervous system

Primary tumors of the central nervous system (CNS) are the second most common neoplasms in children and the leading cause of death in this patient population. The primary objective of this article is to describe the most common pediatric brain tumors and to offer an overview of their respective imaging features, primarily on magnetic resonance imaging. Precise anatomic characterization is essential for developing an appropriate differential diagnosis. Once equipped with this critical information, physicians should be better able to make firm diagnoses, leading to improved disease management and patient outcomes in the setting of CNS tumors of childhood.

Medulloblastoma: atypical CT and MRI findings in children

Posterior fossa mass lesions in children usually present a diagnostic challenge despite their high frequency and the limited number of differential diagnostic possibilities. Consideration of medulloblastoma within the differential diagnosis of such lesions mandates an aggressive surgical approach as residual tumor is a known risk factor for poor prognosis. Preoperative imaging of the entire neuroaxis is critical given the high propensity of drop metastases. In this pictorial presentation, we review and demonstrate less common features of medulloblastomas to facilitate diagnosis in challenging cases.

Sudden death due to medulloblastoma

Intracranial tumours can be accompanied with intracerebral and intracerebellar non-traumatic haemorrhage; in some cases, this might be their first clinical sign. We report a case of a man who suffered sudden death due to medulloblastoma, with intratumoral haemorrhage; his tumour had a hemispheric cerebellar positioning. The cerebral oedema seen at autopsy reflected the immediate cessation of cerebral vascular circulation, leading to sudden death. Acute obstructive hydrocephaly is a mechanism widely known in the literature for causing sudden death.

Adult medulloblastoma and the "dural-tail" sign: rare mimic of a posterior petrous meningioma

The authors describe clinical and radiological features of a 32-year-old male patient with a posterior fossa lesion. The radiological characteristics resembled an extra-axial lesion; a meningioma, with attachment to the tentorium and petrous bone. The histological diagnosis was classical medulloblastoma. We review literature of this atypical presentation of medulloblastoma and "dural-tail" sign, which can be associated with other benign or malignant lesions. The role of magnetic resonance spectroscopy in the diagnosis of primitive neuroectodermal tumors is discussed.

Meduloblastoma: correlação entre ressonância magnética convencional, difusão e espectroscopia de prótons

OBJETIVO: Correlacionar os achados de ressonância magnética convencional, difusão e espectroscopia de prótons nos meduloblastomas, e compará-los aos dados da literatura. MATERIAIS E MÉTODOS: Análise retrospectiva de exames de ressonância magnética pré-operatórios de nove pacientes na faixa pediátrica com diagnóstico histológico de meduloblastoma (oito desmoplásicos e um de células gigantes). Foram considerados dados demográficos e características do tumor como localização, característica morfológica, intensidade de sinal, realce, disseminação e achados na difusão e espectroscopia. RESULTADOS: Na maioria dos casos os tumores apresentaram epicentro no vermis cerebelar (77,8%), sendo predominantemente sólido (88,9%), com hipossinal nas seqüências ponderadas em T1 e iso/hipersinal nas seqüências ponderadas em T2 e FLAIR, realce heterogêneo (100%), sinais de disseminação/extensão tumoral (77,8%) e restrição à movimentação das moléculas de água (100%). A espectroscopia de prótons pela técnica STEAM (n = 6) demonstrou redução da relação Naa/Cr (83,3%) e aumento de Co/Cr (100%) e mI/Cr (66,7%), e pela técnica PRESS (n = 7) evidenciou pico de lactato (57,1%). CONCLUSÃO: O conjunto dos achados macroscópicos obtidos pela ressonância magnética, somado às características bioquímicas dos meduloblastomas, têm sido úteis na tentativa de diferenciação entre os principais tumores da fossa posterior.

MR signal of the solid portion of pilocytic astrocytoma on T2-weighted images: is it useful for differentiation from medulloblastoma?

BACKGROUND AND PURPOSE

Although imaging features of cerebellar pilocytic astrocytoma and medulloblastoma have been described in many texts, original comparisons of magnetic resonance intensity between these two tumours are limited. In the present study the results of magnetic resonance imaging (MRI) were reviewed, focusing especially on the signal intensity of the solid portion of these neoplasms.

METHODS

MR images of ten cerebellar pilocytic astrocytomas and ten medulloblastomas were reviewed. The signal intensities of the solid components were graded on a scale of 1 to 5, with higher scores indicating a signal intensity closer to that of water. The degree of enhancement, tumour cysts and peripheral oedema were evaluated on MR images. When the solid portion was heterogeneous (i.e. mixed signal intensity or degree of enhancement), the dominant area was selected for evaluation.

RESULTS

On T2-weighted images, the signal intensity of the solid portion was equal to that of cerebrospinal fluid (CSF) in 50% of pilocytic astrocytomas. No medulloblastomas showed such hyperintensity. Most medulloblastomas (80%) were isointense to grey matter. On T1-weighted images, the signal intensity varied widely in pilocytic astrocytomas; however, all medulloblastomas were iso- or hypointense to grey matter. The MR enhancement pattern, cystic component and peripheral oedema all varied in both tumour types and no specific features were identified.

CONCLUSION

A signal intensity of the solid portion isointense to CSF on T2-weighted images was characteristic of cerebellar pilocytic astrocytomas; this was not observed in medulloblastomas. Attention to T2-weighted imaging of the solid portions of a tumour is easy and helpful in differentiating between cerebellar pilocytic astrocytoma and medulloblastoma.

OTX1 and OTX2 Expression Correlates With the Clinicopathologic Classification of Medulloblastomas

OTX1 and OTX2 are transcription factors with an essential role in the development of the cerebellum. We previously described a high OTX2 expression in medulloblastoma. Here, we analyzed amplification and mRNA expression of OTX1 and OTX2 in a series of human medulloblastomas. In addition, OTX2 protein expression was analyzed on tissue arrays. The OTX2 gene was amplified in the medulloblastoma cell line D425 and mRNA and protein data showed expression in 114 of 152 medulloblastomas (75%), but not in postnatal cerebellum. Northern blot (n = 10) and reverse transcriptase-polymerase chain reaction (n = 45) analyses demonstrated that virtually all medulloblastomas expressed OTX1, OTX2, or both. OTX2 mRNA expression correlated with a classic medulloblastoma histology (29 of 34 cases), whereas expression of OTX1 mRNA only was correlated with a nodular/desmoplastic histology (9 of 11 cases). Immunohistochemical analysis of a series of classic medulloblastomas detected OTX2 protein expression in 83 of 107 (78%) cases. The OTX2-positive tumors of this series were preferentially localized in the vermis of the cerebellum, whereas OTX2-negative tumors more frequently occurred in the hemispheres of the cerebellum. In addition, OTX2-positive tumors were mainly found in children, but OTX2-negative tumors occurred in 2 patient groups: very young patients (<5 years) and adults (>20 years). Nodular/desmoplastic medulloblastomas are thought to arise from the external granular layer (EGL). However, it is unclear whether classic medulloblastomas also originate from the EGL or from the ventricular matrix. Analysis of human fetal brain showed OTX2 protein expression in a small number of presumptive neuronal precursor cells of the EGL, but not in precursor cells of the ventricular matrix. Combined with data from rodents, our results therefore suggest that both nodular/desmoplastic and at least part of the classic medulloblastomas originate from cells of the EGL, albeit from different regions.

Diffusion-weighted MR imaging and pathologic findings in adult cerebellar medulloblastoma

OBJECTIVES, MATERIALS AND METHODS: The authors present the diffusion-weighted MR imaging and pathologic findings in two adult patients with cerebellar medulloblastoma.

RESULTS

Both presented with a vermian mass of the posterior fossa with low signal on SE T1 weighted images, and moderate enhancement of the mass after gadolinium injection. The tumors were of high intensity on diffusion-weighted images with low ADC value. The ADC values (x10(-3) mm2/s) were respectively 0.60 +/- 0.06 and 0.59+/-0.11 (tumor), and 0.65 +/- 0.04 and 0.67 +/- 0.07 (cerebellar white matter). Tumors were highly cellular and composed of densely packed small round cells with hyperchromatic nuclei and scanty cytoplasm.

CONCLUSION

diffusion-weighted MR imaging may be useful for the diagnosis of cerebellar medulloblastoma, due to their high cellularity and high nuclear-to-cytoplasmic ratio.

From the archives of the AFIP: medulloblastoma: a comprehensive review with radiologic-pathologic correlation

Medulloblastoma is the most common pediatric central nervous system malignancy and the most common primary tumor of the posterior fossa in children. This highly malignant neoplasm occurs more frequently in males and usually before 10 years of age. Clinical symptoms and signs are generally brief, typically less than 3 months in duration, and reflect the strong predilection of this tumor to arise within the cerebellum, most often in the vermis. Although much less common, the disease may also occur in adults, usually in the 3rd and 4th decades of life. Surgical resection, radiation therapy, and chemotherapy have substantially lowered the mortality associated with this tumor, with 5-year survival rates now commonly well above 50%. Still, both dissemination at the time of diagnosis and recurrence remain obstacles in achieving a cure. The tumor has characteristic hyperattenuation on unenhanced computed tomographic scans that reflects the high nuclear-cytoplasmic ratio seen at histologic analysis. The tumor typically appears heterogeneous on images, findings that are related to cyst formation, hemorrhage, and calcification and that are even more pronounced with magnetic resonance (MR) imaging. Evidence of leptomeningeal metastatic spread is present in 33% of all cases at the time of diagnosis and is well evaluated with contrast-enhanced MR imaging of the brain and the spine. Although controversial, postoperative surveillance with MR imaging is performed at most institutions in the hope of facilitating a better outcome. With continued research, treatment of these common neoplasms should improve, perhaps even achieving a cure in the future.

MRI of medulloblastoma in adults

Medulloblastoma has variable appearances on MRI in both children and adults. Adults are more likely to have heterogeneous cerebellar hemisphere tumours, and this is thought to be related to the greater prevalence of desmoplastic tumours in adulthood. Few studies have addressed the MRI features of adult medulloblastoma and the specific characteristics of desmoplastic and classic tumours have not been analysed. Our aim was to analyse the imaging characteristics of desmoplastic (DM) and classic (CM) medulloblastomas in adult. We retrospectively studied preoperative MRI of six men and three women, median age 33 years, range 23-53 years, with pathologically proved medulloblastomas. There were six (67%) with DM. The tumour was in the cerebellar hemisphere in eight patients (89%), including the three with CM, one of which was bilateral. All tumours were heterogeneous, giving predominantly low or isointense signal on T1- and isointense signal on T2-weighted images. Cystic or necrotic areas in all patients were particularly visible on T2-weighted images. Contrast enhancement was absent in one DM and varied from slight to intense in eight (three CM), homogeneous in one DM and patchy in seven. All tumours extended to the surface of the cerebellum and two had well-defined margins. MRI does not allow a clear distinction between DM and CM in adults.

Adult cerebellar medulloblastoma: CT and MRI findings in eight cases

Medulloblastoma is a brain tumor of neuroepithelial origin, which represents 15 to 30% of all pediatric brain tumors, and less than 1% of CNS adult neoplasms. We report the imaging findings of 8 adult patients with medulloblastoma. The mean age was 35 years, ranging from 20 to 65 years, and the male:female rate was 3:5. The tumors were predominantly lateral (63%), hyperdense on CT scans (83%), and on the MRI, hypointense on T1 (100%) and hyperintense on T2 (80%) weighted images. It was seen intratumoral necrosis and cysts in six cases and calcifications in three. Hydrocephalus was observed in 5 cases and brain stem invasion in four. The imaging findings of medulloblastomas in adults are different of those in child, and also nonspecific. Although these tumors are uncommon in adults, they must be considered in the differential diagnosis of cerebellar masses in the posterior fossa of this age group.

Atypical features of medulloblastoma on magnetic resonance imaging: case report and review of the literature

Magnetic resonance imaging (MRI) is the radiologic modality of choice used to evaluate suspected lesions in the posterior fossa, given its greater sensitivity compared with other neuroimaging techniques. The case of a 9-year-old girl with progressive ataxia is presented. MRI of the brain demonstrated nonspecific T2-weighted abnormalities involving the cerebellar vermis with minimal mass effect suggested by asymmetric enlargement of the left superior cerebellar peduncle. Postgadolinium studies showed only minimal enhancement of the left superior cerebellar peduncle. After an MRI of the spine demonstrated drop metastases, a cerebellar biopsy was performed, which revealed an infiltrating medulloblastoma confined to the granular layer and leptomeninges. Hence, MRI is an important ancillary tool in the diagnosis of medulloblastoma, but caution needs to be taken when interpreting imaging studies.

Adult primitive neuroectodermal tumor: proton MR spectroscopic findings with possible application for differential diagnosis

PURPOSE

To assess the utility of proton magnetic resonance (MR) spectroscopy in the clinical categorization of primitive neuroectodermal tumors (PNETs) in adults.

MATERIALS AND METHODS

In vivo proton MR spectroscopy was performed with an echo time of 136 msec in nine adults with PNET, and findings were retrospectively compared with spectroscopic findings of 22 meningiomas, 12 low-grade astrocytomas, eight anaplastic astrocytomas, 23 glioblastomas, and 21 metastases. Nine resonances were semiquantitatively evaluated. Statistical analysis was performed by using Kruskal-Wallis and Mann-Whitney U tests. The Hochberg correction was applied for multiple comparisons. Results were prospectively validated in 24 tumors of the six types included in the study.

RESULTS

The resonances of choice for identifying PNET were alanine (P <.001) and glutamate and glutamine (P =.004), both decreased with respect to meningioma; choline increased with respect to low-grade (P <.001) and anaplastic astrocytoma (P =.055); and lipids at 1.30 ppm decreased and choline and other trimethyl-amine-containing compounds increased with respect to glioblastoma (P <.001 and P =.004, respectively) and metastasis (P <.001 and P =.021, respectively). We developed an algorithm for bilateral differential diagnosis between PNET and other tumor types. The leave-one-out method was used to test the five possible differential situations in the retrospective data set, with the following results: PNET versus meningioma, 31/23/5/3 (number of total/correct/unclassifiable/incorrect procedures); PNET versus low-grade astrocytoma, 21/19/2/0; PNET versus anaplastic astrocytoma, 17/6/9/2; PNET versus glioblastoma, 32/28/2/2; and PNET versus metastasis, 30/27/1/2. In total, 131 consecutive procedures produced 103 (79%) correct classifications and nine (7%) misclassifications. Twenty-five (78%) of 32 possible procedures in the prospective independent test set produced correct classifications and four (13%) produced incorrect classifications.

CONCLUSION

In vivo proton MR spectroscopy provides useful information in clinical differentiation between PNETs and common brain tumors in adults.

Magnetic resonance imaging of pediatric brain tumors: state of the art

Over the past 25 years, magnetic resonance imaging (MRI) has developed into the primary imaging tool for evaluation of the central nervous system. MRI is the essential imaging study in the twenty-first century for the evaluation of the child with a brain tumor for initial preoperative diagnosis, treatment planning and image-guided therapies. This article provides an overview of the locations and MRI features of common pediatric tumors of childhood.

Third ventricular lesion masquerading as suprasellar disease

We discuss the case of a patient who presented with a bitemporal visual field disturbance thought to arise from chiasmatic compression secondary to a suprasellar mass. The patient was ultimately diagnosed with medulloblastoma with diffuse intraventricular disease. Careful review of magnetic resonance (MR) findings in this case demonstrate the apparent suprasellar mass to be within the suprachiasmatic recess of the third ventricle. The role of MR imaging in distinguishing between suprasellar disease involving the third ventricle and primary third ventricular lesions is discussed.

Medulloblastoma in an adult suggestive of external granule cells as its origin: a histological and immunohistochemical study

We describe a rare case of medulloblastoma in an adult woman with histological findings suggesting an origin for this neoplasm in the external granular layer or its remnants. The patient presented with cerebellar dysfunction, and neuroimaging revealed a right cerebellar mass lesion. Pathological examination of the operative specimen revealed a medulloblastoma with occasional areas of neuronal or glial differentiation. Zic protein was also detected immunohistochemically in the tumor cells. The tumor cells were mainly distributed in the subarachnoid space and extended to the cerebellar parenchyma through the perivascular space to form tumor nodules. A suggestive finding, as concerns the origin of this neoplasm, was that the tumor cells were also spread evenly along the subpial zone of the molecular layer, reminiscent of the cellular architecture of the fetal external granular layer.

Neuroradiology of pediatric posterior fossa medulloblastoma

Medulloblastoma of the cerebellum is a common intracranial neoplasm in children and presents many faces in medical imaging. Characteristic or classic features, such as increased attenuation on unenhanced CT, midline location and well defined margins, are commonly present in childhood cases of posterior foassa medulloblastoma, although atypical imaging features are being noted more frequently with the increased dependence on MR as the diagnostic modality of choice. Carefully performed CT and MR both initially provide suitable geography and characteristics, but MR is superior in the detection of pre- or post-operative neoplastic spread elsewhere in the subarachnoid space. Accurate establishment of disease extent is essential in planning both surgical resection and adjuvant therapy.