Uncommon presentation of medulloblastoma

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.

Posterior fossa extra-axial variations of medulloblastoma: a pictorial review as a primer for radiologists

Manifestations of an atypical variant of medulloblastoma of the posterior fossa in extra-axial locations have been reported, and key questions concerning its interpretation have been raised previously. This review illustrated the clinico-radiological and histopathological features of the posterior fossa extra-axial medulloblastoma and described possible management strategies. We thoroughly reviewed all atypical anatomical locations of medulloblastoma reported within the posterior fossa and extra-axial spaces. The main characteristics of diagnostic imaging and histopathological results, primarily the distinctive radiopathological characteristics, were summarized to distinguish between intra- and extra-axial medulloblastoma, or pathologies mimicking this tumor. Most cases of posterior fossa extra-axial medulloblastoma have been reported in the cerebellopontine angle, followed by the tentorial and lateral cerebellar locations. The dural tail sign, which is commonly observed in meningioma, is rarely seen in intra- or extra-axial medulloblastoma and might be associated with other benign or malignant lesions. In addition to magnetic resonance imaging, the proposed new imaging techniques, including advances in modern neuroimaging modalities, were discussed, as potentially efficient modalities for characterizing extra-axial medulloblastoma. Radionuclide imaging and magnetic resonance perfusion imaging are practical alternatives to limit the number of differential diagnoses. We believe that medulloblastoma cases are likely under-reported because of publication bias and frequent tumors in unusual locations. Addressing these issues would help establish a more accurate understanding of this entity.

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.

Cerebellopontine angle medulloblastoma with extensive nodularity in a child: case report and review of the literature

BACKGROUND

Cerebellar medulloblastomas (MBs) are one of the most common posterior fossa tumors in children but rarely occur in the cerebellopontine angle (CPA). Only 39 cases of CPA MBs were reported in the literature, and most of them were classic and desmoplastic MBs.

CASE PRESENTATION

A 22-month-old girl presented with progressive cerebellar ataxia. Magnetic resonance imaging showed a large tumor in the right CPA and obstructive hydrocephalus. Surgical resection was performed and achieved total tumor removal. Microscopic examination and immunohistochemical staining revealed the diagnosis of MB with extensive nodularity. The patient recovered from her symptoms during follow-up and was transferred for adjuvant chemotherapy.

CONCLUSION

MB should be considered as a differential diagnosis of a lesion in the CPA. The treatment and outcome of CPA MBs are similar to cerebellar MBs.

Atypical medulloblastoma: A case series

Medulloblastoma is common in children as a tumor of midline posterior fossa, which arises from vermis and appears as a homogenously enhancing hyperdense mass on computed tomography scan and is associated with the clinical picture of posterior fossa syndrome. This unique clinic-radiological pattern in considered “typical” medulloblastoma, but medulloblastomas does not follow the typical clinic-radiological pattern in a significant number of children and adult cases. We review here the previous reports of atypical or uncommon features of medulloblastoma and add our very rare atypical cases of medulloblastomas to this list. Medulloblastoma should be considered in all midline posterior fossa tumors, hemisphere and cerebellopontine angle despite having clinical and radiological features suggestive of other tumors. Definitive diagnosis requires histologic confirmation in all cases.

Conventional and advanced MRI features of pediatric intracranial tumors: posterior fossa and suprasellar tumors

OBJECTIVE

In this article, we review the most common posterior fossa and suprasellar intracranial neoplasms in the pediatric population. We briefly discuss basic MRI concepts used in the initial evaluation of a pediatric brain tumor and then discuss sophisticated MRI techniques that give insight into the physiology and chemical makeup of these tumors to help the radiologist make a more specific diagnosis.

CONCLUSION

Diagnosis and treatment of pediatric CNS tumors necessitate a multi-disciplinary approach and require expertise and diligence of all parties involved. Imaging is an essential component has evolved greatly over the past decade. We are becoming better at making a preoperative diagnosis of that tumor type, detecting recurrence, and guiding surgical management to avoid injury to vital brain structures.

Review of cerebellopontine angle medulloblastoma

Cerebellopontine angle (CPA) medulloblastomas (MB) are rare lesions with few cases previously described in the literature. We report two further cases of CPA MB. The patients were a 22-year-old man and a 26-year-old woman with a mass developing in the CPA. The preoperative radiological diagnosis was vestibular schwannoma in the first case and petrosal meningioma in the second case. The patients were operated on through a retrosigmoid approach. The intraoperative findings revealed an intra-axial tumour and the histological diagnosis was classic type of MB in both cases. We review the literature and discuss pathological and radiological features and possible pathogenesis of CPA MB, underlining the necessity to consider MB in the differential diagnosis of CPA lesions.

Neuroimaging of pediatric posterior fossa tumors including review of the literature

Conventional, anatomical MRI is an essential tool for diagnosis and evaluation of location, quality, and extent of posterior fossa tumors, but offers limited information regarding tumor grade and type. Advanced MRI techniques such as diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) may improve the specific diagnosis of brain tumors in the posterior fossa in children. In this review the conventional neuroimaging findings, as well as the DWI, and DTI characteristics of common pediatric posterior fossa tumors are discussed and summarized.

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.

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.

Initial management of childhood brain tumors: neurosurgical considerations

Intracranial tumors are the most common solid tumors in children. The infratentorial compartment will be the primary site for 60% to 70% of these tumors, including astrocytomas, medulloblastomas, and ependymomas. Several technological advancements have increased our knowledge of the cell biology of pediatric brain tumors, facilitated earlier diagnosis, and improved neurosurgical resections while minimizing neurological deficits. These in turn have not only improved the survival of children with brain tumors but also their quality of life. Current management strategies in most cases rely on surgery coupled with adjuvant therapies, including radiation therapy and chemotherapy. The vulnerability of the immature brain to adjuvant therapies creates many challenges for the treating physician. We review current diagnostic and therapeutic approaches and outcome for children harboring the most common pediatric brain tumors: astrocytomas (low-grade and high-grade glioma), ependymoma, medulloblastoma, and craniopharyngioma. The emphasis will be on the neurosurgical management of children with these tumors.

Postoperative hemicerebellar inflammation mimicking recurrent tumor after resection of a medulloblastoma. Case report

The authors present the case of a 4-year-old boy in whom a medulloblastoma in the left cerebellar hemisphere was successfully resected with no signs of residual tumor on the postoperative magnetic resonance (MR) images. A second MR imaging study performed 1 month after surgery demonstrated an extensive, contrast-enhancing lesion in the left cerebellar hemisphere, which simulated massive recurrent tumor, and repeated surgery was considered. A third postoperative MR imaging study, performed for evaluation of the craniospinal axis 10 days after the second postoperative study, still showed some contrast enhancement in the left cerebellar hemisphere, but the lesion had almost disappeared. Postoperative hemicerebellar inflammation seemed to be the most likely explanation. This case illustrates that early postoperative inflammation can mimic recurrent tumor on MR images obtained after resection of a medulloblastoma and caution should be taken in interpreting such images. Clinical history, neurological examination, laboratory findings, and repeated MR imaging studies can be helpful in evaluating the patient accurately.

Medulloblastoma in childhood: new biological advances

Medulloblastoma is the most common embryonal tumour in children. Patients with medulloblastoma are currently staged as average-risk or poor-risk on the basis of clinical findings. With current multimodality therapy, nearly 90% of children with average-risk, non-disseminated medulloblastoma have 5-year event-free survival, and those with high-risk disease have a 60-65% survival rate; however, the outcome for younger children, particularly infants, is worse. Children who survive medulloblastoma are at risk of long-term sequelae related to the neurological effects of the tumour, surgery, or radiotherapy, and the additive effects of chemotherapy. Molecular biology has changed our understanding of medulloblastoma and has implications for diagnostic stratification and treatment. As newer biological agents are translated from the lab to the bedside, clinicians need to understand the fundamental signalling pathways that are targeted during therapy. Greater understanding of the molecular biology of medulloblastoma is needed so that more children can be cured or have an improved quality of life.

Pleomorphic xanthoastrocytoma of the cerebellopontine angle in a child

CASE REPORT

The case of a 6-year-old girl with a pleomorphic xanthoastrocytoma (PXA) in the left cerebellopontine angle (CPA) is reported. The clinical, radiological, and histopathological findings are presented.

DISCUSSION

To our knowledge, the presence of PXA in the CPA has not previously been reported. The rare infratentorial locations of PXA (frequently seen in association with ganglioglioma) are reviewed, as well as the other infrequent locations of this tumor. This report adds to the list of differential diagnoses of CPA tumors in children.

[Medulloblastoma presenting as an extra-axial tumor in the cerebellopontine angle]

Differences in the imaging characteristic of adult medulloblastomas have been reported, including involvement of lateral cerebellar hemispheres with an extra-axial appearance. We present a case report of this rare circumstance: a 40 year old man presented with a 3 weeks history of headache, morning vomiting and left hearing difficulties. Magnetic resonance imaging revealed a left cerebellopontine angle (CPA) tumor, like a well circumscribed homogeneously enhancing mass. Through a left suboccipital craniectomy the tumor was totally removed. It presented as a cerebellopontine angle tumor, like a meningioma, and not as an intra-axial tumor. Histological analysis revealed that the tumor was composed of densely packed with highly proliferative cells that produce a dense intercellular reticulin fiber network. Inmunohistochemical analysis showed positive expression to synaptophysin, specific neuronal enolase and cromogranin. Histological diagnosis was crucial to define it as a desmoplastic medulloblastoma the present case and to perform postoperative adjuvant therapy. Neurosurgeons should be aware of the possibility that a CPA tumor is of intraaxial origin, because this increase the variability on pathological diagnosis.

Advances in the diagnosis, molecular genetics, and treatment of pediatric embryonal CNS tumors

Embryonal central nervous system (CNS) tumors are the most common group of malignant brain tumors in children. The diagnosis and classification of tumors belonging to this family have been controversial; however, utilization of molecular genetics is helping to refine traditional histopathologic and clinical classification schemes. Currently, this group of tumors includes medulloblastomas, supratentorial primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumors, ependymoblastomas, and medulloepitheliomas. While the survival of older children with nonmetastatic medulloblastomas has improved considerably within the past two decades, the outcomes for infants and for those with metastatic medulloblastomas or other high-risk embryonal CNS tumors remain poor. It is anticipated that the emerging field of molecular biology will greatly aid in the future stratification and therapy for pediatric patients with malignant embryonal tumors. In this review, recent advances in the diagnosis, molecular genetics, and treatment of the most common pediatric embryonal CNS tumors are discussed.