Neuroimaging of Pediatric Brain Tumors

Tumors of Choroid Plexus and Other Ventricular Tumors

Tumors arising inside the ventricular system are rare but represent a difficult diagnostic and therapeutic challenge. They usually are diagnosed when reaching a big volume and tend to affect young children. There is a wide broad of differential diagnoses with significant variability in anatomical aspects and tumor type. Differential diagnosis in tumor type includes choroid plexus tumors (papillomas and carcinomas), ependymomas, subependymomas, subependymal giant cell astrocytomas (SEGAs), central neurocytomas, meningiomas, and metastases. Choroid plexus tumors, ependymomas of the posterior fossa, and SEGAs are more likely to appear in childhood, whereas subependymomas, central neurocytomas, intraventricular meningiomas, and metastases are more frequent in adults. This chapter is predominantly focused on choroid plexus tumors and radiological and histological differential diagnosis. Treatment is discussed in the light of the modern acquisition in genetics and epigenetics of brain tumors.

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.

Advances in the management of pediatric central nervous system tumors

Central nervous system tumors are the most common pediatric solid tumors and a leading cause of cancer-related mortality and morbidity in this age group. Survival rates have improved significantly over the last decades for most of the tumor types, as a consequence of improvements in neuroimaging, neurosurgery and neuroanesthesia, radiation oncology, and medical oncology. The complexity of the management of these patients requires a multidisciplinary approach and has led to the emergence of a new subspecialty of pediatric neuro-oncologists who are dedicated to the management and follow-up of this population. This review highlights the most critical advances in the diagnostic and treatment modalities of pediatric brain tumors. A specific review of the most common tumor types discusses treatment options, controversies, and ongoing developments, with an emphasis on cooperative trials.

Midline medulloblastoma versus astrocytoma: the position of the superior medullary velum as a sign for diagnosis

PURPOSE

We wish to describe the position of the superior medullary velum (SMV) in midline posterior fossa tumours as a sign in helping to distinguish between midline medulloblastoma and midline astrocytoma.

MATERIAL AND METHODS

Sagittal T1-weighted MRI images of 21 consecutive patients with histologically documented posterior fossa midline astrocytomas (nine cases) and medulloblastomas (12 cases) were reviewed, with respect to the position of the velum medullare superius.

RESULTS

In all medulloblastomas the SMV was superiorly dislocated; in eight astrocytomas it was anteriorly and/or inferiorly disclocated; only in one astrocytoma the SMV presented upward dislocation.

CONCLUSION

In the differential diagnosis between medulloblastoma and astrocytoma the upward dislocation of the SMV is strongly suggestive of medulloblastoma.

Neurosurgical treatment of brain tumors in children

Primary brain tumors are the most common solid neoplasms of childhood. The diagnosis of brain tumors in the general pediatric population remains challenging. Nevertheless, it is clear that refinements in imaging, surgical technique, and adjunctive therapies have led to longer survival and an improving quality of life in children with brain tumors.

Biochemical characterization of pediatric brain tumors by using in vivo and ex vivo magnetic resonance spectroscopy

OBJECT

Magnetic resonance (MR) spectroscopy provides biochemical information about tumors. The authors sought to determine the relationship between in vivo and ex vivo biochemical characterization of pediatric brain tumors by using MR spectroscopy. Their hypothesis was that ex vivo MR spectroscopy provides a link between in vivo MR spectroscopy and neuropathological analysis.

METHODS

In vivo proton MR spectroscopy was performed before surgery in 11 patients with neuroepithelial tumors. During resection, a total of 40 tumor biopsy samples were obtained from within the volume of interest identified on in vivo MR spectroscopy and were frozen immediately in liquid nitrogen. High-Resolution Magic Angle Spinning (HRMAS) was used to perform ex vivo MR spectroscopy in these 40 tumor biopsy samples. Neuropathological analysis was performed using the same biopsy samples, and the tumors were classified as ependymoma, choroid plexus carcinoma, pineoblastoma (one each), and pilocytic astrocytoma, medullobastoma, low-grade glioma, and glioblastoma multiforme (two each). Ex vivo HRMAS MR spectroscopy improved line widths and line shapes in the spectra, compared with in vivo MR spectroscopy. Choline (Cho) detected in vivo corresponded to three different peaks ex vivo (glycerophosphocholine, phosphocholine [PCho], and Cho). Metabolite ratios from in vivo spectra correlated with ratios from ex vivo spectra (Pearson correlation coefficient range r = 0.72-0.91; p < or = 0.01). Metabolite ratios from ex vivo spectra, such as PCho/ total creatine (tCr) and lipid/tCr, correlated with the percentage of cancerous tissue and percentage of tumor necrosis, respectively (r = 0.84; p < 0.001).

CONCLUSIONS

Agreement between in vivo and ex vivo MR spectroscopy indicates that ex vivo HRMAS MR spectroscopy can improve resolution of this modality and provide a link between in vivo MR spectroscopy and neuropathological analysis.

Novel approaches to imaging brain tumors

Brain imaging techniques are assuming a greater range of roles in neuro-oncology. New techniques promise earlier recognition of the spread of tumors to the brain, which is useful in staging of disseminated disease, as well as better definition of small lesions associated with presentations of epilepsy. There is the promise that entirely noninvasive, specific diagnosis of brain tumors may become possible. Imaging methods are being used increasingly to direct and monitor therapy. Preoperative and intraoperative imaging are being used for guiding tumor surgery. An exciting potential goal for greater use of imaging is in the individualization of medical therapies either by analysis of in vitro responses or by visualization of drug responses on the tumor in situ. An important focus for technical development is in the robust integration of complementary information to allow optimization of the sensitivity and specificity of multimodal examinations.

Posterior fossa tumors in children: a case study

Brain tumors are the second most common malignancy to occur during childhood and the posterior fossa is the most common region of the brain affected. Diagnosis and treatment are complex and challenging. Once a child suffering from a posterior fossa tumor is identified, a multidisciplinary team must be assembled to provide comprehensive care through all phases of treatment. The nursing staff is vital to this team because they are often the individuals who coordinate services involved in the care of the child with a posterior fossa tumor. This case study illustrates the phases of diagnosis and treatment of a child with a medulloblastoma and highlights critical care nursing challenges. Following the case study presentation, a summary describes posterior fossa tumors including epidemiology, pathophysiology, clinical manifestations, and outcome. The case study is integrated throughout this review to highlight key issues for critical care nurses to explore.