Pediatric Brain Tumors

Pilocytic astrocytomas are World Health Organization (WHO) grade I tumors. They can occur in any region of the central nervous system, but frequently arise in the cerebellum of children. The tumors often have both cystic and solid components. In some cases, the cystic component may be quite large, with the associated solid tumor mass appearing as a smaller “mural” nodule in the cyst wall.

Brainstem gliomas encompass a number of tumor subtypes, each with its own pathologic and clinical characteristics. Although they can be seen in adult patients, they are far more common in children. There are four types: dorsal exophytic gliomas, tectal gliomas, cervicomedullary gliomas, and diffuse infiltrating pontine gliomas. Dorsal exophytic gliomas are slow-growing low-grade astrocytomas arising from the floor of the fourth ventricle. Intrinsic midbrain tectal gliomas tend to be low-grade astrocytomas, occurring next to the third ventricle and aqueduct of Sylvius. Cervicomedullary tumors typically are low-grade astrocytomas of the upper spinal cord and lower brainstem, although other tumor types can be seen. The most aggressive type is the diffuse infiltrating pontine glioma,. These tumors are WHO grade III or IV and have a very poor prognosis, with median survival of only 9 months despite maximal treatment with radiation and chemotherapy.

Medulloblastomas are WHO grade IV embryonal brain tumors that arise in the cerebellum and tend to disseminate through cerebrospinal fluid (CSF) pathways throughout the brain and spine. They are highly cellular tumors with highly variable prognosis that is not predicted by histologic features. Analysis of their molecular profiles has revealed that this heterogeneity arises because they consist of multiple subclasses associated with distinct demographics, genetics, clinical presentation, and outcome. The large majority of tumors are diagnosed in childhood or adolescence.

Clinical Manifestations. In general, brainstem gliomas produce symptoms reflecting the exact location of the tumor in the brainstem, rate of growth, and presence of CSF flow obstruction. Patients with tectal gliomas often display signs and symptoms of isolated hydrocephalus. Dorsal exophytic brainstem tumors may manifest with headaches due to hydrocephalus combined with ataxia from cerebellar dysfunction. Diffuse pontine gliomas often present with double vision and facial weakness due to cranial nerve VI and VII palsies, accompanied by motor and cerebellar dysfunction of the contralateral limbs. Medulloblastomas can present with ataxia from cerebellar dysfunction, cranial nerve deficits, headache and vomiting from hydrocephalus, or occasionally, signs and symptoms attributable to spinal cord or nerve root compression from extensive tumor dissemination.

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