Brain Tumors

Published on 06/06/2015 by admin

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Last modified 06/06/2015

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57 Brain Tumors

Angela J. Sievert, Jane E. Minturn

Tumors of the central nervous system (CNS) are the most common solid tumors of childhood and the primary source of cancer-related morbidity and mortality in this age group. Benign and malignant tumors may be equally life threatening because of an unfavorable location in the brain or spinal cord and the inability to safely achieve a surgical resection. Survival rates have improved significantly over the past 2 decades because of improvements in neuroimaging, neurosurgical techniques, radiation therapy, chemotherapy, and supportive care.

Nearly half of all childhood brain tumors arise infratentorially—in the brainstem, cerebellum, and fourth ventricle—and are classified according to histology. The most common malignant brain tumor is medulloblastoma, and the most common benign brain tumor is low-grade glioma. A discussion of the common pediatric tumors with emphasis on evaluation, management, and prognosis is outlined in this chapter.

Etiology And Pathogenesis

Central nervous system tumors represent approximately 20% of all childhood cancers with 2.5 to 4 cases diagnosed per 100,000 children per year. There is a slight male predominance (male : female ratio, 1.29) at all ages younger than 20 years, and infratentorial location is more common in children 1 to 15 years of age.

The etiology of most childhood brain tumors is unknown. Specific genetic syndromes, such as neurofibromatosis (NF1 and NF2), tuberous sclerosis, and Li-Fraumeni and Turcot’s syndromes, are associated with a higher incidence of tumors, but this group represents fewer than 10% of pediatric brain tumors. The only known environmental risk factor related to the development of brain tumors is exposure to ionizing radiation. Other exposures such as maternal diet during pregnancy, viral infections, cell phone use, and exposure to magnetic fields have been studied extensively with limited and conflicting data for an association with brain tumor risk.

Understanding the origin of brain tumors has been enhanced by the ability to detect specific molecular genetic alterations in tumor samples and the association of brain tumor development with inherited genetic disorders in which the gene defect is known. This has contributed to our understanding of the underlying biology of brain tumor initiation and progression and has led to the identification of therapeutic targets for drug development.

Clinical Presentation

The presenting symptoms of a brain tumor are determined by tumor location rather than histology. Brain tumors may present with either generalized or localizing symptoms. Generalized symptoms are caused by obstruction of cerebrospinal fluid (CSF) with associated hydrocephalus and increased intracranial pressure (ICP). Increased ICP is more common with fourth ventricular or posterior fossa, pineal, suprasellar, and tectal tumors. Symptoms include headache (particularly in the morning), nausea, vomiting, and fatigue. On examination, paresis of upgaze, sixth cranial nerve palsies, and papilledema are often seen. In infants, macrocephaly, tense fontanelle, failure to thrive, developmental delay, and paresis of upgaze with downward eye deviation (“sun setting”) are common. Posterior fossa tumors, such as cerebellar astrocytomas, often present with increased ICP (Figure 57-1).

Figure 57-1 Clinical presentation of brain tumors.

Localizing symptoms depend on tumor location. Cerebellar tumors commonly present with ataxia and dysmetria. Brainstem tumors may cause cranial nerve deficits (diplopia, facial weakness, swallowing deficits), unsteadiness, and weakness (see Figure 57-1

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