CNS tumors are the most common solid tumors in children and are second to leukemia in overall incidence during childhood. About 1700 new cases occur each year in the United States; the rate is approximately 33 cases per 1 million children under 15 years of age. The incidence peaks before age 10 years and then decreases until a second peak after age 70. For medulloblastoma and ependymoma, males are more affected than females; for other tumor types, no gender differences exist. In the first 2 to 3 years of life, whites are affected more than multiracial children; otherwise incidence rates are essentially equal for whites and multiracial children.
Children with certain inherited syndromes, including neurofibromatosis (types 1 and 2), Li-Fraumeni syndrome, tuberous sclerosis, Turcot syndrome, and von Hippel-Lindau syndrome, have an increased risk for developing a CNS tumor. Most CNS tumors arise in children with no known underlying disorder or risk factor.
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Abnormal Head Size, Shape, and Fontanels Visual Impairment and Leukocoria Vomiting Headaches
Brain tumors can cause symptoms by impingement on normal tissue (usually cranial nerves) or by an increase in intracranial pressure caused either by obstruction of cerebrospinal fluid (CSF) flow or by a direct mass effect. Tumors that obstruct the flow of CSF become quickly symptomatic. Symptoms of increased intracranial pressure are lethargy, headache, and vomiting (particularly in the morning on awakening). Irritability, anorexia, poor school performance, and loss of developmental milestones all may be signs of slow-growing CNS tumors. In young children with open cranial sutures, an increase in head circumference may occur. Optic pathway tumors may lead to loss of visual acuity or visual field defects. Inability to abduct the eye as the result of sixth cranial nerve palsy is a common sign of increased intracranial pressure. Cranial nerve deficits other than sixth nerve palsy suggest involvement of the brainstem. Seizures occur in 20% to 50% of patients with supratentorial tumors; focal weakness or sensory changes also may be seen. Pituitary involvement produces neuroendocrine effects (galactorrhea with prolactinoma, excessive growth with growth hormone secretory tumors, precocious puberty). Cerebellar tumors are associated with ataxia and diminished coordination. A history and physical examination are fundamental for evaluation, which should include a careful neurologic assessment, including visual fields and a funduscopic examination.
If an intracranial lesion is suspected, magnetic resonance imaging (MRI) is currently the examination of choice (Fig. 157-1). Examination of CSF by cytocentrifuge histologic testing is essential to determine the presence of metastatic disease in primitive neuroectodermal tumors, germ cell tumors, and pineal region tumors. A lumbar puncture should not be performed before imaging has been obtained to evaluate for evidence of increased intracranial pressure. If a tumor is
Figure 157-1 Magnetic resonance imaging scan of a 9-year-old boy showing a heterogeneously enhancing fourth ventricular mass (arrow). It was resected, and pathology revealed medulloblastoma.
suspected to have metastatic potential (medulloblastoma), MRI of the entire spine should be obtained before surgery to assess for neuraxial dissemination. A postoperative MRI study of the brain should be obtained within 24 to 48 hours of surgery to assess the extent of resection. During follow-up, magnetic resonance spectroscopy can help distinguish recurrent tumor from radiation necrosis.