Cancer of the Central Nervous System
Jay F. Dorsey, Andrew B. Hollander, Michelle Alonso-Basanta, Lukasz Macyszyn, Leif-Erik Bohman, Kevin D. Judy, Amit Maity, John Y.K. Lee, Robert A. Lustig, Peter C. Phillips and Amy A. Pruitt
Summary of Key Points
Incidence
• An estimated 66,290 new primary tumors of the central nervous system (CNS) will be diagnosed in the United States in 2012, of which approximately one third will be malignant.
• An estimated 4200 new childhood (ages 0 to 19 years) primary benign and malignant CNS tumors will be diagnosed in 2012. Brain tumors are the second most common malignancy among children, second only to leukemias.
• Radiation exposure is the best established risk factor for brain tumors. Hereditary syndromes including neurofibromatosis type 1 and 2, tuberous sclerosis, von Hippel–Lindau, and Li-Fraumeni are associated with higher risk of brain tumors.
Pathology and Classification
• Taking all age groups into account, histologic types of CNS tumors include meningiomas (35%), glioblastomas (16%), other astrocytomas (7%), tumors of cranial and paraspinal nerves (9%), tumors of the sellar region (14%), oligodendrogliomas (2%), ependymomas (2%), and embryonal tumors including medulloblastomas (1%).
• Among children 14 years or younger, histologic tumor types include pilocytic astrocytomas (17%), glioblastomas (3%), other astrocytomas (9%), ependymomas (6%), oligodendrogliomas (1%), embryonal tumors including medulloblastomas (15%), craniopharyngiomas (4%), and germ cell tumors (4%).
• Most brain tumors are supratentorial; notable exceptions include brainstem gliomas, cerebellar pilocytic astrocytomas, medulloblastomas, and ependymomas that involve the posterior fossa.
• Glioblastoma (World Health Organization grade IV astrocytoma) and brainstem gliomas in children carry the poorest prognosis. Pilocytic astrocytomas carry the best prognosis.
Clinical Manifestations
• General signs and symptoms from mass effect, increased intracranial pressure, edema, or shift or destruction of surrounding brain tissue may include changes in personality and cognitive function, headaches, nausea, vomiting, seizures, and papilledema.
• Focal signs and symptoms may include focal seizures, visual changes, speech abnormalities, gait abnormalities, and cranial nerve deficits.
• Posterior fossa tumors often compress the fourth ventricle, causing hydrocephalus, and frequently manifest with ataxia and intractable nausea and vomiting.
• Brainstem gliomas often manifest with a combination of cranial nerve palsies and “long tract” signs such as hemianesthesia or hemiparesis coupled with ataxia in cases with cerebellar involvement.
• Pineal region tumors (germ cell tumors, pineocytomas, and pineoblastomas, as well as gliomas of this region) may compress the aqueduct of Sylvius, causing hydrocephalus. Compression of the pretectal area produces Parinaud syndrome, with paralysis of upgaze, ptosis, and loss of pupillary light reflexes, along with retraction-convergence nystagmus.
Diagnostic Studies
• Magnetic resonance imaging with gadolinium contrast is the most sensitive technique.
• Computed tomography scanning is good for visualizing intratumoral calcifications and bone erosion but poor at visualizing the posterior fossa.
• Positron emission tomography and advanced magnetic resonance imaging techniques may help discriminate between tumor recurrence and radiation necrosis or pseudoprogression.
• Magnetic resonance spectroscopy may help distinguish a high-grade tumor from a low-grade tumor or radiation necrosis.
Therapy
• For most brain tumors, tissue diagnosis is required (an exception may be selected brainstem gliomas).
• Treatment for brain tumors is highly dependent on histologic type. For many tumors (e.g., gliomas, meningiomas, primitive neuroectodermal tumors [PNETs], and ependymomas), maximal surgical resection that is safely feasible is the primary treatment.
• For some tumors (e.g., glioblastomas, PNETs, and germ cell tumors), radiation therapy is an essential adjunct treatment after surgery.
