Brain Neoplasms 

Brain tumors may originate from neural elements within the brain, or they may represent spread of distant cancers. Primary brain tumors arise from CNS tissue and account for roughly half of all cases of intracranial neoplasms. The remainder of brain neoplasms are caused by metastatic lesions. In adults, two thirds of primary brain tumors arise from structures above the tentorium (supratentorial), whereas in children, two thirds of brain tumors arise from structures below the tentorium (infratentorial). Gliomas, metastases, meningiomas, pituitary adenomas, and acoustic neuromas account for 95% of all brain tumors. Classification by tumor cell type is irrelevant to the emergency physician because emergent treatment is the same regardless of the tumor type.

Many review articles have been written on brain tumors, and this discussion at times draws from the consensus of these reviews.^{[1, 2, 3, 4, 5, 6, 7, 8, 9]}

Glioma has recently been in the news with the diagnosis of this malignant brain tumor in May 2008 in Senator Edward M. Kennedy and his death August 25, 2009. For more information on this, see the Medscape Medical News article and the WebMD Health News article.

Tumors of the brain produce neurologic manifestations through a number of mechanisms. Small, critically located tumors may damage specific neural pathways traversing the brain. Tumors can invade, infiltrate, or supplant normal parenchymal tissue, disrupting normal function. Because the brain dwells in the limited volume of the cranial vault, growth of intracranial tumors with accompanying edema may cause increased intracranial pressure. Tumors adjacent to the third and fourth ventricles may impede the flow of cerebrospinal fluid, leading to obstructive hydrocephalus. In addition, tumors generate new blood vessels (ie, angiogenesis), disrupting the normal blood-brain barrier and promoting edema.

The cumulative effects of tumor invasion, edema, and hydrocephalus may elevate the intracranial pressure (ICP) and impair cerebral perfusion. Intracranial compartmental rise in ICP may provoke shifting or herniation of tissue under the falx cerebri, through the tentorium cerebelli, or through the foramen magnum.

Slow-growing tumors, particularly tumors expanding in the so-called silent areas of the brain, such as the frontal lobe, may be associated with a more insidious clinical course. These tumors tend to be larger at detection.

Most primary brain tumors do not metastasize, but if they do metastasize, intracranial spread generally precedes distant dissemination.

Metastatic brain tumors from non-CNS primary tumors may be the first sign of malignancy, or they may herald a relapse. Nonetheless, the signs and symptoms of brain metastases simulate those of primary brain tumors.

Leptomeningeal infiltration may present with dysfunction of multiple cranial nerves.

Frequency

United States

Estimates of the annual incidence rate of primary brain tumors range from 7-19.1 cases per 100,000 population. Metastatic tumors to the brain are more common with more than 200,000 patients per year in the United States with a new diagnosis of intracranial metastases. An increase in the prevalence of HIV infection corresponds to an increase in the occurrence of primary CNS lymphoma. Pituitary adenomas are exceptionally common, and they are frequent incidental findings on autopsy. Autopsy series of patients with systemic cancer show that intracranial metastases are present in 18-24% of patients.

International

The international incidence is not known, but it is thought to parallel that of the United States.

Mortality/Morbidity

• In the United States in 1999, primary cancers of the central nervous system were the cause of death in approximately 13,100 people.
• Brain tumors are the second most common cancer in children, comprising 15-25% of all pediatric malignancies.
• Perhaps no other cancer is as feared as brain tumor since severe disability, including paralysis, seizures, gait disturbances, and impairment of intellectual capacity may occur.

Race

Differences are seen between ethnic groups within the same country, and a 3-fold difference in incidence has been reported between countries worldwide. Developed countries appear to have the highest rates, but this may reflect better registration systems.

Sex

Meningiomas and pituitary adenomas are slightly more common in women than in men.

Males are more likely to be diagnosed with brain tumors than females, with a male-to-female ratio of 1.5:1.

Age

• Tumors in the posterior fossa predominate in preadolescent children, with the incidence of supratentorial tumors increasing from adolescence to adulthood.
• Low-grade gliomas, such as astrocytomas, are more common in younger people than in older people. High-grade gliomas, such as anaplastic astrocytoma and glioblastoma multiforme, tend to originate in the fourth or fifth decade or beyond.
• In children, brain tumors are the most prevalent solid tumor, second only to leukemia as a cause of pediatric cancer. The incidence rate of primary CNS neoplasms is 3.6 cases per 100,000 children each year.