Brain Tumors
A brain tumor is a noncancerous (benign) or cancerous (malignant) growth in the brain, whether it originates in the brain or has spread (metastasized) to the brain from another part of the body.
Brain tumors are equally common among men and women, but some types are more common among men and others are more common among women. Brain tumors are occurring with increasing frequency among older people.
Brain tumors may be primary or secondary. Primary brain tumors originate in the cells within or next to the brain. These tumors may be cancerous or noncancerous. Secondary brain tumors are metastases originating in another part of the body and thus are always cancerous.
Noncancerous tumors are named for the specific cells or tissues in which they originate. For example, hemangioblastomas originate in blood vessels ("hema" refers to blood vessels, and hemangioblasts are the cells that develop into blood vessel tissue). Some noncancerous tumors that originate in embryonic cells may be present at birth.
Most commonly, cancerous brain tumors are metastases from cancer that started in another part of the body. Metastases may grow in a single part of the brain or in several different parts. Many types of cancer--including breast cancer, lung cancer, cancer in the digestive tract, malignant melanoma, leukemia, and lymphoma--can spread to the brain. Lymphomas of the brain are common among people who have AIDS and, for unknown reasons, are becoming more common among people who have normal immune systems. The most common type of primary cancerous brain tumor is a glioma.
 See the table Tumors That Originate In or Near the Brain.
Symptoms
Symptoms occur whether a brain tumor is noncancerous or cancerous. A brain tumor can cause many different symptoms, and symptoms may occur suddenly or develop gradually. Which symptoms develop first and how they develop depend on the tumor's size, growth rate, and location. In some parts of the brain, even a small tumor can have devastating effects. In other parts of the brain, tumors can grow relatively large before any symptoms appear. At first, the tumor pushes and stretches nerve tissue, which can compensate for these changes very well, so symptoms may not develop at first. Symptoms develop when brain tissue is destroyed or the pressure within the skull (intracranial pressure) increases, compressing the brain. Pressure may increase because the tumor is enlarging. Eventually, any brain tumor can increase pressure within the skull.
When the brain tumor is a metastasis from cancer in another part of the body, a person may also have symptoms related to that cancer. For example, a person with a metastasis from lung cancer may have a cough that brings up bloody mucus in addition to symptoms of a brain tumor.
A headache (see Section 6, Chapter 79) is often the first symptom, although most headaches are not caused by brain tumors. A headache due to a brain tumor usually recurs more and more often as time passes. It eventually becomes constant without relief. It is often worse when the person lies down and may awaken the person from sleep. A gradually growing tumor causes a headache that typically is worse when the person first awakens. If headaches with these characteristics start in a person who has not had headaches before, a brain tumor may be the cause.
Brain tumors may produce a change in personality. For example, a person may become withdrawn, moody, and, often, inefficient at work. A person may feel drowsy, confused, and unable to think. Such symptoms are often more apparent to family members and co-workers than to the person. Depression and anxiety, especially if either develops suddenly, may be an early symptom of a brain tumor. Bizarre behavior is unusual. In older people, certain brain tumors cause symptoms that may be mistaken for those of dementia (see Section 6, Chapter 83).
Other common symptoms of a brain tumor include dizziness, loss of balance, and incoordination. Later, as the pressure within the skull increases, nausea, vomiting, lethargy, drowsiness, intermittent fever, and even coma may occur. Some brain tumors cause seizures.
Depending on which area of the brain is affected (see Section 6, Chapter 82), a tumor can cause an arm, a leg, or one side of the body to become weak or paralyzed or can impair the ability to feel heat, cold, pressure, a light touch, or sharp objects. The ability to express or understand language may be lost. Tumors can also affect hearing, smell, and sight (causing such symptoms as double vision and loss of vision). For example, a pituitary tumor may press on the nearby optic nerves (cranial nerve II), which are involved in vision, and thus impair peripheral vision. If the tumor compresses the brain stem, the pulse and breathing rate may become abnormally fast or slow. Any of these symptoms suggests a serious disorder and requires immediate medical attention.
If a tumor blocks the flow of cerebrospinal fluid through the spaces within the brain (ventricles), fluid may accumulate, causing the ventricles to enlarge (a condition called hydrocephalus). As a result, pressure within the skull increases. In addition to other symptoms of increased pressure, hydrocephalus causes difficulty turning the eyes upward. In infants, the head enlarges.
If the pressure within the skull is greatly increased, the brain may be pushed downward because the skull cannot expand. Herniation of the brain (see Section 6, Chapter 87) may result. There are two main types. In a transtentorial herniation, the upper part of the brain (cerebrum) is forced through the narrow opening (the tentorial notch) in the relatively rigid tissue that separates the cerebrum from the lower parts of the brain (cerebellum and brain stem). In people with this type of herniation, consciousness is reduced. The side of the body opposite the tumor may be paralyzed.
In a tonsillar herniation, a tumor that originates in the lower part of the brain pushes the lowest part of the cerebellum (the cerebellar tonsils) through the opening at the base of the skull (the foramen magnum). As a result, the brain stem, which controls breathing, heart rate, and blood pressure, is compressed and malfunctions. If not diagnosed and treated immediately, a tonsillar herniation rapidly results in coma and death.
 See the sidebar Common Symptoms of Some Brain Tumors.
See the sidebar What Is Pseudotumor Cerebri?
Diagnosis
Doctors consider the possibility of a brain tumor in people who have had a seizure for the first time or who have the characteristic symptoms. Although doctors can often detect brain dysfunction by performing a physical examination, other procedures are needed to diagnose a brain tumor.
Standard x-rays of the skull can detect tumors that erode bone (such as a meningioma or pituitary adenoma). However, magnetic resonance imaging (MRI) and computed tomography (CT) are more useful because they can detect all types of brain tumors. They can also show the tumor's size and exact position in great detail. When a brain tumor is detected, more diagnostic procedures are performed to determine the particular kind.
Sometimes a spinal tap (lumbar puncture (see Section 6, Chapter 77)) is performed to obtain cerebrospinal fluid for examination under a microscope. This procedure is performed when doctors suspect that the tumor has invaded the meninges, is compressing the cranial nerves, and is blocking the flow of cerebrospinal fluid. The procedure may also help when the diagnosis or the type of tumor is unclear. Cerebrospinal fluid may contain cancer cells. However, a spinal tap cannot be performed in people who have a large tumor that is increasing pressure within the skull. The removal of cerebrospinal fluid during a spinal tap may cause the tumor to move, resulting in herniation of the brain.
A biopsy of the tumor (removal of a sample of the tumor for examination under a microscope) is usually needed to identify the type of tumor, including whether it is cancerous. A biopsy may be performed during surgery in which all or part of the tumor is removed. If a tumor is difficult to reach, a biopsy may be performed using three-dimensional needle placement (stereotactic biopsy) with CT.
Treatment and Prognosis
Treatment of a brain tumor depends on its location and type. When possible, the tumor is removed surgically. Some brain tumors can be removed with little or no damage to the brain. However, many grow in an area that makes removal difficult or impossible without destroying essential structures. Surgery sometimes causes brain damage that can lead to partial paralysis, changes in sensation, weakness, and impaired intellect. Nevertheless, removing a tumor--whether cancerous or noncancerous--is essential if its growth threatens important brain structures. Even when a cure is impossible, surgery may be useful to reduce the tumor's size, relieve symptoms, and help doctors determine whether other treatments, such as radiation therapy or chemotherapy, are warranted.
Removal of noncancerous tumors is often safe and cures the person. However, very small tumors and tumors in older people may be left in place as long as they are not causing symptoms. Sometimes radiation therapy is given after surgery to destroy any remaining tumor cells. Radiosurgery is used to treat tumors that are small and not readily accessible with traditional surgery. It is also used to treat meningiomas. Radiosurgery uses focused radiation to destroy a tumor rather than an incision to remove it. With radiosurgery, treatment is completed in 1 day.
Most cancerous brain tumors are treated with a combination of surgery, radiation therapy, and chemotherapy. As much of the tumor as can be removed safely is removed, and then radiation therapy is begun. Radiation therapy is given over a course of several weeks. It rarely cures but may shrink a tumor enough to keep it under control for many months or even years. Chemotherapy is used to treat some types of cancerous brain tumors. Chemotherapy appears to be particularly effective in treating anaplastic oligodendrogliomas. Radiosurgery is also used to treat cancerous brain tumors.
Increased pressure within the skull is extremely serious and requires immediate medical attention. Drugs such as mannitol and corticosteroids are usually given by injection to reduce the pressure and prevent herniation. Corticosteroids can often restore function within days, even if the tumor is large. If the tumor is blocking the flow of cerebrospinal fluid through the spaces within the brain, a device may be used to reduce the risk of herniation by draining the cerebrospinal fluid. The device consists of a small tube (catheter) connected to a gauge that measures the pressure within the skull. The tube is inserted through a tiny opening drilled in the skull. This procedure may be performed using a local anesthetic (usually plus a sedative) or a general anesthetic. The tube is removed or converted to a permanent drain (shunt) after a few days. During this time, doctors surgically remove all or part of the tumor or use radiosurgery or radiation therapy to reduce the size of the tumor and thus relieve the blockage.
Treatment of metastases to the brain depends largely on where the cancer originated. Radiation therapy directed at the metastases in the brain is often performed. Surgical removal may benefit people who have only a single metastasis. In addition to traditional treatments, radiosurgery and some experimental treatments, involving chemotherapy and radioactive implants in the tumor, are being tried.
The prognosis for people who have a brain tumor ranges from complete recovery to death, depending on the type and location of the tumor.
End-of-Life Issues: Because people with cancerous brain tumors have a limited life expectancy, establishing advance directives is advisable (see Section 1, Chapter 9). Advance directives can help a doctor determine what kind of care people want if they become unable to make decisions about medical care. Many cancer centers, especially those with hospice facilities, provide counseling and home health services.
See the sidebar Understanding Tumor Treatment.
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