A brain tumor is a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body.
Brain tumors are slightly more common among men than women. Only meningiomas, which are noncancerous, are more common among women. Brain tumors usually develop during early or middle adulthood but may develop at any age. They are becoming more common among older people.
Brain tumors—whether cancerous or not—can cause serious problems because the skull is rigid, providing no room for the tumor to expand. Also, tumors may develop near parts of the brain that control vital functions and cause problems.
There are two main types of brain tumors:
Brain metastases are about 10 times more common than primary tumors. Over 80% of people with brain metastases have more than one metastasis.
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 originate in cells of the embryo (embryonic cells), early in the development of the fetus. Such tumors may be present at birth.
The most common type of primary cancerous brain tumor is a glioma, which has several subtypes. Gliomas account for 65% of all primary brain tumors. However, most cancerous brain tumors are secondary—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, cancers of 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 a normal immune system.
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Brain tumors can cause problems in the following ways:
Symptoms occur whether a brain tumor is noncancerous or cancerous. Noncancerous tumors grow slowly and may become quite large before causing symptoms.
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. As the tumor grows, it pushes and stretches but usually does not destroy nerve tissue, which can compensate for these changes very well. Thus, symptoms may not develop at first.
Many symptoms result from increased pressure within the skull:
Headache (see see Overview of Headache) is the most common and often the first symptom. However, 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 people lie down. The headache may awaken people from sleep. A gradually growing tumor causes a headache that typically is worse when people first awaken. If headaches with these characteristics start in people who have not had headaches before, a brain tumor may be the cause.
Often, increased pressure within the skull also causes mental function to deteriorate and mood to worsen. The personality may change. For example, people may become withdrawn, moody, and, often, inefficient at work. They may feel drowsy, confused, and unable to think. Such symptoms are often more apparent to family members and co-workers than to the affected person. Depression and anxiety, especially if either develops suddenly, may be an early symptom of a brain tumor. People may behave bizarrely. They may become uninhibited or behave in ways they never have before. In older people, certain brain tumors cause symptoms that may be mistaken for those of dementia (see see Dementia).
Later, as the pressure within the skull increases, nausea, vomiting, lethargy, increased drowsiness, intermittent fever, and even coma may occur. Vision may blur suddenly when people change positions.
Depending on which area of the brain is affected (see see Brain Dysfunction by Location), a tumor can do any of the following:
For example, a pituitary tumor may press on the nearby optic nerves (2nd cranial nerves), which are involved in vision, and thus impair peripheral vision. Any of the above symptoms suggests a serious disorder and requires immediate medical attention.
Other common symptoms of a brain tumor include vertigo, loss of balance, and incoordination. Some brain tumors, usually primary tumors, cause seizures.
If a tumor blocks the flow of cerebrospinal fluid through the spaces within the brain (ventricles), fluid may accumulate in the ventricles, causing them to enlarge (a condition called hydrocephalus). As a result, pressure within the skull increases. In addition to other symptoms of increased pressure, hydrocephalus makes turning the eyes upward difficult. In infants and very young children, 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 Fig. 1: Herniation: The Brain Under Pressure) may result. Two common types are
People with metastases to the brain may also have symptoms related to the original cancer. For example, if the cancer originated in the lungs, people may cough up bloody mucus. With metastases, weight loss is common.
Symptoms worsen over time unless the tumor is treated. With treatment, particularly for benign tumors, some people completely recover. For others, life span is shortened, sometimes greatly. The outcome depends on the type and location of the tumor.
Doctors consider the possibility of a brain tumor in people who have had a seizure for the first time or who have characteristic symptoms. Although doctors can often detect brain dysfunction during an examination, other procedures are needed to diagnose a brain tumor.
Magnetic resonance imaging (MRI) is the best test for identifying brain tumors. Computed tomography (CT) is a good alternative. It can identify most brain tumors. Before these tests, a substance that makes the tumor easier to see (a contrast agent for MRI or a radiopaque dye for CT) is injected into a vein. These tests can show the tumor's size and exact position in great detail. When a brain tumor is detected, more diagnostic procedures are done to determine the particular kind.
Sometimes a spinal tap (lumbar puncture—see Fig. 2: How a Spinal Tap Is Done) is done to obtain cerebrospinal fluid for examination under a microscope. This procedure is done when doctors suspect that the tumor has invaded the layers of tissues that cover the brain (meninges). Such tumors may block the absorption of cerebrospinal fluid. A spinal tap 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 done in people who have a large tumor that is increasing pressure within the skull. In these people, removing cerebrospinal fluid during a spinal tap may cause the tumor to move, resulting in herniation of the brain.
Specialized tests can sometimes help with the diagnosis. For example, blood and cerebrospinal fluid may also be tested to check for substances secreted by tumors (called tumor markers) and for gene abnormalities that are characteristic of certain tumors. Identifying certain gene abnormalities can help predict which treatments will be most effective.
A biopsy of the tumor (removal of a sample of the tumor for examination under a microscope) is sometimes needed to identify the type of tumor, including whether it is cancerous. A biopsy may be done during surgery in which all or part of the tumor is removed. If a tumor is difficult to reach, a stereotactic biopsy may be done. For this procedure, a frame is attached to the skull. The frame provides reference points that can be identified on an MRI or a CT scan. These reference points enable doctors to guide the biopsy needle precisely into the tumor.
Treatment of a brain tumor depends on its location and type. When possible, the tumor is removed surgically in a procedure called craniotomy (which involves opening the skull). Some brain tumors can be removed with little or no damage to the brain. However, many grow in an area that makes removal by traditional surgery difficult or impossible without destroying essential structures.
Traditional surgery sometimes causes brain damage that can lead to symptoms such as partial paralysis, changes in sensation, weakness, and impaired mental function. 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.
Surgical removal 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 effective in treating noncancerous tumors such as meningiomas and acoustic neuromas. Therefore, radiosurgery is often used instead of traditional surgery for these tumors. Radiosurgery directs highly focused beams of radiation precisely at the tumor. It does not involve an incision. To focus the radiation more precisely, doctors often use stereotactic techniques, which sometimes involve attaching a frame to the head to provide reference points.
Cancerous brain tumors:
Usually, a combination of surgery, radiation therapy, and chemotherapy is used. 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. Radiosurgery is used when traditional surgery cannot be, especially for the treatment of metastases.
For very aggressive tumors, chemotherapy is given with radiation therapy. Radiation therapy plus chemotherapy rarely cures but may shrink a tumor enough to keep it under control for many months or even years.
After radiation therapy, ongoing chemotherapy is used to treat some types of cancerous brain tumors. Chemotherapy appears to be particularly effective in treating anaplastic oligodendrogliomas.
Increased pressure within the skull:
This extremely serious condition requires immediate medical attention. If people are in a coma or have difficulty breathing, herniation may be the cause. To help such people breathe, doctors insert a plastic tube through the nose or mouth into the windpipe (trachea) and attach it to a ventilator (a procedure called endotracheal intubation). This procedure also helps reduce pressure within the skull until other treatments can be given. Drugs such as mannitol and corticosteroids are usually given by injection to reduce the pressure and prevent herniation. They reduce swelling around the tumor. Within days or sometimes hours, corticosteroids can often restore functions lost because of the tumor and can relieve headache, 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 drain the cerebrospinal fluid and thus reduce the risk of herniation. 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. A local anesthetic (usually plus a sedative) or a general anesthetic may be used. 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 depends largely on where the cancer originated. Radiation therapy directed at the metastases in the brain is often used. Surgical removal may benefit people who have only a single metastasis. Sometimes radiosurgery is used.
People with cancerous brain tumors have a limited life expectancy and are likely to become unable to make decisions about medical care. Consequently, establishing advance directives is advisable (see see Advance Directives). 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.
Last full review/revision June 2013 by Roy A. Patchell, MD