Brain Tumor Increase: Only Some Causes Known

by Food and Drug Administration (FDA)

It was a routine annual physical, and everything checked out fine. Blood pressure normal, electrocardiogram normal, weight good, no particular complaints — except one. The patient, 65-year-old Sylvia Zeidner of Potomac, Md., had been having some peculiar dizzy spells, and she laughingly told the doctor, "I must have a brain tumor."

She did. By taking her joking words seriously, the doctor saved her from more devastating symptoms and possibly saved her life. He sent her for an MRI, or magnetic resonance imaging, a noninvasive test approved by the Food and Drug Administration in the early 1980s that is especially valuable in diagnosing brain tumors. The MRI revealed a large baseball-sized tumor sitting on top of Zeidner's brainstem, in the lower back part of the skull.

Surgery was scheduled for a week later. The day before surgery, the radiologist threaded a catheter — a piece of flexible rubber tubing — from an incision in her groin up through her body to the brain and passed a substance through the catheter that blocked the tumor's blood supply, causing it to shrink. During the nine-hour-long operation the next day, the surgeon successfully removed from her brain a meningioma, a type of tumor (usually benign, not cancerous, as it was in this case) that grows from the meninges, the membrane covering the brain and spinal cord. Afterwards, when she inquired how so large a tumor could have caused so few symptoms, the doctor replied that the tumor had grown very slowly, perhaps over 20 years. The brain had gradually accommodated the tumor's increasing size until the pressure became too much and the brain cried out in protest. Since the brainstem controls vital functions, such as blood pressure, breathing and the beating of the heart, she could have died suddenly if the tumor had grown large enough to affect those vital systems.

In the United States, about 100,000 cases of brain tumors are predicted for 1996, almost double the number of just a decade ago. Of these, about 17,000 will originate from brain tissue and are called primary brain tumors. Secondary (metastatic) brain tumors, those seeded by cancer cells floating in the bloodstream from cancer of the breast, lung, kidney, skin, or other organs, will account for the remainder. (Cancer can spread from other parts of the body to the brain, but primary tumor cells rarely travel outside the brain.) The incidence of brain tumors, both primary and metastatic, appears to be increasing worldwide, especially among the elderly, and no one is sure why.

Only Some Causes Known

Brain tumors are abnormal growths of tissues within the skull. They can be benign, like Sylvia's, or can be malignant, meaning cancerous. Even benign brain tumors can be fatal when removal would damage vital brain centers, or if they are inaccessible because they lie buried deep inside the brain. Individuals of any age can develop brain tumors, but they occur more frequently in older adults and in children under the age of 15. (The only form of cancer that causes more childhood deaths is leukemia.) Certain brain tumors occur exclusively in children and adolescents, others in adults.

The causes of primary brain tumors are unknown. Researchers so far have not been successful in establishing a link between brain tumors and viruses, diet, injury, hormones, certain medications, smoking, alcohol, or other factors.

It is known that people who work with certain chemicals are at risk. Studies have shown that some types of brain tumors occur more frequently among workers in the oil refining, rubber manufacturing, and drug industries and among chemists and embalmers.

Many adults treated as children decades ago for scalp ringworm with high doses of ionizing radiation have developed brain tumors years after exposure.

People who have impaired immunity, such as those with AIDS or those who have undergone organ transplants, are also susceptible to brain tumors.

About 5 percent of primary brain tumors appear to be due to hereditary factors. Sometimes, several members of the same family have brain tumors. Certain rare inherited syndromes, such as neurofibromatosis, the "Elephant Man" disease, increase the risk of developing a brain tumor.

Many parents whose children have developed brain tumors — and who live near toxic waste sites or high-tension power lines — claim that exposure to these environmental hazards is responsible for the tumors. But since brain tumors occasionally occur in random "clusters," epidemiologists say that studies have not been able to prove a connection between such exposure and brain tumors.

Vague or Dramatic

Depending on the tumor's size, type and location, symptoms can be as vague as Sylvia's dizziness or as dramatic as the sudden seizure that shook the left side of the body of Lee Atwater, Republican party chairman, while he was addressing a GOP fund-raiser in 1990.

Eventually, all brain tumor symptoms get worse. Because the space inside the skull is limited, as the tumor grows it causes increased pressure on the brain. The tumor may also block the flow of cerebrospinal fluid, the watery cushion that protects the brain and spinal cord from shock. In young children, whose skulls have not yet fused, the head may enlarge in response to this pressure, causing a condition known as hydrocephalus.

Tumors in some locations produce characteristic symptoms. For example, tumors growing in the brain's occipital lobe, which interprets visual images, often cause lack of vision in part of the visual field of each eye. However, many common symptoms of brain tumors are similar to those of other diseases (see "Distinguishing Symptoms") and can result in misdiagnosis.

About the Author

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