What Is The Brain?

Together, the brain and spinal cord form the central nervous system. This complex system is part of everything we do. It controls the things we choose to do,like walk and talk,and the things our body does automatically,like breathe and digest food. The central nervous system is also involved with our senses; seeing, hearing, touching, tasting, and smelling, as well as our emotions, thoughts, and memory.

The brain is a soft, spongy mass of nerve cells and supportive tissue. It has three major parts: the cerebrum, the cerebellum, and the brain stem. The parts work together, but each has special functions.

The cerebrum, the largest part of the brain, fills most of the upper skull. It has two halves called the left and right cerebral hemispheres. The cerebrum uses information from our senses to tell us what is going on around us and tells our body how to respond. The right hemisphere controls the muscles on the left side of the body, and the left hemisphere controls the muscles on the right side of the body. This part of the brain also controls speech and emotions as well as reading, thinking, and learning.

The cerebellum, under the cerebrum at the back of the brain, controls balance and complex actions like walking and talking.

The brain stem connects the brain with the spinal cord. It controls hunger and thirst and some of the most basic body function, such as body temperature, blood pressure, and breathing.

The brain is protected by the bones of the skull and by a covering of three thin membranes called meninges. The brain is also cushioned and protected by cerebrospinal fluid. This watery fluid is produced by special cells in the four hollow spaces in the brain, called ventricles. It flows through the ventricles and in spaces between the meninges. Cerebrospinal fluid also brings nutrients from the blood to the brain and removes waste products from the brain.

The spinal cord is made up of bundles of nerve fibers. It runs down from the brain through a canal in the center of the bones of the spine. These bones protect the spinal cord. Like the brain, the spinal cord is covered by the meninges and cushioned by brospinal fluid.

Spinal nerves connect the brain with the nerves in most parts of the body. Other nerves go directly from the brain to the eyes, ears, and other parts of the head. This network of nerves carries messages back and forth between the brain and the rest of the body.

What Are Brain Tumors?

The body is made up of many types of cells. Each type of cell has special functions. Most cells in the body grow and then divide in an orderly way to form new cells as they are needed to keep the body healthy and working properly. When cells lose the ability to control their growth, they divide too often and without any order. The extra cells form a mass of tissue called a tumor. Each year, more than 16,000 people find out they have a brain tumor. Tumors are benign or malignant.

Benign brain tumors do not contain cancer cells. Usually these tumors can be removed, and they are not likely to recur. Benign brain tumors have clear borders. Although they do not invade nearby tissue, they can press on sensitive areas of the brain and cause symptoms.

Malignant brain tumors contain cancer cells. They interfere with vital functions and are life-threatening. Malignant brain tumors are likely to grow rapidly and crowd or invade the tissue around them. Like a plant, these tumors may put out "roots" that grow into healthy brain tissue. If a malignant tumor remains compact and does not have roots, it is said to be encapsulated. When an otherwise benign tumor is located in a vital area of the brain and interferes with vital functions, it may be considered malignant (even though it contains no cancer cells).

Doctors refer to some brain tumors by grade - from low grade (grade I) to high grade (grade IV). The grade of a tumor refers to the way the cells look under a microscope. Cells from higher grade tumors are more abnormal looking and generally grow faster than cells from lower grade tumors; higher grade tumors are more malignant than lower grade tumors.

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What Causes Brain Tumors?

The causes of brain tumors are not known. Researchers are trying to solve this problem. The more they can find out about the causes of brain tumors, the better the chances of finding ways to prevent them.

Doctors cannot explain why one person gets a brain tumor and another doesn't, but they do know that no one can "catch" a brain tumor from another person. Brain tumors are not contagious

Although brain tumors can occur at any age, studies show that they are most common in two age groups. The first group is children 3 to 12 years old; the second is adults 40 to 70 years old.

By studying large numbers of patients, researchers have found certain risk factors that increase a person's chance of developing a brain tumor. People with these risk factors have a higher-than-average risk of getting a brain tumor. For example, studies show that some types of brain tumors are more frequent among workers in certain industries, such as oil refining, rubber manufacturing, and drug manufacturing.

Other studies have shown that chemists and embalmers have a higher incidence of brain tumors. Researchers also are looking at exposure to viruses as a possible cause. Because brain tumors sometimes occur in several members of the same family, researchers are studying families with a history of brain tumors to see whether heredity is a cause. At this time, scientists do not believe that head injuries cause brain tumors to develop.

In most cases, patients with a brain tumor have no clear risk factors. The disease is probably the result of several factors acting together.

What Are Primary Brain Tumors?

Tumors that begin in the brain tissue are known as primary brain tumors. Secondary tumors are those that develop when cancer spreads to the brain. Primary brain tumors are classified by the type of tissue in which they begin. The most common brain tumors are gliomas, which begin in the glial (supportive) tissue. There are several types of gliomas:

Astrocytomas arise from small, star-shaped cells called astrocytes. They may grow anywhere in the brain or spinal cord. In adults, astrocytomas most often arise in the brain. In children, they occur in the brain stem, the cerebrum, and the cerebellum. A grade III astrocytoma is sometimes called anaplastic astrocytoma. A grade IV astrocytoma is usually called glioblastoma multiforme.

Brain stem gliomas occur in the lowest, stemlike part of the brain. The brain stem controls many vital functions. Tumors in this area generally cannot be removed. Most brain stem gliomas are high-grade astrocytomas.

Ependynomas usually develop in the lining of the ventricles. They also may occur in the spinal cord. Although these tumors can develop at any age, they are most common in childhood and adolescence.

Oligodendrogliomas arise in the cells that produce myelin, the fatty covering that protects nerves. These tumors usually arise in the brain. They grow slowly and usually do not spread into surrounding brain tissue. Oligodendrogliomas are rare. They occur most often in middle- aged adults but have been found in people of all ages.

There are other types of brain tumors that do not begin in glial tissue. Some of the most common are described below:

Medulloblastomas were once thought to develop from glial cells. However, recent research suggests that these tumors develop from primitive (developing) nerve cells that normally do not remain in the body after birth. For this reason, medulloblastomas are sometimes called primitive neuroectodermal tumors (PNET). Most medulloblastomas arise in the cerebellum; however, they may occur in other areas as well. These tumors occur most often in children and are more common in boys than in girls.

Meningiomas grow from the meninges. They are usually benign. Because these tumors grow very slowly, the brain may be able to adjust to their presence; meningiomas often grow quite large before they cause symptoms. They occur most often in women between 30 and 50 years of age.

Schwannomas are benign tumors that begin in Schwann cells, which produce the myelin that protects the acoustic nerve, the nerve of hearing. Acoustic neuromas are a type of schwannoma. They occur mainly in adults. These tumors affect women twice as often as men.

Craniopharyngiomas develop in the region of the pituitary gland near the hypothalamus. They are usually benign; however, they are sometimes considered malignant because they can press on or damage the hypothalamus and affect vital functions. These tumors occur most often in children and adolescents.

Germ cell tumors arise from primitive (developing) sex cells, or germ cells. The most frequent type of germ cell tumor in the brain is the germinoma.

Pineal region tumors occur in or around the pineal gland, a tiny organ near the center of the brain. The tumor can be slow growing (pineocytoma) or fast growing (pineoblastoma). The pineal region is very difficult to reach, and these tumors often cannot be removed

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What Are Secondary Brain Tumors?

Metastasis is the spread of cancer. Cancer that begins in other parts of the body may spread to the brain and cause secondary tumors. These tumors are not the same as primary brain tumors. Cancer that spreads to the brain is the same disease and has the same name as the original (primary) cancer. For example, if lung cancer spreads to the brain, the disease is called metastatic lung cancer because the cells in the secondary tumor resemble abnormal lung cells, not abnormal brain cells.

Treatment for secondary brain tumors depends on where the cancer started and the extent of the spread, as well as other factors, including the patient's age, general health, and response to previous treatment.

What Is The Treatment For Brain Cancer?

Treatment for a brain tumor depends on a number of factors. Among these are the type, location, and size of the tumor, as well as the patient's age and general health. Treatment methods and schedules often vary for children and adults. A treatment plan is developed to fit each patient's needs.

The patient's doctor may want to discuss the case with other doctors who treat brain tumors. Also, the patient may want to talk with the doctor about taking part in a research study of new treatment methods. Such studies are called clinical trials.

Many patients want to learn all they can about their disease and their treatment choices so they can take an active part in decisions about their medical care. A person with a brain tumor will have many questions, and the doctor is the best person to answer them. Most patients want to know what kind of tumor they have, how it can be treated, how effective the treatment is likely to be, and how much it is likely to cost.

Many people find it helpful to make a list of their questions before they see the doctor. Taking notes can make it easier to remember what the doctor says. Some patients also find that it helps to have a family member or friend with them when they talk with the doctor,either to take part in the discussion or just to listen.

Patients and their families have a lot to learn about brain tumors and their treatment. They should not feel that they need to understand everything the first time they hear it. They will have other chances to ask the doctor to explain things that are not clear.

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Treatment Methods

Brain tumors are treated with surgery, radiation therapy, and chemotherapy. Depending on the patient's needs, several methods may be used. The patient may be referred to doctors who specialize in different kinds of treatment and work together as a team. This medical team often includes a neurosurgeon, a medical oncologist, a radiation oncologist, a nurse, a dietitian, and a social worker. The patient also might work with a physical therapist, an occupational therapist, and a speech therapist.

Before treatment begins, most patients are given steroids, which are drugs that relieve swelling (edema). They also may be given anticonvulsant medicine to prevent or control seizures. If hydrocephalus (a condition which results in fluid accumulation around the brain) is present, the patient may need a shunt to drain the cerebrospinal fluid. A shunt is a long, thin tube placed in a ventricle of the brain and then threaded under the skin to another part of the body, usually the abdomen. It works like a drainpipe: excess fluid is carried away from the brain and is absorbed in the abdomen. (In some cases, the fluid is drained into the heart).

Surgery is the usual treatment for most brain tumors. To remove a brain tumor, a neurosurgeon makes an opening in the skull. This operation is called a craniotomy.

Whenever possible, the surgeon attempts to remove the entire tumor. However, if the tumor cannot be completely removed without damaging vital brain tissue, the doctor removes as much of the tumor as possible. Partial removal helps to relieve symptoms by reducing pressure on the brain and reduces the amount of tumor to be treated by radiation therapy or chemotherapy.

Some tumors cannot be removed. In such cases, the doctor may do only a biopsy. A small piece of the tumor is removed so that a pathologist can examine it under a microscope to determine the type of cells it contains. This helps the doctor decide which treatment to use.

Sometimes, a biopsy is done with a needle. Doctors use a special head frame (like a halo) and CT scans or MRI to pinpoint the exact location of the tumor. The surgeon makes a small hole in the skull and then guides a needle to the tumor. (Using this technique to do a biopsy or for treatment is called stereotaxis).

Stereotactic radiosurgery is another way to treat brain tumors. Treatment is given in just one session; high- energy rays are aimed at the tumor from many angles. In this way, a high dose of radiation reaches the tumor without damaging other brain tissue. (This use of radiation therapy is sometimes called Gamma KnifeŽ Surgery).

Radiation therapy (also called radiotherapy) is the use of high-powered rays to damage cancer cells and stop them from growing. It is often used to destroy tumor tissue that cannot be removed with surgery or to kill cancer cells that may remain after surgery. Radiation therapy is also used when surgery is not possible.

Radiation therapy may be given in two ways. External radiation comes from a large machine. Generally, external radiation treatments are given 5 days a week for several weeks. The treatment schedule depends on the type and size of the tumor and the age of the patient. Giving the total dose of radiation over an extended period helps to protect healthy tissue in the area of the tumor.

Radiation can also come from radioactive materials placed directly in the tumor (implant radiation therapy). Depending on the material used, the implant may be left in the brain for a short time or permanently. Implants lose a little radioactivity each day. The patient stays in the hospital for several days while the radiation is most active.

External radiation may be directed just to the tumor and the tissue close to it or, less often, to the entire brain (sometimes the radiation is also directed to the spinal cord). When the whole brain is treated, the patient often receives an extra dose of radiation to the area of the tumor. This boost can come from external radiation or from an implant.

Chemotherapy is the use of drugs to kill cancer cells. The doctor may use just one drug or a combination, usually giving the drugs by mouth or by injection into a blood vessel or muscle. Intrathecal chemotherapy involves injecting the drugs into the cerebrospinal fluid.

Chemotherapy is usually given in cycles: a treatment period followed by a recovery period, then another treatment period, and so on. Patients often do not need to stay in the hospital for treatment. Most drugs can be given in the doctor's office or the outpatient clinic of a hospital. However, depending on the drugs used, the way they are given, and the patient's general health, a short hospital stay may be necessary.

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Brain Tumors At A Glance

• Brain tumors can be either malignant or benign
• The causes of brain tumors are not known
• Brain tumors can occur at any age
• Primary brain tumors initially form in the brain tissue
• Secondary brain tumors are cancers that have spread to the brain tissue from tissue elsewhere in the body
• The symptoms of brain tumors depend on their size and their location in the brain
• Brain tumors are diagnosed by the doctor based on the results of a medical history and physical examination and results of a variety of specialized tests of the brain and nervous system
• Treatment of a brain tumor depends on the type, location, and size of the tumor, as well as the age and health of the patient