What Is A Brain Tumor?
Brain tumors begin when normal cells in the brain begin to change and mutate. Normal healthy cells die and are replaced. Instead of dying these mutated cells continue to live and increasingly divide into more abnormal cells forming tumors in the membrane, the pituitary gland, the cranial nerves, or the pineal gland. Primary brain tumors refer to tumors that originate in the brain, but more common are secondary brain tumors, also known as metastatic, which occur as a result of cancer from somewhere else in the body. Tumors can be either benign or malignant. Benign tumors are usually not cancer, do not invade nearby tissue, and when removed, do not recur. Malignant tumors are made up of cancer cells. They can press on areas of the brain and disrupt its function and may invade and grow into the healthy tissue around them.
Symptoms of brain tumors can differ depending on the type of tumor or its location and severity. Symptoms caused by brain tumors may include:
- Headache or a feeling of pressure in the brain
- Difficulty with balance
- Changes in behavior patterns such as moodiness, anger, or unexplained personality changes
- Nausea or vomiting
- Loss of movement or feeling in a limb
- Difficulty with speech and/or hearing
These symptoms can often be caused by other medical conditions as well, so please see your physician if you have experienced any of the above symptoms.
Tumors that begin in brain tissue are known as primary brain tumors and 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, however, astrocytomas most often arise in the cerebrum.
- 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.
- Ependymomas usually develop in the lining of the ventricles. They may also occur in the spinal cord.
- Oligodendrogliomas arise in the cells that produce myelin, the fatty covering that protects nerves. These tumors usually arise in the cerebrum. They grow slowly and usually do not spread into surrounding brain tissue. Oligodendrogliomas are rare and occur most often in middle-aged adults.
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).
- 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. 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.
- 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.
Age – While there are certain types of brain tumors that are more common in children, the risk of adult primary brain tumors increase with age and more commonly seen in older adults.
Radiation Exposure – Ionizing radiation, which includes previous radiation for cancer treatment, has been shown in some studies to link to some forms of brain cancer.
Genetics – A small percentage of some brain tumors has been linked to possible genetic factors. These are usually associated with certain cancer predisposition syndromes such as Li-Fraumeni syndrome, neurofibromatosis, tuberous sclerosis, and Turcot’s syndrome. Scientists are still studying the correlation and prevalence of family clusters of certain types of brain cancers to determine their cause.
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. Research and advancement in surgical techniques over the last 20 years have greatly increased the survival rates for patients with brain tumors. Targeted radiation and a better understanding of optimal chemotherapy regimens have not only lengthened the patients’ lives, but also produced less side effects and quicker recoveries. 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. Brain tumors are treated with surgery, radiation therapy, and chemotherapy; depending on the patient's needs, several methods may be used.
Before treatment begins, most patients are given steroids, which are drugs that relieve swelling (edema). They may also be given anticonvulsant medicine to prevent or control seizures. If hydrocephalus 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 and decide if targeted therapy is an option. In certain cases the biopsy is done with a needle, also known as stereotaxis. The surgeon uses robotic navigation to make a small hole in the skull and then guides a needle to the tumor.
Many patients and their families want to learn all they can about brain tumors and the treatment choices so they can take an active part in decisions about medical care. The doctor is the best person to answer these questions. When discussing treatment, the patient may want to talk with the doctor about research studies and clinical trials of new treatment methods.