What causes brain tumors?

What causes brain tumors?

The majority of brain tumors have abnormalities of genes involved in cell cycle control, causing uncontrolled cell growth. These abnormalities are caused by alterations directly in the genes, or by chromosome rearrangements which change the function of a gene.
Patients with certain genetic conditions (i.e., neurofibromatosis, von Hippel-Lindau disease, Li-Fraumeni syndrome, and retinoblastoma) also have an increased risk to develop tumors of the central nervous system. There have also been some reports of people in the same family developing brain tumors who do not have any of these genetic syndromes.
Research has been investigating parents of children with brain tumors and their past exposure to certain chemicals. Some chemicals may change the structure of a gene that protects the body from diseases and cancer. Workers in oil refining, rubber manufacturing, and chemists have a higher incidence of certain types of tumors. Which, if any, chemical toxin is related to this increase in tumors is unknown at this time.
Patients who have received radiation therapy to the head as part of prior treatment for other malignancies are also at an increased risk for new brain tumors.

What are the symptoms of a brain tumor?

The following are the most common symptoms of a brain tumor. However, each person may experience symptoms differently. Symptoms vary depending on the size and location of tumor. Many symptoms are related to an increase in pressure in or around the brain. There is no spare space in the skull for anything except the delicate tissues of the brain and its fluid. Any tumor, extra tissue, or fluid can cause pressure on the brain and result in increased intracranial pressure (ICP), which may result from one or more of the ventricles that drain cerebral spinal fluid (CSF, the fluid that surrounds the brain and spinal cord) becoming blocked and causing the fluid to be trapped in the brain. This increased ICP may cause the following:

headache
vomiting (usually in the morning)
nausea
personality changes
irritability
drowsiness
depression
decreased cardiac and respiratory function and, eventually, coma if not treated

Symptoms of brain tumors in the cerebrum (front of brain) may include:

increased intracranial pressure (ICP)
seizures
visual changes
slurred speech
paralysis or weakness on half of the body or face
drowsiness and/or confusion
personality changes/impaired judgement
short-term memory loss
gait disturbances
communication problems

Symptoms of brain tumors in the brainstem (back of brain) may include:

increased intracranial pressure (ICP)
seizures
endocrine problems (diabetes and/or hormone regulation)
visual changes or double vision
headaches
paralysis of nerves/muscles of the face, or half of the body
respiratory changes
clumsy, uncoordinated walk
hearing loss
personality changes

Symptoms of brain tumors in the cerebellum (back of brain) may include:

increased intracranial pressure (ICP)
vomiting (usually occurs in the morning without nausea)
headache
uncoordinated muscle movements
problems walking (ataxia)

The symptoms of a brain tumor may resemble other conditions or medical problems. Always consult your physician for a diagnosis.

How is a brain tumor diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for brain tumors may include the following:

neurological examination - your physician tests reflexes, muscle strength, eye and mouth movement, coordination, and alertness.
computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. MRI is very helpful for looking at the brain and spinal cord.
x-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
arteriogram (Also called an angiogram.) - an x-ray of the arteries and veins to detect blockage or narrowing of the vessels.
myelogram - a procedure that uses dye injected into the spinal canal to make the structure clearly visible on x-rays.
spinal tap (Also called a lumbar puncture.) - a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.
positron emission tomography (PET) - a type of nuclear medicine procedure. This means that a tiny amount of a radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, PET studies evaluate the metabolism of a particular organ or tissue, so that information about the physiology (functionality) and anatomy (structure) of the organ or tissue is evaluated, as well as its biochemical properties. Thus, PET may detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes such as computed tomography (CT) or magnetic resonance imaging (MRI).
magnetic resonance spectroscopy (MRS) - a procedure that produces images depicting function rather than shape. The equipment requires a special, highly complex facility.
biopsy of the tumor - a procedure in which a sample of tissue is removed (with a needle or during surgery) to be looked at under a microscope.

Diagnosis of a brain tumor depends mostly on the types of cells involved and the tumor location.

What are the different types of brain tumors?

There are many different types of brain tumors. They are usually categorized by the type of cell where the tumor begins, or they are also categorized by the area of the brain where they occur. The most common types of brain tumors include the following:

gliomas
The most common type of primary brain tumor is a glioma. Gliomas begin from glial cells, which are the supportive tissue of the brain. There are several types of gliomas, categorized by where they are found, and the type of cells that originated the tumor. The following are the different types of gliomas:
- astrocytomas
  Astrocytomas are glial cell tumors that are derived from connective tissue cells called astrocytes. These cells can be found anywhere in the brain or spinal cord. Astrocytomas are the most common type of childhood brain tumor, and the most common type of primary brain tumor in adults. Astrocytomas are generally subdivided into high-grade, medium-grade or low-grade tumors. High-grade astrocytomas (glioblastomas) are the most malignant of all brain tumors. Astrocytomas are further classified for presenting signs, symptoms, treatment, and prognosis, based on the location of the tumor. The most common location of these tumors in children is in the cerebellum, where they are called cerebellar astrocytomas. These persons usually have symptoms of increased intracranial pressure, headache, and vomiting. There can also be problems with walking and coordination, as well as double vision. In adults, astrocytomas are more common in the cerebral hemispheres (cerebrum), where they commonly cause increased intracranial pressure (ICP), seizures, or changes in behavior.
- brain stem gliomas
  Brain stem gliomas are tumors found in the brain stem. Most brain stem tumors cannot be surgically removed because of the remote location and delicate and complex function this area controls. Brain stem gliomas occur almost exclusively in children; the group most often affected is the school-age child. The child usually does not have increased intracranial pressure (ICP), but may have problems with double vision, movement of the face or one side of the body, or difficulty with walking and coordination.
- ependymomas
  Ependymomas are also glial cell tumors. They usually develop in the lining of the ventricles or in the spinal cord. The most common place they are found in children is near the cerebellum. The tumor often blocks the flow of the CSF (cerebral spinal fluid, which bathes the brain and spinal cord), causing increased intracranial pressure. This type of tumor mostly occurs in children younger than 10 years of age. Ependymomas can be slow growing, compared to other brain tumors, but may recur after treatment is completed. Recurrence of ependymomas results in a more invasive tumor with more resistance to treatment. Two percent of brain tumors are ependymomas.
- optic nerve gliomas
  Optic nerve gliomas are found in or around the nerves that send messages from the eyes to the brain. They are frequently found in persons who have neurofibromatosis, a condition a child is born with that makes him/her more likely to develop tumors in the brain. Persons usually experience loss of vision, as well as hormone problems, since these tumors are usually located at the base of the brain where hormonal control is located. These are typically difficult to treat due to the surrounding sensitive brain structures.
- oligodendrogliomas
  This type of tumor also arises from the supporting cells of the brain. They are found commonly in the cerebral hemispheres (cerebrum). Seizures are a very common symptom of these tumors, as well as headache, weakness, or changes in behavior or sleepiness. These tumors have a better prognosis than most other gliomas, but they can become more malignant with time. Four percent of brain tumors are oligodendrogliomas.
metastatic tumors
In adults, metastatic brain tumors are the most common type of brain tumors. These are tumors that begin to grow in another part of the body, then spread to the brain through the bloodstream. When the tumors spread to the brain, they commonly go to the part of the brain called the cerebral hemispheres, or to the cerebellum. Often, a patient may have multiple metastatic tumors in several different areas of the brain. Lung, breast, and colon cancers frequently travel to the brain, as do certain skin cancers. Metastatic brain tumors may be quite aggressive and may return even after surgery, radiation therapy, and chemotherapy.
meningiomas
Meningiomas are usually benign tumors that come from the meninges or dura, which is the tough outer covering of the brain just under the skull. This type of tumor accounts for about 25 percent of brain tumors. They are slow growing and may exist for years before being detected. Meningiomas are most common in older patients, with the highest rate in people in their 70s and 80s. They are commonly found in the cerebral hemispheres just under the skull. They usually are separate from the brain and can sometimes be removed entirely during surgery. They can, however, recur after surgery and certain types can be malignant.
Schwannomas
Schwannomas are benign tumors, similar to meningiomas. They arise from the supporting cells of the nerves leaving the brain, and are most common on the nerves that control hearing and balance. When schwannomas involve these nerves, they are called vestibular schwannomas or acoustic neuromas. Commonly, they present with loss of hearing, and occasionally loss of balance, or problems with weakness on one side of the face. Surgery can be difficult because of the area of the brain in which they occur, and the vital structures around the tumor. Occasionally, radiation (or a combination of surgery and radiation) is used to treat these tumors.
pituitary tumors
The pituitary gland is a gland located at the base of the brain. It produces hormones that control many other glands in the body. These glands include the thyroid gland, the adrenal glands, the ovaries and testes, as well as milk production by pregnant women, and fluid balance by the kidney. Tumors that occur in or around the area of the pituitary gland can affect the functioning of the gland, or overproduce hormones that are sent to the other glands. This can lead to problems with thyroid functioning, impotence, milk production from the breasts, irregular menstrual periods, or problems regulating the fluid balance in the body. In addition, due to the closeness of the pituitary to the nerves to the eyes, patients may have decreased vision.
Tumors in the pituitary are frequently benign, and total removal makes the tumors less likely to recur. Since the pituitary is at the base of the skull, approaches for removal of a pituitary tumor may involve entry through the nose or the upper gum. Certain types of tumors may be treated with medication, which, in some cases, can shrink the tumor or stop the growth of the tumor.
primitive neuroectodermal tumors (PNET)
PNET can occur anywhere in the brain, although the most common place is in the back of the brain near the cerebellum. When they occur here, they are called medulloblastomas. The symptoms depend on their location in the brain, but typically the patient experiences increased intracranial pressure. These tumors are fast growing and often malignant, with occasional spreading throughout the brain or spinal cord.
medulloblastomas
Medulloblastomas are one type of PNET that are found near the midline of the cerebellum. This tumor is rapidly growing and often blocks drainage of the CSF (cerebral spinal fluid, which bathes the brain and spinal cord), causing symptoms associated with increased ICP. Medulloblastoma cells can spread (metastasize) to other areas of the central nervous system, especially around the spinal cord. A combination of surgery, radiation, and chemotherapy is usually necessary to control these tumors.
craniopharyngiomas
Craniopharyngiomas are benign tumors that occur at the base of the brain near the nerves from the eyes to the brain, and the hormone centers. These tumors comprise only one percent of all brain tumors diagnosed in the US. Symptoms include headaches, as well as problems with vision. Hormonal imbalances are common, which may lead to poor growth in children. Symptoms of increased intracranial pressure may also be seen. Although these tumors are benign, they are hard to remove due to the sensitive brain structures that surround them.
pineal region tumors
Many different tumors can arise near the pineal gland, a gland that helps control sleep and wake cycles. Gliomas are common in this region, as are pineal blastomas. In addition, germ cell tumors, another form of malignant tumor, can be found in this area. Benign pineal gland cysts are also seen in this location, which makes the diagnosis difficult between what is malignant and what is benign. Biopsy or removal of the tumor is frequently necessary to tell the different types of tumors apart. Persons with tumors in this region frequently experience headaches or symptoms of increased intracranial pressure. Treatment depends on the tumor type and size.

Treatment for brain tumors:

Specific treatment for brain tumors will be determined by your physician based on:

your age, overall health, and medical history
type, location, and size of the tumor
extent of the condition
your tolerance for specific medications, procedures, or therapies
expectations for the course of the condition
your opinion or preference

Treatment may include (alone or in combination):

surgery
Surgery is usually the first step in the treatment of brain tumors. The goal is to remove as much of the tumor as possible while maintaining neurological function. A biopsy is also done to examine the types of cells the tumor is made of for a diagnosis. This is frequently done if the tumor is in an area with sensitive structures around it that may be injured during removal.
chemotherapy
radiation therapy
steroids (to treat and prevent swelling especially in the brain)
anti-seizure medication (to treat and prevent seizures associated with intracranial pressure)
placement of a ventriculoperitoneal shunt (Also called a VP shunt.)
This is a tube that is placed into the fluid filled spaces of the brain called ventricles. The other end of the tube is placed into the abdomen to help drain excess fluid that can build up in the brain and cause an increase in pressure in the brain.
supportive care (to minimize the side effects of the tumor or treatment)
rehabilitation (to regain lost motor skills and muscle strength; speech, physical, and occupational therapists may be involved in the healthcare team)
antibiotics (to treat and prevent infections)
continuous follow-up care (to manage disease, detect recurrence of the tumor, and to manage late effects of treatment)

Newer therapies that may be used to treat brain cancer include the following:

stereotactic radiosurgery - a new technique that focuses high doses of radiation at the tumor site from many different angles, while sparing the surrounding normal tissue, with the use of photon beams from a linear accelerator or cobalt x-rays.
gene therapy - a special gene is added to a virus that is injected into the brain tumor. An antivirus drug is then given which kills the cancer cells that have been infected with the altered virus.
chemotherapy wafers - wafers containing a cancer-killing drug, BCNU, are inserted directly into the area of the brain tumor during surgery.

Long-term outlook for a person with a brain tumor:

Prognosis greatly depends on all of the following:

type of tumor
extent of the disease
size and location of the tumor
presence or absence of metastasis
the tumor's response to therapy
your age, overall health, and medical history
your tolerance of specific medications, procedures, or therapies
new developments in treatment

As with any cancer, prognosis and long-term survival can vary greatly from individual to individual. Prompt medical attention and aggressive therapy are important for the best prognosis. Continuous follow-up care is essential for a person diagnosed with a brain tumor. Side effects of radiation and chemotherapy, as well as second malignancies, can occur in survivors of brain tumors.
Rehabilitation for lost motor skill and muscle strength may be required for an extended amount of time. Speech therapists and physical and occupational therapists may be involved in some form of rehabilitation. More research is needed to improve treatment, decrease side effects of the treatment for this disease, and develop a cure. New methods are continually being discovered to improve treatment and to decrease side effects.
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