What is a Brain Tumor?
A brain tumor is an abnormal mass of tissue in which some cells grow and multiply uncontrollably in a way that is unregulated by the mechanisms that control normal cells. The growth of a tumor takes up space within the skull and interferes with normal brain activity by increasing pressure in the brain, by shifting the brain or pushing against the skull, and by invading and damaging nerves and healthy brain tissue. The location of a brain tumor influences the type of symptoms that occur because different functions are controlled by different parts of the brain.
Tumors can be benign, which means they are noncancerous and will not spread, or malignant, which means they are cancerous. Cancerous brain tumors are further classified as either primary or secondary tumors. Primary tumors start in the brain and rarely metastasize (spread) to other parts of the body outside of the central nervous system (CNS). Secondary tumors spread to the brain from another site such as the breast or lung.
Causes, Incidence and Risk Factors
Risk Factors: The cause of primary brain tumors is unknown. There are many possible risk factors that could play a role.
- Radiation therapy to the brain, used to treat brain cancers, increases the risk for brain tumors up to 20-30 years afterwards.
- Exposure to radiation at work or to power lines, as well as head injuries, smoking, and hormone replacement therapy have NOT yet been shown to be factors.
- The risk of using cell phones is hotly debated. However, most recent studies have found that cell phones, cordless phones, and wireless devices are safe and do not increase the risk.
- People with impaired immune systems have an increased risk of developing central nervous system lymphomas. Organ transplantation, HIV infection, and chemotherapy are some medical factors that can weaken the immune system.
- Gender: In general, brain tumors are slightly more likely to occur in men than in women. Some specific types of brain tumors, such as meningiomas, are more common in women.
- Age: Most brain tumors in adults occur between the ages of 65-79. Brain tumors also tend to occur in children younger than age 8.
- Ethnicity: The risk for primary brain tumors in Caucasians is around two times higher (with gliomas) than in people of other races.
- Only 5-10% of primary brain tumors are associated with genetic disorders including neurofibromatosis (NF1/NF2 gene), Turcot syndrome (APC gene), Li-Fraumeni syndrome (TP53 gene), Gorlin Syndrome (PTCH gene) and Tuberous Sclerosis (TSC1 and TSC2 gene).
Many genetic abnormalities that cause brain tumors are not inherited but occur as a result of environmental or other factors that affect genetic materials (DNA) in the cells. Researchers are studying various environmental factors (such as viruses, hormones, chemicals, and radiation) that may trigger the genetic disruptions that lead to brain tumors in susceptible individuals. They are also working to identify the specific genes that are affected by these environmental triggers.
Primary malignant brain tumors account for about 2% of all cancers. However, brain and spinal cord cancer are the second most common type of cancer in children, after leukemia. According to the American Cancer Society, about 24,000 people in the United States are currently diagnosed each year with a malignant brain or spinal cord tumor.
About 13,000 people die from cancerous brain tumors each year. Recent advances in surgical and radiation treatments have significantly extended average survival times and can reduce the size and progression of malignant gliomas. The survival rates in people with brain tumors depend on many different variables:
- The type of tumor
- Location and size of tumor (these factors determine whether or not a tumor can be surgically removed)
- Tumor grade (for malignant tumors, grade I is least cancerous and grades IV and V are the most dangerous). Grading a tumor can help predict its growth rate and tendency to spread. Grading is based on the appearance of the tumor cells as seen under a microscope.
- Patients age
- Patient’s ability to function
- How far the tumor has spread
Brain tumors may have a variety of symptoms ranging from headache to stroke. Different parts of the brain control different functions, so symptoms will vary depending on the tumor’s location.
Possible symptoms of a brain tumor include:
- A new seizure in an adult
- Gradual loss of movement or sensation in an arm or leg
- Unsteadiness or imbalance, especially if it is associated with headache
- Loss of vision in one or both eyes, especially if the vision loss is more peripheral
- Double vision, especially if it is associated with headache
- Hearing loss with or without dizziness
- Speech difficulty of gradual onset
- Other symptoms may also include nausea or vomiting that is most severe in the morning, confusion and disorientation, and memory loss.
- Headache: Although headaches are probably the most common symptom of a brain tumor, most people with headaches – even persistent or severe headaches – do not have a tumor. However, some kinds of headaches are particularly worrisome. A steady headache that is worse in the morning than the afternoon, a persistent headache that is associated with nausea or vomiting, or a headache accompanied by double vision, weakness, or numbness all suggest a possible tumor or possibly another neurological disorder.
- A change in behavior: The development of an “I don’t care” attitude, memory loss, loss of concentration, and general confusion may all be subtle signs. In this case, an evaluation by a neurologist may be an important step, but a CT or MRI will also help.
- Infertility or abnormal cessation of menstruation (also known as amenorrhea)
- Troubles that seem to be caused by other diseases or concerns: A seizure that results from a fall or the discovery of what appears to be a subarachnoid hemorrhage (a type of stroke) may actually be caused by tumors.
If you are concerned that you or someone you know might have a brain tumor, call your primary care physician. If symptoms persist, an MRI or CT scan can facilitate the diagnosis. Early detection and treatment may increase survival. A doctor can often identify signs and symptoms that are specific to the tumor location. Some tumors may not cause symptoms until they are very large. Then they can lead to a rapid decline in the person’s health. Other tumors have symptoms that develop slowly.
The specific symptoms depend on the tumor’s size, location, how far it has spread, and related swelling. The most common symptoms are:
- Seizures (especially in older adults)
- Weakness in one part of the body
- Changes in the person’s mental functions
Headaches caused by brain tumors may:
Be worse when the person wakes up in the morning, and clear up in a few hours
Occur during sleep
Be accompanied by vomiting, confusion, double vision, weakness, or numbness
Get worse with coughing or exercise, or with a change in body position
Other symptoms may include:
- Change in alertness (including sleepiness, unconsciousness, and coma)
- Changes in hearing
- Changes in taste or smell
- Changes that affect touch and the ability to feel pain, pressure, different temperatures, or other stimuli
- Confusion or memory loss
- Difficulty swallowing
- Difficulty writing or reading
- Dizziness or abnormal sensation of movement (vertigo)
- Eye abnormalities
- Eyelid drooping
- Pupils different sizes
- Uncontrollable movements
- Hand tremor
- Lack of control over the bladder or bowels
- Loss of balance
- Loss of coordination
- Muscle weakness in the face, arm, or leg (usually on just one side)
- Numbness or tingling on one side of the body
- Personality, mood, behavioral, or emotional changes
- Problems with eyesight, including decreased vision, double vision, or total loss of vision
- Trouble speaking or understanding others who are speaking
- Trouble walking
Other symptoms that may occur with a pituitary tumor:
- Abnormal nipple discharge
- Absent menstruation (periods)
- Breast development in men
- Enlarged hands, feet
- Excessive body hair
- Facial changes
- Low blood pressure
- Sensitivity to heat or cold
Diagnosis/Signs and Tests
Brain tumors are great mimics of other neurological disorders, and many of the common symptoms could indicate other medical conditions. The best way to identify a brain tumor usually involves a neurological examination, brain scans, and/or an analysis of the brain tissue. Doctors use the diagnostic information to classify the tumor from the least aggressive (benign) to the most aggressive (malignant). In most cases, a brain tumor is named for the cell type of origin or its location in the brain. Identifying the type of tumor helps doctors determine the most appropriate course of treatment.
A neurological examination is a series of tests to measure the function of the patient’s nervous system and physical and mental alertness. If responses to the exam are not normal, the doctor may order a brain scan or refer the patient to a neurologist or neurosurgeon, who will then order a brain scan.
Some types of scans use a contrast agent (or contrast dye), which helps the doctor see the difference between normal and abnormal brain tissue. The contrast agent is injected into a vein and flows into brain tissue. Abnormal or diseased brain tissue absorbs more dye than normal healthy tissue. The most common scans used for diagnosis are as follows:
MRI (Magnetic Resonance Imaging) is an imaging technique that uses magnetic fields and computers to capture images of the brain on film. It does not use x-rays. It provides pictures from various planes, which permit doctors to create a three-dimensional image of the tumor. The MRI detects signals emitted from normal and abnormal tissue, providing clear images of most tumors.
CT or CAT Scan (Computed Tomography) combines sophisticated x-ray and computer technology. CT can show a combination of soft tissue, bone, and blood vessels. CT images can determine some types of tumors, as well as help detect swelling, bleeding, and bone and tissue calcification. Usually, iodine is the contrast agent used during a CT scan.
PET Scan (Positron Emission Tomography) provides a picture of the brain’s activity, rather than its structure, by measuring the rate at which a tumor absorbs glucose (a sugar). The patient is injected with deoxyglucose that has been labeled with radioactive markers. The PET scan measures the brain s activity and sends this information to a computer, which creates a live image. Doctors use PET scans to see the difference between scar tissue, recurring tumor cells, and necrosis (cells destroyed by radiation treatment).
A biopsy is a surgical procedure in which a sample of tissue is taken from the tumor site and examined under a microscope. The biopsy will provide information on types of abnormal cells present in the tumor. The purpose of a biopsy is to discover the type and grade of a tumor. A biopsy is the most accurate method of obtaining a diagnosis.
An open biopsy is done during a craniotomy. A craniotomy involves removing a piece of the skull in order to get access to the brain. After the tumor sample is removed, the bone is usually put back into place. A closed biopsy (also called a stereotactic or needle biopsy) may be performed when the tumor is in an area of the brain that is difficult to reach. In a closed biopsy, the neurosurgeon drills a small hole into the skull and passes a narrow hollow needle into the tumor to remove a sample of tissue.
Once a sample is obtained, a pathologist examines the tissue under a microscope and writes a pathology report containing an analysis of the brain tissue. Sometimes the pathologist may not be able to make an exact diagnosis. This may be because more than one grade of tumor cells exists within the same tumor. In some cases, the tissue may be sent to another institution for additional analysis.
Specific Tumor Types
There are more than 120 types of brain tumors. Today, most medical institutions use the World Health Organization (WHO) classification system to identify brain tumors. The WHO classifies brain tumors by cell origin and how the cells behave, from the least aggressive (benign) to the most aggressive (malignant). Some tumor types are assigned a grade, ranging from Grade I (least malignant) to Grade IV (most malignant), which signifies the rate of growth. There are variations in grading systems, depending on the tumor type. The classification and grade of an individual tumor helps predict its likely behavior.
Tumors may occur at any age, but many types of tumors are most common in a certain age group. In adults, gliomas and meningiomas are most common. Gliomas arise from the brain tissue itself, from the supporting cells of the brain, the glial cells, such as astrocytes, oligodendrocytes, and ependymal cells. Around 80% of malignant primary brain tumors are known collectively as gliomas. The gliomas are divided into three types:
- Astrocytic tumors include astrocytomas (less malignant), anaplastic astrocytomas, and glioblastomas (most malignant). This is the most common form of glioma, accounting for about 60% of malignant primary brain tumors.
- Oligodendroglial tumors develop from oligodendrocyte glial cells, which form the protective coatings around nerve cells. This type of tumor can vary from less malignant to very malignant. In most cases they occur in mixed gliomas, which are made up of both astrocytic and oligodendrocytic tumors. They usually occur in younger and middle-aged adults.
- Glioblastomas (AKA grade IV glioma, malignant glioma) are the most aggressive type of primary brain tumor.
Meningiomas are usually benign tumors that develop in the membranes that cover the brain and spinal cord (the meninges). These tumors:
- Occur most commonly between the ages of 40 – 70
- Are much more common in women
- Are usually (90% of the time) benign, but still may cause devastating complications and death due to their size or location. Some are cancerous and aggressive.
Medulloblastomas are always located in the cerebellum, which is at the base and toward the back of the brain.
- These fast-growing high-grade tumors represent about 15-20% of pediatric brain tumors and 20% of adult brain tumors.
Other primary brain tumors in adults are rare. These include:
- Ependymomas: They are derived from the cells lining the ventricles in the lower part of the brain and the central canal of the spinal cord. They are one of the most common type of brain tumor in children.
- Pituitary tumors
- Primary lymphoma of the brain
- Pineal gland tumors
- Primary germ cell tumors of the brain
Treatment can involve surgery, radiation therapy, and chemotherapy or a combination thereof. Brain tumors are best treated by a team involving a neurosurgeon, radiation oncologist, oncologist, or neuro-oncologist, and other health care providers, such as neurologists and social workers.
Early treatment often improves the chance of a good outcome. Treatment, however, depends on the size and type of tumor and the general health of the patient. The goals of treatment may be to cure the tumor, relieve symptoms, and improve brain function.
Surgery is the modality of choice for most brain tumors and is usually accomplished via craniotomy. This involves opening the skull in order to resect the tumor. Some tumors may be completely removed. Those deep inside the brain or invade the surrounding brain tissue may have to be debulked instead of entirely removed. Debulking is a procedure to reduce the tumor’s size. Even if the tumor cannot be completely removed, surgery may still help reduce pressure and relieve symptoms.
Radiation therapy is used for certain tumors and chemotherapy may be used along with surgery or radiation treatment. Other medications used to treat primary brain tumors may include:
- Corticosteroids, such as dexamethasone to reduce brain swelling
- Osmotic diuretics, such as urea or mannitol to reduce brain swelling and pressure
- Anticonvulsants, such as evetiracetam (Keppra) to reduce seizures
- Pain medications
- Antacids or histamine blockers to control stress ulcers
Comfort measures, safety measures, physical therapy, and occupational therapy may be needed to improve quality of life. The patient may need counseling, support groups, and similar measures to help cope with the disorder.
Patients may also consider enrolling in a clinical trial after talking with their treatment team.
Legal advice may be helpful in creating advanced directives such as a power of attorney.
Survival rates for brain tumors vary widely depending on the type of tumor and multiple factors, including age. Survival rates tend to be higher with younger patients and decrease with age.