Overview of Brain Tumors

It is a distressing experience for a patient to learn that he or she has been diagnosed with a brain tumor. However, each year researchers learn more about brain tumors and the best way to treat them, and the prognosis (predication about the future course of the disease) for many tumors is better today than it was even just a few years ago. This article may be helpful to your general understanding of the types of brain tumors, symptoms, diagnosis, and various treatment options. Keep in mind, though, that each brain tumor is unique. Your doctor will be the best source of information about your specific condition and its prognosis.

Classifying Brain Tumors
Brain tumors are abnormal growths of new and unnecessary cells in or on the brain. It is thought that tumors occur when genetic factors or environmental damage impair normal cells so that they multiply and divide rapidly. There are many different kinds of brain tumors, which are classified in different ways depending on where the tumor originates, how quickly the tumor grows, and how destructive the tumor is.

Brain tumors are usually classified as either benign or malignant. Benign tumors tend to be slow-growing clusters of cells that rarely spread. Tumors are classified as malignant when they grow aggressively, invade other parts of the body, cause damage to critical functions, or are life threatening. Malignant tumors are also known as cancerous.

Brain tumors that originate in the brain itself are called primary tumors. Primary brain tumors can start in the brain tissue, the brain lining (meninges), the skull, the nerves, or the pituitary gland. Tumors that originate somewhere else in the body and move into the brain are called metastatic tumors. Metastatic tumors are always malignant, since by definition they have invaded the brain from another part of the body. Very few primary brain tumors are benign, and even these tumors sometimes become malignant.

Tumors are graded to indicate their degree of malignancy using a system developed by the World Health Organization (WHO). This system classifies tumors into four groups (WHO Grade I through IV) depending on factors such as how abnormal the cells are, how quickly the tumor is growing, the potential for invasion or spread of the tumor, and the blood supply of the tumor. Grade I tumors are considered benign and usually have very good survival rates. Grade II tumors are slow growing, but sometimes invade nearby tissue and/or recur after treatment. Grade III tumors have more abnormal cells and grow faster than Grade II tumors. Grade IV tumors are the most malignant. They grow rapidly and spread widely.

Although these classifications can be helpful, diagnosis and classification of tumors does change. An early diagnosis may later be revised once a sample of the tumor is obtained and examined. In addition, as tumors grow they can be re-classified into higher-grade tumors.

Symptoms
The symptoms of brain tumors vary depending on the type of tumor and the individual, and may appear gradually if the tumor grows slowly. Symptoms are caused by tissue damage and pressure on the brain. Symptoms may also be caused by a buildup of fluid around the tumor, or the blockage of fluid by the tumor. Brain tumors often cause mental changes, which can produce symptoms such as problems with motor skills, problems with memory or communication, or changes in behavior or temperament. Headaches are another common symptom, especially headaches that are worse in the morning. Brain tumors may also cause seizures.

Diagnosis
Often the first diagnostic step is a neurological examination. A complete neurological examination checks eye movement and vision, hearing, sensation, reflexes, balance and coordination, motor skills, thinking and memory. After the neurological exam, the doctor may order imaging studies and lab tests to confirm the existence of a tumor and to gather more information about the type of tumor and its location. In addition, diagnostic tests are often used after treatment to monitor the outcome and recurrence of tumors. These diagnostic tests may include one or more of the following:

CT Scan (Computerized Tomography)
A CT scan directs x-rays from multiple angles to a specific body part. This creates detailed images of various cross-sections of tissues and bony structures, which can help identify the tumor’s location and can sometimes help determine the tumor’s type. CT scans can also detect swelling, bleeding, or other conditions associated with the tumor. Often CT scans are combined with a radiographic contrast media (dye) that is injected prior to the scan. The contrast dye highlights light and dark areas of the scan and makes it easier to identify abnormalities. This is known as a CT scan with myelogram. MRI

Magnetic Resonance Imaging (MRI) combines computer technology, a magnetic field, and radio waves to produce a two-dimensional image of a "slice" of the patient’s anatomy. This process is radiation free, and the radio waves are harmless. MRI scans produce highly detailed images from different angles and often make it easier to identify abnormal tissue, especially when tumors are located near bone. Sometimes a contrast dye is used, as in a CT scan with myelogram.

PET
Positron Emission Tomography (PET) scans create color-coded pictures of brain activity by measuring levels of a low-dose radioactive sugar substance injected prior to the scan. The PET scan measures the consumption rate of the sugar substance in different parts of the brain. This is helpful in detecting recurrent tumor growth, and may help distinguish the grade of malignancy in an existing tumor.

X-rays
Plain x-ray films of the skull may be used to determine the condition of the skull and the effect of the tumor on bony structures.

Bone Scan
Bone scans, also known as nuclear imaging, are used to detect areas of unusual activity in the bones using low levels of radioactive elements. Bone scans are highly sensitive and can reveal abnormalities that are too small to appear on other imaging tests. Bone scans involve the use of an injection and a scanner that produces images showing abnormal bone activity in darker shades.

Lumbar Puncture
A lumbar puncture, or spinal tap, may be used to obtain a sample of cerebrospinal fluid to look for substances that indicate the presence of a tumor.

Evoked Potentials Studies
Evoked potential testing involves stimulating the nerves using an electrical impulse. The transmission of that impulse along the spinal cord to the brain is then monitored via electrodes on the scalp.

Endocrine Evaluation
Samples of blood and urine may be taken during the diagnostic process to measure hormone levels. This can help in diagnosing pituitary tumors.

EEG
An electroencephalogram (EEG) is a test that measures the electrical activity of the brain and looks for abnormalities. Electrodes detect patterns of electrical activity in the brain waves (electrical impulses between brain cells).

Brain Tumor Biopsy
After preliminary diagnostic tests are done, the exact diagnosis for a brain tumor is usually obtained through a biopsy, a surgical procedure in which the surgeon gathers a sample of the tumor. The tumor tissue and cells are then examined under a microscope.

The procedure used to obtain the tumor specimen (sample) depends on many factors including the tumor location and the patient’s health. Biopsies can be performed two ways. A needle biopsy can be performed through a small hole drilled in the skill. Often surgical image guidance systems are used to guide the needle to the tumor. Tumor specimens can also be obtained using an open surgical procedure.

Treatment Options
Brain tumor treatment often requires the expertise of several specialists including a neurosurgeon, neuroradiologist, pathologist, oncologist, and pain management specialist.

The type of treatment usually depends on the patient’s symptoms and health, imaging studies, and biopsy results. Many patients require a combination of non-surgical and surgical treatments. Each case is evaluated on an individual basis and the treatment is designed to meet the patient’s needs.

Non-Surgical Treatment

Radiation Therapy
Radiation therapy can help to control disease by killing and eliminating cancer cells, shrinking a tumor, or preventing growth. Radiation targets the DNA of a malignant cell because it is more susceptible to radiation than a normal cell. Altering a cell’s DNA interferes with its ability to divide and grow.

Standard external beam radiation therapy applies multiple treatments of radiation to the brain. Each treatment damages both malignant and normal cells, but the normal cells repair the damage more quickly. Recently, a new form of radiation therapy, called stereotactic radiosurgery, has been developed which targets the tumor with smaller doses of radiation from multiple points around the head that combine into an intense dose at the site of the tumor. This allows surgeons to focus the radiation to the tumor while sparing the normal tissue around it. This type of radiation therapy is delivered using technology called the Gamma Knife. Radiosurgery can be an effective treatment for many benign and malignant tumors.

Chemotherapy
Chemotherapy treats and controls cancer by using drugs that destroy cancer cells by interfering with cell growth and its ability to reproduce. There are many types of chemotherapy drugs that may be combined with other treatments. Chemotherapy drugs can even be implanted in the brain during surgery in the form of wafers that secrete the drug into the tumor. However, chemotherapy is not effective or recommended for all types of brain tumors.

Pain Therapy
Pain therapy is also called palliative treatment – the goal is to relieve pain, reduce symptoms, and prevent complications. These are treatments that do not cure the disease, but rather improve the patient’s quality of life. Treatment may include anti-inflammatory medication, oral or IV narcotics, and morphine pain pumps.

Surgical Treatment
The goal of surgery, whether the brain tumor is benign or malignant, is remove the tumor completely without injuring normal brain tissue. Even after surgical resection (partial removal) or excision (complete removal), some tumors require non-surgical treatment such as radiation or chemotherapy.

Surgical Considerations

Tumor Location : Not all brain tumors are operable.

Chemotherapy or Radiation: These treatments can affect a patient’s white blood cell count. A low white blood cell count can compromise the body’s ability to fight infection and heal a surgical wound.

General Health: Certain treatments affect appetite leading to weight loss and general health deterioration. Further, good nutrition is essential to wound healing.

Recovery
The amount of time the patient is hospitalized depends on the type of procedure performed and the side effects experienced. For example, the side effects from radiation therapy or chemotherapy can be significant and may include nausea, loss of appetite, and fatigue. Fortunately, these side effects are treatable.

After surgery, the treating physician closely monitors the patient’s condition and recovery. Periodic re-evaluation may require new lab tests and imaging studies. Pain management may be a component of long-term treatment. Rehabilitation to regain or adjust to loss of neurological function may be necessary. Additionally, the treating physician may add nutritional support to the patient’s recovery program.

Types of Tumors
The following section provides a brief summary of several of the most common types of brain tumors, and highlights the most common treatments.

Benign Brain Tumors

Meningiomas
A meningioma is a tumor that develops from the lining of the brain and spinal cord. It is the most common benign brain tumor in adults. A few meningiomas are malignant. The cause of meningiomas is unknown; however, some meningiomas are associated with specific genetic disorders, such as neurofibromatosis. Symptoms include seizure, headaches and loss of brain function (sensory problems, loss of coordination, etc.). Meningiomas usually grow slowly and may be treated at first with observation over time. For large meningiomas, surgery is usually the preferred treatment.

Acoustic neuromas
Acoustic neuromas (a.k.a. vestibular schwannomas) are tumors arising from a cranial nerve. The tumor is usually benign and slow growing. The most common symptoms are hearing loss, ringing in the ears, vertigo (dizziness), and headaches. Options for treatment include observation, radiosurgery, and surgical resection. The ideal treatment in most cases is complete microsurgical tumor resection.

Pituitary tumors
Pituitary tumors are tumors of the pituitary gland, which produces hormones to regulate the other glands in the body. These tumors may or may not secrete hormones. Often symptoms develop based on the type of hormone secreted. Some pituitary tumors are treated with medication alone, other with surgery, some with radiation, and some with a combination of all three treatments. Pituitary tumors represent approximately 10-15% of all brain tumors. They are most common in the third and fourth decade of life, and males and females are equally affected.

Colloid cysts
Colloid cysts are benign tumors that only occur in the third ventricle, an area involved with cerebrospinal fluid flow. Tumors in this area can be life threatening by blocking the flow of cerebrospinal fluid, causing a condition called hydrocephalus. Hydrocephalus may cause headaches, nausea, vomiting, and even comas, which can lead to death. If the tumor is large enough, most neurosurgeons will treat the condition with surgical removal. Sometimes a ventricular shunt (a tube from the ventricles) is needed, which diverts and drains the cerebrospinal fluid and relieves pressure. Arachnoid cysts

An arachnoid cyst is a sac of cerebrospinal fluid that develops in the brain. Some of these cysts may develop in infancy, but often they are undiagnosed until a head injury occurs. Arachnoid cysts may cause no symptoms for a long time until they are large enough to put pressure on the brain or cause a deformity. Sometimes surgery is needed to create space around the cyst. Other cysts can be treated with a shunt.

Craniopharyngiomas
Craniopharyngiomas are benign tumors located above and behind the pituitary gland. These tumors grow slowly, but can cause vision problems or pituitary dysfunction. There is debate on how these tumors should be treated. Many neurosurgeons advocate surgical removal followed by radiation. In some cases, draining the cyst fluid may control the symptoms and halt growth.

Choroid plexus papillomas
Choroid plexus papillomas are benign tumors that occur in the brain’s ventricular system from the cells that make spinal fluid. Treatment is usually surgical removal.

Hemangioblastomas
Hemangioblastomas are benign tumors of blood vessels that are often associated with cysts. They are usually treated with surgical removal, with or without radiation therapy.

Epidermoid and dermoid tumors
Epidermoid and dermoid tumors are benign tumors containing accumulated left over skin tissue within the head or spinal canal. The tumors usually require surgical removal.

Malignant Brain Tumors

Primary Malignant Brain Tumors
The majority of primary brain tumors are malignant. Most primary malignant brain tumors arise from glial cells, which are tissues of the brain other than nerve cells or blood vessels. Unfortunately, these tumors can grow quickly and be very destructive. Management of these tumors depends primarily on the health of the patient and the location of the tumor. When feasible, treatment typically includes surgical removal followed by radiation and/or chemotherapy. Metastatic Brain Tumors

Metastatic tumors account for 10-15% of all brain tumors. The most common tumors that spread to the brain are those that originate in the lung, the breast, the kidney, or melanomas (skin cancer). Historically, the prognosis for metastatic brain tumors has been bleak. However, recent advances, including the advent of stereotactic radiosurgery, have led to better outcomes in survival rates and quality of life.