Craniotomy For Brain Tumors
According to the American Brain Tumor Association (ABTA), over 190,600 people were diagnosed with brain tumors in the United States in 2003. Of those, about 40,600 were diagnosed with a primary brain tumor (one that comes from cells of the brain itself), and about 150,000 were diagnosed with a metastatic brain tumor, or one that spread to the brain from another part of the body. Brain tumors do not discriminate by gender, age, or race. They can affect anyone.
WHAT IS A BRAIN TUMOR?
A brain tumor is defined as a mass of unnecessary and abnormal cells growing in the brain. When a cell divides too rapidly because internal mechanisms that regularly check its growth are damaged, the cell can eventually grow into a tumor. Symptoms or signs of a brain tumor can be caused by pressure on the brain and surrounding tissues or by irritation of neural structures. Extreme irritation of nerve tissue (which may result in seizures) or loss of function may occur.
TYPES OF BRAIN TUMORS
As mentioned above, brain tumors can be classified into two main types: primary or metastatic. Primary brain tumors originate from the cells of the brain or its immediate surroundings and usually remain within the brain. Metastatic (secondary) brain tumors are tumors that originate elsewhere in the body, such as the breast or lung, and spread to the brain, most often through the bloodstream. Primary tumors may be either benign (slow-growing or less aggressive) or malignant (cancerous, fast0growing or more aggressive). Metastatic tumors are cancerous (malignant).
Brain tumors vary widely in terms of their location, the type of tissue involved, and their degree of malignancy. In adults, tumors originating from the inner lining of the skull are among the most common benign brain tumors. These are called meningiomas. Other common benign tumors are those arising from large nerves at the base of the brain. These are called schwannomas. Vestibular schwannomas (also known as acoustic neuromas) are benign tumors of nerves that are important in hearing and balance. They tend to grow very slowly. Tumors of the pituitary gland are also common. They are referred to as pituitary adenomas.
Rarely, all these types of benign tumors may become malignant. In addition, unless treatment manages to destroy or remove every tumor cell, even benign tumors can recur or continue to grow, sometimes many years after their initial treatment.
Tumors that arise from brain tissue range form relatively slowly growing tumors (low-grade) to rapidly growing and highly destructive tumors (high-grade). Gliomas are tumors that arise not from nerve cells, but rather from cells called glial cells or astrocytes, which support and assist nerve cells. A common type of high0grade glioma is the glioblastoma. An ependymoma is a type of glioma that arises from the ependymal cells, which line the fluid spaces of the brain and center of the spinal cord. Oligodendrogliomas form from a type of glial cell called an oligodendrocyte
The most common glial tumors in children and adults are astrocytomas. Astrocytomas are tumors formed by astrocytes, which are an abundant type of glial cell named for their star-like shape. Some types of astrocytomas that are seen most commonly in children are considered to be benign tumors, but astrocytomas that occur in adults are more commonly malignant. Anaplastic astrocytomas are intermediate in aggressiveness between astrocytomas and glioblastomas.
According to a 2001 report from the Central Brain Tumor Registry of the United States:
- Meningiomas represent 25.7 percent of all primary brain tumors, making them the most common benign brain tumors.
- Glioblastomas represent 23 percent of all primary brain tumors. They are the most common primary malignant brain tumors found in adults.
- Nerve sheath tumors (acoustic neuromas, vestibular schwannomas, neurilemmomas) represent 6.9 percent of all primary brain tumors.
- Pituitary brain tumors represent 6.2 percent of all primary brain tumors.
- Astrocytomas represent 6 percent of all primary brain tumors.
- Anaplastic astrocytomas represent 3.9 percent of all primary brain tumors.
- Lymphomas, named for a type of cell that is present in the blood, represent 3 percent of all primary brain tumors.
- Oligodendrogliomas represent 2.7 percent of all primary brain tumors.
According to the National Brain Tumor Foundation, the average age for an adult to be diagnosed with a primary brain tumor is 53. However, for both glioblastomas and meningiomas, the average age of onset is 62. In addition, gliomas are more common in men, but meningiomas are more common in women.
WHAT CAUSES A BRAIN TUMOR?
The causes of brain tumors are still unknown. Thus, they cannot be prevented. However, research indicates that brain tumors appear when specific genes on the chromosomes of a cell are damaged and no longer function properly. Many of these genes help to regulate the rate at which a cell divides. Others repair damage to the cell’s genes. In still other cases, damage to a gene may interfere with a cell’s planned self-destruction. Some individuals may be born with partial defects in one or more of these genes.
Tumors have the ability to produce substances called angiogenesis factors that promote the growth of blood vessels. These new blood vessels increase the supply of nutrients to the tumor, forcing the tumor to become dependent on these new vessels.
Hopefully, the body’s immune system would detect an abnormal cell and kill it. However, tumors may produce substances that prevent the immune system from recognizing the abnormal tumor cells and eventually overtake all internal and external systems that monitor cell growth.
SYMPTOMS OF A BRAIN TUMOR
Symptoms of a brain tumor may include headaches, nausea, vomiting, seizures, weakness on one side of the body, an unbalanced walk, behavioral and cognitive symptoms, vision or hearing problems, balance problems, or memory and personality changes.
DIAGNOSING A BRAIN TUMOR
Nowadays, tumors are usually diagnosed by radiologic examination, including MRI and CT scans. Before your doctor can recommend a course of treatment, you need to be thoroughly evaluated. Your evaluation may include a medical history, physical examination, thorough neurological examination and diagnostic tests. Your doctor will document your symptoms and determine the extent to which these symptoms affect your daily living. He or she can then order various diagnostic tests to determine more precisely the nature and extent of the tumor.
Diagnositc tests that are used to determine the status of a tumor may include:
- Angiogram: This test can identify the blood vessels supplying a brain tumor.
- Computed Tomography (CT): A CT (also known as a CAT scan) provides anatomical information about the status of organs and tissues. This test uses an x-ray beam to produce a two-dimensional, computerized map of the body.
- Magnetic Resonance Imaging (MRI): The MRI uses a powerful magnetic field to produce a detailed anatomical picture of the head or spine and surrounding structures. This test measures the health of cells and how well they are functioning.
- Positron Emission Tomography (PET): This test can map the biological function of an organ, detect subtle metabolic changes, and sometimes even help to determine if a tumor is benign or malignant.
TREATMENT OPTIONS
The treatment options for a tumor depend primarily on its size, type and location and on the age and overall health of the patient. Brain tumors (whether primary or metastatic, benign or malignant) are usually treated with surgery, radiation, and/or chemotherapy-alone or in various combinations.
SURGERY
It is generally accepted that complete or nearly complete surgical removal of a brain tumor is beneficial for a patient. The primary goal of a surgery is to remove as much of the tumor as possible without injuring brain tissue important to the patient’s neurological function (such as the ability to speak, walk, use his or her hands, ect.). If the tumor cannot be completely removed, surgery can still reduce or control tumor size. New surgical techniques can minimize the risk and discomfort of surgery.
In most cases, surgeons create a large opening (or “craniotomy”) to ensure that they can get to a tumor. Subtle differences in appearance between normal tissue and a tumor are used to guide its removal.
Sometimes a biopsy is obtained before proceeding with a larger operation. The biopsy can be obtained through a smaller craniotomy or with special guidance techniques to obtain a “stereotactic biopsy”. A stereotactic biopsy is performed when a neurosurgeon uses a small instrument that is guided in three dimensions to remove a small sample of tissue from the area of the brain. Computers are used to determine precise information about tumor location from a CT or MRI scan. Often, a small piece of tumor may be retrieved through an opening in the skull that is only a few millimeters wide. The goal of the biopsy is to obtain a small sample of tissue to guide doctors in determining the best treatment plan.
Sophisticates surgical navigation systems are also used to assist the surgeon with localization and orientation. These symptoms allow surgeons to accurately correlate a position inside the brain with what is seen on imaging studies (CT, MRI, PET, angiograms). This guidance information may reduce the risks and improve the extent of tumor removal/
Some patients have or will develop a problem with the circulation or absorption of spinal fluid. The cerebrospinal fluid (CSF) is produced inside the brain, travels through the ventricles of the brain and down the spine, and is then absorbed at the surface of the brain. If the flow is blocked, or if absorption of the fluid is impaired, the fluid can build up and cause pressure on the brain. The accumulation of fluid can be treated by internal drainage of the fluid to another part of the body in a procedure called shunting. The fluid is usually drained from the ventricles of the brain to the abdomen (ventriculo-peritoneal shunt).
The choice of treatment and the decision as to when to perform an operation should be determined by a neurosurgeon. It is important to keep in mind that surgery does have its limitations. Although every precaution will be taken to avoid complications, potential risks may include infection, excessive bleeding both during and after surgery, difficulty swallowing, stroke, seizures, weakness or paralysis, and other problems. Ask your doctor to speak with you about potential side effects.
RADIATION
Radiation is a commonly used treatment for brain tumors. It affects both normal and tumor cells. The goal of radiation therapy is to selectively kill tumor cells while leaving normal brain tissue unharmed. This may be accomplished in two ways. In standard external beam radiation therapy, multiple treatments of standard-dose “fractions” of radiation are applied to the brain. Each treatment induces damage to both healthy and normal tissue. By the time the next treatment is given, most of the normal cells have repaired the damage, but the tumor tissue has not. This process is repeated for a total of 10 to 30 treatments (depending on the type of tumor). Ideally, 98 percent of the tumor is killed, and 98 percent of the normal tissue survives.
The second way to selectively kill tumor cells is to focus an intense dose of radiation on the tumor from many points around the head. This process is called radiosurgery and uses special computers and methods to deliver the radiation to accomplish the treatment. The tumor receives a relatively large amount of radiation, but the radiation dose to the surrounding normal brain is very low because the delivered radiation has been spread out among so many different delivery points on the surface of the brain. These many delivery points all converge on the tumor tissue. Radiosurgery has been used both as an alternative to, and in combination with, conventional radiation and/or surgery.
“Stereotactic radiotherapy”, or “fractionated radiosurgery”, can be used to deliver multiple treatments of low-dose radiation while matching the shape of the delivered radiation to the lesion. More radiation can be given to the tumor, and less to the surrounding normal brain. This technique improves the safety and effectiveness of radiation therapy. It also makes it possible to treat tumors that are larger than those that can be managed with conventional radiosurgery. Depending on the type of tumor, there are two pieces of medial equipment commonly used for delivering stereotactic radiosurgery- a Linear Accelerator (LINAC) and a Gamma Knife. The LINAC will deliver focused x-ray beams to the tumor. The Gamma Knife (not a standard knife-a large machine) delivers gamma rays at low intensity to the tumor.
The risks of radiation therapy include injury to normal tissue outside the tumor. For long-term survivors, there is also the risk of developing a second cancer as the result of radiation affecting the adjacent normal tissue.
While it is true that radiation and chemotherapy are more often used for malignant, residual, or recurrent tumors, decisions as to what treatment to use are made on an individual basis for each patient and depend on a number of factors. New combinations of therapy are being developed each year.
CHEMOTHERAPY
Chemotherapy uses special drugs designed to kill tumor cells. Chemotherapy can be a primary (first) therapy, or an adjuvant (additional) therapy. However, not every brain tumor will respond to chemotherapy. Chemotherapy treatment may be administered in a hospital, outpatient facility, doctor’s office, or even in a patient’s own home. Treatment cycles will vary depending on the drug (or drugs) being used.
Chemotherapy affects both normal and tumor cells, and thus the amount that can be given is often limited by the side effects on normal cells. Tissues with the fastest-growing cells are most affected. Thus, such tissues as hair, the lining of the mouth and stomach, and the bone marrow (which produces blood cells) may be most obviously affected.
Although chemotherapy may improve overall survival in patients with the most malignant primary brain tumors, it does so in only a fraction of the patients (about 20 percent). A number of patients and their doctors choose not use chemotherapy because of the potential side effects (lung scarring, suppression of the immune system, nausea, ect).
Chemotherapy works by inflicting cell damage that is better repaired by normal tissue than by tumor tissue. The aim of another class of drugs is not to kill the tumor cells, but rather to block further tumor growth. In some cases, growth modifiers have been used to stop the growth of tumors resistant to other treatments. A surgeon can also use chemotherapy-impregnated wafers at the time of surgery. The wafers slowly secrete a chemotherapeutic agent into the region of the tumor. Additional experimental therapies involve direct infusion of chemoptherapy agents into the brain or into blood vessels leading to the brain.
INVESTIGATIONAL THERAPIES
Gene therapy may be an exciting option for treating brain tumors. Gene therapy is the transfer of genetic material into a tumor cell to destroy the cell or discontinue cell growth. This treatment aims to correct the underlying defects in the genes that led to the initial formation of the tumor. Various combinations of therapy are being developed each year. Intensive research is being done to develop additional new therapies. At some point, if conventional therapies prove unsuccessful, you may be asked to participate in an experimental protocol. You will be provided with extensive information including risks, benefits, and alternatives before nay therapy is instituted.
RECOVERAY AFTER SURGERY
Following surgery, you will be taken to the intensive care unit (after perhaps spending a short time in the recovery room) for close observation. You will be discharged from the hospital when your doctor feels it is appropriate. Your physician will give you appropriate medication to prevent or treat potential problems.
NEUROSURGEON’S ROLE IN TREATMENT OF BRAIN TUMORS
Neurosurgeons are the medical specialists trained to help patients suffering from brain tumors as well as a host of other illnesses, ranging from carpal tunnel syndrome to epilepsy and Parkinson’s disease. Neurosurgeons provide operative and nonoperative care (prevention, diagnosis, evaluation, treatment, critical care, and rehabilitation) of neurological disorders.
