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Keywords
Acoustic Neuromas (Vestibular Schwannomas) «» Anaplastic Astrocytomas «» Astrocytomas «» Chordomas «» Craniopharyngiomas «» Desembryoplastic Neuroepithelial Tumors «» Ependymomas «» Fibrillary Astrocytomas «» Glioblastoma Multiforme (GBM) «» Gliomas «» Hemangioblastomas «» Lymphomas «» Meningiomas «» Metastases «» Myxopapillary Ependymomas «» Neurofibromatosis «» Oligodendrogliomas «» Pleomorphic Xanthoastrocytomas (PXA) «» Subependymomas
What are brain and spinal cord tumors?
What causes brain and spinal cord tumors?
What are some specific types of primary brain and spinal cord tumors?
Who is at risk?
What are the symptoms of brain tumors?
What are the symptoms of spinal cord tumors?
How are brain and spinal cord tumors diagnosed?
How are brain and spinal cord tumors treated?
What are brain and spinal cord tumors?
Brain and spinal cord tumors are abnormal growths of tissue found inside the skull or the bony spinal column. Regardless of their location in the body, tumors are usually classified as benign (non-cancerous) if the cells that make up the growth are similar to other normal cells, grow relatively slowly, and are confined to one location. Tumors are called malignant (cancerous) when the cells are very different from normal cells, grow relatively rapidly, and have a tendency to spread to other locations in the body.
In most parts of the body, benign tumors are not particularly harmful. This is not necessarily true in the brain and spinal cord, collectively called the Central Nervous System (CNS). Because both of these structures are housed within rigid, bony quarters (the skull and spinal column), any abnormal growth can place pressure on sensitive tissues and impair function. Also, any tumor located near vital brain structures or sensitive spinal cord nerves can seriously threaten health. If a benign tumor is found deep inside the brain, surgery to remove it may be very risky because of the chances of damaging vital brain centers. On the other hand, a benign tumor located near the brain's surface can often be removed surgically without significant risk of damage to normal brain.
An important difference between malignant tumors in the brain and spinal cord and those elsewhere in the body lies with their potential to spread. While malignant cells elsewhere in the body can easily spread to the brain and spinal cord, malignant tumors of the CNS rarely spread to other body parts. Laboratory and clinical investigators are exploring the basis of these unusual characteristics of CNS tumors, because these unique properties may suggest new strategies to prevent or treat them.
What causes brain and spinal cord tumors?
When newly formed tumors begin within the brain or spinal cord, they are called primary tumors. Primary CNS tumors rarely grow from neurons (nerve cells that perform the nervous system's important functions) because once neurons are mature they no longer divide and multiply. Instead, most tumors are caused by out-of-control growth of cells that surround and support neurons.
In a small number of individuals, primary tumors may result from specific genetic diseases (such as neurofibromatosis or tuberous sclerosis) or from exposure to radiation or cancer-causing chemicals. Although smoking, alcohol consumption, and certain dietary habits are associated with some types of cancers, they have not been linked to primary brain and spinal cord tumors. In fact, the cause of most primary CNS tumors remains a mystery. Scientists do not know exactly why and how cells in the nervous system, or elsewhere in the body, lose their normal identity as nerve, blood, skin, or other cell types and grow uncontrollably. Some of the possible causes under investigation include viruses, defective genes, and certain chemicals.
Metastatic tumors, on the other hand, are caused by cancerous cells that shed from tumors in other parts of the body, travel through the bloodstream, burrow through the blood vessel walls, latch onto CNS tissue, and spawn new tumors inside the brain or spinal cord.
About 25% of patients with metastatic cancers have spread of the tumor within the CNS. The top two culprits that lead to these secondary (metastatic) CNS tumors are lung and breast cancer. Other, less frequent causes of CNS metastases include renal (kidney) cancer, lymphoma (a cancer affecting immune cells), prostate cancer, and melanoma (skin) cancer. Brain and spinal cord tumors are not contagious or, at this time, preventable.
What are some specific types of primary brain and spinal cord tumors?
Acoustic neuromas (also known as vestibular schwannomas) are benign tumors that arise from the vestibular nerve (which is a nerve that controls equilibrium). These tumors generally grow slowly and cause problems mainly by compressing the cochlear nerve which can cause progressive hearing loss. There can also be compression of the brainstem and other nearby structures which can lead to a sense of imbalance, loss of sensation in the face, weakness of facial muscles, headaches, double vision, and hydrocephalus. Acoustic neuromas are rare and have an incidence of 10 per million people per year. There are some genetic error which can be associated with this condition, namely neurofibromatosis, where acoustic neuromas can be seen on both sides.
Astrocytomas belong to a class of tumors called gliomas, which arise from supporting cells in the CNS called glial cells. Astrocytomas can be either high-grade or low-grade depending on their aggressiveness. Low-grade astrocytomas usually grow slowly over an extended period of time and are more often found in children, whereas the high-grade tumors are much more aggressive, grow more rapidly, and tend to be more common in adults. These tumors can occur anywhere within the brain or spinal cord. Some of the common subtypes of low-grade astrocytomas include juvenile pilocytic astrocytoma (JPA), fibrillary astrocytoma, pleomorphic xantroastrocytoma (PXA), and desembryoplastic neuroepithelial tumors (DNET). The two most common high-grade astrocytomas are anaplastic astrocytoma and glioblastoma multiforme (GBM). The latter is the most aggressive form of glioma, and while these tumors do not spread throughout the body like other forms of cancer, they can cause symptoms by invading and destroying the brain. GBMs can arise spontaneously or can form from progression of lower grade gliomas after many years. While GBMs are mainly found in the cerebral hemispheres (the main portions of the brain), they can also occur in the brain stem, cerebellum, and spinal cord. GBMs usually affect men more commonly than women, and are more common between the fourth and sixth decade of life.
Chordomas are rare tumors that are usually found in the spine and base of the skull. Even though they are malignant and can spread to other organs, they tend to grow fairly slowly. These cancers develop from the remnants of a structure called the notochord, which is involved in the formation of the spine during the early stages of development. Normally, the tissues derived from the notochord disappear in the developing embryo; however, sometimes small amounts of the notochord tissue remain which can give rise to these tumors. While chordomas can occur anywhere along the spine, most of them tend to be found at the bottom of the spine (sacrum and coccyx) or at the base of the skull. Most patients with chordomas are male and in their fourth to seventh decade of life with an average age of 55 years. As malignant tumors, chordomas can cause death by direct growth or by spreading to other organs, especially the lungs. These cancers occur spontaneously, and are not known to be related to trauma, environmental factors, hereditary factors, or diet.
Craniopharyngiomas are benign tumors that are commonly found close to the pituitary gland and hypothalamus at the base of the brain. They account for about 9% of all brain tumors in children, but only 1% of brain tumors in adults – males and females are affected equally. The median age at diagnosis is eight years; and the incidence peaks between six and eleven years of age with almost 70% occurring before the age of 20. The behavior of craniopharyngiomas is generally unpredictable and their origin is not well understood. This cancer does not usually spread to other parts of the body; however, it has a tendency to invade local tissues. And since it arises in or near the pituitary gland, it often results in deficiencies of the various hormones that are produced by this gland. These tumors can cause symptoms at any age, but those that present in childhood are relatively fast growing, have a more aggressive course, and tend be more difficult to treat.
Ependymomas are a rare type of gliomas that develop from the ependymal cells which line the ventricles (fluid-filled spaces) of the brain and the central canal of the spinal cord. While they can be found in any part of the brain or spinal cord, they are typically seen in the cerebellum (in children) and the spinal cord (in adults). The occurrence of these tumors seems to peak at age 5 years and then again at age 34. As with most other tumors, ependymomas are graded based on the degree of aggressiveness, with Grade 1 tumors more slow-growing and Grade 3 tumors growing more rapidly. The different subclasses of ependymomas, based on grade, include myxopapillary ependymomas and subependymomas (Grade 1), typical ependymomas (Grade 2), and anaplastic (malignant) ependymomas (Grade 3). As with most brain tumors, the cause of ependymomas is unknown.
Gangliogliomas are benign tumors of the brain that arise from nerve cells. The subtypes of these rare tumors include gangliocytomas (also called ganglioneuromas) which are tumors of nerve cells only, and gangliogliomas which are composed of both nerve cells and supportive cells, called glial cells. These tumors are most common found in the temporal lobe and the third ventricle of the brain, although they might also occur in the spinal cord. Gangliogliomas are slow growing, have distinct margins, and rarely metastasize (spread to other parts of the central nervous system). They are most often seen in children and young adults, with a complete cure often possible after optimum treatment.
Hemangioblastomas are rare vascular tumors that occur mainly in the spinal cord and the cerebellum. They generally occur sporadically, but also exist in the hereditary form (25% of hemangioblastomas) in a disease called von Hippel-Lindau (VHL). Hallmarks of VHL include cerebellar and retinal hemangioblastomas, pancreatic cysts and cancers, and kidney masses. Hemangioblastomas are generally benign, but can cause local symptoms by compression of neural structures or bleeding. Most of these tumors are found in young adults and children; however, sporadic tumors generally occur in the sixth or seventh decade of life, with median age at presentation being 47 years of age.
Lymphomas are cancerous tumors of the lymph cells, which are part of the body's immune system. Some lymphomas in the brain will have spread from lymphomas in other parts of the body, but it is also possible for lymph cells in the brain to become cancerous, in which case the entity is called primary CNS (central nervous system) lymphoma. Although most people who develop these tumors have a normal immune system, rarely CNS lymphoma may affect people whose immune system is not properly functioning, such as people with AIDS or those receiving anti-rejection medications after an organ transplant. This tumor primarily affects individuals age 60 years and older.
Meningiomas are tumors that develops from the meninges, the membrane that surrounds the brain and spinal cord. Most of these tumors are benign and slow growing, but a small group, classified as atypical or malignant tumors, can have more aggressive features. Meningiomas develop about twice as frequently in women as compared to men, although they can occur in both sexes and at any age. In fact, meningiomas are thought to be the most common type of primary brain tumor, accounting for about 26% of all primary brain tumors. Although usually benign, these tumors sometimes reoccur after treatment, but there is currently no method to predict those tumors that are more susceptible to recurrence. The only known risk factor for meningiomas is previous exposure of the head to ionizing radiation, such as x-rays. There are also certain chromosomal abnormalities that have been associated with meningiomas; however, except for these instances, the reason for development of meningiomas is unknown.
Oligodendrogliomas are low-grade tumor that arise from a specific type of glial cell within the brain called oligodendrocytes, which make up a supportive network for the nerves of the brain and spinal column. Oligodendrogliomas tend to occur in the frontal, temporal, and parietal lobes of the brain, but may occur anywhere along the brain and spinal cord. These tumors are found most commonly in adults between the ages of 30 and 50, with an incidence of about one new case per 100,000 individuals per year. These tumors are classified according to their grade based on the aggressiveness, and can be found as pure oligodendrogliomas or mixed with astrocytomas, as in oligoastrocytomas.
Research studies suggest that new brain tumors arise in more than 40,000 Americans each year. About half of these tumors are primary, and the remainder are metastatic.
Individuals of any age can develop a brain tumor. In fact, they are the second most common cause of cancer-related death in people up to the age of 35, with a slight peak in occurrence among children between the ages of 6 and 9. However, brain tumors are most common among middle-aged and older adults. People in their 60s face the highest risk -- each year 1 of every 5,000 people in this age group develops a brain tumor.
Spinal cord tumors are less common than brain tumors. About 10,000 Americans develop primary or metastatic spinal cord tumors each year. Although spinal cord tumors affect people of all ages, they are most common in young and middle-aged adults.
What are the symptoms of brain tumors?
The brain orchestrates behavior, movement, feeling, and sensation as well as controlling automatic functions like breathing and heartbeat. Many of these important functions are controlled by specialized brain areas. For example, the brain's left and right hemispheres jointly control hearing and vision; the front part of each hemisphere controls voluntary movements, like writing, for the opposite side of the body; and the brain stem is responsible for basic life-sustaining functions, including blood pressure, heartbeat, and breathing.
As a result, brain tumors can cause a wide array of symptoms depending on their size, type, and location. Certain symptoms are quite specific because they result from damage to particular brain areas. Other, more general, symptoms are triggered by increased pressure within the skull as the growing tumor encroaches on the brain's limited space or blocks the flow of cerebrospinal fluid (which bathes the brain and spinal cord). Some of the more common symptoms of a brain tumor include:
Headaches: More than half of people with brain tumors experience headaches. Because the skull cannot expand, the growing mass places pressure on pain-sensitive areas which causes recurrent headaches, often at irregular periods, and can last several minutes or hours. They may worsen when coughing, changing posture, or straining; and as the tumor grows, headaches often last longer, become more frequent, and grow more severe.
Seizures: The abnormal tissue found in a brain tumor can disrupt the normal flow of electricity through which brain cells communicate. The resulting bursts of electrical activity cause seizures with a variety of symptoms, such as convulsions, loss of consciousness, or loss of bladder control. Seizures that first start in adulthood (in a patient who has not been in an accident or had an illness that causes seizures) are a key warning sign of brain tumors. Sometimes, seizures are the only sign of a slowly growing brain tumor.
Nausea and Vomiting: Increased pressure within the skull can cause nausea and vomiting. These symptoms sometimes accompany headaches.
Vision or Hearing Disturbances: Increased intracranial pressure can also decrease blood flow in the eye and trigger swelling of the optic nerve, which in turn causes blurred vision, double vision, or partial visual loss. In addition, tumors growing on or near sensory nerves often trigger visual or hearing disturbances, such as ringing or buzzing sounds, abnormal eye movements, and partial or total loss of vision or hearing. Tumors that grow in the brain's occipital lobe, which interprets visual images, may also cause partial vision loss.
Behavioral and Cognitive Symptoms: Because they strike at the core of the individual's identity, changes in behavior and personality can be the most frightening and devastating symptoms of a brain tumor. These symptoms usually occur when the tumor is located in the brain's cerebral hemispheres, which are responsible, in part, for personality, communication, thinking, behavior, language, and other cognitive functions.
Motor and Balance Problems: When tumors affect brain areas responsible for command of body movement, they can cause motor symptoms, including weakness or paralysis, lack of coordination, or trouble with walking. Often, muscle weakness or paralysis affects only one side of the body. In addition, brain tumors that disrupt the normal control of equilibrium can cause dizziness or difficulty with balance.
What are the symptoms of spinal cord tumors?
Lying protected inside the bony spine, the spinal cord contains bundles of nerves that carry messages between the brain and the body, such as instructions from the brain to move an arm or information from the skin that signals pain. A tumor that forms on or near the spinal cord can disrupt this communication and lead to symptoms. Such tumors generally cause problems by exerting pressure on the spinal cord or the nerves that exit from it, or by restricting the cord's supply of blood. Common symptoms that result from this include:
Pain: Normally, the spinal cord carries important warnings about pain from the body to the brain. By putting pressure on the spinal cord, a tumor can trigger these circuits and cause pain that feels as if it is coming from various parts of the body. This pain is often constant, sometimes severe, and can have a burning or aching quality.
Sensory Changes: Many people with spinal cord tumors suffer a loss of sensation. This usually takes the form of numbness to touch, decreased skin sensitivity to temperature and pain, or a "pins-and-needles" sensation (paresthesia).
Motor Problems: Since nerves control the muscles, tumors that affect nerve communication can trigger a number of muscle-related symptoms. Early symptoms include muscle weakness; spasticity in which the muscles stay stiffly contracted; and impaired bladder and/or bowel control. If untreated, symptoms may worsen to include muscle wasting and paralysis. In addition, some people develop an abnormal walking rhythm known as ataxia.
The parts of the body affected by the symptoms mentioned above vary with tumor location along the spinal cord. In general, symptoms strike body areas at the same level or at a level below that of the tumor. For example, a tumor midway along the spinal cord (thoracic spine) can cause pain that spreads over the chest in a girdle-shaped pattern and gets worse when the individual coughs, sneezes, or lies down. A tumor that grows in the top fourth of the spinal column (cervical spine) can cause pain that seems to come from the neck or arms. And a tumor that grows in the lower spine (lumbar spine) can trigger back or leg pain.
In some cases, one or more tumors extend over several sections of the spinal cord. This results in symptoms that are spread over various parts of the body. Sometimes sensory symptoms occur in a patchy, confusing pattern in which some parts of the body are unaffected even though they lie between affected areas.
How are brain and spinal cord tumors diagnosed?
Research has made major strides in the ability to detect and diagnose CNS tumors. However, the first test is often a traditional neurological exam which examines eye movements, eye reflexes, pupil's reaction to light, tendon reflexes, hearing, sensation, balance and coordination, movement, and muscle strength in the face, arms, and legs.
The next step in diagnosing brain tumors often involves imaging the brain with special techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). These imaging modalities have dramatically improved the diagnosis of CNS tumors in the recent years and have allowed clear determination of size, location, and sometimes even the type of tumor. While a CT scan can provide a good idea of where the tumor is located in the brain as well as helping to detect swelling, bleeding, or other associated conditions, an MRI can provide detailed and high resolution images that reveal further characteristics about the tumor.
A third imaging technique, called positron emission tomography (PET), provides a picture of brain activity (metabolism) which can be used to crudely distinguish malignant from non-malignant tissue since the former tends to have higher metabolic activity. This technique, however, is not widely used in tumor diagnosis due to the presence of better imaging modalities (CT and MRI) and because of the need for elaborate and expensive equipment.
While imaging is sometimes helpful in determining the type of tumor, this is not always the case and sometimes a definitive tissue diagnosis -- obtained through a biopsy -- is necessary in order to devise a course of treatment. A biopsy is a surgical procedure in which a small sample of tissue is taken from the suspected tumor and examined under the microscope by a pathologist to determine the exact nature of the tumor. In order to make their diagnosis, pathologists look for certain features which include abnormal changes in the cell membranes as well as problems in the cell nucleus, which normally controls cell characteristics and growth. For example, cancerous cells may grow small finger-like projections on their normally smooth surface or have extra nuclei.
Using this information, the pathologist provides a diagnosis of the tumor type. The tumor may also be classified as benign or malignant and given a numbered score that reflects how malignant it is. This score can help doctors determine how to treat a tumor and predict the likely prognosis for the patient.
Often, if the decision is made to perform surgical removal of the tumor, a separate biopsy procedure is not performed and instead a sample of the tumor is sent to the pathologist after it has been removed in the operating room.
How are brain and spinal cord tumors treated?
There are three main treatment modalities used in the treatment of CNS tumors: surgery, radiation, and chemotherapy. For some patients, doctors may suggest a new treatment still being tested. In any case, the doctor will recommend a treatment or a combination of treatments based on the tumor's location and type, any previous treatment the patient may have received, and the patient's medical history and general health.
Surgery is usually the first step in treating an accessible tumor - that is, a tumor that can be removed without unacceptable risk of neurological damage. Fortunately, research has led to advances in neurosurgery that make it possible for doctors to reach many tumors that were previously considered inaccessible. These new techniques and tools equip neurosurgeons to operate in the tight, vulnerable confines of the CNS. Among the recently developed tools that are in use in the operating room is stereotactic navigation. This technology utilizes a computer which uses information from a brain CT or MRI to create a three-dimensional map of the brain. This map is then used to help the surgeon guide special, computer-assisted tools which make it possible to approach certain difficult-to-reach tumors with greater precision. Many procedures can be performed using this approach, including biopsy, certain types of surgery, and planting radiation pellets in a tumor.
While surgery may be the beginning and end of treatment for benign tumors, if the tumor is malignant, then doctors often recommend additional treatment following surgery, including a combination of radiation, chemotherapy, and/or experimental treatments. These treatments are also used for an inaccessible or inoperable tumor, which is one that cannot be removed surgically because of the risk of severe nervous system damage. These tumors are frequently located deep within the brain or near vital structures such as the brain stem - the part of the brain that controls many crucial functions including breathing and heart rate.
In radiation therapy, the tumor is bombarded with beams of energy that kill tumor cells. Traditional radiation therapy usually begins a week or two after surgery, and continues for about 6 weeks. The dosage is fairly uniform throughout the treated areas, making it especially useful for tumors that are large or have infiltrated into surrounding tissue.
However, when traditional radiation therapy is given to the brain, it may also cause damage to healthy tissue. Depending on the type of tumor, doctors may be able to choose a modified form of radiation therapy to help prevent this and to improve the effectiveness of treatment. Modifying therapy can be as simple as changing the dosage schedule and amount of radiation that a patient receives. For example, an approach called hyperfractionation uses smaller, more frequent doses.
Another form of radiation therapy is called stereotactic radiosurgery, The Gamma Knife, one of several types of radiosurgery, combines precise computer-assisted guidance tools and a sharply focused beam of radiation energy to deliver a single, precise dose of radiation. Despite its name, the Gamma Knife does not require a surgical incision. Physicians using this tool have found it can help them reach and treat some small tumors that are not accessible through surgery.
Internal radiation includes a technique called brachytherapy, or interstitial radiation, in which doctors implant small, radioactive pellets directly into tumors. The pellets may be left in permanently or for a few days, weeks, or months. This technique can deliver a large dose of radiation to the tumor while minimizing radiation of normal tissue.
Chemotherapy uses tumor-killing drugs that are given orally or injected into the bloodstream. Because not all tumors are vulnerable to the same anticancer drugs, doctors often use a combination of drugs for chemotherapy.
Chemotherapy drugs generally kill cells that are growing or dividing rapidly, making them more deadly to malignant tissue, which contains a high proportion of growing and dividing cells, than to most normal cells. There are cells within the body, however, that also grow relatively rapidly under normal conditions and these include skin, hair, and intestinal cells. As a result, chemotherapy can cause side effects with regard to these tissues leading to skin reactions, hair loss, or digestive problems. Research scientists are promising drugs to learn if they can improve treatment for brain and spinal cord tumors and reduce side effects.
In another technique, doctors place disc-shaped wafers soaked with chemotherapeutic drugs directly into tumor tissue, usually after surgical removal of most of the tumor. This increases the dose of life-prolonging drugs while limiting side effects since less of the drug spreads elsewhere in the body.
Tumors, surgery, and radiation therapy can all result in swelling inside the CNS. Doctors may prescribe steroid anti-inflammatories for short or long periods to reduce this swelling. Examples of such drugs include dexamethasone, methylprednisolone, and prednisone. Anti-seizure medications may also be prescribed for patients with brain tumors since the presence of tumor within the brain can increase the likelihood of seizures.
Among patients who have metastatic CNS tumors, doctors usually focus on treating the original cancer in addition to the brain or spinal cord metastasis. Often the original cancer is treated first; however, when a metastatic tumor causes serious disability or pain, doctors may recommend surgery or other treatments for the metastasis first in order to reduce symptoms even if the original cancer has not yet been controlled.
Whether new treatment approaches involve surgery, radiation therapy, chemotherapy, or completely new avenues to treating CNS tumors, carefully planned clinical trials of new and experimental therapies are vital for identifying promising treatments and learning the best applications of current therapies. Experimental treatments, in turn, would not be possible without research by basic and clinical scientists who identify new approaches.
