What is a brain tumor?
Brain tumors are the most common solid tumors in children. Approximately 2,200 children in the US are diagnosed with a brain tumor each year. Brain tumors, either malignant or benign, are tumors that originate in the cells of the brain. A tumor is an abnormal growth of tissue.
A benign tumor does not contain cancer cells and usually, once removed, does not recur. Most benign brain tumors have clear borders, meaning they do not invade surrounding tissue. These tumors can, however, cause symptoms similar to cancerous tumors because of their size and location in the brain.
Malignant brain tumors contain cancer cells. Malignant brain tumors are usually fast growing and invade surrounding tissue. Malignant brain tumors very rarely spread to other areas of the body, but may recur after treatment. Sometimes, brain tumors that are not cancer are called malignant because of their size and location and the damage they can do to vital functions of the brain.
Brain tumors can occur at any age. Brain tumors that occur in infants and children are very different from adult brain tumors, both in terms of the type of cells and the responsiveness to treatment.
Anatomy of the brain
The central nervous system (CNS) consists of the brain and spinal cord. The brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respirations, temperature, hunger and every process that regulates our body.
The brain can be divided into the cerebrum, the brainstem, and the cerebellum:
- Cerebrum (supratentorial, or front of brain) - composed of the right and left hemispheres. Functions of the cerebrum include: initiation of movement, coordination of movement, temperature, touch, vision, hearing, judgment, reasoning, problem solving, emotions and learning.
- Brainstem (midline, or middle of brain) - includes the midbrain, the pons, and the medulla. Functions of this area include: movement of the eyes and mouth, relaying sensory messages (i.e., hot, pain, loud), hunger, respirations, consciousness, cardiac function, body temperature, involuntary muscle movements, sneezing, coughing, vomiting and swallowing.
- Cerebellum (infratentorial, or back of brain) - located at the back of the head, its function is to coordinate voluntary muscle movements and to maintain posture, balance and equilibrium.
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-Frameni syndrome and retinoblastoma) also have an increased risk to develop tumors of the central nervous system. There have also been some reports of children 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.
Children 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 child may experience symptoms differently. Symptoms vary depending on 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 the following symptoms:
- Increased intracranial pressure (ICP) - caused by extra tissue or fluid in the brain. Pressure may increase because one or more of the ventricles that drain cerebrospinal fluid (CSF, the fluid that surrounds the brain and spinal cord) has been blocked, causing the fluid to be trapped in the brain. Increased ICP can cause the following:
- Personality changes
- Decreased cardiac and respiratory function and eventually coma if not treated
Symptoms vary depending upon which part of the brain the tumor is found. Symptoms of brain tumors in the cerebrum (front of brain) may include:
- Visual changes
- Slurred speech
- Paralysis or weakness on half of the body or face
- Increased intracranial pressure (ICP)
- Drowsiness or confusion
- Personality changes
Symptoms of brain tumors in the brainstem (middle of brain) may include:
- Endocrine problems (diabetes or hormone regulation)
- Visual changes or double vision
- Paralysis of nerves/muscles of the face or half of the body
- Respiratory changes
- Increased intracranial pressure (ICP)
Symptoms of brain tumors in the cerebellum (back of brain) may include:
- Increased intracranial pressure (ICP)
- Vomiting (usually occurs in the morning without nausea)
- Uncoordinated muscle movements
- Problems walking (ataxia)
The symptoms of a brain tumor may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
How is a brain tumor diagnosed?
In addition to a complete medical history and physical examination of your child, diagnostic procedures for a brain tumor may include:
- Neurological exam - your child's 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.
- X-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones and organs onto film.
- Bone scan - pictures or x-rays taken of the bone after a dye has been injected that is absorbed by bone tissue. These are used to detect tumors and bone abnormalities.
- Angiogram - a dye is used to visualize all the blood vessels in the brain in order to detect certain types of tumors.
- Myelogram - an x-ray of the spine, similar to an angiogram.
- Lumbar puncture/spinal tap - a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing. CSF is the fluid which bathes the brain and spinal cord.
Diagnosis of a brain tumor depends mostly on the types of cells in which the tumor begins and the tumor location.
What are the different types of brain tumors?
The different types of brain tumors include the following:
The most common type of 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 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. Astrocytomas are generally subdivided into high-grade or low-grade tumors. High-grade astrocytomas 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 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.
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, but may have problems with double vision, movement of the face or one side of the body or difficulty with walking and coordination.
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.
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 the child 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.
PNET can occur anywhere in the brain of a child, 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 child experiences increased intracranial pressure. These tumors are fast growing and often malignant, with occasional spreading throughout the brain or spinal cord.
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 needed to control these tumors.
Craniopharyngioma are benign tumors that occur at the base of the brain near the nerves from the eyes to the brain and the hormone centers. Most persons with this type of brain tumor develop symptoms before the age of 20. Symptoms include headaches, as well as problems with vision. Hormonal imbalances are common, including poor growth and short stature. 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.
Many different tumors can arise near the pineal gland, a gland which helps control sleep and wake cycles. Gliomas are common in this region, as are pineal blastomas (PNET). In addition, germ cell tumors, another form of malignant tumor, can be found in this area. Tumors in this region are more common in children than adults and make up 3 to 8 percent of pediatric brain tumors. 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 child's physician based on:
Your child's age, overall health and medical history
Type, location, and size of the tumor
Extent of the disease
Your child's tolerance for specific medications, procedures or therapies
Expectations for the course of the disease
Your opinion or preference
Treatment may include (alone or in combination):
Lumbar puncture/spinal tap (to test pressure in the central nervous system, to look for suspicious cells, and give medication if needed)
Bone marrow transplantation
Supportive care (for 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).
Long-term outlook for a child with a brain tumor:
Prognosis greatly depends on:
The type of tumor
The extent of the disease
Size and location of the tumor
Presence or absence of metastasis
The tumor's response to therapy
The age and overall health of your child
Your child's 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 child 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.