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Copyright ABTA, 1991
Fifth Edition
 A PRIMER
OF BRAIN TUMORS
A Patient's Reference Manual
...in the hope that through knowledge comes comfort and strength...
American Brain Tumor Association
2720 River Road
Des Plaines, Illinois 60018-4110
(847) 827-9910
We suggest you use this booklet as a reference. Read those
topics which apply to your situation at the present time. In the
future, you may find it helpful to read other sections.
CONTENTS
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SECTION 1 What is a brain tumor?
DEFINITION
Brain tumors are tumors that grow in the brain. A tumor is an
abnormal growth caused by cells reproducing themselves in an uncontrolled
manner.
When doctors describe tumors in parts of the body other than the
brain, they use the words benign (meaning harmless) or malignant
(meaning cancerous). These meanings change, however, when referring
to tumors in the brain.
Benign brain tumors:
A benign brain tumor consists of benign (harmless) cells
and has distinct boundaries. Surgery alone may cure this type of
tumor.
Malignant brain tumors:
A malignant brain tumor is life-threatening. It may be
malignant because it consists of cancer cells, or it may be called
malignant because of its location. In other words, a brain tumor
composed of benign cells--but located in a vital area--is still
considered malignant.
A malignant brain tumor made up of cancerous cells may spread
or seed (metastasize) to other locations in the brain or spinal
cord. It can invade and destroy healthy tissue so it cannot function
properly. Malignant tumors grow the way a plant does, with "roots"
invading various tissues. Or, they can shed cells that travel to
distant parts of the brain. Some cancerous tumors, however, remain
localized.
Malignant brain tumors seldom metastasize outside the brain
and spinal cord. [Central Nervous System
(CNS)]
The bones of the skull hide brain tumors. The doctor can not
feel or see them during a routine examination. Scans produce pictures
that suggest a particular type of tumor. Only a sample
of tumor examined under a microscope can provide an exact diagnosis
. If this type of examination is not possible, an educated assumption
is made based on available test results.
Often, the damage done by brain tumors is due to their size. Because
the skull is bone, it cannot expand to make room for even a small
mass growing within it. As a result, the tumor presses on and displaces
normal brain tissue. This pressure may damage or destroy delicate
brain tissue. Many of the symptoms of a brain tumor are caused by
this pressure. Sometimes, a tumor may cause blockage of fluid that
flows around and through the brain. This blockage can also create
increased pressure. Some brain tumors also cause swelling due
to accumulation of fluid (edema). Size, pressure, and swelling
all create this "mass effect."
CATEGORY
Tumors that start in the brain are primary brain tumors.
Metastatic brain tumors are tumors formed by cancer cells
that start elsewhere in the body and spread to the brain.
Naming Tumors
Tumor names depend on where the tumor originated, its pattern
of growth, and whether it is cancerous or not. The following are
some general names of tumors:
ADENOMA A usually benign tumor arising from a gland; for example,
pituitary adenoma.
BLASTOMA A malignant tumor whose cells have undeveloped(embryonic)
characteristics; for example, medulloblastoma or glioblastoma multiforme.
CARCINOMA A malignant tumor that arises from skin or the lining
of the digestive, respiratory, and urogenital systems; for example,
lung cancer (small cell carcinoma) or colon cancer (adenocarcinoma).
SARCOMA A malignant tumor that arises from connective tissue,
blood vessels, or the lymph system; for example, osteosarcoma.
GLIOMA The general name for a tumor that arises from the supportive
tissue of the brain; for example, astrocytoma or oligodendroglioma.
It may be benign or malignant.
Some tumors may undergo further change (mutation). A benign
growth may become malignant. In some tumors, a lower-grade tumor
may recur as a higher-grade tumor.
Grading Tumors
Tumor grade indicates the degree of malignancy. Grade is based
on the tumor's tendency to spread (infiltrate), its growth
rate, and its similarity to normal cells.
Tumors with distinct borders (circumscribed), considered
grade I, are sometimes referred to as benign or mildly malignant.
Those tumors either do not grow or grow slowly.
Infiltrating tumors are those that tend to grow into surrounding
tissue. Of the infiltrating tumors, the terms low-grade, mid-grade,
and high-grade are frequently used. However, the exact system
used to grade tumors varies with each specific family of tumors.
Tumors often contain several grades of cells. The highest or most
malignant grade of cell found during microscopic examination determines
the grade, even if most of the tumor is a lower grade.
Tumor diagnosis by name and by grade is very important for
both treatment and prognosis.
SECTION 2 What are the parts of the brain
and what does each part do?
The brain--a soft, spongy mass of nerve and supportive tissue--sits
inside the skull. The base of the brain is connected to the spinal
cord. The brain, the spinal cord, and the nerves that extend out
from the brain and spinal cord into various parts of the body, act
together to send information to the brain and relay instructions
from the brain.
This chapter discusses the various parts of the brain. You can
jump to a discussion of a particular part by clicking on the links
(usually-blue or purple depending on your web-browser)
Words in this section that appear in BOLD FACE PRINT refer
to brain structures or areas.
The brain is made up of four main structures, plus a number of
other specialized areas. To begin with, the brain is covered by
three membranes.
MENINGES
The meninges are three, thin layers of tissue (membranes)
that completely cover the brain and the spinal cord. The three layers
of meninges are the dura mater, the arachnoid, and
the pia mater. Spinal fluid flows in the space between the
arachnoid and the pia mater membranes. This is the called the subarachnoid
space.
The tentorium is a flap of the dura mater that separates
the cerebral hemispheres from the other major structures
of the brain. Supratentorial refers to the area above the
tentorium. Infratentorial refers to the area below the tentorium.
(see figure 1)
MAIN STRUCTURES OF THE BRAIN
Cerebrum
1. The largest area of the brain is the Cerebrum. It consists
of two hemispheres or halves, the right and left cerebral hemispheres.
The right cerebral hemisphere controls the left side of the body.
The left cerebral hemisphere controls the right side of the body.
The outer layer of the cerebrum--called the cerebral cortex--is
made up of gray matter. The inner portion of the cerebrum is white
matter. In addition, there are areas of gray matter, called basal
ganglia, deep within the brain.
Gray matter is composed of nerve cells. These cells control brain
activity. White matter is composed of myelinated nerve cell axons
that carry information between nerve cells in the brain and spinal
cord. Oligodendrocytes and astrocytes are support cells that help
maintain the myelin covering of nerve axons and nerve cell bodies,
respectively.
Deep indentations called fissures divide each half(hemisphere)
of the cerebrum into four lobes (sections): Frontal Lobe,
Parietal Lobe, Temporal Lobe, and Occipital Lobe.
Each lobe controls a specific group of activities. (see figure 2)
Frontal Lobe: The frontal lobe of each hemisphere controls
voluntary muscle movements on the opposite side of the body.
The frontal lobe of the dominant hemisphere controls speech and
writing. (The dominant hemisphere is the left hemisphere in all
right-handed and some left-handed individuals, and the right hemisphere
in most left-handed people.) Other frontal lobe activities include
intellectual functioning, thought processes, behavior, and memory.
Parietal Lobe: The parietal lobe receives and interprets
sensations. These sensations include pain, temperature, touch, pressure,
size, shape, and body-part awareness. Other activities of the parietal
lobe are hearing, reasoning, and memory.
Temporal Lobe: The temporal lobe is involved in the understanding
of sounds and spoken words, as well as emotion and memory.
Occipital Lobe: The occipital lobe is involved in the understanding
of visual images and the meaning of written words.
Cerebellum
2. The Cerebellum is the second largest area of the brain.
It consists of two hemispheres or halves connected by the vermis
. The cerebellum connects to the brain stem. (see figure
3)
The cerebellum, together with the thalamus and cerebrum
, controls skilled muscular coordination, including walking
(gait) and speech (articulation).
Pons
3. The Pons coordinates the activities of the cerebrum
and cerebellum by relaying impulses between them and
the spinal cord. The pons contains the origins of the 5th, 6th,
7th, and 8th cranial nerves. (see figure 5)
Medulla Oblongata
4. The Medulla Oblongata controls breathing (respiration),
heart beat, and vomiting. It connects the brain with the spinal
cord. It contains the origins of the 9th, 10th, 11th, and 12th cranial
nerves. (see figure 5)
Besides these four main structures, many other specialized nerve
structures are part of the brain.
VENTRICLES AND CHOROID PLEXUS
There are four connected cavities or ventricles in the
brain. Inside each ventricle are structures called choroid plexus.
The choroid plexus forms spinal fluid, which flows through the ventricles
and the subarachnoid space surrounding the brain and spinal
cord. (see figure 4)
There are two lateral ventricles, one in each cerebral
hemisphere. The third ventricle is beneath the corpus callosum
and surrounded by the thalamus. The fourth ventricle is between
the hemispheres of the cerebellum. It is an expansion of
the central canal of the medulla oblongata.
The cerebral aqueduct, called the aqueduct of Sylvius
, is a narrow canal connecting the 3rd and 4th ventricles.
HYPOTHALAMUS
The hypothalamus makes up part of the wall of the thirdventricle
and is the base of the optic chiasm. It controls water
balance, sleep, temperature, appetite, and blood pressure. The hypothalamus
coordinates patterns of activity and controls emotions. It is also
the control center for the pituitary gland. (see figure 5)
THALAMUS
The thalamus surrounds the third ventricle. It monitors
input from the senses and acts as a relay station for the sensory
center of the cerebrum. (see figure 5)
LIMBIC SYSTEM
The limbic system, together with the hypothalamus, controls
hunger, thirst, emotional reactions, and biological rhythms. In
addition, it coordinates complex activities requiring a sequence
of performance steps. (see figure 5)
CRANIAL NERVES
There are 12 pairs of cranial nerves: (see figure 6)
NUMBER NAME FUNCTION
------------------------------------------------------------
1 Olfactory Smell
2 Optic Vision
3 Oculomotor Eye movement
4 Trochlear Eye movement
5 Trigeminal Facial sensation
6 Abducent Eye movement
7 Facial Face movement
8 Vestibulocochlear Hearing and balance
9 Glossopharyngeal Taste and gag reflex
10 Vagus Involuntary muscles (heart, stomach,
intestines, throat, chest)
11 Accessory Voluntary muscles of the neck
12 Hypoglossal Tongue movement
BRAIN STEM
The brain stem controls basic functions, including blood pressure,
heart beat, and breathing (respiration). It is the bottom-most
portion of the brain, connecting the cerebral hemisphereswith
the spinal cord. Several structures are part of the brain stem:
(see figure 5)
Pons Reticular Formation
Medulla Oblongata Midbrain
RETICULAR FORMATION
The reticular formation is the central core of the brain stem
. It controls consciousness, eating and sleeping patterns, drowsiness
and attention. The reticular formation connects with all parts of
the brain and brain stem. (see figure 5)
MIDBRAIN
The midbrain is the short portion of the brain stem between
the pons and the cerebral hemispheres. The midbrain
is a relay center for sight and hearing. (see figure 5)
POSTERIOR FOSSA (also called the
Infratentorium)
This is the area within the skull that houses the cerebellum
and the brain stem. The tentorium separates it
from the cerebral hemispheres. (see figure 1)
SUPRATENTORIUM
The supratentorium is the area above the tentorium (Tentorium:
a flap of membrane, part of the meninges). It contains the cerebral
hemispheres and other brain structures. (see figure 1)
PINEAL BODY
The pineal body lies below the corpus callosum. It produces
the hormone melatonin. This function of this hormone is not known.
(see figure 4)
SELLAR REGION (also Suprasellar, Parasellar)
The sellar region is the area around the sella turcica.
The sella turcica is the hollow of skull bone that contains the
pituitary gland. (see figure 5)
PITUITARY GLAND (Hypophysis)
The pituitary gland is attached to and receives messages from
the hypothalamus. The pituitary gland is composed of two
lobes, the anterior and the posterior. This gland secretes several
important hormones. (see figure 5)
Medical terminology used to describe anatomy
and location:
anterior/posterior front, forward/back, behind
fossa a depression or hollow of bone
hyper/hypo high, over/low, under
para beside, next to, beyond
sella a small, saddle-shaped depression of bone
sub under, near
supra/infra above, over/below, under
SECTION 3 Who gets brain tumors?
Primary brain tumors occur in people of all ages. Metastatic brain
tumors are much more common in adults.
- Primary malignant brain tumors are the second most common cause
of cancer death in children up to 15 years old.
- They are the second most common cause of cancer death in people
ages 15 to 34.
- They are the third most common cause of cancer death in males
ages 35 to 54.
In 1990, primary malignant brain tumors represented about 1.5%
of all cancers diagnosed and 2% of the cancer deaths.
WHAT CAUSES A BRAIN TUMOR?
The cause of primary brain tumors is unknown. Environmental agents,
familial tendencies, viral causes, and other possibilities are under
investigation.
Brain tumors are not contagious.
STATISTICS
Accurate statistics for the frequency and outcome of brain tumors
are not available. It is estimated that in the United States in
1990, there were 20,500 new cases of primary brain tumor .
New cases of metastatic brain tumor diagnosed in 1990 were
estimated to be at least 20,700. The combined estimate of 41,200
new cases of brain tumor included both benign and malignant brain
tumors.
These statistics are based on the 1989 United States population
of 249,000,000 people, and an incidence rate of 8.2 per 100,000
for primary brain tumors, and an incidence rate of 8.3 per 100,000
for metastatic brain tumors.
The various types of brain tumors occur with different frequency
in children and in adults.
The most common childhood tumors are:
1. Astrocytoma
2. Medulloblastoma
3. Ependymoma
The most common adult tumors are:
1. Metastatic brain tumors from lung, breast, melanoma, and other
cancers
2. Glioblastoma Multiforme
3. Anaplastic (Malignant) Astrocytoma
4. Meningioma
SECTION 4 What are the symptoms of brain
tumors?
INTRODUCTION
Brain tumors are often difficult to diagnose because their symptoms,
which serve as clues for the medical specialist, can be hard to
pin down.
In general, the symptoms depend on the size of the tumor and the
part of the brain affected. But as a tumor grows, it can affect
other parts of the brain, producing new symptoms. The tumor may
grow into other areas of the brain, or the "mass effect"
may cause the additional symptoms. (See Section 1)
Additionally, the symptoms produced by a brain tumor often mimic
the symptoms of other diseases--and vice versa.
Because symptoms may appear gradually, and because they are often
not clear-cut, it may be a long time between the beginning of symptoms
and the actual diagnosis.
INCREASED INTRACRANIAL PRESSURE (IICP)
Some patients with brain tumors develop increased intracranial
pressure. IICP occurs for several reasons:
- An increase in the mass within the rigid bones of the skull
because of tumor growth
- Blockage of the flow of cerebrospinal fluid (CSF)
- Swelling of the tissue around the tumor due to the accumulation
of fluid (edema)
When a tumor blocks the normal flow of CSF within the brain, hydrocephalus
occurs. Hydrocephalus causes increased pressure within the skull,
and the increased pressure damages the delicate structures of the
brain.
Symptoms of IICP are:
- Headache usually just after waking and lessening as the
day goes on
- Vomiting usually just after waking, with or without nausea
- Mental changes, often sluggishness or drowsiness
- Uncoordinated, clumsy movements
- Seizures
SYMPTOMS LISTED BY TUMOR LOCATION
Symptoms are what the patient reports to the doctor: sensations,
feelings, descriptions.
Signs are what the doctor can observe, either directly
or as the result of various tests.
For simplicity, we use the term symptom to mean both signs and
symptoms.
Brain Stem Tumors (Midbrain, Pons, Medulla Oblongata)
Tumors of the brain stem can produce a variety of symptoms. The
most common symptoms are vomiting, usually just after awakening,
and a clumsy, uncoordinated walk (ataxic gait). Muscle weakness
on one side of the face causes a one-sided smile or drooping eyelid.
Difficulty in swallowing (dysphagia) and difficulty with
speech (dysarthria) are also common symptoms. In addition, abnormalities
in the functioning of the eye nerves produce "crossed eyes"
or decreased vision. Headache, usually just after awakening, may
also occur. Head tilt, drowsiness, hearing loss, one-sided muscle
weakness (hemiparesis), and personality changes may be present.
Symptoms may develop gradually.
Cerebellopontine Angle Tumors (Usually Acoustic Nerve Tumors)
The earliest symptom is ringing or buzzing in the ear (tinnitus).
Less often, dizziness (vertigo) may occur. As the tumor grows,
additional symptoms such as deafness, and others similar to those
of a brain stem tumor may occur. (see figure 3)
Cerebral Hemisphere Tumors
Frontal Lobe Tumors
Common symptoms include one-sided paralysis (hemoplegia),
seizures, defective memory, impaired judgment, and personality or
mental changes. If the tumor is at the base of the frontal lobe,
loss of sense of smell (anosmia), impaired vision, and a
swollen optic nerve (papilledema) may occur.
Mental or personality changes and a clumsy, uncoordinated walk
(ataxic gait) are common symptoms if the tumor involves both
the left and right frontal lobes. (see figure 2)
Parietal Lobe Tumors
Seizures, speech disturbances if the tumor is in the dominant
(usually left) hemisphere, and loss of ability to write(agraphia)
are common symptoms. Spatial disorders, such as difficulty with
body orientation in space or recognition of body parts, may also
occur. (see figure 2)
Occipital Lobe Tumors
Blindness in one direction (hemianopsia) and seizures are
common symptoms. (see figure 2)
Temporal Lobe Tumors
These tumors usually are "silent." They often cause
no symptoms other than occasional seizures or language disorders
(dysphasia). (see figure 2)
Subcortical Tumors
One-sided paralysis (hemiplegia) is the most common symptom.
These tumors may invade other lobes of the cerebral hemispheres
and produce symptoms common to tumors in those locations.
If the tumor invades the thalamus, the sense of touch may be impaired.
Meningeal Brain Tumors
These tumors cause symptoms usually because of pressure and compression
rather than by growth into brain tissue. Symptoms depend on the
location of the tumor. (See the description of symptoms by location.)
Metastatic Brain Tumors
Symptoms depend on the location of the tumor or tumors in the
brain. Headache, nausea, and vomiting are common, because of the
swelling (edema) that frequently accompanies these tumors.
For specific symptoms, see the description of symptoms by location.
Midline Tumors (Craniopharyngioma, Optic Nerve Glioma, Tumors
of the Thalamus and Sellar areas)
Headaches, nausea and a swollen optic nerve (papilledema)
are the most common symptoms of these tumors. These symptoms are
due to an increase in intracranial pressure. Other symptoms are
abnormal eye movement (nystagmus) and vision, and alteration
of personality or consciousness. In addition, impairment of glandular
functions may cause either delayed or accelerated growth. The development
of a water balance problem (diabetes insipidus) is possible.
Posterior Fossa Tumors (Tumors of the Fourth Ventricle, Cerebellar
Tumors)
Headaches, nausea, and a swollen optic nerve (papilledema)
due to increased intracranial pressure are the most common symptoms.
A clumsy, uncoordinated walk (ataxic gait), swaying,
and staggering may occur. Tremors, as well as difficulty with other
types of coordination and speech are also frequent symptoms. Nerve
irritation may cause pain in the back of the head.
Spinal Cord Tumors
Symptoms of these tumors depend on the nerves involved. (see figure
8) Tumors of the thoracic area may cause a "girdle pain"
in the chest that worsens with coughing or sneezing. This pain is
often worse when the person is lying down. Tumors in the cervical
or lumbar areas may cause neck, arm, back, or leg pain. Weakness,
muscle wasting or spasms, and sensory changes are other common symptoms.
Decrease or lack of bowel or bladder control may occur, depending
on the location of the tumor.
SECTION 5 How are brain tumors diagnosed?
INTRODUCTION
The diagnosis of a brain tumor begins in the doctor's office.
The doctor begins by asking the patient a number of questions to
get a complete history of the symptoms. Then he or she will do a
basic neurological examination.
NEUROLOGICAL EXAMINATION
A basic neurological examination includes the following:
- Eye movement, pupil reaction, and eye reflex tests
- Hearing tests using a ticking watch or tuning fork
- Reflex tests using a rubber hammer
- Balance and coordination tests. Heel-to-toe walking. Heel-to-shin
movements. Balance with feet together and eyes closed. Rapid alternating
movements such as touching the finger to the nose with eyes closed.
- Sense of touch tests using a pin point and cotton ball
- Sense of smell tests using various odors
- Facial muscle tests--smiling, grimacing
- Tongue movement, gag reflex tests
- Head movement tests
- Mental status tests. Asking for the current time and date. Asking
who is President.
- Abstract thinking test. Asking for the meaning of "a stitch
in time saves nine."
- Memory tests. Asking to have a list of objects repeated. Asking
for a description of the food eaten at breakfast yesterday. Asking
for a description of the events of last Thanksgiving.
If the results of this examination lead the physician to suspect
a brain tumor may be present, additional testing will be scheduled.
Neurological specialists perform several diagnostic tests for
brain tumors. These include:
SCANS
Scans are done in place of conventional x-rays, which are not
able to show tumors behind bone. Different types of imaging devices
are used to perform brain scans. The most commonly used devices
for both diagnosis and follow-up are the Computerized Axial Tomographer
(CT or CAT) and the Magnetic Resonance Imager (MRI). Positron Emission
Tomography (PET) is also available, but it tends to be used more
for research than for routine diagnosis.
CT or CAT
This machine combines an x-ray device and computer. Before the
CT scan begins, the person being examined is given an injection
of a special dye (contrast) material. This dye helps make
any abnormal tissue more evident. Then the patient lies on a table
that slides into a doughnut-shaped opening. While the patient lies
very still, the CT scanner circles the head, and x-rays penetrate
the brain. Absorption of the x-rays varies with the type of tissue
penetrated. A ring of detectors measures the amount of rays remaining
after their path through the brain.
Thousands of thin cross section readings are fed into the computer
which then transforms the data into a picture.
MRI
The MRI is a tunnel-shaped piece of equipment. The person being
examined lies on a table that slides into the tunnel. Inside the
scanner, a magnetic field surrounds the patient's head while radio
energy is beamed to the area. No x-rays are used. The magnetic
field causes atoms in the brain to change direction. The radio waves
cause another change of direction. When the beam stops, the atoms
relax and return to their original position. During relaxation,
the atoms give off signals in differing amounts and at different
intervals of time. Antennas pick up these signals and feed them
into a computer which assembles a picture. Because different atoms
have their own characteristic radio signals, the computer can distinguish
between healthy and diseased tissue. A contrast material (Gadolinium)
may be used with the MRI.
Because the MRI ignores bone which can obstruct CT images, this
device provides clearer pictures of tumors located near bone. The
MRI can also produce a wider variety of image angles. The MRI can
detect edema but has difficulty distinguishing edema from tumor.
Some tumors have calcification, which the MRI cannot detect. MRI
imaging takes longer than a CT scan, and it is very noisy. Patients
with cardiac monitors, pacemakers, or surgical clips cannot take
an MRI because of the magnetic fields.
PET
In a PET scan, a low-dose radionuclide produced by a cyclotron
(an atom smashing radiation unit) is coupled to a chemical such
as glucose (a sugar) and injected into the patient. The PET scanner
rotates around the patient's head, detecting the rays emitted by
the radioactive sugar. Highly malignant tumors consume glucose at
a higher rate than normal brain.
Measurements of brain activity (determined by concentrations of
the glucose) feed into a computer, which produces a color-coded
moving picture or a gray scale image of the brain as it converts
food (glucose) into energy.
The use of PET is limited because cyclotrons are scarce.
The following type of scan may be used with tumors having a
large blood supply. (vascular)
RN (Radionuclide)
A radionuclide (RN) scan uses short-lived radioactive material
injected into a vein in the arm. The scanner moves back and forth
over the patient's head, plotting a chart. The chart shows the various
concentrations of the injected material in the brain.
The contrast materials used with CT or MRI scanners concentrate
in diseased tissue in larger quantity than in healthy tissue. The
radioactive materials used with RN scanners also concentrate in
diseased tissue. In all three cases, the concentration is due to
the leakiness of blood vessels in and around brain tumors. The concentration
of contrast materials or radioactive drug outlines abnormalities
such as tumors.
A neuroradiologist interprets the computer images produced by
the CT, MRI, PET, and RN scans. The pictures help establish a tentative
diagnosis. Scans do not show a specific type of tumor. Only examination
of an actual sample of tumor tissue can provide an exact diagnosis.
LUMBAR PUNCTURE (Spinal Tap)
Lumbar puncture is used to obtain a sample of spinal fluid. The
fluid is then examined in a laboratory to determine if tumor cells,
infection, protein, or blood is present. Lumbar puncture is also
used to inject a dye before a myelogram. A myelogram is
a test used primarily for spinal tumors.
Lumbar puncture is never done if there is suspicion of increased
intracranial pressure because of the risk of the brain bulging
through an opening in a membrane, muscle, or bone. (herniation)
On an experimental basis, tests of spinal fluid may help identify
tumor markers (substances which indicate the presence of
a tumor). A tumor marker is important. Colon cancer patients, for
example, have their blood tested every few months. The doctor looks
for an increase in a substance known as CEA. When CEA increases,
it is almost certain that the colon cancer has returned or is growing.
Thus, CEA serves as an early warning system for treatment to begin.
Unfortunately, most brain tumors have no tumor markers. (At this
time, pineal region tumors are the only brain tumors that can sometimes
be diagnosed using markers.)
ELECTROENCEPHALOGRAM (EEG)
An EEG is used to record electrical activity of the brain, particularly
of the cerebral hemispheres, using electrodes attached to the scalp.
BIOPSY
A biopsy is a surgical procedure used to remove a small amount
of tumor tissue. The neurosurgeon then submits samples of the tumor
tissue to a neuropathologist for analysis. An accurate diagnosis
is then possible.
For those areas not easily reached via an open biopsy, a surgeon
can, through a small hole made in the skull, use stereotaxic instrumentation
to obtain a "closed" biopsy. Stereotaxic instrumentation
allows the surgeon to precisely position a biopsy probe in three-dimensional
space to allow access almost anywhere in the brain. In most instances,
therefore, it is possible to obtain tissue for diagnosis, if it
is desired. When biopsy is not performed, diagnosis relies solely
on scan test results and their interpretation.
The following tests are used primarily for pre-operative information
rather than for diagnosis:
ANGIOGRAM OR ARTERIOGRAM
After injection of a contrast material into a deep artery, x-rays
follow the flow of the material through the blood vessels of the
brain. This test usually requires prior sedation, as it can be uncomfortable.
The angiogram shows the position of the blood vessels near the tumor
and the extent of the tumor's blood supply. (vascularity)
MRI angiography will be available at many medical centers in the
near future. This will, to a great extent, replace invasive arteriography.
EVOKED-POTENTIALS
Evoked-potential testing uses small electrodes to measure the
electrical activity of nerves. The test can be used to determine
areas controlled by an individual nerve. Evoked- potentials may
serve as a guide during the surgical removal of tumors growing around
important nerves.
SECTION 6 What are the different types
of brain tumors?
Classification is the grouping of tumors on the basis of
their characteristics. Each tumor is then given a unique name. Several
different brain tumor classification systems are now in use. The
consistent naming of brain tumors is very important when gathering
statistics for incidence, etiology (cause), effectiveness
of treatment, and prognosis.
The following is an alphabetical list of the most common brain
tumors. Included in the list are alternate names commonly in use.
Acoustic Neuroma (Neurilemmoma, Schwannoma, Neurinoma)
The acoustic neuroma is a benign tumor of the nerve of hearing
(the acoustic or 8th cranial nerve). It is located in the angle
between the cerebellum and the pons, in the posterior fossa. This
tumor grows very slowly.
Acoustic neuromas occur in adults, particularly in their middle
years. Females are twice as likely to have this tumor as males.
Acoustic neuromas account for about 9% of all brain tumors.
Common symptoms are loss of hearing in one ear and buzzing
or ringing in the ear (tinnitus), with dizziness occurring less
commonly. If the tumor also affects the adjacent 7th nerve (facial
nerve), facial paralysis and loss of facial sensation may occur.
Other symptoms may include difficulty in swallowing, impaired eye
movement, taste disturbances, and unsteadiness.
Often, total surgical removal is possible.
For additional information about acoustic neuromas, contact
the Acoustic Neuroma Association, P. O. Box 398, Carlisle, PA 17013,
717/249-4783.
Adenoma (See Pituitary Adenoma)
Astrocytoma
Astrocytomas are tumors that arise from astrocyte cells-- part
of the supportive tissue of the brain. These cells are named for
their star-like shape.
There are different classification systems used to grade astrocytomas.
One system grades these tumors on a scale of I to IV. In that system,
grade I tumors tend to be benign and grade IV tumors the most malignant
(glioblastoma multiforme). Other classification systems, including
the World Health Organization, separate astrocytomas into distinct
types that more closely reflect outcome. Important types of astrocytomas,
in increasing degree of malignancy, are: the benign juvenile pilocytic
astrocytoma, astrocytoma, anaplastic astrocytoma, and glioblastoma
multiforme. In addition, these tumors may be classified by the nervous
system location in which they occur, such as optic nerve glioma
or brain stem astrocytoma (or glioma). The astrocytoma can also
be mixed with oligodendroglioma and/or ependymoma tumor elements.
These tumors are then called mixed gliomas.
Because grading systems vary, we have divided the astrocytomas
into three groups: low-grade astrocytomas, mid-grade and high-grade
astrocytomas.
Low-Grade Astrocytoma
Low-grade astrocytomas often have well-defined borders. Some low-grade
astrocytomas form cysts or are enclosed in a cyst. Metastasis is
rare. Although these tumors are usually slow growing, they can invade
large areas.
The lowest grade astrocytomas are the juvenile pilocytic astrocytomas
, and subependymal giant cell astrocytomas.
Juvenile pilocytic astrocytomas occur mainly in children.
They are considered to be the most benign of the astrocytomas. Cerebellar
astrocytomas and optic nerve gliomas are often pilocytic
tumors.
The subependymal giant cell astrocytoma is the ventricular
tumor typically associated with tuberous sclerosis.
Infiltrating low-grade astrocytomas are a bit more malignant.
These are called low-grade astrocytoma or astrocytoma. They are
often found in the temporal lobe of the cerebral hemispheres.
Location of the tumor often determines treatment. Complete surgical
removal is sometimes possible for accessible (accessible
tumors can often be surgically removed without causing severe neurological
damage) tumors. After total surgical removal, periodic follow-up
with MRI or CT scans may be the only additional care required. Radiation
therapy is used for incompletely removed or inoperable low-grade
astrocytomas, or for those that recur. Chemotherapy for these is
uncommon except for recurrences. Intracavitary radiation may be
effective for cystic tumors.
Mid- and High-Grade Astrocytoma
These astrocytomas are truly malignant tumors. Included in the
mid-grade group are the gemistocytic astrocytoma, anaplastic
astrocytoma, and malignant astrocytoma. The high-grade
group is represented by the glioblastoma multiforme and a
variant, the gliosarcoma.
The mid- and high-grade astrocytomas grow more rapidly than low-grade
tumors and tend to invade nearby healthy tissue. These tumors recur
more frequently than some lower grade tumors because their tendency
to spread into surrounding tissues (invasiveness) makes it difficult
to completely remove them during surgery.
Treatment is based on the extent of the spread of the tumor. Surgery
followed by radiation therapy is the treatment of choice for accessible
high-grade astrocytomas. Inoperable tumors are usually treated with
radiation therapy. Chemotherapy is frequently given after surgery
and/or radiation therapy; chemotherapy is most effective for the
mid-grade astrocytomas. Investigational immunotherapy treatments
are also available.
Recurrent tumors
Many malignant tumors cannot be removed completely during surgery
because they have spread into surrounding tissues. They therefore
tend to recur. Surgery may be used to treat accessible recurrent
astrocytomas. Conventional radiation therapy may be given if it
was not done as an initial treatment. Focused high-dose focal radiation
therapy, such as implantation of radiation directly into the
tumor (interstitial radiation) can be used if conventional radiation
therapy has already been given. Chemotherapy is also used to treat
recurrent tumors. It appears to be more effective for the mid-grade
tumors.
For additional information, refer to the ABTA publications
About Glioblastoma Multiforme and Malignant Astrocytoma;
Radiation Therapy of Brain Tumors: Part I and Part II; Chemotherapy
of Brain Tumors; Immunotherapy of Brain Tumors.
Brain Stem Glioma
Brain stem glioma may be a an astrocytoma, anaplastic astrocytoma,
glioblastoma multiforme, a mixed tumor. This tumor location is more
common in children than in adults.
MRI images are superior to CT images for detecting these tumors.
Brain stem gliomas are not always solely in the center of the
brain stem. They may have external branches as well. Because of
their location, most brain stem tumors are inoperable. It may be
possible to biopsy their external parts, however, to establish an
exact diagnosis.
The treatment of choice is radiation therapy to the posterior
fossa. An increased number of smaller dosage treatments of radiation
(hyperfractionation) is under investigation as a replacement for
conventional daily radiation therapy.
Chordoma
The chordoma occurs at the base of the skull or the end of the
spine. It is an extradural (outside the dura mater) tumor
and usually is benign. However, it frequently invades adjacent bone.
This rare tumor represents .2% of all primary CNS tumors. It is
found most often in people ages 21 to 40.
Chordomas appear on MRI and CT scans, but a biopsy is necessary
to determine an exact diagnosis.
Often, complete surgical resection is possible for the spinal
chordoma. A combination of surgery followed by radiation is the
usual treatment for skull-base tumors. Because of their proximity
to delicate brain structures, charged particle radiation rather
than conventional radiation is often used.
Choroid Plexus Papilloma
This is a rare, benign tumor most common in children under the
age of 12. About 4% of primary brain tumors in that age group are
choroid plexus papillomas. It represents less than 1% of all primary
brain tumors.
In children, the most common location of this tumor is the lateral
ventricles. The fourth ventricle is the most common site in adults.
Choroid plexus papillomas grow slowly within the ventricles. They
eventually block the flow of cerebrospinal fluid. This causes hydrocephalus
and increased intracranial pressure.
Both CT and MRI scans detect these tumors.
The treatment of choice is surgery. Tumor removal resolves the
hydrocephalus in half of the patients. The remaining patients require
a shunt in addition to resection. The rare inoperable or malignant
form of this tumor (choroid plexus carcinoma) may be treated with
radiation. The choroid plexus papilloma however is generally resistant
to radiation therapy (radioresistant).
CNS Lymphoma (Primary Malignant Lymphoma)
In addition to affecting people with healthy immune systems, this
disease is common in persons whose immune system is not functioning
properly. People with malfunctioning immune systems include those
who have undergone organ transplants or those infected with the
AIDS virus. The incidence of CNS lymphoma is increasing in people
with healthy and unhealthy immune systems.
The most common site of the CNS lymphoma is one of the cerebral
hemispheres. Multiple tumors may be present. Metastasis is common.
Symptoms include confusion, lethargy, memory loss, muscle weakness
in one area of the body (localized hemiparesis), and seizures.
CNS lymphomas appear on CT and MRI, but exact diagnosis follows
a biopsy.
Surgery or biopsy alone may be performed, depending on the exact
location, size, and number of tumors. Radiation therapy is often
effective as these tumors are responsive to this treatment (radiosensitive).
Steroids and chemotherapy may also be used. Temporary blood brain
barrier disruption before chemotherapy is under investigation.
Cysts (Dermoid Cyst, Epidermoid Cyst)
Cysts are tumor-like masses.
Dermoid cysts
Dermoid cysts are distinct masses and are almost always benign.
The treatment of choice is surgical removal. If they return, growth
is very slow and there may be a long interval before any sign of
recurrence.
These cysts are more common in the spine than in the brain. The
incidence in the brain (intracranial) is greatest in children
under the age of 10. Dermoid cysts are most common in the spine
in young people between ages 10 and 20.
Dermoid cysts in the brain are usually found in the midline of
the cerebellum or the adjacent meninges. The cavity of the fourth
ventricle or at the base of the brain on the under surface of the
frontal lobes are also common sites.
In the spine, the cysts occur most commonly in the lower end
of the spine (lower lumbar area).
Epidermoid cysts
These cysts are more common than dermoid cysts. They are usually
benign, but they will slowly recur if not removed completely. Unlike
the dermoid variety, they occur more frequently in the brain than
in the spine.
Epidermoid cysts are most common in middle-aged adults. The most
common sites in the brain for these cysts are the cerebellopontine
angle (see figure 3) and the pituitary area.
The treatment of choice is surgical removal.
Craniopharyngioma
This is a benign, congenital tumor. It is cystic and occurs primarily
in children and adolescents.
Craniopharyngiomas occur in the sellar region. They often involve
the third ventricle, optic nerve, and pituitary gland. These are
localized tumors that grow by expansion. Malignancy and metastasis
are unknown.
Increased intracranial pressure causes many of the symptoms of
these tumors. Other symptoms result from involvement of the optic
chiasm and pituitary gland. Obesity, delayed development, decreased
vision, and a swollen optic nerve (papilledema) are common.
Surgery is the treatment of choice. Radiation therapy for incompletely
removed tumors follows. In children younger than 3, radiation is
delayed if possible.
Ependymoma
Ependymomas arise from ependymal cells, which form the lining
of the ventricles and central canal of the spinal cord. Overall,
5% of all intracranial tumors are ependymomas. They represent 9%
of all gliomas. The spinal ependymoma accounts for 60% of all gliomas
in the spinal cord.
Ependymomas of the cerebral hemispheres occur primarily in children
and adolescents.
Benign (low-grade) ependymomas are more common than malig- nant
ones. There are three groups of the benign tumors: myxopapillary
ependymoma (commonly found in the spine); papillary ependymoma
(extremely rare, located in the cerebellopontine angle--see
figure 3); and subependymoma [often found in the 4th ventricle
and extending into the enlarged space between the cerebellum
and the medulla (cisterna magna of the subarachnoid space)].
Anaplastic ependymoma is the malignant form of this tumor.
Occasionally these tumors seed to other locations in the centralnervous
system.
The usual treatment is surgery followed by radiation therapy.
Often, a shunt is necessary to relieve the increased intracranial
pressure that frequently accompanies this tumor. Chemotherapy is
used for recurrent tumors, and new clinical trials use chemotherapy
for initial treatment along with surgery and radiation.
For additional information, refer to the ABTA publication About
Ependymoma.
Gangliocytoma (Ganglioneuroma)
Ganglioglioma
These rare tumors arise from ganglia. A ganglion is a group of
nerve cells. (Ganglia is the plural of ganglion.) Gangliocytomas
are tumors of mature ganglion cells. Gangliogliomas are tumors of
both mature nerve (ganglion) and supportive (glial)
cells.
These tumors most frequently occur in children and young adults.
Tumors arising from ganglia represent .4% of all primary brain tumors.
The most common site is the temporal lobe of the cerebral hemispheres.
They may also occur in the spine.
These tumors are small, slow growing, and have distinct margins.
Metastasis and malignancy are rare.
Surgery is the treatment of choice.
Glioblastoma Multiforme (GBM)
Glioblastoma multiforme is one of the most malignant and difficult
brain tumors to treat. GBM is the most common primary brain tumor
of middle-aged adults. GBM represents 30% of all primary brain tumors.
Surgery alone rarely controls the GBM because cells of the tumor
stray throughout the brain. Thus, radiation therapy almost always
follows surgery or biopsy. Many physicians advocate aggressive chemotherapy
as well to control new tumor growth. The GBM is the subject of much
research because it is the most common and potentially destructive
brain tumor.
While many tumors contain a mixture of cell types, GBM is the
most mixed (heterogeneous) of brain tumors. It is this characteristic
that makes it difficult to treat. While one cell type is responsive
to treatment and dies off, other types are waiting to take over.
Because some systems classify the GBM as a grade IV astrocytoma,
you may wish to read the section on high-grade astrocytomas.
For additional information, refer to the ABTA publication About
Glioblastoma Multiforme and Malignant Astrocytoma .
Glioma
This is a general name for tumors that arise from the glial (supportive)
tissue of the brain. Gliomas are the most common primary brain tumors.
Astrocytomas, ependymomas, oligodendrogliomas, and tumors with mixtures
of two or more cell types are the most common gliomas. See Astrocytoma,
Ependymoma, Oligodendroglioma, or Mixed Glioma .
Hemangioblastoma
This benign, tumor-like mass arises from blood vessels. It is
often cystic. There may be single or multiple tumors. Hemangioblastoma
represents about 2% of all primary brain tumors. Lindau disease
and von Hippel-Lindau disease are hereditary forms of this tumor.
Hemangioblastoma is most frequent in the 35-to-45 age group. The
most common site is the cerebellum. It is slow growing and does
not metastasize.
This tumor causes increased intracranial pressure and cerebellar
dysfunction. Symptoms are headache, vomiting and nausea, gait disturbance,
and balance problems.
Both CT and MRI scans are capable of detecting the hemangioblastoma.
Angiography is done before surgery to confirm the diagnosis and
provide information about the tumor's blood supply.
Surgery is the treatment of choice. Incompletely removed tumors
or tumors attached to the brain stem may be treated with radiation
therapy.
Inoperable Brain Tumors
Any brain tumor may occur in a part of the brain that is inaccessible
to the neurosurgeon. The brain stem, thalamus, motor area, and deep
areas of gray matter are often considered to be inoperable areas.
Biopsy alone for diagnosis may be performed if the tumor cannot
be removed. Occasionally, even biopsy may not be possible. Treatment
is then based on the assumed type of tumor.
Often, radiation and chemotherapy are used to treat high-grade
inoperable tumors, or low-grade inoperable tumors which cause severe
symptoms. Other low-grade inoperable tumors may require no treatment.
Repeat periodic CT or MRI scans are used to follow the progress
of these tumors.
Lymphoma
See CNS Lymphoma
Medulloblastoma (MDL)
This malignant tumor grows rapidly. It is the second most common
tumor in children. Thirty percent of these tumors occur in adults.
The MDL is always located in the cerebellum.
Medulloblastoma is an invasive tumor, and it frequently metastasizes
to other parts of the central nervous system via the spinal fluid.
This tumor may infiltrate the floor of the fourth ventricle and
extend into its cavity. It may also infiltrate the meninges. The
medulloblastoma may spread (metastasize) outside the brain
and spinal cord (central nervous system), although this is uncommon
(about 5 - 7%).
Treatment consists of surgical removal of as much tumor as possible.
Radiation to the tumor area and the entire brain and spinal cord
follows. Very young children are often treated first with chemotherapy.
Radiation is delayed until they are older. This tumor is very responsive
to radiation therapy (radiosensitive).
"High risk" patients receive chemotherapy as part of
their initial treatment. Recurrent tumors may require a second surgery
followed by chemotherapy.
For additional information, refer to the ABTA publication About
Medulloblastoma.
Meningioma
This benign tumor arises from the meninges. The meningioma represents
more than 20% of all primary brain tumors. It commonly occurs in
middle-aged adults. The most common sites are the cerebral hemispheres,
and the midline. The meningioma also occurs in the spine.
The meningioma is a slow growing tumor with distinct borders.
It produces symptoms by compression rather than by invasion of brain
tissue.
If the tumor is accessible, the treatment of choice is surgery.
Radiation therapy may be of value if the tumor is not entirely resected.
Malignant meningioma is less common. Occurring in the same locations
as meningioma, it is difficult to eliminate solely by surgery. Generally,
radiation therapy is given either alone or with experimental chemotherapy.
For additional information, refer to the ABTA publication About
Meningioma.
Metastatic Brain Tumors
Metastatic brain tumors are tumors formed by cancer cells that
arise elsewhere in the body and spread to the brain. Body cancers
that frequently spread to the brain include:
- lung cancer
- breast cancer
- colon cancer
- melanoma
- kidney cancer
Metastatic brain tumors may appear anywhere in the brain or spine.
Multiple tumors frequently occur.
If the primary cancer is under control, surgery is the treatment
of choice for single brain tumors. Radiation is the treatment of
choice for multiple tumors. Chemotherapy may also be used in addition
to either surgery or radiation therapy.
Mixed Glioma
These are tumors that contain a high proportion of more than one
cell type. Frequently, the mixed glioma contains both astrocytes
and oligodendrocytes, or astrocytes and ependymoma cells.
The behavior of these tumors is similar to tumors composed of
the highest grade of cell found in the tumor.
Neurofibromatosis (von Recklinghausen's Disease)
This is a genetic (hereditary) disease. Patients develop
skin discolorations and tumors on peripheral nerves (neurofibromas).
Brain tumors may also develop, particularly bilateral acoustic neuromas
and optic nerve gliomas.
For additional information about neurofibromatosis, contact
The National Neurofibromatosis Foundation, 141 Fifth Avenue, Suite
7-S, New York, NY 10010, 212/460-8980.
Oligodendroglioma
These are tumors of the supportive (glial) tissue of the brain.
They most frequently occur in middle-aged individuals. The most
common site is in a cerebral hemisphere. This tumor represents at
least 4% of all primary brain tumors.
Oligodendrogliomas frequently contain cells of astrocytoma. Pure
oligodendrogliomas are usually slow growing and relatively low-grade,
although malignant forms are possible. Often, these tumors are present
for many years before diagnosis.
The treatment of choice is surgical removal of as much tumor as
possible, followed by radiation therapy. Chemotherapy for oligodendrogliomas
is under investigation. Recurrence is not unusual.
For additional information, refer to the ABTA publication About
Oligodendroglioma.
Optic Nerve Glioma
Most tumors in this location occur in children under the age of
10. The pilocytic astrocytoma is the most common tumor of this area.
These tumors are slow growing. The malignant tumors anaplastic astrocytoma
and glioblastoma multiforme may also occur in this location.
The optic chiasm is the most common site. Other frequent locations
are one of the optic nerves or the hypothalamus.
Symptoms of tumors in this area include loss of visual acuity,
rapid movement of the eyeballs (nystagmus), and "crossed
eyes" (strabismus), developmental delay, and abnormal
thinness (emaciation).
The MRI is the scanner of choice for diagnosis.
For tumors of one optic nerve, surgery is the treatment of choice.
Radiation therapy is the treatment of choice for tumors of the chiasm.
Chemotherapy may also be given.
Pineal Region Tumors
The pineal gland is located in the posterior portion of the third
ventricle. Pineal region tumors represent less than 1% of all primary
brain tumors. However, 3% to 8% of childhood brain tumors occur
in the pineal region.
The most common tumor of the pineal region is the germinoma. Germinomas
represent over one-third of the tumors in this region. Germinomas
of the pineal region are most common in teen-agers.
Additional tumors found in this area include other embryonal type
tumors, teratomas, astrocytomas, pineocytomas, and pineoblastomas.
Embryonal tumors in the pineal region are the only brain tumors
that may be diagnosed by tumor markers found in the cerebrospinal
fluid. The markers are alpha-fetoprotein and beta HCG (human chorionic
gonadotropin).
Symptoms are due to obstructive hydrocephalus and involvement
of the optic pathways. Headache, nausea and vomiting, lethargy,
and double vision (diplopia) are common.
Surgery is possible in some individuals. If surgery is not possible,
biopsy alone for diagnosis is performed. The usual treatment for
these tumors is radiation therapy. The germinomas in particular
are very responsive to radiation therapy (radiosensitive).
If hydrocephalus is present, steroids are often prescribed. A shunt
procedure may be necessary if the hydrocephalus is not controlled
by steroids. Chemotherapy for astrocytomas and germinomas is under
investigation.
Pituitary Adenoma
This is a benign, slow growing tumor of the pituitary gland. It
represents 8% of all intracranial tumors. Pituitary adenomas most
commonly occur in young or middle-aged adults.
The pituitary adenomas are classified as secreting or non-secreting.
The majority are secreting tumors and are further classified by
the hormone secreted.
If the tumor secretes prolactin, impotence (inability
to perform sexual intercourse) in males and
amenorrhea (stoppage of menstruation) and galactorrhea
(secretion of milk) in females are common symptoms. This is
the most common secreting pituitary adenoma. If the tumor secretes
growth hormone (HGH), giantism (excessive size) or
acromegaly (enlargement of the extremities: hands, feet)
occurs. ACTH secretion causes Cushing's Disease. The rare
TSH secreting tumors cause hyperthyroidism (excessive
activity of the thyroid gland).
The adenomas often invade the optic chiasm. The most common symptoms
of optic chiasm involvement are visual loss and headache.
For secreting pituitary adenomas, complete surgical removal is
the treatment of choice. BromocriptineR is a drug that may be used
to reduce the size of prolactin-secreting adenomas. For larger,
non-secreting adenomas, radiation therapy follows partial surgical
removal.
PNET (Primitive Neuroectodermal T
umor)
This name refers to a collection of many different brain tumors.
All of these tumors contain undeveloped brain cells and are highly
malignant tumors. They all tend to spread throughout the CNS. The
name PNET encompasses medulloblastomas, the malignant forms of pineal
cell tumors, malignant ependymomas, and other tumors. Except for
the medulloblastoma, all PNETs are rare.
Surgery followed by radiation therapy is the treatment of choice
for these tumors. Radiation therapy is frequently delivered to the
entire brain and spine.
Spinal Tumors
The types of tumors found in the spine vary by location.
Locations are defined as follows: (see figures 7 and 8)
TUMOR LOCATION COMMON TUMOR TYPESExtradural Metastatic tumors, chordoma
(outside the dura mater)
Intradural (beneath the dura mater)Extramedullary
Schwannoma, meningioma
(outside the spinal cord but inside the dura)
Intramedullary Astrocytoma, ependymoma
(within the spinal cord)
Primary spinal cord tumors are most often intradural and extramedullary.
Some symptoms of spinal tumors are due to compression of the spinal
cord and usually have a gradual onset. Muscle weakness is common.
If the tumor infiltrates the spinal cord, pain is common.
Treatment of spinal tumors depends on whether the tumor is primary
or metastatic, its exact location and type. Surgery is the treatment
of choice for intradural, extramedullary tumors. Malignant, partially
resected, or inoperable tumors are treated with radiation therapy.
Chemotherapy may also be used.
Subependymoma
See Ependymoma
Tuberous Sclerosis (Bourneville's Disease)
This is a hereditary disease involving the skin, heart, kidney,
and nervous system. It is more common in males than females. The
disease becomes obvious in childhood.
Subependymal giant cell astrocytoma is the ventricular tumor associated
with tuberous sclerosis. It is a benign tumor. The foramen of Monro
is the most common location. This tumor occurs in half the patients
with tuberous sclerosis.
For more information about tuberous sclerosis, contact the
National Tuberous Sclerosis Foundation, 8000 Corporate Drive, Suite
120, Landover, MD 20785, 1-800-225-6872.
SECTION 7 How are brain tumors treated?
INTRODUCTION
Treatment of a brain tumor is different from treatment of tumors
in other parts of the body. First, brain surgery requires far more
precision and highly sophisticated instruments. Second, the brain
itself prevents many therapeutic drugs from entering it. Third,
both the therapies used to treat brain tumors and side effects of
these therapies are quite complicated. Experienced, multi-disciplinary
medical professional teams offer the most up-to-date treatment opportunities.
The brain tumor specialist recommends one or several treatment
methods based on information from the various diagnostic tests.
The patient, family, and health-care providers discuss the plan
of treatment. Probable outcome (prognosis), the patient's
current health status, goals for treatment, and issues concerning
quality of life are all considered. The discussion includes an outline
of future treatment options and information about available support
services.
Treatment modalities include surgery, radiation therapy, chemotherapy,
immunotherapy, or a combination of these treatments.
SURGERY
Surgery is the treatment of choice for accessible brain
tumors. Accessible tumors are those which can be surgically removed
without causing severe neurological damage. Tumors located in gray
matter or deep within the brain may be inaccessible.
The goal of surgery is to remove all visible tumor. Many benign
tumors are treated only by surgery. Most malignant tumors require
additional treatment. Malignant tumors lack distinct borders. They
often invade nearby normal brain tissue. Tumor cells may also spread
throughout the brain and spine by way of the cerebrospinal fluid.
But, even partial tumor removal is beneficial.
The purpose of surgery is:
- to remove as much tumor as possible
- partial removal (debulking) of a tumor provides relief
of symptoms, improved quality of life, and a smaller tumor
burden for other treatment modalities
- to help establish an exact diagnosis
- removal of a sample of tumor to be examined under a microscope
in the laboratory provides an exact diagnosis
- to determine the extent of the tumor
- the neurosurgeon sees the actual tumor in the brain
- to provide access for other treatments, such as newer forms
of radiation
- during surgery, implants may be placed or radiation may
be delivered
Biopsy alone is performed when the tumor is inoperable or when
surgery must be delayed. Resection (surgical removal of a
tumor) is the treatment of choice whenever possible.
Biopsy (Surgical removal of a sample of tumor)
Biopsy is the removal of a small quantity of tumor for microscopic
examination to determine an exact diagnosis. Needle biopsy uses
a narrow, hollow needle. A small hole (called a burr hole)
is drilled in the skull and the needle passes through the hole under
CT guidance (stereotaxic biopsy). Tumor tissue is removed
from the core of the needle. Stereotaxic biopsy is more exact than
free-hand biopsy, and is considered by many practitioners to be
safer. This technique is usually available at major medical centers.
Resection of a Tumor
If the tumor is accessible and the patient's general health is
good, resection is the treatment of choice. The goal of surgery
is to remove as much tumor as possible.
The most commonly performed surgery for removal of a brain tumor
is a craniotomy. The neurosurgeon makes an incision into
the scalp. Removal of a piece of bone exposes the area of brain
over the tumor. Location and removal of the tumor then takes place.
After resection and bone replacement, the skin is sewn together.
Sometimes, replacing the bone is not necessary. For example, the
muscles in the back of the head are very strong and can protect
the brain by themselves.
The neurosurgeon has a wide choice of tools to use in removing
brain tumors. Commonly used tools are the surgical laser, ultrasonic
aspirator, and operating microscope. Other tools include evoked
potentials, ultrasound imaging, and stereotactic apparatus. Usually,
all of these surgical tools are available at major medical institutions.
The tools used for surgical removal depend on the type of tumor
and its location.
SURGICAL TOOLS
Stereotactic localization
This technique is used for needle biopsies, laser microsurgery,
and implantation. It provides precise information about tumor location
without direct visual access. Stereotaxy provides a three-dimensional
map of the brain.
During surgery, a rigid frame holds the patient's head in place.
Attached to the frame is a scanning device which accurately pinpoints
the location of the tumor.
Laser microsurgery
The laser is a surgical tool. It may be used in addition to or
in place of a scalpel. The laser is capable of immense heat and
power when focused at close range. It destroys tumor cells by vaporizing
them. The laser is frequently used with stereotactic localization.
Ultrasonic aspiration
This tool uses ultrasonic waves to cause vibration. The vibration
breaks the tumor into small pieces. The pieces are then aspirated
(sucked out).
RADIATION THERAPY
Many tumors are radiosensitive--their cells readily die when exposed
to radiation. Conventional radiation therapy uses external
beams of either x or gamma rays aimed at the tumor. The therapy
is given over a period of several weeks.
Other types of radiation also are available. One of these is interstitial
radiation--implanting radioactive seeds directly into a tumor.
Stereotactic radiosurgery delivers a high, single dose of
radiation to a small, well-defined area. Another technique is photodynamic
therapy. A light sensitive drug is given through a vein and
concentrates in the tumor. Then, during a surgical procedure, a
special light activates the drug. Hyperthermia uses heat
to kill tumor cells. Also available are other forms of radiation
energy, dosages, and schedules.
For additional information, refer to the ABTA publications
Radiation Therapy of Brain Tumors: Part I and Part II.
CHEMOTHERAPY
Chemotherapy uses special chemicals to poison tumor cells. Tumor
cells are more vulnerable to these chemicals than healthy cells.
Chemotherapy may be used before, during, or after surgery and radiation
therapy. Recurrent tumors are treated with chemotherapy as well.
In very young children, chemotherapy is used to delay radiation
therapy.
Many drugs have anti-brain tumor activity. But it is difficult
to predict which tumors will respond to which chemicals and to what
degree. For this reason, treatment often consists of a combination
of drugs.
Some treatment methods include drugs that help other drugs reach
the tumor in greater concentration.
The blood-brain barrier is a natural mechanism that protects the
brain. It inhibits certain classes of drugs from reaching tumor
cells. MannitolR disrupts the blood-brain barrier temporarily. Other
methods used to increase drug delivery to tumor are drug injection
into an artery or spinal fluid, reservoirs and pumps, or the surgical
placement of drug-saturated wafers.
Certain chemicals are used to make other treatments more effective.
For example, radiosensitizers are thought to make radiation therapy
more effective.
For additional information, refer to the ABTA publication Chemotherapy
of Brain Tumors.
STEROIDS
Steroids control the swelling due to accumulation of fluids
(edema) often associated with brain tumors. Dexamethasone (DecadronR),
prednisolone, and prednisone are examples of these drugs. Steroids
may be used temporarily following surgery or during radiation because
these treatments often cause edema. Long-term use is for relief
of symptoms. Because of the potential side effects of this class
of drugs, long-term use requires close monitoring.
IMMUNOTHERAPY
The immune system is the body's natural defense against disease.
Immunotherapy uses biological response modifiers (BRMs)to
fight tumor cells. BRMs are substances that either kill tumor cells
directly or stimulate production of other substances to control
tumor growth. Immunotherapy researchers study the response of the
body to a tumor and the events that allow a tumor to grow.
Research in a variety of areas holds much promise for future treatment.
Experimentally, several biological response modifiers now are in
use. Laboratory studies explore other substances.
The routine use of immunotherapy is possible in the future.
For additional information, refer to the ABTA publication Immunotherapy
of Brain Tumors.
ONCOGENES
Oncogene research may eventually lead to new treatments for or
the prevention of brain tumors. It is an active area in cancer research.
Proto-oncogenes are normal genes that direct normal growth
and development. Alterations in proto-oncogenes may activate them
into oncogenes. Oncogenes cause cancer. Activation probably
requires a series of events. Research seeks to identify oncogenes
and determine what activates them.
SECTION 8 Figures
Figure 1: Meninges and ventricles of the brain
Figure 2: Functions of the cerebral hemispheres
Figure 3: View from the bottom of the brain
Figure 4: Lateral view of the brain and spinal cord
Figure 5: Cross section of the head
Figure 6: Cranial Nerves
Figure 7: Cross section of vertebra and spinal cord
Figure 8: Spinal cord and nerve roots
We are extremely grateful to the literally thousands of people
whose generosity has made this Primer possible. We express particular
appreciation to those who contributed their time and talents:
Gail Segal, Medical Writing, Chicago, Illinois
Victor A. Levin, MD Technical Review, Department of Neuro-Oncology,
University of Texas, M. D. Anderson Cancer Center, Houston, Texas
Barbara Steiger, Manuscript Editin,g Highland Park, Illinois
Marv Glick Design, Graphic Design, Chicago, Illinois
Diane Falk, Medical Illustration, Zion, Illinois
To learn more about American Brain Tumor Association, contact
the office at 847-827-9910, or the Patient and Family Line: (800)
886-2282, or by email: info@abta.org.
Return to the ABTA Homepage
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