of the Central Nervous System
Cancer of the Brain and Spinal Cord
Signs and Symptoms of Brain Tumors
The Anatomy of
the Central Nervous System
The central nervous system
(CNS) is made up by the brain and spinal cord. This complex
system controls both things that we intentionally think about
and do, like walking and talking, and essential body functions
that occur without specific thought on our part, such as
breathing and digesting food. The CNS is also involved with the
five senses of seeing, hearing, touching, tasting, and smelling,
as well as emotions, thoughts, and memory.
The brain is a soft, spongy
organ that is made up of nerve cells and tissue. It is divided
into three major sections: the cerebrum, the cerebellum, and the
The cerebrum is the largest
part of the brain, and is divided into two halves, called the
right and left hemispheres. The right hemisphere controls the
left side of the body and the left hemisphere controls the right
side of the body. Each hemisphere is further divided into
sections called lobes. There are four lobes in each hemisphere:
the frontal, parietal, occipital, and temporal, and each lobe is
responsible for certain functions.
- The frontal lobe is
responsible for attention, thought, reasoning, behavior,
movement, sense of smell, and sexual urges.
- The parietal lobe is
responsible for intellect, reasoning, the sensation of
touch, response to internal stimuli, some language and
reading functions, and some visual functions.
- The occipital lobe is
primarily responsible for vision.
- The temporal lobe is
responsible for behavior, memory, hearing and visual
pathways, and emotions.
The cerebellum is much smaller
than the lobes of the brain, and sits at the back of the brain
under the cerebrum. It is responsible for balance and
coordination and controls complex actions like walking and
The third part of the brain,
the brainstem, connects the brain to the spinal cord. It
controls some of the most important and necessary body
functions, such as breathing and maintaining body temperature
and blood pressure. It also controls hunger and thirst.
The spinal cord is made up of
bundles of nerve fibers, called vertebra. It starts at the base
of the brain and extends a little more than halfway down the
back. Spinal nerves connect the brain with other nerves
throughout the body and carry messages back and forth between
the brain and the rest of the body.
In order to protect the central
nervous system from injury or damage, several protective
barriers exist. Three thin membranes, called meninges, cover the
entire brain and spinal cord forming a thin protective layer. In
addition, a thin, watery fluid, called cerebrospinal fluid (CSF),
cushions the brain and spinal cord and offers further
protection. CSF is produced in four hollow spaces in the brain,
called ventricles, and flows through the ventricles and in the
spaces between the meninges. It also brings nutrients from the
blood to the brain and removes waste products from the brain.
The bony structures of the skull and vertebra provide the final
layer of protection for the central nervous system.
Cancer of the
Brain and Spinal Cord
Cancer can occur in any part of
the brain or spinal cord. Cancer cells are abnormal cells that
divide too often and without any order. In 1997, about 18,000
new brain tumors were diagnosed, a 50% increase from only ten
years ago. They are rare tumors, representing only 1.5% of all
cancers reported in the United States.
The causes of central nervous
system tumors are not known, and scientists cannot explain why
brain tumors develop in healthy adults. Certain factors,
however, have been identified that may increase a person's
chance of developing a brain tumor. For example, workers in the
oil refining, rubber manufacturing, and drug manufacturing
industries have higher rates of certain types of brain tumors.
Researchers are also studying families in whom multiple members
have developed the same type of brain tumor to see whether
heredity plays a role. They are also looking at the connection
between viral infections and exposure to radiation and the
development of brain tumors. There is no research to suggest
that head injuries cause or increase a person's risk for
developing a brain tumor. Because most patients diagnosed with a
brain tumor have no identifiable risk factors, it is believed
that brain tumors result from a number of factors acting
Tumors which start in the brain
are called primary brain tumors and are classified according to
the kind of cell from which the tumor seems to originate. The
most common primary brain tumor in adults comes from cells in
the brain called astrocytes that make up the blood-brain barrier
and contribute to the nutrition of the central nervous system.
These tumors are called gliomas (astrocytoma, anaplastic
astrocytoma, or glioblastoma multiforme) and account for 65% of
all primary central nervous system tumors. The following table
explains other types of brain tumors, the cells from which the
tumors most likely come, and the functions of those cells.
substance called myelin, which covers the nerves and
helps information to travel quickly between the brain
and other parts of the body.
ventricles and aids in the circulation of cerebrospinal
protect the brain and spinal cord.
||Part of the
immune system, the body's primary defense against
infection and foreign substances.
myelin that protects the acoustic nerve, the nerve of
neuroectodermal cell or Primitive nerve tumors (PNET)
normally do not remain in the body after birth.
Cancer from other parts of the
body can spread to the brain and cause secondary tumors through
a process called metastasis. Although it is possible for cancer
from anywhere in the body to spread to the brain, it happens
most often with cancers of the breast and lung. The cells of a
metastatic brain tumor resemble the cells of the organ where the
tumor started, not brain cells. For example, if a tumor starts
in the breast and spreads to the brain, the cells of the brain
tumor will resemble abnormal breast cells, not abnormal brain
Symptoms of Brain Tumors
The symptoms of both primary and
metastatic brain tumors depend mainly on the location in the
brain and the size of the tumor. Since each area of the brain is
responsible for specific functions, the symptoms will vary a
great deal. Tumors in the frontal lobe of the brain may cause
weakness and inability to move on one side of the body, known as
paralysis, mood disturbances, difficulty thinking, confusion and
disorientation, and wide emotional mood swings. Parietal lobe
tumors may cause seizures, numbness or paralysis, difficulty
with handwriting, inability to perform simple mathematical
problems, difficulty with certain movements, and loss of the
sense of touch. Tumors in the occipital lobe can cause loss of
vision in half of each visual field, visual hallucinations, and
seizures. Temporal lobe tumors can cause seizures, perceptual
and spatial disturbances, and inability to understand simple of
multi-step commands, known as receptive aphasia. If a tumor
occurs in the cerebellum, the person may have difficulty
maintaining their balance, known as ataxia, loss of
coordination, headaches, and vomiting. Tumors in the
hypothalamus may cause emotional changes, and changes in the
perception of hot and cold. In addition, hypothalamic tumors
may affect growth and nutrition in children. With the exception
of the cerebellum, a tumor on one side of the brain causes
symptoms and impairment on the opposite side of the body. For
example, a tumor on the left side of the brain may cause
numbness in the right arm.
As a brain tumor grows, it
invades the healthy tissue in the brain, often causing further
deterioration. Because of the limited space within the skull,
the tumor may place pressure on the brain. There may also be a
buildup of fluid around the tumor, a condition known as edema.
Both of these may cause frequent headaches that are often
unrelieved by over-the-counter medications. Headaches are the
most common presenting symptom for patients with brain tumors.
Since all of these symptoms can
be caused by other problems, you must be seen by a physician to
have your symptoms properly evaluated. Your physician may refer
you to a neurologist, a doctor who specializes in diagnosing and
treating disorders of the brain and central nervous system, or
to an oncologist, a doctor who specializes in diagnosing and