Source: Cancer Resource Room
Medulloblastoma is a brain cancer
that occurs in children and young adults.
Like all cancers, it is caused by abnormal
cells that grow and divide without control.
The growing cells form a tumor or lump
in the brain that keeps getting bigger.
Medulloblastoma can spread to nearby parts
of the brain and spinal cord, but not
usually to other parts of the body.
Brain tumors like medulloblastoma take
up space inside the skull. Because the
skull is hard bone and cannot expand,
the tumor presses on normal parts of the
brain causing problems in brain function.
Pressure on the brain causes symptoms
such as headache, loss of balance, nausea,
vomiting, and sleepiness. The symptoms
are often worst in the morning.
In addition to pressure directly on the
brain, medulloblastoma grows in a space
that gets blocked off as the tumor gets
larger. The brain and spinal cord are
surrounded by fluid called cerebrospinal
fluid (it is easier to call it, “CSF”).
This fluid needs to flow all around the
spinal cord and brain. The growth of a
tumor like medulloblastoma can block the
flow of CSF causing a back-up, like a
dam in a river. When the CSF gets backed
up, that causes pressure on the brain,
too. Giving the patient a steroid medication
can sometimes decrease fluid pressure.
Other patients need the fluid drained
away from the brain with something called
a shunt. It consists of a long, thin tube
that drains fluid away from the brain.
Draining this fluid helps relieve the
symptoms caused by pressure on the brain.
Medulloblastoma is most common in young
children. The typical age at the time
of diagnosis is around 7-8 years old,
but it can occur in younger children as
well as in adults. The tumor appears most
often in the part of the brain where the
cerebellum, fourth ventricle and brain
Medulloblastoma starts in this
area but easily invades nearby tissue
or spreads (metastasizes) to other parts
of the brain and spinal cord. As many
as 30% of patients have disease spread
at the time the tumor is first diagnosed.
But less than 5% of patients have tumor
spread anywhere else in the body. If
it spreads outside the brain and spinal
cord, it usually goes to the bones.
The diagnosis of medulloblastoma begins
with a history and physical exam. The
medical history is the story of the patient’s
health and present symptoms. The details
of each symptom are explored. For example,
if the symptom is headache, the questions
will include how long the headaches have
been happening, when during the day they
occur, how long they last, what other
symptoms happen along with the headaches,
does anything relieve the headaches, what
medications have been tried, and so on.
the symptoms of medulloblastoma?
Of the many symptoms that may be caused
by medulloblastoma, the most common are:
- nausea and vomiting
- changes in vision (blurred or double
- loss of coordination
- slurred speech
- poor balance
Many questions about a patient’s
general health are asked. After the patient’s
health history, a thorough physical exam
is done. The most important part is a
test of all the brain and spinal cord
functions called a “neurological”
exam. This helps to match up the history
with the physical findings.
When the history and physical exam are
complete, some other tests may be done.
Some blood tests are done just to check
the patient’s general state of health.
Other tests are specially for diagnosing
a brain tumor. The most useful are a CT
scan and MRI of the brain. These imaging
tests can show the location and size of
the tumor. It also shows what effect the
tumor has on other parts of the brain.
The location of a tumor in the fourth
ventricle and cerebellum and its particular
appearance of the tumor on the MRI image
makes a diagnosis of medulloblastoma likely.
Another imaging test for brain tumors is
called a PET scan. Although this test
is not used for the diagnosis of medulloblastoma,
it may be in the future. PET stands for
Positron Emission Tomography. These scans
require an injection of glucose (a sugar
molecule) that has been made mildly radioactive.
The brain uses the glucose for energy.
Some parts of the brain use more glucose
than others. The PET scanner picks up
the amounts of radioactivity coming from
different parts of the brain as the glucose
is used up. When a tumor is present, it
shows on the PET scan because the tumor
cells use an abnormal amount of the radioactive
Other tests are done for finding if there
is spread of tumor to the spine. One is
a spine MRI, sometimes done at the same
time as the brain MRI. Children may be
given sedative medication or anesthesia
for the MRI because it is necessary to
lie very still in the MRI scanner. They
need an IV for anesthesia and for something
called the contrast dye. Contrast dye
makes the MRI more capable of showing
areas of abnormal cells. Another test
called a spinal tap is done 10 –
14 days after surgery. A spinal tap removes
a small amount of CSF (cerebrospinal fluid)
so it can be tested for tumor cells. It
is done by putting a long, thin needle
in the space between the spinal bones
and the spinal cord. This is the space
the CSF flows through. A spinal tap is
uncomfortable so children are sedated
by an anesthesiologist for these procedures.
In older patients all that is needed is
some novacaine in the skin where the needle
The diagnosis of medulloblastoma can be
made with some certainty from the history,
physical exam, and the CT and/or MRI.
But confirming the diagnosis only happens
after the tumor is removed and a pathologist
looks at the tumor tissue under a microscope.
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