Anatomy - Brain Tumours
A tumour is an abnormal
mass of tissue that grows on or inside the body. It
is known as primary if located where its growth first
started, or secondary if it began growing elsewhere
in the body and metastasized, or spread, to its present
location. Most primary brain tumours do not metastasize
outside the brain. Inside the skull, tumours can grow
almost anywhere: within brain tissue, from the meninges,
or inside the ventricular system. They can be encapsulated
(self-contained) or interwoven with blood vessels, nerves,
or other brain structures from which they cannot be
removed without devastating consequences. Metastatic
tumours are usually well localised, may occur alone
or in clusters, and may spread throughout much of the
brain. A benign tumour usually is encapsulated, does
not spread to other areas of the body, grows slowly,
and often causes problems by compressing brain tissue.
A malignant tumour grows uncontrollably, spreads throughout
the brain, and destroys brain tissue.
What symptoms can it cause?
A brain tumour may at first
cause the vague feeling of being "unwell." This may
be followed by other, more specific symptoms: dull,
persistent headache; nausea or vomiting; generalized
weakness; vision problems. Because the left side of
the brain governs the right side of the body, and vice
versa, a tumour will cause specific weakness or loss
of movement on the opposite side of the body. Some symptoms
may be caused by the increased pressure inside the skull
from brain swelling, which can temporarily be treated
with a steroid medication. Because brain tissue is irritated
by the tumour, the brain can temporarily "short-circuit"
as its normal electrical activity is interrupted. These
periods of uncontrolled brain activity can cause seizures,
which may be generalised and cause contractions of all
parts of the body, loss of consciousness or bladder
and bowel function.The
seizures may instead be of a focal nature, affecting
only one arm, a leg, or part of the face. Seizures usually
can be controlled with anticonvulsant medications.
How is it evaluated?
A detailed history-taking of
the patient's symptoms and a physical examination are
done first, followed by any of several tests, such as
x-ray studies, Computerised Tomography (CT) scans, Magnetic
Resonance Imaging (MRI), and angiograms. All findings
are used to evaluate the patient's symptoms, determine
the tumour's exact location, and provide the physician
with a tentative diagnosis of the tumour type. During
surgery, ultrasound imaging may be used to pinpoint
the tumour's precise location and help the surgeon plan
his approach for its removal. If an emergency craniotomy
is required, an extensive workup may not be possible.
Growing from abnormal
cells of the meninges, meningioma is a slow-growing
tumour that shares the dura's rich blood supply.
It is very often attached to dura and so may be
immediately visible when the dura is opened.
It is usually a benign
tumor and well encapsulated, but removal may be
complicated by its size, firmness, and attachment
to vital blood vessels or brain tissues. A large
meningioma or one that is difficult to remove
may require a long, tedious surgery and can cause
further brain swelling and blood loss. Often the
dura removed during tumour surgery may be replaced
with other body tissue (fascia) or a dura substitute.
Glial cells support the
brain's functioning nerve network and are the
site of tumours inside the brain. Gliomas are
"graded" according to their degree of malignancy.
Often when the dura is opened, the brain is swollen
but otherwise may appear normal. The "centre"
of the glioma may readily be identified, but because
the tumour gradually spreads into surrounding
tissue the boundaries of a glioma are harder to
It may take months for
the cells around the edges of the tumor to appear
abnormal, yet they can be affected long before
they "show" themselves. This is why glioma usually
cannot be removed completely, as even one remaining
cell can continue the tumor's growth.
Often lying close to the
brain's surface, where it irritates the normal
tissue around it, a metastatic tumour is one that
began in another body organ and traveled in the
bloodstream to the brain. Grown from a "seed"
of non-brain tissue (from the breast, kidney,
or lung, for example) a metastatic tumour often
can be separated from the surrounding brain more
easily. If only a single lesion exists, all or
part of it usually can be surgically removed.
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