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A brain tumor is a mass created by abnormal and uncontrolled growth
of cells either found in the brain (neurons, glial cells, epithelial
cells, myelin producing cells etc.) (primary brain tumors) or
originating in another part of the body and spreading to the brain
(secondary brain tumors or metastatic brain tumors). Brain tumors are
usually located in the posterior third of the brain in childhood and
in the anterior two-thirds of the brain in adulthood.
Primary brain tumors
Primary brain tumors are named due to the cell types, from which
they are originated. Frequently encountered histologic brain tumor
types are glioma, glioblastoma, astrocytoma, oligodendroglioma,
medulloblastoma, meningioma and neuroglioma. Tumors can be benign and
are usually, but not necessarily, localized to a small area. They can
also be malignant and invasive (i.e., spreading to neighboring areas).
Brain cells can be damaged by tumor cells by (i) directly being
compressed from growth of the tumor, (ii) indirectly being affected
from inflammation ongoing in and around the tumor mass, (iii) brain
edema (swelling) or (iv) increased pressure in the skull (due to brain
edema or to the blockage of the circulation of the cerebrospinal
Metastatic brain tumors
Secondary or metastatic brain tumors take their origins from tumor
cells which spread to the brain from another location in the body.
They are more frequent than primary brain tumors. Approximately, one
quarter of metastatic cancers spread to brain. Lungs and breasts are
most common locations from which secondary brain tumors originate.
Tumor cells travel to brain by blood vessels. Since brain has no
lymphatic drainage system like other organs (cerebrospinal fluid
system acts like lymphatic system in the brain), spreading of tumor
cells by lymphatic route (which is very typical for cancers of other
organs) is impossible for brain. Different from primary brain tumors,
metastatic tumor masses may occur in various remote locations in the
brain. Highly aggressive brain tumors like glioblastoma may also be
observed in more than one location but usually in the advanced stages
of the disease.
Symptoms and complications of brain tumors
Local tissue damage (either by direct or indirect mechanisms)
causes focal neurologic symptoms, which vary due to the location of
the brain tumor. Hemiparesis, aphasia, difficulty speaking, ataxia,
hemihypoesthesia (numbness and decreased sensation of touch on one
side of the body) and localized headache are some of the symptoms
occurring due to the local effects of the brain tumor. Increased
pressure in the skull or brain edema cause more generalized symptoms
like generalized headache, nausea and vomiting, loss of consciousness
(stupor or coma) and intellectual decline. Seizures due to the local
irritating effect of the brain tumor or metabolic changes caused by
the cancer are also frequently observed. Since the development of the
skull is incomplete during infancy, infants with brain tumor may have
increased head perimeter, bulging fontanelles or separated sutures.
Neurologic examination reveals local (specific to the location of
the tumor) or generalized neurologic changes. Slowly progressive
nature of the neurologic symptoms is suggestive of a possible brain
tumor and the diagnosis is confirmed by CT scan or MRI of the head.
Angiography, EEG examination or brain biopsy may aid in diagnosis in
difficult cases. Although slow progression is an important hallmark of
the disease, some brain tumors may enlarge very quickly and thus may
cause sudden neurologic changes. Treatment includes the surgical
removal of the tumor mass or the destruction of the tumor cells by
radiation (radiotherapy) and/or drugs (chemotherapy) in cases with
contraindications for a surgical operation.
Primary or secondary, brain tumors may cause herniation of the
brain (displacement of one part of the brain tissue due to mass effect
of a lesion, usually causing the compression of the neurons
controlling the respiratory system in the brainstem and eventually
death) and permanent neurologic changes including intellectual
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Treatment of brain tumors
Treatment takes into account whether the tumor is a primary brain
tumor or a metastatic one. Metastatic disease requires treatment of
the original tumor site if applicable. Some primary brain tumors
respond to certain forms of therapy better than others.
The main modalities of therapy for brain tumors include:
- Radiotherapy augmented by brain dehydrating measures.
to view various chemotherapy regimens used in treating brain tumors.