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Cranial
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Brain Tumors
What’s a tumor?
Tumors are collections of abnormal tissue created by a
process of rapid cell division, which accumulate a great mass of cells in one
area of the body.Once established,tumor cells may rapidly spread throughout the
body damaging multiple organs.
The mechanism which causes the cells to mutate and begin
forming a tumor is unknown, but these cells divide and become a mass very
quickly. As the tumor grows, or swells, it kills off the adjacent healthy tissue
by robbing the healthy tissue of nutritional support. In fact, in a tumor, the
rate of cell division is so accelerated that it will capture blood vessels for
the sake of its own nourishment at the expense of surrounding tissue; this adds
to the “health” and rate growth rate of the tumor.
The rate of cell division determines whether a tumor is
benign or malignant. Benign tumors are slow growing and usually not harmful, if
removed. Benign tumors also have a low recurrence rate. Malignant tumors,
however, are fast growing and considered “cancerous”, meaning that they will
continue to grow and spread until the host organism is dead.
A brain tumor, whether primary (originating in the brain)
or a metastatic (spread from an existing cancer source), is competing with the
healthy tissue of the brain as it grows. Because each area of the brain has
a specific function, the area attacked by tumor growth is in large part the
variable between a positive prognosis, or a negative prognosis.The area of the
brain where the tumor manifests is also a key determinant in whether it can be
removed. In the brain, the growth of a tumor, or lesion of any kind, is an
increased risk because the brain is a confined area surrounded by skull.As the
tumor grows, it increases the mass of the brain, in turn increasing the
intra-cranial pressure (ICP).ICP must remain constant for normal brain
function.
Brain Metastasis
A Metastasis is any tumor produced from errant cells that
separate from a tumor and travel through the blood stream until they find a
place to relocate, and begin growth of a new tumor. Metastasis is the true
definition of cancer, because it indicates that the cancer is aggressively
spreading (Fig.1).
Figure
1
Brain metastasis is usually indicative of an advanced state
of cancer. Unfortunately, brain metastasis is terminal and the purpose of any procedure or treatment is to
extend life and/or increase the quality of life while the patient is
alive. Usually the prognosis for survival is in months, but survival can be extended to years in some cases.
Incidence and Prevalence: Brain metastasis is the
most common of all brain tumors, and the number of metastases diagnosed each
year outnumber all other brain tumors put together. As many as one in four
cancer patients will develop brain metastases (www.neurosurgery.org)
The age bracket with the highest risk of brain metastasis is between 45 and 64 years of age, with a peak between the
ages of 50 and 54 years (p.924 Brain Tumors). It is possible that multiple
metastases will develop, but is usually dependent on the type of primary
cancer.
Site of Predilection: The majority of metastases are found at the
interface of the white and gray matter of the cerebrum. The cerebrum is the main portion of the
brain in the upper area of the cranium. The rest of the tumors are typically
found in the cerebellum region, and only occasionally in the brainstem.
Clinical Presentation: Metastasis will present symptoms either as
the result of increased ICP (intra-cranial pressure), or the
irritation/destruction of neurons in a localized area of the brain.
The most common symptoms are:
·
Headache
·
Focal Weakness
·
Mental and behavioral disturbance
·
Seizure – an attack of epilepsy (which is a
disturbance of the electrical activity of the brain causing
convulsions and loss of consciousness)
·
Ataxia – the failure of muscle coordination and
irregularity of muscular action.
·
Aphasia – a defect in or loss of the power of
expression by speech, writing, or signs. Or loss of
comprehension of the spoken
or written language due to injury or disease of the brain centers.
·
Visual Field Defect
·
Sensory Change
Radiologic Evaluation: Contrast enhanced
magnetic resonance imaging (MRI) is the best test for
diagnosing brain metastasis.Magnetic resonance imaging is basically a photograph of the
brain’s tissues,used to highlight those tissues that do not have a uniform
makeup.By adding a contrast agent, the
lesion(s) are more likely to show up on the image.MR imaging is also used to determine the total number of
metastases, and their location.If the patient has a known primary cancer, the combination of
clinical symptoms and the appearance of a lesion on the MRI is
usually enough evidence for a diagnosis.However,physicians must be conscious that there are many other
possible reasons for a lesion to present itself on a MRI, and not jump to conclusions.A primary source of cancer should be identified and many tests
should be given, to ensure that the diagnosis is conclusive, including a
biopsy, which analyses a tissue sample from the tumor.
General Management Plan: Once diagnosed, the highest
level of success for treating brain metastasis is typically found using:corticosteroids
(used to alleviate brain swelling), radiotherapy
(localized doses of radiation to the area of metastasis over time), surgery (removal of as much of the
tumor as possible), stereotactic radiosurgery (an intense dose of radiation targeted at the area of
metastasis).Also used if thought to be beneficial:chemotherapy(cytotoxic
drugs that combat tumor growth) and brachytherap (a small amount of radioactive
material implanted into the area of metastasis).
If the metastasis is proven to be radiosensitive or
chemosensitive, WBRT (whole brain radiation therapy) or chemotherapy should be
used for treatment. If the tumor is a
recurrent tumor, and there is no medical risk and the patient does not have a
limited systemic disease, then radiosurgery and/or WBRT should be used for
treatment.If the metastasis is not
radiosensitive or chemosensitive, and the patient has a limited systemic
disease, then a surgical resection of the accessible lesion should be
done.Finally, if there was WBRT prior
to surgical resection, then radiosurgery should be used; if not, WBRT should be
given.
A management plan for patient’s diagnosed with brain
metastasis is used to improve or optimize the length of time the patient has
left to live.Often treatments are used
together in various combinations to best suit the individual patient. Each
patient has a different medical history and so should be treated to their
specific needs.
Surgical Management: The largest factor in the decision to
operate and remove a portion, or all of a tumor, is its accessibility and
proximity to sensitive areas of the brain which may be compromised during the
operation. However, if there are
extenuating circumstances like advanced edema, increased ICP, or other
threatening medical conditions which could be alleviated by surgical removal of
the tumor, then these considerations should take precedence in the decision to
operate.It is imperative that the
exact location of the lesion is calculated using MRI, and/or computer
tomography (CT) before surgery begins.
If there are critical tissue structures adjacent to the tumor,
radiosurgery may be recommended.
As much of the tumor should be extricated during surgery as
possible, without damaging the healthy tissue.
Approximately two-thirds of patients with brain metastases have multiple
lesions, which makes the removal of tumors difficult and often
ineffectual.If there are one or more
tumors easily accessible, and there is a clear advantage for their removal,
then the decision can be made to operate.
Radiation Therapy: Whole brain radiation therapy (WBRT) is the
most widely and commonly used treatment for patients with brain
metastasis.WBRT has been shown to
alleviate the effects of the cancer, as well as extend the life of the patient.WBRT is also the most effective way to
target the growth of very small tumors that are not picked up by MRI or CT.
WBRT is also used post-operatively as a deterrent for the re-growth of tumor
cells.
There are side effects from radiation.Side effects are determined by a variety of
conditions, for example, how long the treatment has been undergone, how high
the doses of radiation are, and individual susceptibility.Side effects of radiation therapy
include:hair loss, dry skin that can
lead to peeling in large sheets, headaches, nausea, lethargy, otitis media
(inflammation of the inner ear), and brain edema leading to increased ICP.
There are also cases of extreme dementia in survivors of WBRT for longer than a
year.
The longer the patient is exposed to radiation the more
severe the side effects of radiation become. Therefore, if the projected
survival is longer that one year, radiation doses need to be carefully
calculated and used with other treatment combinations to maximize therapeutic
effects while minimizing potential complications.
Chemotherapy: The success of chemotherapy in the treatment
of brain metastasis is not encouraging.
In most cases, brain metastases develop in spite of chemotherapy used to
treat the primary cancer.There is also
reason to believe that the blood-brain barrier is preventative in chemotherapy
drugs reaching their target.
Chemotherapy is still used, however, in combination with other
treatments for those tumors that do respond.
Management Outcome: Brain metastasis represents an advanced
state of cancer.The best that can be
hoped for in the treatment of brain metastasis is the alleviation of suffering,
and extended survival if possible.With
a favorable prognosis, patients diagnosed with brain metastasis typically live
for 18-24 months after diagnosis.
Primary Brain Tumors
Primary brain tumors develop from the tissues of the brain. The cell mutations that become tumors are sub-divided
into categories by their parent tissues. The following classification system used to group primary brain tumors is the
product of the World Health Organization.
I. Tumors of the Neuropithelial Tissue: This grouping of tumors develops from the supporting cells of the nervous system.
There are nine different subcategories of tumors that fall into this group, and each subcategory has more than one type of tumor identified with it.
The following will be an overview of many of the more common types of tumors in the Neuropithelial group.
The first subcategory is Astrocytic tumors:
Low-Grade Astocytomas
These tumors are fairly common and generally have a favorable prognosis when diagnosed and treated.
Incidence and Prevalence: Approximately 15% of all adult brain tumors are low-grade astrocytomas.
It’s believed that low-grade astrocytomas affect approximately one in 100,000 adults annually. They appear more
frequently among males, and the median age for these tumors to develop is around 35 years of age.
Site of Predilection: Low-grade astrocytomas are most commonly found in the frontal lobe of the brain,
and have a tendency to develop in the convexity (outer part). The second most common place for low –grade astrocytomas
to form is in the temporal lobe.
Clinical Presentation: There are three ways in which low-grade astrocytoma can affect the brain and produce symptoms:
- By damaging neurons,
- exerting local pressure on the surrounding
area, and
- increasing ICP (intra-cranial pressure).
The most common outward symptoms are headache, lethargy, and personality change due to increased ICP. Epileptic seizure is
found to occur in over half of all low-grade astrocytoma patients. The effects of neurological damage are specific to the
area of the brain affected by the tumor, as each area of the brain has a different function.
Radiologic Evaluation: CT (computed tomography) scanning and MRI (magnetic resonance imaging) are both useful
in detecting low-grade astrocytomas. MRI is considered more conclusive because it is known to frequently detect smaller
tumors that CT scans. There is also a PET (position emission tomography) scan that is very useful because it reveals low-grade
astrocytomas as ‘cold spots’, and more malignant areas of the tumor as ‘hot spots’. In this way, PET scans can be used to decide
the best location to perform a biopsy (analysis of tumor tissue). All of these tests are important in diagnosing the tumor’s presence
and determining it’s location, and are helpful in indicating the proper management plan for the patient.
General Management Plan: There is not an overwhelming consensus as to the best management for low-grade astrocytoma patients.
Usually, immediate surgical removal of the tumor is practiced, but there is not necessarily a confirmed basis of support for the success
of early surgery. In fact, there is evidence that patients who underwent early surgery (whether biopsy or resection), and received radiation
therapy, did not show any advantage over patients who underwent radiation therapy alone. Whether post-operative or used by itself, radiation
therapy seems to have a positive effect on life expectancy. Therefore, surgical management of low-grade astrocytoma is an issue of physician
discretion and preference when considering the patient’s individual circumstances, but radiation therapy is recommended.
Surgical Management: If surgery is the route decided upon, an effort should be made to remove all tumor tissue and residual edema
(dead area surrounding tumor), unless the tumor is located in a sensitive area of the brain. Because the transition between healthy brain tissue
and low-grade astrocytoma cells is not often easy to decipher, it is prudent for the surgeon to err on the conservative side once nearing the outside
edges of the tumor, especially in critical areas of the brain.
Using information from the CT scan and MR images, it is possible to closely calculate the location of the tumor prior to surgery.
Astereotactic craniotomy may be the best choice for low-grade astrocytoma surgery, because this procedure passes a catheter to the
tumor’s center using CT and MRI, which the surgeon can then follow as a mark during surgery.A stereotactic biopsy is also effective
if the MRI and CT indicate that there is no evidence of mass effect from the tumor on the brain. It removes only a small portion of the tumor
for analysis. The stereotactic biopsy procedure allows the patient to minimize the stress of a full-scale operation while providing a more
definitive diagnosis from the removed tissue.Another decision to be made is whether to include radiation therapy prior to, or after surgery.
Radiation Therapy: Use of radiation therapy does not have any clear statistical benefit, but there is some evidence to show that
radiation therapy correlates to longer life expectancy, so it should be strongly considered as a management tool. The benefit of post-operative
radiation therapy is very controversial. It does appear that higher doses of radiation after surgery produce higher survival rates than lower doses
of radiation, but again the evidence is inconclusive. The patient should understand the potential risks and benefits of radiation therapy, and be
consulted by their physician. There are side effects of radiation therapy that include: hair loss, dry skin that can lead to peeling in large sheets,
headaches, nausea, lethargy, otitis media (inflammation of the inner ear), and brain edema leading to increased ICP. There are also cases of extreme
dementia in survivors of WBRT(whole brain radiation treatment) for longer than a year. The physician must recommend the use of radiation therapy for
each individual case based on personal experience.
Chemotherapy: There is currently no evidence that chemotherapy is beneficial to the treatment of low-grade astrocytoma patients.
Management Outcome: Patients with low-grade astrocytomas have a median life expectancy of 7.5 years. There is a ten-year survival rate
for between 20-30% of patients, and a five-year survival rate for approximately a 50% of low-grade astrocytoma patients.
Anaplastic Astrocytoma
There is a very high death rate associated with anaplastic (malignant) astrocytomas. They are also one of the two most common primary brain tumors,
and tend to strike adults in their prime. The effect anaplastic astrocytoma has on society is amplified by the quickness of death after diagnosis,
as well as the age group most affected.
Incidence and Prevalence: Anaplastic astrocytoma represent 26.6% of all primary brain tumors. Most cases of diagnosed anaplastic astrocytoma
are found in patients between 35 and 70 years old, and tend to be more commonly found in men than in women. The cause of these tumors is unknown, and has
not been linked to hereditary or environmental factors conclusively.
Site of Predilection: Anaplastic astrocytoma are most commonly found in the front or temporal regions of the brain, but may be found in other areas.
They are almost always rooted in the deep white matter of the brain, and because of their location, can often infiltrate more than one functional area at a time.
Clinical Presentation: The signs and symptoms of anaplastic astrocytomas are mostly the result of where the tumor develops in the brain. Because
each area of the brain is responsible for performing a specific function, the damage caused by the tumor will show itself by loss of function in one area. The patient
may have difficulty doing something they were up until then able to do with no problem. For example: memory loss, loss of motor skills, or muscular weakness on one side.
Approximately 50% of patients with anaplastic astrocytoma experience slight personality and memory alterations. Other signs that indicate the presence of an anaplastic
astrocytoma include headache, seizure, raised intracranial pressure (ICP), and a stiff neck.
The rate at which these symptoms appear is equally important. Symptoms that become apparent gradually are generally more favorable, and mean that the tumor is slow-growing,
and indicates a longer life expectancy. The quicker the symptoms advance, the more aggressive the tumor is, and therefore life expectancy tends to be shorter.
Radiologic Evaluation: Any time a brain tumor is suspected, a CT (computed tomography) or MRI (magnetic resonance imaging) should be done. Each test should be
done twice; once without using a contrast agent, and again with a contrast agent (used to highlight any bleeding, edema or calcification). A circular or ring-shaped, single
lesion that shows up on the image should be assumed to be an anaplastic astrocytoma until proven otherwise. If the patient has a history of tumor removal, using PET (position emission tomography)
is also helpful to determine whether the tumor is recurrent or not.
General Management Plan: The treatment of anaplastic astrocytomas is case specific and is difficult to create a single formula for. Each tumor contains a variety of different kinds
of cells that may respond differently to each method of treatment. So, the goal of the management plan is to use as many combinations of treatment as necessary, in order to wipe out as many tumor
cells as possible. Ideally, a combination will be found that slows the growth of the tumor enough to increase life expectancy.
Surgery should be performed to remove as much of the tumor as possible. Following surgical removal, adult patients should receive one or multiple forms of radiation therapy. CT scans and MR Is
should be done immediately after surgery, and then again one month later to check the response of the tumor to treatment, and look for recurrent growth. Chemotherapy should be used unless it is
evaluated to be ineffective. A second operation in order to remove re-growth of tumor tissue may be necessary.
Increased ICP is a common complication that arises from anaplastic astrocytomas and should be treated with corticosteroids, although some patients may suffer from side effects of cortiscosteroids
which include, altered body image, obesity, stress fractures, and psychosis.
Surgical Management Plan: It is widely recommended that anaplastic astrocytomas should be removed at the earliest possible convenience, using CT and MRI to calculate the location and composition.
It is also recommended that tissue analysis is done from tissue removed during surgery. However, anaplastic astrocytomas can look identical to other maladies of the brain, and a complete assessment of the
patient’s medical history should be made before surgery. Surgery is the best opportunity to remove large amounts of cells that could be resistant to treatment. An image guided stereotactic biopsy that removes
only a small portion of the tumor for analysis may be performed prior to surgery to confirm diagnosis if safety is a consideration due to the location of the tumor, or the patients medical condition.
Radiation Therapy: Radiation therapy is the most effective tool known for the treatment of anaplastic astrocytoma when used with surgery. Use of localized doses of radiation produce the best results
and can be administered externally by, radiotherapy (localized doses of radiation to the area of metastasis over time), and stereotactic radiosurgery (an intense dose of radiation targeted at the area of metastasis),
or internally through brachytherapy (a small amount of radioactive material implanted into the area of metastasis). The intensity of dosage is dependent on how severe the patient’s situation is. Higher intensity
doses can be given for shorter periods of time if the situation is critical. Lower doses are recommended over a longer period of time because of the potential side effects of radiation. CT scans and MRIs are used
to track the tumors response to radiation over time, and are usually administered every three months.
Chemotherapy:
Chemotherapy is used both in conjunction with radiation therapy, and by itself after radiation therapy has run its course. There have been multiple studies that show the use of chemotherapy, together with radiation
therapy, works to extend life expectancy. The chemotherapy agent BCNU is almost exclusively used in the treatment of anaplastic astrocytoma, and is typically administered intravenously for a period of 1-3 days,
and then repeated in 8-10 weeks. Use of BCNU must stop after 12-18months, regardless of the success of the treatment. Tamoxifen is a chemotherapeutic agent used to slow drug resistance and is fairly recent in its
accepted use, but may also be beneficial. New chemotherapy agents are being developed for experimental use constantly.
Management Outcome: Because of the vast diversity in the cellular composition of anaplastic astrocytoma tumors, the outcome of treatment varies. The nature of these tumors is to persistently recur in the
same location until all available methods of treatment are exhausted. As already stated, the object of treatment is to extend life expectancy, as it has been found that the majority of anaplastic astrocytoma patients
maintain their functional abilities while living, and the quality of life is worth extending. The majority of patients will die within 24 months after diagnosis and long-term survival is still estimated at 25-36 months.
Younger patients tend to have a better prognosis.
Glioblastoma
There is a very high death rate associated with glioblastomas. They are the most common primary brain tumors, and tend to strike adults in their prime. The effect glioblastomas have on society is amplified by the
quickness of death after diagnosis, as well as the age group most affected.
Incidence and Prevalence: Glioblastomas represent 27.7% of all primary brain tumors, and are responsible for more than half of the cases found in adults. Most cases of diagnosed glioblastoma are found
in patients between 45 and 60 years old, and tend to be more commonly found in men than in women. The cause of these tumors is unknown, and has not been linked to hereditary or environmental factors conclusively,
but the incidence of glioblastomas is on the rise, especially in people over 75 years of age.
Site of Predilection: Glioblastomas are most commonly found in the front or temporal regions of the brain, does not mean that they cannot be found in other areas. They are almost always rooted in the
deep white matter of the brain, and because of their location, can often infiltrate more than one functional area at a time. Some glioblastomas appear on the surface of the brain, growing out from the spot where the
gray matter meets the white matter. A malignant tumor found on the surface of the brain should therefore not be assumed to be a metastatic tumor without further investigation. Clinical Presentation: The signs and
symptoms of glioblastomas are mostly the result of where the tumor is develops in the brain. Because each area of the brain is responsible for performing a specific function, the damage caused by the tumor will show
itself by the patient having difficulty doing something they were up until then able to do with no problem; memory loss, loss of muscle coordination. Glioblastoma patients are highly sensitive to functional deterioration.
Other signs that indicate the presence of a glioblastoma include headache, seizure, raised intracranial pressure (ICP), and stiff neck.
The rate at which these symptoms appear is equally important. Symptoms that become apparent over time are generally favorable, and mean that the tumor is slow-growing, and may lead to a longer life expectancy. The
quicker the symptoms advance, the more aggressive the tumor is, and therefore life expectancy tends to be shorter. Patients with glioblastomas commonly have a history of unexplained seizures, and glioblastomas are
also associated with slow deterioration of neurologic functions. For example: memory loss, or loss of motor skills, or muscular weakness on one side. Approximately 50% of patients with glioblastomas experience slight
personality and memory alterations.
Radiologic Evaluation: Any time there is the possibility of a brain tumor, a CT (computed tomography) scan or MRI (magnetic resonance imaging) should be done. These tests should be done twice, once without using
a contrast agent, and then again with a contrast agent (used to highlight any bleeding, edema or calcification). A single lesion that shows up on the image with a circular pattern should be assumed to be a glioblastoma until
proven otherwise. If the patient has a history of tumor removal, using PET (position emission tomography) is also helpful to determine whether the tumor is recurrent or not.
General Management Plan: The treatment of glioblastoma is case specific and is difficult to create a single formula for. Each tumor is different and contains a variety of different kinds of cells that may respond
differently to each method of treatment. So, the goal of the management plan is to use as many combinations of treatment as necessary in order to wipe out as many tumor cells as possible. Ideally, a combination will be found
that slows the growth of the tumor enough to increase the patients life expectancy.
Surgery should be performed to remove as much of the tumor as possible. Following surgical removal, adult patients should receive one or multiple forms of radiation therapy. CT scans and MRIs should be made immediately after
surgery, and then one month later to check the response of the tumor to treatment, and to look for the rate of recurrent growth. Chemotherapy should also be used unless it is evaluated to be ineffective. A second operation may
be necessary to remove re-growth of tumor tissue.
Surgical Management Plan: Surgery is the best opportunity to remove large amounts of cells that could be resistant to other forms of treatment, like radiotherapy and chemotherapy. It is widely recommended that the
tumor should be removed at the earliest possible convenience, using CT and MRI to calculate its location and composition, and that tissue analysis is done from tissue removed during surgery. It has been documented that the removal
of all glioblastoma tissue that shows on the radiologic images greatly increases the patient’s quality of life.
Glioblastomas can look identical to other maladies of the brain, and a complete assessment of the patient’s medical history should be made before surgery. An image guided stereotactic biopsy, which removes only a small portion of
the tumor for analysis, may be performed for a more complete diagnosis if safety is a consideration due to the location of the tumor, or the patients health.
Radiation Therapy: Radiation therapy is the most effective tool known for the treatment of glioblastoma, when used with surgery. Use of localized radiation produces the best results and can be administered externally by,
radiotherapy (localized doses of radiation to the area of metastasis over time), and stereotactic radiosurgery (an intense dose of radiation targeted at the area of metastasis). Most glioblastoma patients fail brachytherapy (a small
amount of radioactive material implanted into the area of metastasis). The intensity of radiation dosage is dependent on how severe the patient’s situation is. Higher intensity doses can be given for shorter periods of time if the
situation is critical. Lower doses are recommended over a longer period of time because of the potential side effects of radiation. CT scans and MRIs are used to track the tumors responsiveness to radiation over time, and are usually
administered every three months following surgery.
Chemotherapy: Chemotherapy is used both in conjunction with radiation therapy and by itself after radiation therapy has run its course. There have been multiple studies that show that the use of chemotherapy with radiation
therapy works to extend life expectancy. The agent BCNU is almost exclusively used in the treatment of anaplastic astrocytoma, and is typically administered intravenously over a period of 1-3 days, and then repeated in 8-10 weeks.
Use of BCNU must stop after 12-18months, regardless of the success of the treatment. Tamoxifen is a chemotherapeutic agent used to slow drug resistance that may also be useful, and is fairly recent in its accepted use. New chemotherapy
agents are being developed for experimental use constantly.
Management Outcome: Because of the vast diversity in the cellular composition of glioblastoma tumors, the outcome of treatment varies. The nature of these tumors is to persistently recur in the same location until all available
methods of treatment are exhausted. The median survival of patients with glioblastoma, after treatment is 37 weeks, and is considerably less for patients over 60 years old.
The second sub-category of Tumors of the Neuroepithelial Tissue: Ogliodendroglioma
Ogliodendroglioma
Incidence and Prevalence: Ogliodendrogliomas only make up 4-7% of all primary brain tumors diagnosed. They are an uncommon tumor and usually occur in people between the ages of 30 and 50 years old. Evidence shows that equal
numbers of males and females develop ogliodendrogliomas.
Site of Predilection: Usually found imbedded in the white matter of the cerebral hemispheres of the brain, ogliodendrogliomas can spread into the cortex (the outer layer of the brain), and even into the leptomeninges (compose the
arachnoid membrane of the brain), and dura layer. Ogliodendrogliomas are usually supratentorial (situated above the tentorium) and found toward the front portion of the brain. It is also possible for ogliodendrogliomas to develop near to the
ventricular system and form intraventricular oligodendrogliomas, causing intraventricular hemorrhage.
Clinical Presentation: The best indicator of ogliodendrogliomas is the increasing occurrence of unexplained seizures over a number of years. The slow onset of symptoms is a positive sign that the tumor is slow-growing and will
therefore have a favorable prognosis. Other symptoms of ogliodendrogliomas are focal neurologic deficit, and headache due to increased intracranial pressure (ICP), and hemorrhage. Many ogliodendrogliomas will calcify.
In cases of intraventricular oligodendrogliomas, increased (ICP) is associated with visual disturbances, headache and papilledema (dead tissue surrounding the lesion).
Radiologic Evaluation: Both CT and MR Is should be used in diagnosing any intracranial lesion. There should be two of each done; one set without a contrast agent and one set with a contrast agent. Since oligodendrogliomas
are usually found in the extreme outer layers of the brain, and also have a more than 60% chance of calcification, using a CT agent that will enhance calcification makes it possible to diagnose. Ogliodendrogliomas will typically not show
up clearly on the enhanced CT or MRI, but its position and tendency to calcify are fairly solid evidence as to its type. Ogliodendrogliomas have a tendency to be more obviously enhanced on a radiologic image if they are malignant (fast growing),
and are usually accompanied with areas of bleeding and necrosis (an area of dead tissue).
General Management Plan: The agreed upon first step in the management plan for ogliodendrogliomas is to perform a biopsy and analyze a tissue sample. Once diagnosis has been confirmed by biopsy, there is not a clear management plan
for ogliodendrogliomas. The treatment options include surgical removal, radiation therapy and chemotherapy, but it is under debate which treatment approach or combination of treatments is best. A management plan should be based on the individual
tumor and the patients medical history. The largest area of debate stems from whether treatment is worthwhile if the patient’s neurological functions are intact because of the risks of surgery and radiation. The patient should be consulted and
fully understand the risks of all treatment options as well as the risks of non-treatment.
Surgical Management: There is a general feeling among researchers that surgical removal of part or all of the ogliodendroglioma promotes a longer survival rate, as long as the tumor is in an area that is accessible and not in close proximity
to any vital areas or structures of brain function. If surgery is to be performed in areas where there may be risk to speech, motor or sensory functions, the use of technology that shows the surgeon which of the surrounding areas are sensitive
(electrophysiologic mapping), and using local anesthesia may prove beneficial.
Radiation Therapy: Radiation therapy is highly controversial in the case of ogliodendrogliomas and has no evidence to support its use. There is a possibility that limited stereotactic radiosurgery, which delivers a targeted dose of radiation
to the tumor may be a valuable tool in the future, but its effectiveness is not currently known.
Chemotherapy: If surgical removal has been performed and there is residual tumor tissue, or recurrent growth of the tumor, the use of chemotherapy may be considered. The use of chemotherapy should be limited to those tumors of an aggressive
(or anaplastic) nature. There is some excitement that ogliodendrogliomas will respond to some chemotherapy agents based on preliminary evidence.
Management Outcome: The typical survival range of a patient diagnosed with an ogliodendroglioma falls anywhere between one and ten years, with the average probably being around five years. The best prognosis for survival continues to be the
slow advent of clinical symptoms.
The third sub-category of Tumors of the Neuroepithelial Tissue: Ependymomas
Ependymomas
Ependymomas grow from the ependymal cells that surround the cerebral ventricles and the central canal of the spinal cord.
Incidence and Prevalence: Intracranial ependymomas are not common and account for only 1.8 - 7.8% of all tumors. These tumors do not discriminate between the sexes, but the majority tend to present more frequently in children, unless the tumors
are located supratentorially and then they are more commonly found in older patients.
Site and Predilection: Adults usually develop ependymomas in the supratentorial (above the tentorium) areas of the brain. Supratentorial ependymomas arise from either the ventricular wall or from left over fetal ependymal cells that rest in the
white matter of the brain. The more aggressive anaplastic ependymomas in adults are most frequently found in the brain’s cerebral hemispheres.
Clinical Presentation: Signs and symptoms of ependymomas in adults are: headache, nausea/vomiting, seizure, lethargy, behavioral change, intellectual loss, papilledema, hemiparesis (muscular weakness on one side), apraxia (loss of learned skills)
or visual field loss. Supratentorial ependymomas can often cause ventricular compression and midline shift. Hydrocephalus (see hydrocephalus) is very common with tumors of the ventricular wall.
Radiologic Evaluation: MRI (magnetic resonance imaging) is the most important tool used for diagnosis of ependymomas, and surgical planning. Multiple MRIs should be taken, and the brainstem and spinal cord should also be imaged. MRIs are
invaluable in planning a surgical procedure, as the images taken together can be used to calculate where the tumor is located and how best to approach it. Ependymomas usually show up as middle to high-density areas on CT (computed tomography) scans, and show
enhancement with a contrast agent. If the diagnosis of ependymomas near the fourth ventricle is not certain, a sample of cerebral spinal fluid (CSF) should be taken and analyzed for tumor cells.
General Management: The management goal should be to extend the survival of the patient by using all available treatment and technology in combinations that will best maximize that patients needs. It is recommended that surgery should be attempted
in every case of diagnosed ependymoma, with the purpose being to remove all evidence of the tumor. Following surgery, the success of the tumor removal should be used, with knowledge of the tumor history, to decide the next phase of treatment. Tumor re-growth
typically occurs in the first 22-24 months following surgery. If a tumor is recurrent, then a decision must be made whether to re-operate or not.
Radiation therapy, chemotherapy, a combination of radiation and chemotherapy, or the decision to rely on the operation alone, are the recognized options for management. Most patients end up undergoing radiation, chemotherapy, or both, after surgery.
Radiation therapy is beneficial in most cases
Surgical Management: Surgery is used to remove as much of the ependymoma as possible, to get a tissue sample for analysis, and if necessary, to restore normal csf flow through the brain. While the goals of surgery are straight forward, the reality
of each tumor is complex. Ependymomas are infiltrative and often difficult to fully remove. They spread like tentacles through brain tissue and can grow through the walls of the fourth ventricle. Once the tumor is located using radio imaging, the position of the
tumor dictates the ease with which it can be accessed during surgery.
Often, removal of ependymomas growing along the ventricle wall are easier to extract than the tumors lodged in the white matter of the cerebellum, because these tumors are interwoven with cranial nerves and tend to compress the brainstem and regional arteries.
Surgical removal of these tumors is a delicate process and requires precise dissections and patience.
Radiation Therapy: The proven benefit for the use of post-operative radiation therapy is variable and susceptible to the sensitivity of the tumor to radiation. Two types of treatment are traditionally used; whole brain irradiation (WBI), or craniospinal
irradiation (CSI), but recently focus has shifted to using localized radiation techniques, like radiotherapy (localized doses of radiation).
Chemotherapy: There are several reports of chemotherapy increasing the longevity of ependymoma patients if used in combination with surgery and radiation therapy. It is thought that when used with radiation, chemotherapy helps alter the composition of
the tumor sufficiently to prevent re-growth.
Management Outcome: There is an average five-year survival rate for 50% of ependymoma patients who undergo treatment.
II. Tumors of the Cranial and Spinal Nerves: There are three categories of tumors of the cranial and spinal nerve tissue in this group listed by the World Health Organization. Acoustic neurinoma, is the most commonly diagnosed tumor of the three.
Acoustic Neurinoma
Incidence and Prevalence: The great majority of acoustic neurinomas are slow-growing, benign tumors, and account for 6-8% of intracranial primary tumors. Most of these present in patients during middle age, in their 50s or 60s. Acoustic neurinomas are
slightly more prevalent in females than in males.
There is a small percentage of acoustic neurinomas that are unique and more aggressive called NF-2s. This 2-4% sub-category of acoustic neurinomas gets its name from the gene that is known to cause them; they are hereditary and tend to present earlier, often in the patients twenties.
Site of Predilection: It is believed that acoustic neurinomas grow from tissue at the point of transition between the tissue of the central nerve coverings (glial), and the tissue of the outer nerve coverings (Schwann cells and fibroblasts). The tumor is typically found
in the auditory (ear) canal, or fully in the cerebellopontine angle near the pons; the pons are responsible for linking all the areas of the brain together. It is sometimes difficult to know which nerve acoustic neurinomas initiate from, but the superior and inferior vestibular nerves,
as well as, but less often, the cochlear nerve, are all known producers of these lesions.
Clinical Presentation: Hearing loss is the most common symptom of acoustic neurinoma, along with tinnitus (a ringing or buzzing sound in the ear), and loss of balance. Headache, facial numbness, and diplopia (double vision) are also symptoms, but usually indicate that the
tumor has had a long time to grow, and is large enough to cause them. Because acoustic neurinomas are slow-growing tumors, it may take many years for a tumor to grow to be 2cm, which is considered large.
Radiologic Evaluation: Magnetic resonance imaging (MRI) is the definitive test used in diagnosis of acoustic nerinomas. They show up best on T2 weighted images when the MRI is used with a contrast agent, gandolinium, and even small tumors are identifiable. Computed tomography
(CT) is also useful in detecting the lesions, and is important for highlighting bone structure, and the surrounding tissues and structures of the brain. If a CT is done first and acoustic neurinoma is suspected, then a MRI should follow to confirm or disprove the diagnosis. CT and MRI are
also used to deduce tumor size.
General Management: The average acoustic neurinoma grows at a rate of only 2mm per year, and with increasing technology they are being detected in earlier and earlier stages of their development. Earlier detection has led to more options in the treatment of acoustic neurinomas.
Instead of immediately operating, it is now advised that the growth rate of the tumor be monitored, and surgery be put off until necessary, to preserve the patients hearing. During surgery there is a high risk of hearing loss and of damaging nerves used for control of the facial muscles.
As the tumor grows, loss of hearing is unavoidable, but if the growth rate is slow, and the patient still has total or partial hearing capabilities, then it may be advantageous to postpone surgery until all functional hearing is gone. This allows more time for the patient to learn how to
communicate without the use of sound, and increases their overall quality of life.
It is not always possible to wait until hearing loss is complete, there are cases where it is necessary to operate quickly. In some situations, when growth of the tumor is more aggressive, or if there was a late diagnosis, or the tumor is compromising a function of the brain, surgery to
remove the tumor should take place immediately.
There are three surgical approaches to choose between. A decision of which approach to use should be based on the location and size of the tumor, and the experience of the surgeon. Acoustic neurinomas are located in an extremely delicate area and surgery is a laborious process. Each
step of the surgery has to be performed precisely to avoid any damage to the surrounding nerves and arteries. After surgery, there is a short period of hospital recovery and observation, and then radiation therapy should begin if needed.
Surgical Management: The choice of surgical approach is determined by the location of the tumor, the amount of hearing the patient still retains, and the surgeons preference based on experience. The translabyrinthine operative approach is a more direct route into the cerebellopontine
angle, while the middle cranial fossa approach is used for tumors all, or mostly within the auditory canal, and is often chosen in an attempt to preserve hearing. The third approach is the suboccipital/retrosigmoid operation and provides extensive access to the cerebellopontine angle, but can
destroy any remaining hearing, and causes high risk of neurological damage by exposing sensitive nerve tissues during surgery. It is also possible to combine the different approaches if better access is needed during the course of surgery. The results for all three approaches are about the same,
except that the middle cranial fossa approach has a higher incidence of epilepsy and dysphasia (speech impairment).
Post-operative care is recommended after a lengthy surgery and the patient should be kept under close surveillance until the threat of any side-effects or negative reactions to the procedure has passed.
Radiation Therapy: Traditional radiotherapy (localized doses of radiation), is known to significantly decrease the risk of tumor recurrence following surgery. Stereotactic radiosurgery, applies doses of radiation directly to the tumor and is used on an experimental basis if the tumor is
under 3cm. Stereotactic radiosurgery can also provide an alternative for patients who do not wish to undergo surgery.
Chemotherapy: The benefit of chemotherapy in treating acoustic neurinomas has not been proven.
Management Outcome: Because of surgical advances, the death rate for acoustic neurinomas is very low. However, the loss of brain function due to surgery, like hearing loss and facial-muscle paralysis, is still very high.
III. Tumors of the Meninges: There are four categories of tumors in the meninges grouping, according to the World Health Organization’s classification system. The most commonly diagnosed tumor is in the category of tumors that arise from the meningothelial cells. We will be discussing the sub-category of meningiomas.
Meningioma
Meningiomas are fairly well documented tumors, and are usually benign (slow growing). Meningiomas are further defined by their area of origin in the brain.
Incidence and Prevalence: Meningiomas account for around 20% of primary brain tumors that are diagnosed. Out of every 100,000 people with primary brain tumors, there are 2-3 people that develop meningiomas. There is a greater tendency for memingiomas to occur in older patients, and there is a higher incidence
among women, which peaks in the 70-79 year old age group.
Site of Predilection: The majority of meningiomas are found distributed between the parasagittal/falcine (parallel to the falx that separates the two sides of the cerebrum; the major functioning area of the brain), in the convexity (outer curved area of the brain), and the sphenoid ridge (wedge-shaped bone at
the base of the skull). There are many other areas of the brain which can host a meningioma, but are less likely to: surasellar (tuberculum), posterior fossa, olfactory groove, middle fossa/Meckel’s cave, tentorial, peritorcular, lateral ventricle, foramen magnum, orbit/optic nerve sheath.
Clinical Presentation: There are no common presenting symptoms unique to meningiomas. In fact, in many cases where the presence of a meningioma is diagnosed, there is no prior history of signs indicative of the tumor. It is possible, however, that meningioma patients will experience a wide variety of symptoms
directly related to the location of the tumor, including: Headache, paralysis, seizures, personality change and/or confusion, visual impairment, and occasionally, by a bump on the head. Each meningioma is then further described by its location, as there seems to be a correlation between location and cellular composition.
Radiologic Evaluation: Like other primary brain tumors, computed tomography (CT) and Magnetic Resonance imaging (MRI) are the most commonly used diagnostic tests for meningiomas. CT is valuable in showing any damage or involvement of the bone and will pick up most meningiomas. The more powerful MRI is slightly
more accurate in depicting the extent, and oftentimes composition, of a meningioma. MRIs should be used in conjunction with CT for a confirmed diagnosis. It is also possible for CT and MRI to detect more aggressive anaplastic (malignant) tumors based on their composition in many cases. Magnetic Resonance Angiography (MRA)
is another radiologic test used to take a picture of the arterial system in the brain and determine if the arteries are clear.
General Management: The management and surgical approach of each meningioma is dictated by its location. Meningiomas are typically slow-growing and do no infiltrate brain matter, therefore there is a strong possibility that surgery will provide a curative treatment. The goal of surgery is to remove all traces of
tumor tissue. Radiation therapy is then used to discourage tumor re-growth.
Surgical Management: By using the information gained by CTs and
MRIs, it is possible to calculate the location and size of the
tumor, as well as if there has been any damage to the surrounding
brain structures. Each location will require specific management for
that location. The surrounding brain structures should be assessed
to determine the most appropriate approach during surgery, and to
minimize any risk to those structures important in normal brain
function. If surgery is successful, and all of the tumor tissue is
removed, then the survival rate is high (Fig.2). After surgery, the
patient should receive radiotherapy to prevent the tumor from
recurring. If the meningioma does reappear, then the decision of
whether to operate again must be made or other treatment
possibilities must be found.
Figure
2
Radiation Therapy: Whole brain radiotherapy (WBRT) may be used in the post-operative treatment of meningiomas, and is more effective than localized radiation treatment because of the tumors typical growth patterns. The treatment doses of radiation are lower that for more aggressive tumors. Brachytherapy (radioactive
bits implanted into the tumor) is not used widely, but there has been some evidence of its benefit.
Chemotherapy: Chemotherapy has been used as additional, or adjuvant, treatment for meningiomas in extreme cases, but is not used as a standard treatment.
Management Outcome: If meningiomas recur after surgery, despite radiotherapy, the survival rate of the patient is drastically reduced. The overall survival rate and success of surgical treatment for patients with meningioma is high, but each tumor location has its own management outcome:
Convexity meningiomas- have a high success rate in their total removal. Complications may include tumor attachment to the middle cerebral artery.
Parasagittal and falcine meningiomas - usually can be fully removed; however, the presence and involvement of the sagittal sinus can create a complication in parasagittal tumors.
Olfactory groove and tuberculum sellae meningiomas – require delicate dissection because of their proximity to important arteries and structures of the brain, but are usually removed successfully.
Sphenoid wing meningiomas – are subject to complex operation for their removal, but most surgeries are highly successful. In some cases the position of the tumor creates a higher risk to the anterior arteries and many of the cranial nerves.
Cavernous sinus meningiomas - There is much higher risk in the removal of these meningiomas. The decision to operate should include the size of the tumor, and the deterioration of the patient’s quality of life (morbidity). There is a 76% chance that the tumor can be totally removed, and
with each operation there is a 4% chance of serious neurologic damage and a 2.4% chance of death. As for the impact of surgery on the patients quality of life regarding neurologic dysfunction, in 80% of patients their level of function remains the same, in 6% of patents their condition worsens after surgery, and in 14%
of cases their condition improves.
Posterior fossa and petroclival meningiomas – have a relatively high success rate of surgical removal despite the proximity to the inner ear canal and cranial nerves during operation.
Foramen magnum meningiomas – are considered posterior fossa meningiomas, but have a much higher risk involved in their removal. Injury to the lower cranial nerves post-operatively is the primary cause of neurological damage, and the patient’s head and neck should be immobilized following surgery.
Intraventricular meningiomas – are usually highly successful in their surgical removal, if the transcallosal approach is used.
Pineal region meningiomas – surgical removal is highly successful.
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