Astrocytoma


Astrocytoma

Description, Causes and Risk Factors:

A glioma (any neoplasm derived from one of the various types of cells that form the interstitial tissue of the brain, spinal cord, pineal gland, posterior pituitary gland, and retina) derived from astrocytes (one of the large neuroglia cells of nervous tissue).

An astrocytoma is a tumor that arises from the star-shaped cells (astrocytes) that form the supportive tissue of the brain. Other supportive cells of the brain include oligodendrocytes and ependymal cells. Collectively, these cells are known as glial cells and the tissue they form is known as glial tissue. Tumors that arise from the glial tissue including astrocytomas are collectively referred to as gliomas.

Astrocytoma

The World Health Organization (WHO) classifies astrocytomas into four grades depending on how fast they are growing and the likelihood that they will spread (infiltrate) to nearby brain tissue. Noninfiltrating astrocytomas usually grow more slowly than the infiltrating forms. Infiltrating or diffuse astrocytomas are more common than noninfiltrating astrocytomas. They are generally more common in men and are most common in the cerebral hemispheres of adult patients. In children they occur both in the cerebral hemispheres as well as the brain stem. Tumors from oligodendrocytes (oligodendrodendrogliomas) are also in the category of infiltrating gliomas and can occasionally be difficult to distinguish from astrocytomas. Some infiltrating gliomas are categorized as mixed oligodendroglioma-astrocytoma (oligoastrocytoma).

Astrocytoma causes are currently unknown. There are some supposed risk factors, such as genetic factors. For instance, children with neurofibromatosis are thought to have a higher risk of developing an astrocytoma.

Grades:

    Grade I astrocytoma is usually a noninfiltrating tumor. The most common type of grade I astrocytoma is pilocytic astrocytoma which is also known as juvenile pilocytic astrocytoma (JPA). This tumor grows slowly but can become very large. Pilocytic astrocytoma occurs most often in the cerebellum, cerebrum, optic nerve pathway and brainstem. This tumor occurs most often in children and teens and accounts for 2% of all brain tumors.

  • Grade II astrocytoma is also called low-grade astrocytoma or diffuse astrocytoma and is usually an infiltrating tumor. This tumor grows relatively slowly and usually does not have well-defined borders. It occurs most often in adults between the ages of 20 and 40.

  • Grade III astrocytoma is also called anaplastic (malignant) astrocytoma because this tumor grows more quickly than a grade II astrocytoma. Anaplastic astrocytoma occurs most often in adults between the ages of 30 and 50, and accounts for 4% of all brain tumors.

  • Grade IV astrocytoma is also called glioblastoma multiforme (GBM) and is the most aggressive type of nervous system tumor. It is also referred to as glioblastoma multiforme because of its wide variety of appearances under the microscope. Rarely, non-glial tissue elements can exist in a glioblastoma. The most common variant of GBM showing these additional tissue elements is called a mixed glioblastoma-sarcoma, or gliosarcoma. GBM occurs most often in adults between the ages of 50 and 80, is more common in men, and accounts for 23% of all primary brain tumors.

Symptoms:

Symptoms of astrocytomacan develop slowly depending on the area of the brain involved. Other symptoms can develop more quickly due to increased pressure within the skull, known as raised intracranial pressure (ICP). The pressure can increase because of a blockage in the ventricles (fluid-filled spaces in the brain), which leads to a build-up of cerebrospinal fluid (CSF). CSF is the fluid that surrounds and protects the brain and spinal cord. The increased pressure may also be caused by the tumor itself.

Raised intracranial pressure can cause headaches, sickness (vomiting) and problems with vision.Other symptoms such as fits (seizures) and changes in behavior and personality can occur because of the position of the tumor in the brain.

A tumor of the frontal lobe of the brain may cause gradual changes in mood and personality. There may also be paralysis (inability to move) on one side of the body.

A tumor in the temporal lobe of the brain may cause problems with coordination and speech, and may affect memory. If the parietal lobe of the brain is affected it may be difficult to write and do other similar tasks. An astrocytoma in the cerebellum may lead to problems with coordination and balance.

Diagnosis:

Your doctors need to find out as much as possible about the type, position and size of the tumor so they can plan your treatment. You may have a number of tests and investigations.

The doctor will examine you thoroughly and test your reflexes and the power and feeling in your arms and legs. They will look into the back of your eyes using an ophthalmoscope to see if the nerve at the back of the eye is swollen. This can be caused by edema (swelling of the tissues within the brain), which may occur because of an increase in the amount of fluid in the brain.

You may have a CT or MRI scan to find the exact position and size of the tumor.

CT scan: A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of the body. The scan is painless but takes 10-30 minutes. CT scans use small amounts of radiation, which is very unlikely to harm you or anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

You may be given a drink or injection of a dye which allows particular areas to be seen more clearly. For a few minutes, this may make you feel hot all over. If you are allergic to iodine or have asthma you could have a more serious reaction to the injection, so it is important to let your doctor know beforehand.

MRI scan: This test is similar to a CT scan but uses magnetism instead of x-rays to build up a detailed picture of areas of your body. Before the scan you may be asked to complete and sign a checklist. This is to make sure it's safe for you to have an MRI scan.

Before having the scan, you'll be asked to remove any metal belongings including jewellery. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium and can help the images from the scan show up more clearly.

During the test you will be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It is painless but can be slightly uncomfortable and some people feel a bit claustrophobic during the scan. It's also noisy but you'll be given earplugs or headphones.

Biopsy: To give an exact diagnosis, a sample of cells is sometimes taken from the tumor and examined under a microscope. The biopsy involves an operation and you may have to stay in hospital for a few days. There are different ways of doing the biopsy, depending on the position of the tumor in the brain. Your doctor will discuss with you whether a biopsy is necessary in your case and exactly what the operation involves.

Treatment:

The treatment for astrocytoma depends on a number of things, including your general health and the size, grade and position of the tumor. The results of your tests will enable your doctor to decide on the best type of treatment for you. There are some risks associated with treatment to the brain and your doctor will discuss these with you.

Your treatment will usually be planned by a team of specialists known as a Multidisciplinary Team (MDT). The team will usually include a doctor who operates on the brain (neurosurgeon), a doctor who specializes in treating illnesses of the brain (neurologist), a doctor who specializes in treating cancer (an oncologist), a specialist nurse, and possibly other healthcare professionals, such as a physiotherapist or a dietitian.

If you have raised intracranial pressure, it is important that this is reduced before treatment begins. You may be given steroid drugs to reduce swelling around the tumor. If you have raised intracranial pressure due to a build-up of cerebrospinal fluid (CSF), a tube (shunt) may have to be inserted into your brain to drain off the excess fluid. If you experience seizures, you may be given anticonvulsant medicines to help prevent them.

Consent: Before you have any treatment, your doctor will give you full information about its aims and what it involves. They will usually ask you to sign a form saying that you give your permission (consent) for the hospital staff to give you the treatment. No medical treatment can be given without your consent.

Benefits and disadvantages of treatment: Treatment can be given for different reasons and the potential benefits will vary depending on the individual situation. If you have been offered treatment that aims to cure your cancer deciding whether to have the treatment may not be difficult. However, if a cure is not possible and the treatment is to control the cancer for a period of time, it may be more difficult to decide whether to go ahead.

Surgery: Where possible, surgery is the first type of treatment for an astrocytoma. The aim of surgery is to remove as much of the tumor as possible without damaging the surrounding brain tissue. Depending on the size, position and spread of the tumor, it may not be possible to remove it completely and you may need further treatment.

    Grade 1 astrocytoma in the cerebellum can often be removed completely by surgery.

  • Grade 2 tumors and high-grade tumors are more difficult to treat because of their tendency to spread.

  • For grade 3 and 4 tumors, surgery is usually followed by radiotherapy and sometimes chemotherapy.

Some tumors cannot be reached by surgery or the risk of damage to the surrounding brain cells may be too high. Your doctor will discuss other forms of treatment if surgery is not possible.

Radiotherapy: Radiotherapy treatment uses high-energy rays to destroy the cancer cells. It is often used after surgery to destroy any remaining tumor cells. It may be used alone to treat astrocytoma, or with chemotherapy if surgery is not possible.

Chemotherapy: Chemotherapy is the use of anti-cancer (cytotoxic) drugs, which destroy cancer cells. It may be given alone to treat an astrocytoma, or with surgery and radiotherapy.

Sometimes, topical chemotherapy can be given via a 'wafer', which is placed in the affected area of the brain following surgery to remove the tumor. The wafer contains a chemotherapy drug. This method of giving chemotherapy is only used for high-grade tumors that cannot be completely removed by surgery.

Medicines for seizures: If you experience seizures you may be given a medicine called an anticonvulsant to help prevent them.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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