Glioma

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}} A glioma is a type of primary central nervous system(CNS) tumorthat arises from glial cells. The most common site of involvement of a glioma is the brain, but they can also affect the spinal cord, or any other part of the CNS, such as the optic nerves.

Classification

By type of cell

Gliomas are named according to the specific type of cell they most resemble. The main types of gliomas are:

• ependymomas-- ependymal cells
• astrocytomas-- astrocytes
• oligodendrogliomas-- oligodendrocytes
• Mixed gliomas, such as oligoastrocytomas, contain cells from different types of glia.

By grade

Gliomas are further categorized according to their grade, which is determined by pathologicevaluation of the tumor.

• Low grade gliomas are well-differentiated, slower growing, biologically less aggressive, and portend a better prognosis for the patient.
• High grade gliomas are undifferentiated or anaplastic, fast growing and can invade adjacent tissues, and carry a worse prognosis.

There are numerous grading systems, but the most commonly used system is the World Health Organization(or WHO) grading system for astrocytomas. The WHO system assigns astrocytomas a grade from 1 to 4, with 1 being the least aggressive and 4 being the most aggressive. Various types of astrocytomas are given corresponding WHO grades.

WHO grading system for astrocytomas

• WHO Grade 1 — e.g. pilocyticastrocytoma
• WHO Grade 2 — e.g. diffuseastrocytoma
• WHO Grade 3 — e.g. anaplastic(malignant) astrocytoma
• WHO Grade 4 — glioblastoma multiforme(most common glioma in adults)

The prognosis is worst for Grade-4 gliomas, with an average survival time of 12 months. Overall, few patients survive beyond 3 years. [1] [2]

By location

The gliomas can also be roughly classified according to their location:

• infratentorial : mostly in children (70%)
• supratentorial : mostly in adults (70%)

Symptoms

Symptoms of gliomas depend on which part of the central nervous system is affected. A brain glioma can cause headaches, nauseaand vomiting, and cranial nervedisorders as a result of increased intracranial pressure. A glioma of the optic nervecan cause visual loss. Spinal cord gliomas can cause pain, weaknessor numbnessin the extremities. Gliomas do not metastasize by the bloodstream, but they can spread via the cerebrospinal fluidand cause "drop metastases" to the spinal cord.

Pathology

High grade gliomas are highly vascular tumors and have a tendency to infiltrate. They have extensive areas of necrosisand hypoxia. Often tumor growth causes a breakdown of the blood-brain barrierin the vicinity of the tumor. As a rule, high grade gliomas almost always grow back even after complete surgical excision.

On the other hand, low grade gliomas grow slowly, often over many years, and can be followed without treatment unless they grow and cause symptoms.

Treatment

Treatment for brain gliomas depends on the location and the grade. Often, treatment is a combined approach, using surgery, radiation therapy, and chemotherapy. The radiation therapy is in the form of external beam radiation or the stereotacticapproach using radiosurgery. Spinal cord tumors can be treated by surgery and radiation. Gene therapyusing lytic viruses or prodrug converting retroviruses and adenoviruses is another new development for the treatment of gliomas. Temozolomideis a chemotherapeutic drug that is able to cross the blood-brain barriereffectively and is being used in therapy.

External links

• GPnotebook-2147090429
• Merck Home06-088b

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Glioma Wikipedia article Glioma.