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- Several characteristics of brain tumors distinguish them from other types of tumors.
- • Even the most malignant brain tumors rarely metastasize outside the nervous system.
- • The location of a tumor often determines whether a neurological deficit occurs.
- • The most common brain tumor, the astrocytoma, ranges from a low- to high-grade type (the grade of each tumor
- is based on its microscopic features and determines type of treatment and prognosis).
- • Even tumors regarded as slow growing or more benign can produce symptoms as severe and life-threatening as
- malignant tumors. This is because they may occur in a vital area of the brain or because when they reach a
- critical size there is no room for them to expand within the surrounding skull. This puts significant pressure on
- key structures.
- • The brain has no lymphatic blood vessels to remove the products of tumor dissolution, so the tumor may not
- appear to shrink on CT or MRI scans even if treatment is successful.
- • Treatment of a tumor can result in a new neurological deficit. A temporary or permanent loss of function can
- occur after surgery and problems of brain swelling can occur during radiation treatments, for example.
- • Unless a dramatic, early and sustained improvement occurs after therapy, it may be difficult for a long time to
- determine the response to treatment. Treatments may themselves produce temporary neurological deterioration
- that might take weeks or months to clear.
