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active smoking. Infective agents have long been thought to be associated with gliomas. Gliomas may be associated with infections of TB, toxoplasma gondii, BK povavirus, JC virus, and Simian virus 40, which was a contaminant of the poliovirus from 1955 to 1962. Gliomas can be induced in animals by directly injecting viruses into the brain. The avian sarcoma virus produces gliosarcoma tumors in rats, rous sarcoma virus produces gliosarcomas in dogs and the polyomavirus produces glial tumors in rats.
PRESENTING SIGNS AND SYMPTOMS
The most common presentation in patients with brain tumors is a progressive neurological deficit, usually with motor weakness. Headaches present 54% of the time and seizures 26% of the time. The symptoms experienced depend on which part of the brain the tumor affects. In a patient with a headache associated with a brain tumor, the headache is usually worse in the morning and often made worse by coughing, straining and bending forward. 40% of the time, the headaches may be associated with nausea and vomiting and temporarily relieved by vomiting. If the headache is associated with a neurological deficit or seizure, usually a mass of some type is expected. The headache may be due to increased intracranial pressure because of the tumor itself, the swelling around the tumor, possibly bleeding in and around the tumor or obstruction of the normal water collecting system resulting in hydrocephalus. Sometimes the tumor invades the covering of the brain, the brain vessels or even covering of the skull, resulting in headache.
BRAIN TUMOR TYPES
If a brain tumor is suspected it can be of many different types. There are tumors that have spread from other areas of the body known as metastasis. The cells are usually the same as seen in the primary focus of the tumor. If the tumor is not spread from some place else it is known as a primary CNS tumor. The tumor can be of glial cell type called gliomas, accounting for 50% of primary brain tumors. These can be further divided into astrocytomas and oligodendrogliomas. Meningiomas encompass 25%. Pituitary adenomas make up 5% of primary brain tumors as does acoustic neuromas and schwannomas. Craniopharyngioma comprise 2.5% of primary brain tumors similar to ependymomas. There may be tumors of the neurons themselves called medulloblastomas, primitive neuroectodermal tumors, ganglioneuromas, and gangliogliomas. Other primary brain tumors include pineocytomas, pineoblastomas, neurofibromas, melanomas, sarcomas, lymphomas, hemangioblastomas, glomus jugular tumors, dermoid cyst, epidermoid cyst, colloid cyst, chordomas, lipoma, germinomas and still others. In most brain tumors it is the histological type that determines the malignancy and therefore patient survival. Finding the tumor and treating it earlier usually leads to longer survival. If symptoms progress quickly over a short period of time with a neurological deficit or symptoms then usually it is a high grade tumor the alterations of genetic expressions. New lab techniques have lead to further clarification of the genetics of the brain tumors.
BRAIN TUMOR FORMATION
The genome of malignant tumors shows multiple changes and is prone to multiple defects. If the gene is affected, either multiplied or deleted, the protein that that gene encodes for likewise changes. This leads to multiple cellular abnormalities, including possibly uncontrolled growth and proliferation. Initial insult (Continued on page 39)
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