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A brain tumor is an abnormal growth of cells within the brain, which can be cancerous (malignant) or non-cancerous (benign). It is defined as any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself (neurons,glial cells (astrocytes, oligodendrocytes, ependymal cells, myelin-producingSchwann cells), lymphatic tissue, blood vessels), in the cranial nerves, in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancersprimarily located in other organs (metastatic tumors).
Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and in the anterior two-thirds of the cerebral hemispheres in adults, although they can affect any part of the brain.
Symptoms of brain tumors may depend on two factors: tumor size (volume) and tumor location. The time point of symptom onset in the course of disease correlates in many cases with the nature of the tumor (“benign”, i.e. slow-growing/late symptom onset, or malignant, fast growing/early symptom onset) is a frequent reason for seeking medical attention in brain tumor cases..
Large tumors or tumors with extensive perifocal swelling edema inevitably lead to elevated intracranial pressure (intracranial hypertension), which translates clinically into headaches, vomiting (sometimes without nausea), altered state ofconsciousness (somnolence, coma), dilatation of the pupil on the side of the lesion (anisocoria), papilledema (prominent optic disc at the funduscopic eye examination). However, even small tumors obstructing the passage of cerebrospinal fluid (CSF) may cause early signs of increased intracranial pressure. Increasedintracranial pressure may result in herniation (i.e. displacement) of certain parts of the brain, such as the cerebellar tonsils or the temporal uncus, resulting in lethalbrainstem compression. In young children, elevated intracranial pressure may cause an increase in the diameter of the skull and bulging of the fontanelles.
Depending on the tumor location and the damage it may have caused to surrounding brain structures, either through compression or infiltration, any type offocal neurologic symptoms may occur, such as cognitive and behavioralimpairment, personality changes, hemiparesis, hypoesthesia, aphasia, ataxia, visual field impairment, facial paralysis, double vision, tremor etc. These symptoms are not specific for brain tumors-they may be caused by a large variety of neurologic conditions (e.g. stroke, traumatic brain injury). What counts, however, is the location of the lesion and the functional systems (e.g. motor, sensory, visual, etc.) it affects.
A bilateral temporal visual field defect (bitemporal hemianopia-due to compression of the optic chiasm), often associated with endocrine disfunction-eitherhypopituitarism or hyperproduction of pituitary hormones and hyperprolactinemia is suggestive of a pituitary tumor.
Metastatic cancers are far more common than primary tumors of the brain and spinal cord.
Apart from exposure to vinyl chloride or ionizing radiation, there are no known environmental factors associated with brain tumors. Mutations and deletions of so-called tumor suppressor genes are thought to be the cause of some forms of brain tumors. Patients with various inherited diseases, such as Von Hippel-Lindau syndrome, multiple endocrine neoplasia, neurofibromatosis type 2 are at high risk of developing brain tumors. It is alleged that mobile phones/cell phones might be a cause of brain tumors, according to one report.[4] (see Mobile phone radiation and health) There is an association of brain tumor incidence and malaria, suggesting that the anopheles mosquito, the carrier of malaria, might transmit a virus or other agent that could cause a brain tumor.[5] Malignant brain tumor incidence andAlzheimer’s disease prevalence are associated in 19 US states. The two diseases may share a common cause, possibly inflammation.