A brain tumor is an abnormal growth of cells within the brain, whichcan be cancerousor non-cancerous (benign). It is defined as any intracranial tumor created byabnormal and uncontrolled cell division, normally either in the brain itself (neurons, glial cells astrocytes, oligodendrocytes,ependymalcells), lymphatic,bloodvessels, in the cranial nerves (myelin-producing Schwanncells), in the brain envelopes (meninges), skull, pituitary andpinealgland, or spread from cancers primarily located in other organs (metastatictumors).
Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and inthe anterior two-thirds of the cerebral hemispheres in adults, althoughthey can affect any part of the brain.
Signs and symptoms
Symptoms of brain tumors may depend on two factors: tumor size (volume) andtumor location. The time point of symptom onset in the course of diseasecorrelates in many cases with the nature of the tumor ("benign", i.e.slow-growing/late symptom onset, or malignant, fast growing/early symptomonset) is a frequent reason for seeking medical attention in brain tumor cases.
Large tumors or tumors with extensive perifocal swelling (edema) inevitablylead to elevated intracranial pressure (intracranial hypertension), whichtranslates clinically into headaches, vomiting (sometimes without nausea), alteredstate of consciousness (somnolence,coma), dilatation ofthe pupil on the side of the lesion (anisocoria),papilledema(prominent opticdisc at the funduscopic eye examination). However, even small tumorsobstructing the passage of cerebrospinal fluid (CSF) may cause early signsof increased intracranial pressure. Increased intracranial pressure may result in herniation(i.e. displacement) of certain parts of the brain, such as the cerebellar tonsils or the temporal uncus, resulting inlethal brainstemcompression. In young children, elevated intracranial pressure may cause an increasein the diameter of the skull and bulging of the fontanelles.
Depending on the tumor location and the damage it may have caused tosurrounding brainstructures, either through compression or infiltration, any type of focal neurological symptoms may occur,such as cognitiveand behavioralimpairment, personality changes, hemiparesis,hypoesthesia,aphasia, ataxia, visualfield impairment, facial paralysis, double vision, tremor etc. Thesesymptoms are not specific for brain tumors—they may be caused by a largevariety of neurological 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 ofthe opticchiasm), often associated with endocrine dysfunction—either hypopituitarismor hyper production of pituitary hormones and hyperprolactinemia is suggestive of a pituitarytumor.