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What is a Brain Tumour?
WHO Classification

Benign tumour: slow growth, non-infiltrative character, low recurrence rate, amenable to complete surgical removal (depending on location), usually does not require adjuvant radiotherapy or chemotherapy.

Cerebrospinal fluid: a clear, colourless fluid in which the central nervous system is, and which is also present in the chambers of the brain.  It acts as a cushion for the brain and spinal cord, and due to immersion, the weight of the brain is greatly reduced.  It also acts as a medium through which harmful substances are removed by the one way traffic to blood, as well as serving as a transport medium for hormones and other substances.

Computed tomography scanner: special scanner based on ionising radiation—x-ray beams are channelled through many planes in order to get high resolution pictures with good bony-structure representation.  Quick, relatively cheap, and more widely available. (

Contrast enhancement: this is the injection of special substances during magnetic resonance and/or computed tomography scans which can significantly aid in identifying tumours and their margins.

Fibre-tracking: this is a special neuronavigation technique where it is possible to project the course of neural pathways within the vicinity of the proposed operation site.

Functional magnetic resonance imaging: a special brain mapping technique where areas of the brain responsible for crucial functions like speech and arm and leg function can be visually identified, thereby permitting the neurosurgeon to exercise maximum caution by guiding extent of permissible tumour removal without compromise of function in those sensitive areas.

Gammaknife surgery: this is based on the principle of focussing a large number of radiation beams on a small, predetermined area in order to destroy tumour cells.  Surrounding tissue remains undamaged, as the critical dose of radiation is achieved only in the planned vicinity where the gamma radiation beams intersect.

Gliomas: the collective name for tumours arising from glial cells—these are cells which nerve cells provide support and nutrition, help in maintaining metabolic balance, aid in the formation of nerve sheaths, and take part in signal transmission.

Histology: the “science of tissue”—in this context meaning the cellular characteristics of the tumour process in question

Intra-operative magnetic resonance imaging scanner:  this permits real-time control and guidance of tumour removal during the operation itself. (

Malignant tumour: fast growth, infiltrative character, high recurrence rate—often with a higher degree of malignancy, usually requires surgical treatment in conjunction with adjuvant radiotherapy and/or chemotherapy. They carry a relatively negative prognosis, with the primary difference between the various grades of malignancy being length of life-expectancy.

Magnetic resonance tomography scanner: special scanner based on the use of a powerful magnet many times the strength of the Earth’s gravitational field used to get high resolution pictures in three planes with good soft-tissue representation.  Slow, relatively expensive, and not so widely available.  No ionising radiation involved.  (

Metastases:  the local or distant spread of tumour cells.

Motor deficit: muscle weakness, decrease in strength.

Necrosis: is essentially “dead tissue” or “tissue death”.

Neuronavigation:  special markers similar to stickers are placed in various locations on the head and behind both ear, and scans—either magnetic resonance, or computed tomography, or both--are then performed.  This then allows the neurosurgeon to “navigate” during the operation using a sophisticated computer setup with an interactive program and a special pointer using these points as reference frames, and with a three-dimensional representation of the tumour.

Neurophysiological tests: electroencephalography (graphical representation of the electrical activity of the brain), evoked potentials (electrical potential recorded following presentation of a stimulus): brainstem auditory evoked potentials, motor evoked potentials, sensory evoked potentials, visual evoked potentials—these are used peri- and intraoperatively to assess and control nerve function.

Positron emission tomography: a special scan performed after the administration of a small quantity of radioactive substance. (

Space-occupying lesion: any formation or growth within the skull which causes what is known as a mass-effect—meaning exertion of pressure on surrounding structures with/without consequent of a raise in intracranial pressure.

Sensory deficit: altered or diminished sensation.

Stereotactic biopsy: this is a diagnostic option where special scans are made using a stereotactic frame, and following careful preparation and calculation of several measurements, the equivalent of a “key-hole” operation is performed with the aim to take tissue samples for a biopsy.

last changed 27/05/2011.

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