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Jargon buster

A comprehensive list of the terms and words you will come across in relation to brain tumours.


Gamma Knife ®

"The trade name for a machine which delivers beams of low-dosage gamma radiation to a tumour from many different positions around the patient. This allows it to target the tumour very accurately, whilst giving minimal radiation to the surrounding healthy tissue. This is known as stereotactic radio surgery. Despite the word 'knife' appearing in the name, no actual knife is used."


A set of instructions, carried on the chromosomes within each cell, that is transferred from parent to offspring. The function of a gene can be to determine something about who you are e.g. whether you have long or short eyelashes, or it can help to control processes, such as when your cells should start and stop dividing.

Genetic condition

A condition that is caused by an abnormality in the genes. This could either be inherited from our parents, or caused by an acquired change (mutation) in our own genes. Such mutations can occur randomly, due to a mistake being made when the gene is copied during cell division, or be due to some environmental factor.

Germ cell

The cells in the body that develop into sperm or eggs (reproductive cells). They contain half the number of chromosomes of a somatic cell (body cell) i.e. 23 chromosomes, so that when the egg and sperm unite, the resulting cell has 46 chromosomes (23 pairs)


A condition where a person's eye-sight is affected by a build-up of pressure within the eye. The pressure can be caused by a build-up of fluid, inflammation or something pressing against the nerve connecting the eye from the brain (optic nerve)

Gliadel® wafer

Small wafers or discs the size of a 5p coin containing the chemotherapy drug called carmustine. They are implanted in the brain and dissolve gradually releasing the drug. They are only licensed for people with high grade gliomas, or with glioblastomas that have returned after treatment. At least 90% of the tumour must also have been removed before they can be used.

Glial cell

A type of brain cell that supports and protects the nerve cells (neurons) in the brain, by providing them with oxygen and nutrients, and by removing dead cells. There are three main types of glial cells - astrocytes, oligodendrocytes and ependymal cells. Glioma is a brain tumour that grows from any type of glial cell.


A glioma is a tumour that grows from a type of cell in the brain called a glial cell.

There are different types of glial cells - the main types being astrocytes, oligodendrocytes and ependymal cells – giving rise to astrocytomas, oligodendrogliomas and ependymomas, respectively.

Gliomas are the most common type of brain tumour.


Brain tumours are graded by the World Health Organisation (WHO) from 1 - 4, according to how they behave i.e. how fast they grow and how likely they are to spread within the brain.

Tumours graded 1 and 2 are slow-growing, and are sometimes referred to as 'benign' or low grade. The word 'benign' is used less nowadays as it is not thought to be helpful in describing the tumour, as these low grade tumours are still serious.

Tumours graded 3 and 4 are fast-growing, more aggressive tumours, sometimes referred to as 'malignant' or 'cancerous', meaning they are more likely to get bigger more quickly and sometimes spread to other parts of the brain or spinal cord.

Grey matter

Particular types of cells that are found in the outer layer of the cerebral hemispheres (the cerebral cortex) and also in the cerebellum and spinal cord. They are involved in muscle control, sensory perception (such as seeing and hearing), memory, emotions, speech, decision-making and self-control