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  • Perception

    Awareness and understanding of our environment.

  • Peripheral nervous system

    The part of the nervous system that includes the nerves outside the brain and spinal cord. They connect the central nervous system to other parts of the body. Abbreviated to PNS.

  • Peripheral vision

    Parts of our vision that is outside our centre of gaze, outside our point of focus.

  • PET scan

    Positron emission tomography scan. A test that uses a special camera to see how organs and tissues are working.

  • Petechiae

    Small red dots or spots due to bleeding under the skin.

  • PFS

    Progression-free survival (PFS) means the length of time that a tumour doesn’t grow significantly.

    It is not the same as overall survival, which means how long someone will live. A more accurate description of PFS would be PFD – progression-free duration

  • Pharmacoresistance

    Resistance to pharmaceutical drugs. For example, pharmacoresistant epilepsy does not respond to anti-epileptic drugs.

  • picc line

    Peripherally Inserted Central Catheter. A tube that is passed through a vein, often in the arm or chest, to end up in a large vein near the heart. The other end is left outside the body and is used to deliver chemotherapy drugs straight into the blood. It can also be used to take blood samples. It is a type of central line and can be left in place for some time.

  • Pituitary gland

    Found at the base of the brain, it is the ‘master’ gland of the body’s endocrine system. Working with the hypothalamus, it controls other hormone-producing glands in the body to regulate different body functions, such as heart rate, body temperature as well as growth and development.

  • Placebo

    A medicine or procedure that has no actual biological or chemical therapeutic effect. It is generally used as a control in testing new drugs, but sometimes for the psychological benefit to the patient through their believing they are receiving treatment . This is known as the placebo effect.

  • Placebo effect

    When giving an inactive substance (such as sugar, distilled water, or saline solution) improves a patient’s condition simply because the person has the expectation that it will be helpful.

  • Platelet

    A type of blood cell that helps to stop bleeding when there has been an injury to the body, such as a cut. Platelets do this by helping the blood to clot.

  • Polymer 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.
    Also known as Gliadel® wafers.

  • Pons

    Part of the brainstem, it connects the medulla oblongata and the midbrain. It relays signals from the cerebrum to the cerebellum. It is involved with sleep, breathing, bladder control, hearing, facial and eye movements, posture and other functions.

  • Portacath

    A way of taking blood or delivering medicines straight into the blood, without having to insert a needle each time.

    Similar to a central line, except that the tube does not exit the body via the arm or chest. Instead, a small chamber (port) is implanted under the skin in the chest. The chemotherapy drugs are then injected into the port using a special needle.
    The advantage is that you can’t see the portacath
    and there are not have tubes coming out of the body, which have to be kept dry.

  • Posterior fossa

    A small space at the back of the skull containing the cerebellum, brain stem and fourth ventricle.

  • Primary brain tumour

    A tumour which begins in the brain (rather than spreading from somewhere else in the body)

  • Primitive cell

    An unspecialised immature cell from early in our development as an embryo. They include stem cells.

  • Principal investigator

    The lead researcher for a clinical trial. They are responsible for the scientific and technical direction of the study.

  • Prognosis

    The likely course and expected outcome of a medical condition.

  • Progression-free survival

    Progression-free survival (PFS) means the length of time that a tumour doesn’t grow significantly.

    It is not the same as overall survival, which means how long someone will live. A more accurate description of PFS would be PFD – progression-free duration

  • Psychosis

    A severe mental health problem that disrupts perception, thinking, emotion and behaviour. It might include hallucinations or delusions.

  • Puberty

    A period in a human’s development when the body matures sexually, causing various physical, psychological and behavioural changes. There is no set age when it starts. For girls, it is usually between 8 – 14 years; for boys, 9-14 years.

  • Quality of life

    A term used to describe the physical and emotional wellbeing of people in their daily lives

  • Radiation

    A stream of high energy particles or electromagnetic waves that can be used to destroy tumour cells.

  • Randomised clinical trial

    A clinical trial in which patients are randomly allocated to the different treatments under investigation.

  • Referral

    When a doctor directs a patient to another doctor e.g. a GP directs a patient to a specialist

  • Rehabilitation

    Treatments designed to aid the recovery from illness, injury or disease to as normal a condition as possible.

  • Resection

    The surgical removal of an organ or structure, such as a tumour. Partial resection: Removal of part of a tumour Total resection: Removal of all of a tumour

  • Respite care

    A break from caring, while the person you care for is looked after by someone else. This can be a volunteer, a paid carer, a family member or a friend.

  • Retina

    The layer of light-sensitive cells at the back of the eye

  • RNA sequencing

    A way to study which genes are active in a cell by looking at its RNA.

  • RNA1

    A type of RNA that helps cells make proteins. RNA stands for Ribonucleic acid – a type of nucleic acid similar to DNA.

  • Sandpit

    A sandpit is a discussion forum, aiming to discuss problems and brainstorm solutions through free thinking and collaboration. To do this, it draws on the expertise of professionals in a variety of areas. 

  • Sarcopenia

    Loss of muscle strength and mass as we age.

  • Screen/ screening test

    A test to look for particular changes in a person’s or tumour’s DNA.

  • scRNA Seq

    A method for studying the activity of single cells by looking at their RNA.

  • Sedative

    A drug that calms a patient, reducing anxiety and making you sleepy. It can be given before certain medical procedures to make them less stressful.

  • Seizure

    A sudden burst of uncontrolled electrical activity in the brain, that temporarily disrupts the normal working of the brain. It can cause a range of symptoms from minor physical signs, such as an arm or leg twitching; strange sensations or thought disturbances: to a physical convulsion and loss of consciousness.

  • SEN

    Special Educational Needs that affect a child’s ability to learn. These could include: reading & writing; ability to understand things; concentration levels; physical needs or impairments; or the behaviour or ability to socialise. If your child needs more support than the school can provide through SEN, they may need an education, health and care (EHC) plan. You can ask your local authority for an assessment.


    Special Educational Needs Co-ordinator. The person who is responsible for and co-ordinates additional support that some pupils will need in school. All mainstream schools must have a SENCO.

  • Shunt

    A tube that is inserted to drain excess cerebrospinal fluid from the brain to another part of the body, where it can easily be eliminated. This is to prevent a build-up of pressure on the brain, as caused by hydrocephalus. During an operation, one end of the tube will be inserted into the area of the brain where the fluid is collecting, and the other end will usually run through to the abdomen. From here it can be absorbed into the blood stream and eliminated from the body in the usual way, as urine when you go the toilet. The shunt usually has a valve to control the flow of fluid and make sure it doesn’t drain too quickly. You may be able to feel the valve under your scalp.

  • Somatic cell

    Any cell in the body that is not a reproductive/germ cell i.e. any cell other than sperm or eggs.

  • Somnolence syndrome

    Period of excessive drowsiness, impaired concentration and fatigue that can follow 4 -6 weeks after radiotherapy, particularly to the head.

  • Spatial transcriptomics

    A technique to study what genes are active and where they are inside bodily tissue.

  • Specials

    Unlicensed medicines, which have been specially manufactured or imported, for the treatment of an individual patient after being ordered by specified healthcare professionals.

  • Squint

    Inability for both eyes to look in the same direction. Also known as strabismus.

  • SRS

    Stereotactic radiosurgery (SRS) is stereotactic radiotherapy treatment that is given in one session. Despite its name, SRS doesn’t involve actual surgery.

  • Stem cell

    An unspecialised, primitive cell that is able to grow into any one of the body’s different cell types. They play a part in the body’s ability to renew and repair itself.

  • Stereotactic radiosurgery

    Stereotactic radiosurgery (SRS) is stereotactic radiotherapy treatment that is given in one session. Despite its name, SRS doesn’t involve actual surgery.