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glossary - a

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Absence seizure – a type of generalised seizure where the person briefly loses awareness and becomes blank or unresponsive. Absences often last a few seconds and the person is unconscious. If they are walking they might carry on walking.

Absorb  - when the AED is broken down in the body and gets into the blood stream.

Action potential or nerve impulse  – the messages sent and received by neurones.

Active ingredient  – the chemical part of a drug that works on the body to control or treat a condition or disease.

Acute side effect  – a side effect that starts soon after a drug is taken, or when the dose of a drug is increased. These side effects can vary from one drug to another and from one person to another. They include headaches, dizziness and drowsiness. The effect usually goes away after a few weeks.

Add-on (or adjunctive) therapy - medication taken in addition to another medication.

Adherence  – when someone takes their medication as they have agreed with their doctor. This is a more modern term than ‘compliance’ (doing what your doctor tells you to), and implies that there has been some discussion between the individual and their doctor to agree upon a plan of treatment. Whether someone is adherent or not is a measure of how closely they adhere (or 'stick to') taking their medication or treatment as agreed.

Adjunctive treatment  – adding an extra drug to a drug (or drugs) that is already being taken. This is also called ‘add-on therapy’.

Adverse events  - another term for 'side effects'. These are effects of medication that happen alongside the effects you are expecting (the reason you are taking it). Side effects are usually, but not always, unwanted.

AED (anti-epileptic drug)  - medication that aims to control epilepsy and stop seizures.

Agonist  – a substance that helps another substance to work better.

Ambulatory EEG  – when someone has EEG monitoring and they can move and walk around. The EEG electrodes are held in place on the head with tape, and connected to a recorder that is worn on a belt. This means that the EEG recording can be done over a longer period of time, and can be done at home, during day-to-day activities. Ambulatory EEG is often done when someone has had a standard EEG but had no seizures. Because ambulatory EEG is done over a longer time than a standard EEG, it is more likely that a seizure will happen and the information can be recorded.

Amino acid  – a substance that is a building block of proteins.

Antagonist  – a substance that prevents, or gets in the way of, another substance.

Anticonvulsants – another name for anti-epileptic drugs, used to treat epilepsy. This term is misleading because not all epileptic seizures include convulsions.

Anti-epileptic drugs (AEDs) – medication which aims to control epilepsy and stop seizures from happening. There are many different AEDs and they work in different ways and stop different types of seizures. Up to 70% of people with epilepsy could have their seizures stopped with the right AEDs.

Asleep seizures  – sometimes called 'nocturnal seizures', these seizures happen when someone is asleep. These seizures are related to sleep. While most people have asleep seizures while they are sleeping at night, if they fall asleep during the day they could have asleep seizures. This term does not say what sort of seizures happen, only when they happen.

Ataxia  – unsteady or shaky movement caused by the brain not being able to control posture and body movement. This can be a side effect of some anti-epileptic drugs.

Atom  – the smallest unit of matter, made up of protons (positively charged particles), electrons (negatively charged particles) and neutrons (uncharged particles).

Atonic or atonic seizure – a type of generalised seizure where the person’s muscles suddenly lose tone, go floppy, and they fall down (usually forwards) if they are standing up. Although the seizures themselves don’t hurt, the person might hurt themselves, especially their head and face, when they fall. These seizures are usually very brief and the person becomes conscious again very quickly. This is sometimes called a ‘drop attack’.

Aura – a type of simple focal seizure that becomes a generalised seizure (see secondarily generalised seizure). Auras are usually strange sensations, such as a strange smell, funny taste, or strange ‘rising’ feeling in the stomach. The person will be conscious and aware that the aura is happening. Auras are also sometimes called ‘warnings’ because they warn the person that a generalised seizure is coming.

Automatism  – this is an automatic movement that has no purpose. Automatisms can happen in complex partial seizures and often look very strange or unusual. They include lip-smacking, making chewing movements, repeatedly picking up objects or pulling at clothes.

Autonomic nervous system  – part of the nervous system that control involuntary, unconscious actions of the body (for example, the beating of the heart and the activity of the bladder and bowels)

Axon  – sometimes called a nerve fibre, this is the part of the neurone that carries messages away from the cell body of the neurone.

Axon hillock  – part of the neurone that acts as a 'bridge between the axon and the cell body.