glossary - s
Second line drug – AEDs that are usually used alongside other AEDs (rather than on their own). These are also called ‘add-on’ drugs.
Secondarily generalised seizures – seizures that start as a focal seizure (in part of the brain) but the seizure activity spreads and affects the whole of the brain. In simple terms these are ‘small seizures’ that become ‘big seizures’. The focal seizure start is sometimes called an ‘aura’ or ‘seizure warning’, and the seizure usually spreads to become a tonic clonic seizure.
Seizure – a sudden, short-lived event that causes a change in the person’s behaviour, awareness or consciousness. There are lots of different causes and types of seizures including epileptic seizures, hypoglycaemic (diabetic) seizures, non-epileptic seizures, syncope (fainting), and seizures caused by a heart problem. In epilepsy we often refer to ‘epileptic seizures’ as just ‘seizures’ which can be quite confusing!
Seizure control - when seizures are completely stopped, an the person experiences no seizures any more. This is usually achieved by taking AEDs.
Seizure-free – when a person’s seizures are fully controlled and stop happening (they don't have seizures any more). This is usually achieved by taking AEDs.
Seizure threshold – every person’s individual level of resistance to seizures. Anyone could have an epileptic seizure under the right circumstances, but most people don’t if they have a high level of resistance to them. Seizures might suddenly start in a person with a low seizure threshold, or an accident or infection could lower a person’s threshold and they could start having seizures.
Serum levels – a way of monitoring the amount of AED in a person’s body. See therapeutic drug monitoring.
Severe Myoclonic Epilepsy in Infancy (SMEI) (also called Dravet Syndrome) – A rare childhood epilepsy syndrome that starts in a child’s first few years of life. The child has jerking seizures, usually on one side of the body. They may also be photosensitive (have seizures triggered by flashing lights or patterns). Learning, speech and general development may be affected.
Side effects – 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. They are also called ‘adverse events’.
Simple focal seizures (SFS) – seizures that involve a small part of the brain. In SFS the person is fully conscious and aware of what is happening. What exactly happens depends on where in the brain the seizure is (the frontal, temporal, occipital or parietal lobes) and what that part of the brain does. SFS are sometimes called ‘auras’ or ‘warnings’ if they become secondarily generalised seizures. Some symptoms, such as a strange ‘rising’ feeling in the stomach (like when you go on a fairground ride and ‘lose your tummy at the top’) or pins and needles, can happen in people who do not have epilepsy but can also be a type of SFS.
Site of action – the place in the body where the drug works. In the case of AEDs this is the brain.
SPECT (Single Photon Emission Computerised Tomography) – a type of scan or way of imaging the brain that combines CT and PET scans. SPECT might be used if a person is being considered for epilepsy surgery.
Spinal cord – a large bundle of nerves, inside the spine, that connect the brain with the nerves of the body.
Spontaneous remission – when seizures stop or go away of their own accord (rather than stopping because of taking AEDs).
Status epilepticus (‘status’ for short) – a state that happens when a seizure does not stop of its own accord (prolonged seizures) or a series of seizures happen without the person recovering in between. Status officially happens when a seizure continues for 30 minutes. Status can be life-threatening in a tonic clonic seizure, and has to be stopped with emergency medication.
Steady state – where medication has been taken for a few days and if a blood test is taken, the blood levels are a reliable measure of the concentration of the drug in the body. Steady state usually happens after about five 'half-lives' of the drug (the time taken for the amount of drug in the body to reduce by half). Half-lives vary between AEDs but if the half-life is 12 hours, steady state would happen after two and a half days.
Structural cause – a physical cause for a person's epilepsy, such as a lesion, tumour or scar tissue.
Structural imaging – when scans are used to look at the structure of the brain.
Subclinical seizure – a seizure that can be seen on an EEG but can’t been seen by looking at the person (they have no obvious symptoms of a seizure).
SUDEP (Sudden Unexpected Death in Epilepsy) – when a person with epilepsy suddenly dies and no reason for their death can be seen. SUDEP usually happens at night when the person is in bed, and it is not usually seen by anyone else (unwitnessed). Although we don’t know for sure, it is thought that SUDEP happens during a seizure, and the person’s breathing or heart stops.
Sulci – 'valleys' in the surface of the cerebrum.
Symptomatic epilepsy – epilepsy where there is a known physical cause of the person’s seizures. This could be due to a scar on the brain, an accident or head injury, or a stroke or brain tumour. Structural causes can often be seen on an MRI.
Synapse – the point at which two neurones connect. The neurones may be separated by a small space called a synaptic gap.
Synaptic terminal – part of the neurone that connects with the dendrites of the next neurone.
Synaptic vesicles – small sacs found inside neurones, containing neurotransmitters.
Syncope – when someone loses consciousness and collapses because the oxygen getting to their brain temporarily stops. This can be because of a drop in blood pressure, a change in the heart beat (and not enough blood is pumped through the heart), or because of a reduced amount of oxygen in the blood. Syncope can look like an epileptic seizure but usually starts with typical symptoms such as feeling light-headed, or reduced or blurred vision. Syncope is also another word for ‘faint’.
Systemic – refers to the body as a whole rather than a particular part or organ.