Epileptic seizures are caused by a disturbance in the electrical activity of the brain. There are many different types of epileptic seizure. Any of us could potentially have a single epileptic seizure at some point in our lives.
Whether you, or someone you know, has had a single seizure or has been diagnosed with epilepsy, it may help to identify the type of seizures that are relevant to you, and how they affect you.
Types of Seizures
Seizures are divided into two main types: focal seizures (also called partial seizures) and generalised seizures. Epileptic seizures always start in the brain.
The brain has two sides called hemispheres. Each hemisphere has four parts called lobes. Each lobe is responsible for different things such as vision, speech and emotions.
Focal (partial) Seizures
In focal seizures the seizure starts in, and affects, just part of the brain sometimes called the ‘focus’ of the seizures. It might affect a large part of one hemisphere or just a small area in one of the lobes.
What happens during the seizure depends on where in the brain the seizure happens and what that part of the brain normally does.
Simple Focal Seizures
In simple focal seizures (SFS) a small part of one of the lobes of the brain is affected. The person is conscious (aware and alert) and will usually know that something is happening and will remember the seizure afterwards.
Some people find their simple focal seizures (SFS) hard to put into words. During the seizure they may feel ‘strange’ but not able to describe the feeling afterwards. This may be upsetting or frustrating for them.
SFS are sometimes called ‘warnings’ or ‘auras’ because, for some people, a SFS develops into another type of seizure. The SFS is then a warning that another seizure will happen (see secondarily generalised seizures below).
Temporal lobe simple focal seizures may include:
• a ‘rising’ feeling in the stomach (like the feeling you get on a fairground ride where you ‘leave your tummy at the top’)
• deja vu (feeling like you’ve ‘been here before’) or jamais vu (where familiar things seem new)
• getting an unusual smell or taste
• a sudden intense feeling of fear or joy.
Frontal lobe simple focal seizures may include:
• a strange feeling like a ‘wave’ going through the head
• stiffness or twitching in part of the body (such as an arm or hand).
Parietal lobe simple focal seizures may include:
• a feeling of numbness or tingling
• burning sensations or a feeling of heat
• a sensation that an arm or leg feels bigger or smaller than it actually is.
Occipital lobe simple focal seizures may include:
• visual disturbances such as coloured or flashing lights
• hallucinations (seeing something that isn’t actually there).
Complex focal seizures
Complex focal seizures (CFS) affect a bigger part of one hemisphere (side) of the brain than a simple focal seizure. The person’s consciousness is affected and they may be confused. They might make strange or repetitive movements that have no purpose (called ‘automatisms’). They may wander around, or behave strangely, and they may not be aware of what they are doing.
They might be able to hear you, but not fully understand what you say or be able to respond to you. They may not react to you they would normally. If you speak loudly to them, they may think that you are being aggressive and so they may react aggressively towards you.
Temporal lobe complex focal seizures may include:
• picking up objects for no reason or fiddling with clothing
• chewing or lip-smacking movements
• muttering or repeating words that don’t make sense
• wandering around in a confused way.
These CFS may start with a simple focal seizure and may last around two or three minutes.
Frontal lobe complex focal seizures may include:
• making a loud cry or scream
• making strange postures or movements such as cycling or kicking.
Secondarily Generalised Seizures
Sometimes focal seizures spread from one side (hemisphere) to both sides of the brain. This is called a secondarily generalised seizure because it starts as a focal seizure and then becomes generalised. When this happens the person becomes unconscious and will usually have a tonic clonic (convulsive or shaking) seizure. If this happens very quickly, they may not be aware that it started as a focal seizure.
Generalised seizures affect both sides of the brain at once and can happen without warning. The person will be unconscious (except in myoclonic seizures), even if just for a few seconds. Afterwards they will not remember what happened during the seizure.
Absences (Petit Mal)
Absence seizures are more common in children than adults and can happen very frequently. During an absence a person becomes unconscious for a short time. They may look blank and stare, or their eyelids might flutter. They will not respond to what is happening around them. If they are walking they may carry on walking but will not be aware of what they are doing.
Absences can be confused with daydreaming. However, unlike daydreaming, someone who is having an absence will not usually respond. Also, if blank spells happen when someone is doing something that they enjoy, such as talking or playing a game, then this is less likely to be daydreaming.
In typical absences, the person becomes blank and unresponsive for a few seconds. Because the seizures are so brief, they may not be noticed.
A typical absences often last a bit longer than typical absences. They often have some physical movement with them such as a brief head nod.
In a tonic seizure the person’s muscles suddenly become stiff. If they are standing they often fall, usually backwards, and may injure the back of their head. Tonic seizures tend to be very brief and happen without warning.
Myoclonic means ‘muscle jerk’. Muscle jerks are not always due to epilepsy (for example, some people have them as they fall asleep).
Myoclonic seizures are brief but can happen in clusters (many happening close together in time) and often happen shortly after waking.
In myoclonic seizures the person is conscious, but they are classified as generalised seizures. This is because the person is likely to have other seizures (such as tonic clonic seizures) as well as myoclonic seizures.
Tonic Clonic (convulsive) Seizures (Grand Mal)
At the start of the seizure:
• the person becomes unconscious
• their body goes stiff and if they are standing up they usually fall backwards
• they may cry out
• they may bite their tongue or cheek.
During the seizure:
• they jerk and shake (convulse) as their muscles relax and tighten rhythmically
• their breathing might be affected and become difficult or sound noisy
• their skin may change colour and become very pale or bluish
• they may wet themselves.
After the seizure (once the jerking stops):
• their breathing and colour return to normal
• they may feel tired, confused, have a headache or want to sleep.
A person’s seizures usually last the same length of time each time they happen and stop by themselves. However, sometimes seizures do not stop or one seizure follows another without the person recovering in between. If this goes on for 30 minutes or more it is called status epilepticus or ‘status’.
Status is not common, but it can happen in any type of seizure and the person may need to see a doctor. Status in a tonic clonic (convulsive) seizure is a medical emergency and the person will need urgent medical help