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.
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, they may be confused and make strange movements (called ‘automatisms’).
Generalised and secondarily generalised seizures
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.
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.
Absences (sometimes called petit mal)
Absence seizures, or petit mal seizures, are more common in children than adults and can happen very frequently. During an absence a person becomes unconscious for a short time.
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.
In an atonic seizure (or 'drop attack') the person’s muscles suddenly relax and they become floppy. If they are standing they often fall, usually forwards, and may injure the front of their head or face.
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.
Tonic clonic seizures
At the start of the seizure the person becomes unconscious their body goes stiff and if they are standing up they usually fall backwards. During the seizure they jerk and shake (convulse) as their muscles relax and tighten rhythmically.
Clonic seizures are convulsive seizures but the person's body does not go stiff at the start.