In generalised seizures the epileptic activity is in both halves of your brain. The main types of generalised seizure are tonic-clonic, absence, myoclonic, tonic and atonic.
In tonic-clonic seizures, you will fall to the floor. In some other types of generalised seizure the epileptic activity misses a small part of your brain and makes your symptoms more limited. For example, in absence seizures, you don’t fall to the floor. In a myoclonic seizure, the symptoms are jerking in just a part of your body, and you rarely fall to the floor.
This is the most common and widely recognised generalised seizure. There are two phases to this type of seizure: the ‘tonic’ phase, followed by the ‘clonic’ phase.
The tonic phase
You lose consciousness and, if standing, will fall to the floor. Your body goes stiff because all your muscles contract. You may cry out because your muscles contract, forcing air out of your lungs. Your breathing patterns change, so there is less oxygen than normal in your lungs. Because of this, the blood circulating in your body is less red than usual. This causes your skin (particularly around your mouth and under your finger nails) to appear blue in colour. This is called ‘cyanosis’. You may bite your tongue and the inside of your cheeks.
The clonic phase
After the tonic phase has passed, the clonic phase of the seizure begins. Your limbs jerk now because your muscles tighten and relax in turn. You may occasionally lose control of your bladder and/or bowels. It is not possible to stop the seizure, and no attempts should be made to control your movements, as this could cause injury to your limbs.
After a tonic-clonic seizure
After a short time, your muscles relax and your body goes limp. Slowly you will regain consciousness, but may well be groggy or confused. You will gradually return to normal but may not be able to remember anything for a while. It’s usual to feel sleepy and have a headache and aching limbs. Recovery times can be different for different people. Some people will quickly want to get back to what they were doing. Some people will need a short sleep and others will need plenty of rest.
‘Post’ means after and ‘ictal’ refers to a seizure. After a tonic-clonic seizure, some people may be very confused, tired or have memory loss. This is known as a post-ictal state. A post-ictal state can last from minutes to days.
During an absence seizure, you are unconscious for a few seconds. You appear to be daydreaming or switching off. You don’t know what is happening around you, and you can’t be brought out of it.
Because anybody can daydream at any time, absences can be very hard to spot. It’s possible to have hundreds of absence seizures a day, preventing you from fully taking part in daily activities. You could also miss out on tiny pieces of information or events. This may be mistaken for lack of attention or concentration.
The word myoclonic comes from ‘myo’ meaning muscle, and ‘clonus’ meaning jerk. So in a myoclonic seizure your muscles jerk.
Myoclonic seizures can sometimes cause your whole body to jerk. More usually, they only cause jerking in one or both arms and sometimes your head. Although it may not be obvious, during the seizure, you are unconscious for a very brief time.
Even though the seizures are brief, they can be extremely frustrating. For example, they often result in spilt drinks or similar accidents.
The most common time for myoclonic seizures to happen is first thing in the morning.
Myoclonic seizures are similar to the jerks that some people have when falling asleep. These jerks when falling asleep are not epilepsy.
In a tonic seizure all your muscles tighten. Your body stiffens and you fall over unless you are supported. Tonic seizures usually last less than 20 seconds and most often happen during sleep.
In an atonic seizure you lose all muscle tone and drop heavily to the floor. The seizure is very brief and you are usually able to get up again straight away. You are not confused afterwards.
Because your body usually falls forward in an atonic seizure, you are at risk of banging your head on furniture or other hard objects. If you have frequent atonic seizures, extra safety precautions – like protective headgear – make sense. Epilepsy Action can provide further information on this.
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Updated July 2011To be reviewed July 2013