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Seizure Disorders

Statistics

UK [1]

What is it?

A seizure is caused by a temporary change in the way the brain cells work. (The old name for a seizure was a 'fit').

The brain is like a computer which consists of a vast network of nerve cells called neurons. Throughout peoples lives literally billions of electrical messages are fired between these cells, controlling every single thing people think, feel or do.

The body has its own inbuilt balancing mechanisms. These ensure that messages usually travel between nerve cells in an orderly way. However sometimes - quite without warning - an upset in brain chemistry causes the messages to become scrambled. When this happens the neurons fire off faster than usual and in bursts. It's this disturbed activity that triggers off a seizure.

During a seizure people may black out or experience a number of unusual sensations or movements. The whole thing usually only lasts a matter of seconds or minutes, after which the brain cells return to normal.

Epilepsy can affect anyone, at any age and from any walk of life. Boys and men tend to be slightly more prone than girls and women - though no one really knows why. Many of those who develop epilepsy start having seizures during childhood, but it can develop at any age.

Types

There are over 40 types of seizure, ranging from seizures which can go totally unnoticed by other people right through to the classic tonic-clonic seizure - the one which most people think of when they hear the word ‘epilepsy’. This potential for confusion is one of the factors that can make diagnosing epilepsy so difficult.

The two main different types of seizure are partial and generalised. Partial seizures involve part of the brain, while generalised seizures involve the whole brain. Just to complicate things, partial seizures can become generalised seizures if the epileptic activity spreads to the whole brain.

Partial seizures

Simple partial
Occurs in just part of the brain - the type of symptoms depend on the area of the brain involved. Symptoms include one or more of the following: twitching, numbness, sweating, dizziness, nausea, disturbances to hearing, vision, smell or taste, strong déja vu etc. These symptoms last for several seconds and then go away. The person remains fully aware. These seizures often progress to other types of seizure and can therefore act as a warning or 'aura'.

Complex partial
This common form of seizure includes temporal lobe epilepsy and psychomotor seizures. Poeople may behave strangely - plucking at their clothes, smacking lips, swallowing repeatedly or wandering around as if drunk - these actions are called automatisms. Other symptoms are similar to simple partial seizures but people may not remember them afterwards. People are not aware of their surroundings or of what they are doing.

Sleep seizures
Some people only experience seizures during their sleep. They can often be missed if nobody witnesses them. People may find this type of seizure less troublesome than those occurring during the day.

Generalised seizures

Tonic-clonic
The most common sort of generalised seizure - used to be known as ‘Grand mal’. Tonic phase - The muscles contract, the body stiffens and then - Clonic phase - jerks uncontrollably. People may let out a cry as air is forced out of the lungs and the lips may go blue due to lack of oxygen. People lose consciousness - when they come round they cannot remember anything. They will need time to recover - from minutes to, in some, hours.

Absence
This generalised seizure is literally an absence - a momentary lapse in awareness - used to be called "Petit Mal’. More common in children and teenagers. People stop what they are doing, stare, blink or look vague for a few seconds before carrying on with what they were doing. Onlookers may think they were just daydreaming or may not notice.

Other generalised seizures
Sometimes, the activity that starts as a simple partial or complex seizure can spread to the whole brain resulting in a tonic-clonic seizure. This is known as a secondary generalised seizure. Often the person will experience the simple partial seizure as an 'aura' or warning but sometimes the spread of epileptic activity can be so quick that the person appears to go straight into a tonic-clonic seizure. This can cause problems with diagnosis of the seizure type until the necessary tests are done and the specialist can see where the activity first occurs.

Other generalised seizures include atonic seizures (all muscle tone is lost and the person simply drops), tonic seizures (the body stiffens and the person will fall over if unsupported) and myoclonic seizures which cause brief forceful jerks.

Non-Epileptic Attack Disorder
Not all seizures are epileptic in origin. This is why, when making an initial diagnosis doctors will conduct various tests to rule out other causes. People with epilepsy can experience non-epileptic seizures as well.

Non-epileptic seizures are also sometimes referred to as pseudo-epileptic seizures, pseudoseizures, psychogenic seizures or Non-Epileptic Attack Disorder. These seizures are identical to epileptic seizures, but the difference is that they are not epileptic in nature.

Non-epileptic seizures can be symptoms of various psychological factors, specific to the person concerned. The management of non-epileptic seizures will therefore need to be considered on an individual basis and the options discussed with the epilepsy specialist.

Causes

Sometimes the reason epilepsy develops is obvious: brain damage caused by a difficult birth; a severe blow to the head; a stroke that starves the brain of oxygen; or an infection of the brain such as meningitis. In some people the tendency to have seizures runs in the family. It's not epilepsy itself which is inherited but a low trigger point or 'seizure threshold'. This leads the brain cells to change their behaviour in circumstances that wouldn't cause a seizure in other people. Very occasionally the cause is a brain tumour. But for most - six out of 10, in fact - the exact cause is a mystery.

Some people can pinpoint certain factors which spark seizures off. These include:

Further information

Acknowledgements: This section has been developed with the help of Epilepsy Action.

[1] Epilepsy Action (n.d.) What is epilepsy? [accessed 04/02/08].