In simple terms, epileptic seizures happen when changes in brain chemistry cause the complex electrical messages travelling between our billions of nerve cells to become scrambled. Some people lose consciousness, others show hardly any symptoms. But after a matter of minutes or even seconds, the brain cells are back to normal and seizure is over.

There are over 40 different types of seizure, affecting different individuals in very different ways. They fall into two categories; “generalized” (involving the whole brain) or “partial” (originating in one part of the brain).

“Tonic-clonic” seizures (once known as “grand mal”) are the most common of the generalized types. In this kind of epileptic “fit”, you may fall down unconscious, your body stiffening (the tonic phase) and then jerking uncontrollably (the clonic phase). During the seizure you may make strange sounds, dribble, bit your tongue or be incontinent. It only lasts for a few minutes but, while the person having the seizure can’t remember what has happened, it can be distressing to witness.

Another kind of generalized attack is the “absence seizure”. Once known as “petit mal”, this is a lapse in awareness in which you may stop what you are doing, stare or look as if you are daydreaming for a few seconds – before carrying on as usual. It is more common in children (especially girls) and in teenagers than in adults. Although some people may have many “absences“ a day; they can be hard to spot and diagnose. Generalized seizures also include “atonic” seizures or “drop attacks”, in which the person suddenly falls down; and “myoclonic” seizures, in which the muscles jerk briefly.

“Partial” seizures may be “simple”, with a range of symptoms including jerking, pins and needles, dizziness and strange distortions of sensation – such as déjà vu, or things seeming abnormally large or small. These symptoms are sometimes known as an “aura” and may be warning of a more generalized seizure to come.

Alternatively, “partial” seizures may be “complex”, causing people to act oddly – for instance swallowing repeatedly or appearing drunk. These behaviours are called “automatisms” and the person having the seizure is unaware of what is going on.

Epilepsy can affect anyone, and at any age. For most people there is no clear cause, but for the minority some kind of damage to the brain following a stroke, a blow to the head, an infection (such as meningitis) or a difficult birth may be to blame. Sometimes a tendency to seizures can be inherited. There are also common “trigger factors” – alcohol, stress, fever, lack of sleep and (in women) changing hormones, for example. And although it remains a controversial point, some people believe that certain foods can trigger seizures.