It might be the smell of burnt rubber, or the sound of music playing, or a feeling of déjà vu that marks the start of an epileptic episode. What is this warning sign of epilepsy and what can it tell us?
Many seizures start with a warning symptom known as an epileptic aura. The medical term “aura” should not be confused with the mystical aura that supposedly surrounds a living body, although both descriptions come from the Greek for “breeze” or “breath”.
In some circumstances the aura itself may be the entire extent of the epileptic episode, in others there is progression to a full-blown seizure, according to neurologist Dr Andrew Rose-Innes.
People experience widely varied auras. For some, the aura is emotional: a sudden feeling of anxiety, tension or fear. For others, it takes the form of a specific sensation that only they can feel, such as cooling or warming, a particular taste, or a sound (sometimes musical). In some cases the aura appears as a particular odour, often unpleasant, such as burning rubber.
The aura can also manifest in certain people as a feeling of déjà vu – where people or places appear strangely familiar; or its opposite, jamais vu – where people or situations that should be familiar, appear strange. Frequently, the aura is something that the person finds impossible to describe – simply a “funny feeling”.
Experienced epileptics learn to recognise the aura, and can prepare themselves for the seizure – by lying down in a safe place, for example.
"For me, it was a smell of bananas. When I smelt that, I'd just sit down wherever I was before the blackness came," says Vusi Mahlasela, one of South Africa's most gifted and respected musicians.
What the aura can tell us
The presence of an aura implies that the seizure starts in one part of the brain, and is therefore a "partial" seizure. This may go on to become a generalised convulsion. Sometimes this is so rapid that the aura is not apparent. Seizures that seem to involve both hemispheres of the brain simultaneously, do not start with a true aura.
The quality of the aura will indicate which particular region of the brain is being abnormally activated. For example, a hallucination of smell is most likely to originate in one of the temporal lobes, whereas involuntary twitching of one hand (not really an aura as it is not a sensation, but having exactly the same significance) will suggest a focus in the opposite frontal lobe.
Information of this sort will prompt a careful search in these parts of the brain for underlying lesions that might be causing the seizures in the first place. Also, the fact that the seizure is a partial one will mean that certain medications (and in some cases, surgery) are more likely to be effective than in a primarily generalised seizure, where an aura will not be present.
What you should do when you feel an aura coming on
Since awareness can be lost very rapidly, and in some cases without warning, those prone to seizures need to be very circumspect about certain activities. Having a seizure while driving, swimming, bathing alone or using machinery, for example, has the potential for harm to self or others.
If you are engaged in one of these activities when you experience your aura, get yourself out of harms way immediately. Park next to the road, get out of the pool or bath, put the machine away, and sit or lie down in a safe place.
What you should do when somebody suffers an epileptic fit
Epileptic seizures are generally brief (usually seconds to minutes), but usually alter awareness, and may cause complete loss of consciousness.
If this happens, you should:
Don't try to force anything, not even a soft object or your fingers, into the person’s mouth. The teeth or object may break and fragments may be inhaled or you may even get bitten;
Protect the person from injury. Clear the area of furniture or other objects that may cause injury. Cradle the head with a pillow if it is on a hard surface, but don't restrain the person's movements.
Turn the person onto one side with the head down. This allows drainage of saliva and prevents inhalation of vomit.
The vast majority of seizures will end spontaneously after a minute or two, and no specific treatment is necessary.
Occasionally, seizures do not stop, a situation known as status epilepticus. This is a medical emergency, has a high mortality, and requires immediate medical attention. Get the person to a hospital or doctor as soon as possible, says Dr Rose-Innes.