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Reviewed by Dr Anthony Marson, lecturer in neurology
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What is epilepsy?
Epilepsy is a
condition in which people have seizures or 'epileptic attacks'.
There are many different types of attacks, ranging from minor
symptoms noticed only by the affected person, to convulsions, the most easily
recognised type of epileptic attack.
Important facts about the attacks are:
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where in the brain they start
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how they spread
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how much of the brain is affected.
Is it possible to divide the attacks into groups?
Epileptic attacks are divided into two main groups.
Partial Attacks
Partial (focal) attacks
These attacks start in a specific part of the white matter
of the brain (cerebral cortex). The starting point of the abnormal electrical
activity is called the 'focus'. During attacks, they can either stay
there, spread to the surrounding areas or eventually spread to involve the
whole brain.
It is most important to determine the very first symptoms of
an attack, as this will indicate where the focus is.
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If the person has twitches in the right hand, the focus
must be in the left half of the brain. In general, the left side of the brain
controls the right side of the body.
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If the attack starts with a flash of light, the focus is in
the area at the back of the brain (the occipital lobe) that deals with
vision.
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If there are hallucinatory experiences, which can be the
awareness of a strange taste or smell or a sensation of déja vu, the attack
comes from a temporal lobe situated at the sides of the brain.
Simple partial attacks
Are characterised by the sufferer being alert, awake and
knowing what is going on. These types of attacks are often called auras (from
Greek = breath), especially when they progress to more severe
attacks.
It is an advantage for the person to be able to communicate
with those around them during the attack and, for instance, be able to tell
people that the attack is not dangerous and that it will stop by itself.
Complex partial attacks
In this type of attack, the person loses awareness and is,
therefore, unable to communicate or remember what happened. It is often
preceded by a simple partial attack.
Because awareness is lost the person may stare into space or
do automatic things like make chewing or lip-smacking movements, pick at
clothing or nearby objects or get up and wander around in a confused manner.
Attacks typically last a few minutes.
These attacks can be embarrassing and socially disabling.
Most complex partial attacks start in the temporal lobe.
They can be difficult to control with medication and are sometimes cured by
surgery.
Secondary generalised attacks
When the attack spreads to involve the whole brain, the victim
will have what is called a secondary generalised tonic clonic seizure. This is
also known as a convulsion or grand mal attack.
Doctors currently prefer to use the term tonic clonic seizure
as it is descriptive of what happens during the attack: first the person goes
stiff (tonic) and then shakes (clonic).
Breathing may stop during the attack and the person's
skin may turn blue.
Shaking typically lasts one to two minutes, but can go on for
longer. When the shaking stops, it may be impossible to rouse the person for a
few minutes.
During attacks, people may be injured by falling to the floor.
They may bite their tongue or become incontinent.
During a tonic clonic seizure, it is important to remove all
sharp or heavy objects near the person, and to put them on his or her side in
the recovery position. Nothing should ever be put in the mouth of someone
having a tonic clonic seizure.
Generalised attacks
In this type of attack there is no focus. Generalised
seizures occur due to abnormal electrical activity occurring spontaneously on
both sides of the brain.
Many of the epilepsies that cause generalised seizures are
thought to have a genetic basis. There are a number of types of generalised
attacks
Generalised tonic-clonic seizure
As well as occurring in people with a focal epilepsy, those
with a generalised epilepsy can have tonic clonic seizures.
It is very important for doctors to be able to distinguish
between tonic clonic seizures with a generalised onset and those with a partial
onset, as the treatment and investigation differs.
Tonic clonic seizures with a generalised onset will occur
without warning.
For tonic clonic seizures with a focal onset, patient will
usually get a warning (aura) and may also be experiencing simple partial or
complex partial attacks.
Absence seizures
In this type of attack, the person briefly loses awareness
and stares into space (usually for less than 10 seconds) and makes an immediate
recovery. During the attack the patient may blink their eyes.
Sometimes absences can occur with great frequency, up to 100
times a day, and therefore it may be a serious problem, for instance when the
person is in school and their condition goes unrecognised.
Other generalised types of attacks
Myoclonic: short, symmetrical twitches of
the arms and legs - similar to those which most people experience as they fall
asleep. Myoclonic seizures usually occur in the morning within an hour or so of
waking.
Atonic attacks: in this type of attack,
the muscles suddenly relax causing the person to fall to the ground. Often
injuries to the head or face result.
What are epilepsy syndromes?
So far, we have concentrated on different types of epileptic
attacks. It is important to remember that epilepsy is not a single condition
but a group of conditions.
In order to get a better understanding of epilepsy, for example
cause and prognosis, the different types of epilepsy have been categorised into
syndromes. In other words, patients who are similar with respect to the
following are grouped together:
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types of attacks
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age at first attack
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EEG changes
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family history
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CT or
MRI scan
abnormalities.
Examples of partial epilepsy syndromes
It is important to be able to categorise, where possible, the
epilepsy syndrome that the patient has, as this will influence the choice of
treatment and the eventual outcome.
Temporal, frontal, parietal or occipital lobe epilepsy lobe
epilepsy
The majority of the partial epilepsy syndromes are named
according to the site of the focus, eg temporal lobe epilepsy. If a lesion has
been found on MRI/CT (eg congenital abnormality or tumour) then the epilepsy is
referred to as symptomatic.
If no lesion is found then the epilepsy is referred to as
cryptogenic. For the symptomatic epilepsies, prognosis depends largely upon the
pathology that the epilepsy is symptomatic of.
Rolandic epilepsy
This is termed an idiopathic partial epilepsy, and may well be
largely genetically determined.
In this condition, there are usually localised abnormal
muscle movements (focal motor attacks) affecting one side of the face, usually
at night, accompanied by guttural noises and over production of
saliva.
The victim is awake during the attack which might progress to
a secondary generalised tonic clonic seizure. The electroencephalogram (EEG)
shows characteristic focal spikes in the motor area. The prognosis is always
good. Most people have only a few attacks, and they stop by the age of 15. Some
degree of reading difficulty may occur, but intelligence is normal.
Examples of generalised epilepsy syndromes
Childhood and juvenile absence epilepsy
These are two of the generalised epilepsies and are thought to
be genetic in origin.
In these two syndromes, absence seizures are experienced. Not
surprisingly, childhood absence epilepsy has its onset in childhood, and
juvenile absence epilepsy in the teenage years. Both are accompanied by
characteristic EEG changes, 'spike waves' in the tracing occurring
about three times per second.
Around 70 to 80 per cent gain control of the attacks on
treatment, which can usually be withdrawn in the later teenage years without
seizure recurrence.
Some children will go on to develop other generalised seizure
types. They usually have normal intelligence.
Juvenile myoclonic epilepsy
This is another idiopathic generalised epilepsy that typically
starts in the teenage years.
It is thought to represent 5 to 10 per cent of all cases among
young people and adults. Patients experience myoclonic seizure, particularly
within an hour or so of waking. The majority will also experience tonic clonic
seizures, and about a third will experience absence seizures. The EEG will
usually show photosensitivity, ie extra activity when looking at the light.
Seizures are often precipitated by sleep deprivation or alcohol.
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Based on a text by Dr. Jørgen Alving, consultant
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Last updated 03.08.2005
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