UNDERSTANDING EPILEPSY
Types of seizures
Approximately 30 percent of seizures can’t be classified, which probably reflects the complexity of brain function, but where they can be classified they can be divided into two main groups: partial or focal and generalised.
Partial or focal seizures start in one part of the brain (that is at a focal point in the brain) and, affect that part of the body controlled by that part of the brain. Generalised seizures involve the whole brain and therefore involve the whole body.
Classification of unprovoked recurring seizures or epilepsy
It is not uncommon for people with epilepsy to experience more than one seizure type.
Figure 1: Epilepsy syndromes are named in reference to the lobe or that part of the brain in which the seizure activity originates eg. temporal lobe epilepsy.
Partial or Focal seizures
Simple partial seizures
Simple partial seizures are localised seizures, affecting only one part of the brain. The symptoms the person experiences will depend on the function that part of the brain controls. The seizure may involve the involuntary movement or stiffening of a limb, feelings of déjà vu or fear, an unpleasant smell or taste, or sensations in the stomach such as ‘butterflies’ or nausea. The person remains fully conscious throughout the seizure. The seizure usually lasts for less than a minute and then the person recovers. These seizures are often experienced subjectively - an onlooker may not know the seizure is occurring unless the person discloses they are having a seizure.
Figure 2. Partial or focal seizures originate in one part of the brain.
Complex partial seizures
This type of seizure also affects only one part of the brain but the person’s conscious state is altered. These seizures sometimes involve staring and can be confused with absence seizures, but usually the staring lasts longer and the person is confused aferwards. The person may often appear confused and dazed and may do strange actions like fiddle with their clothes, make chewing movements or unusual sounds, turn in circles, wander or even run. The seizure usually lasts for one to two minutes but the person may be confused and drowsy for some minutes to several hours afterwards. People sometimes unknowingly become quite irritable or aggressive if restrained during or immediately after the seizure.
Secondarily generalised seizures
Secondarily generalised seizures are so called because they only become generalised (where the activity spreads to both sides of the brain) after the partial seizure has begun. These occur when a burst of electrical activity in a focal area of the brain (the partial seizure) spreads throughout the brain.
This event can be so brief that the person does not recall or recognise it; an onlooker may only notice the tonic clonic seizure and not be aware a partial seizure preceded the convulsion. The generalised convulsive stage of these seizures usually lasts no more than 1-3 minutes, similar to primary generalised seizures. Secondarily generalised seizures occur in more than 30 percent of people with partial seizures.
Figure 3. Seizures that begin in one part of the brain [primary focal seizures] and spread to involve the whole brain are called secondarily generalised seizures.
Generalised seizures
There are many types of generalised seizures, some convulsive (involving body stiffening and jerking) and others non-convulsive.
Figure 4.Seizures that immediately involve the whole brain are called primary generalised seizures
Absence seizures (previously known as petit mal)
This is a brief, non-convulsive event, usually occurring in the young and involves the whole brain. With this type of seizure, the person’s awareness and responsiveness are impaired. They simply stare, their eyes might roll back or their eyelids flutter and in some cases there may be hand movements.
It can be difficult to tell the difference between absence seizures and daydreaming. However, absence seizures start suddenly, cannot be interrupted, last a few seconds, then stop suddenly and the person resumes what they were doing. Although these seizures usually last less than 10 seconds, they can occur many times daily and thus be very disruptive to learning.
Myoclonic seizures
Myoclonic seizures are brief, shock-like jerks of a muscle or a group of muscles, usually lasting no more than a second or two, which at times can result in a fall. They can happen in isolation or in clusters and often occur soon after waking or before going to bed when the person is tired. These seizures are so brief it is difficult to recognise the person's consciousness has been affected.
Tonic seizures
In tonic seizures the body’s muscle tone is greatly increased and the body, arms, or legs suddenly stiffen. These seizures most often occur in clusters during sleep but can occur in isolation. Seizures can occur when the person is awake and if the person is standing they will fall quite heavily, often injuring their head. Seizure duration is usually less than 20 seconds. Protective headwear is advisable to minimise constant injury.
Atonic seizures
Atonic seizures cause a sudden loss or decrease of normal muscle tone and the person falls to the ground if they are standing. Seizures usually last less than 15 seconds. Often called 'drop attacks' these seizures can cause head or facial injury; wearing protective headwear may minimise injury.
Tonic clonic seizures (previously known as grand mal)
Tonic clonic seizures are generalised seizures involving the whole brain. It is the seizure type most people think of when they think of epilepsy. Some people may experience an ‘aura’ such as a feeling of déjà vu, a strange feeling in the stomach or a strange taste or smell, just before the seizure begins. The aura itself is a simple partial seizure and this information is vital to give to the diagnosing doctor.
During a tonic clonic seizure a person’s body stiffens and they fall to the ground unconscious if they are standing (the tonic phase). Their limbs then begin to jerk in strong, rhythmic movements (the clonic phase). The person may dribble from the mouth, go blue or red in the face, or lose control of their bladder and/or bowel. These seizures are often described as convulsive seizures. They may have bitten their tongue and may have blood in their saliva.
Although this type of seizure can be frightening to watch, the seizure itself is unlikely to harm the person having the seizure. They may, however, vomit or bite their tongue and can sometimes injure themselves if they hit nearby objects as they fall or convulse.
The seizure normally stops after a few minutes. At this time the person is usually confused and drowsy. They may have a headache and want to sleep. This drowsiness can last for a number of hours or occasionally longer. People often complain of muscle aches after these seizures.
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