Generalised Seizures
This describes an event where the abnormal electrical activity affects all or most of the brain from the outset. Consequently, the symptoms tend to be general and involve most of the body.
There are 6 types of generalized seizures -:
- Tonic-clonic (previously called grand mal or generalized convulsion). These may be either primary or secondary in nature.
- Absence seizures (previously called petit mal)
- Myoclonic seizures or Juvenile myoclonic seizures
- Tonic seizures
- Clonic seizures
- Atonic seizures
Tonic-Clonic seizures
This type of seizure is the commonest seizure event accounting for about 60% of all types. The seizure event may be preceded by a prodromal period, (period of precursor symptoms) which may manifest as a change in mood or behaviour and during which, the patient feels different, lasting hours or days. This is not part of the seizure itself.
They may or may not then experience an aura or vague warning, which is itself, part of the seizure and precedes the other manifestations. It may be a strange feeling in the stomach or a strange smell and can take many forms. In such cases the individual would normally be able to take steps to avoid danger.
However, the description of an aura is not commonly obtained in tonic-clonic seizures. This may be due to memory loss (retrograde amnesia) for events immediately preceding the seizure. Following the aura, if present, the child then goes rigid due to intense sustained muscular contractions and becomes unconscious. This is the tonic phase.
During this phase air is forced out of the lungs causing the individual to cry out or make a strange noise. The bladder also contracts and urinary and faecal incontinence may occur. The jaw muscles contract and the teeth clench together often with biting of the inside of the lips and the tongue. If the child is standing they may fall heavily to the ground and may sustain serious injury.
During the tonic phase breathing ceases and the child may begin to turn a blue colour (central cyanosis).
After a few moments the rigidity is periodically relaxed and the clonic phase begins. This phase is characterized by rhythmic jerking of the muscles causing the whole body to shake (convulse) uncontrollably. Frothing at the mouth often occurs. Breathing returns in the clonic phase but is erratic. This phase may last for a few seconds to several minutes. On average the entire event will last about 3-5 minutes.
The child will then gradually regain consciousness but is often dazed and confused (the post epileptic or post-ictal state). The child gradually regains consciousness but will be confused and disorientated for at least half an hour after regaining consciousness and may not recover full memory function for some time (hours).
They may also complain of a headache and feel terrible with the desire to lie down and sleep. In some cases the child may remain unresponsive following the seizure. In other cases they may become aggressive with disturbed behaviour. This post-ictal state may persist for several hours, or up to days following the seizure.
Afterwards, muscles are often sore and aching due to the intense contractions and the tongue, which has often been severely bitten, may be sore.
Tonic-clonic seizures may be subdivided into 2 main types -:
- Primary Generalised Epilepsy - This type of epilepsy invariably begins in childhood or adolescence. There is no structural abnormality of the brain to be found on investigation to account for the seizures and a genetic predisposition is likely. Prognosis is generally good with treatment.
- Secondary Generalised Epilepsy - This may arise from a partial seizure, which spreads out of its localized area to involve the entire brain, or it may be secondary to other causes such as drugs, metabolic disorders, head injury, etc. Such seizures are more difficult to control.
Absence Seizures
Absence seizures are another type of generalised epilepsy that invariably begins in childhood. There is no convulsion with this form of seizure. Activity ceases, and there is a brief (seconds only) loss of awareness. The child may stare and there may be some twitching of the eyelids. A few muscle jerks may occur. The child does not fall over. The attack is normally over in a few seconds, when normal activity is resumed. There is no post-ictal state.
Although attacks are brief, they can be frequent and may occur hundreds of times a day in young children interfering with behaviour and school performance.
Myoclonic Seizures
This is another type of generalized seizure. It is also known as juvenile myoclonic epilepsy. Myoclonic seizures describe isolated muscle jerking. This type of epilepsy begins in adolescence and is characterised by sudden muscular contractions usually on awakening. These normally affect one or both arms. There may be a brief period of loss of consciousness.
Patients with myoclonic seizures can get worse if put on the wrong medication, (such as carbamazepine). The prognosis is excellent with this form of epilepsy, but over 95% of cases will relapse if medication is stopped. A related syndrome is that of tonic-clonic seizures on awakening.
Tonic Seizures
Tonic seizures cause a brief loss of consciousness. The body becomes rigid and the person falls to the ground. There is no subsequent convulsion or clonic phase and the child regains consciousness. Injury may be sustained during the fall.
Clonic Seizures
Clonic seizures cause loss of consciousness with rhythmic muscular jerking. There is no preceding stiffness or rigidity.
Atonic Seizures
Atonic seizures cause a brief loss of consciousness with sudden loss of muscle tone so that the child falls to the ground.
