About Seizures
About Seizures
Many people in the community have seizures. 1 in 20 (5%) children will have a seizure of some form during childhood. About 1 in 200 (0.5%) children have epilepsy ie. a neurological condition in which the child has a predisposition to recurrent, unprovoked seizures.
Epileptic seizures occur when there is a momentary 'imbalance' within electrical and chemical circuits in the brain, such that groups of brain cells fire off in an abnormal fashion. This may create a temporary disturbance in the way the brain controls awareness and responsiveness may cause unusual sensations or abnormal movements and postures. What happens during a seizure reflects what parts of the brain are involved.
There are many different types of seizures. The following describes the classification of seizure types from the International League Against Epilepsy ILAE, 1981. A major distinction that doctors try to make is between partial (focal) seizures, where the seizure activity arises in a localised part of the brain (usually on one side), and generalised seizures, where epileptic activity begins all over the brain simultaneously.
Partial (focal) seizures
Partial (focal) seizures occur when the seizure activity arises in a localised part of the brain, usually on one side, and consciousness may or may not be impaired. The manifestations of the seizure depend on the part of the brain involved with the abnormal electrical discharge. Partial seizures are classified according to whether there is impairment of consciousness or not.
- Simple partial seizures
Simple partial seizures arise in parts of the brain not responsible for maintaining consciousness, typically the movement or sensory areas. Consciousness is NOT impaired and the effects of the seizure relate to the part of the brain involved. If the site of origin is the motor area of the brain, bodily movements may be abnormal (e.g. limp, stiff, jerking). If sensory areas of the brain are involved the person may report experiences such as tingling or numbness, changes to what they see, hear or smell, or very unusual feelings that may be hard to describe. Young children might have difficulty describing such sensations or may be frightened by these.
- Complex partial seizures
Complex partial seizures arise in parts of the brain responsible for maintaining awareness, responsiveness and memory, typically parts of the temporal and frontal lobes. Consciousness is lost and the person may appear dazed or unaware of their surroundings. Sometimes the person experiences a warning sensation or ìauraî before they lose awareness , essentially the simple partial phase of the seizure. Behaviour during a complex partial seizure relates to the site of origin and spread of the seizure. Often the person's actions are clumsy and they will not respond normally to questions and commands. Behaviour may be confused and they may exhibit automatic movements and behaviours e.g. picking at clothing, picking up objects, chewing and swallowing, trying to stand or run, appearing afraid and struggling with restraint. Colour change, wetting and vomiting can occur in complex partial seizures.
Following the seizure the person may remain confused for a prolonged period and may not be able to speak, see, or hear if these parts of the brain were involved. The person has no memory of what occurred during the complex partial phase of the seizure and often needs to sleep.
- Partial seizures becoming secondarily generalised
Seizures which begin as simple or complex partial seizures may progress due to spread of epileptic activity all over one or both sides of the brain leading to a secondarily generalised seizure. This part of the seizure looks like a generalised tonic clonic seizure.
Generalised seizures
Generalised seizures occur when epileptic activity begins all over the brain simultaneously and consciousness is always impaired in generalised seizures.
- Tonic-clonic seizures
Tonic-clonic seizures (sometimes called 'grand mal') produce sudden loss of consciousness, with the person commonly falling to the ground, followed by stiffening (tonic) and then rhythmic jerking (clonic) of the muscles. Shallow or ìjerkyî breathing, bluish tinge of the skin and lips, drooling of saliva and often loss of bladder or bowel control generally occur. The seizures usually last a couple of minutes and normal breathing and consciousness then returns. The person is tired following the seizure and may be confused. There is no aura prior to a tonic clonic seizure.
- Absence seizures
Absence seizures (sometimes called 'petit mal') produce a brief cessation of activity and loss of consciousness, usually lasting 5-30 seconds. Often the momentary blank stare is accompanied by subtle eye blinking and mouthing or chewing movements. Awareness returns quickly and the person continues with the previous activity. Falling and jerking do not occur in typical absences.
- Myoclonic seizures
Myoclonic seizures are sudden and brief muscle contractions that may occur singly, repeatedly or continuosly. They may involve the whole body in a massive jerk or spasm, or may only involve individual limbs or muscle groups. If they involve the arms they may cause the person to spill what they were holding. If they involve the legs or body the person may fall.
- Tonic seizures
Tonic seizures are characterised by generalised muscle stiffening, lasting 1-10 seconds. Associated features include increased pulse, brief cessation of breathing, flushed face, bluish skin discolouration and drooling. When tonic seizures occur suddenly with the child awake they may fall violently to the ground and injure themselves. Tonic seizures often occur during sleep. Fortunately, tonic seizures are rare and usually only occur in severe forms of epilepsy.
- Atonic seizures
Atonic seizures produce a sudden loss of muscle tone which, if brief, may only involve the head dropping forward ('head nods'), but may cause sudden collapse and falling ('drop attacks').
From these descriptions, it can be appreciated that the exact type of seizure may be difficult for a witness to determine. For example, a seizure with stopping and staring could be a complex partial seizure or an absence seizure. A large, convulsive seizure (grand mal) may be a generalised tonic-clonic seizure, myoclonic seizure, tonic seizure or partial seizure which became secondarily generalised. A sudden fall to the ground ('drop attack') can occur with myoclonic, tonic or atonic seizures or a partial seizure involving the movement areas. Determination of the exact type of seizure is important and is obtained from patient and observer descriptions, home video recordings, EEG testing and sometimes video EEG monitoring.
It is also important to remember that many episodic behaviours and disorders in children can mimic epilepsy, including breath holding spells, normal sleep jerks, day dreaming, fainting, migraine, heart and gastrointestinal problems, and psychological problems.