Electroencephalogram Health Dictionary

(See also FIT; SEIZURE.) Epilepsy is the name given to any condition in which a person suffers repeated ?ts or seizures. It is present in one in 200 (0·5 per cent) of the population and up to 5 per cent of all children will have had a ?t by the age of 12, although most of these are harmless accompaniments of an acute feverish illness.

It is a recurrent and paroxysmal disorder starting suddenly and ceasing spontaneously due to occasional sudden excessive rapid and local discharge of the nerve cells in the grey matter (cortex) of the BRAIN. Epilepsy always arises in this way from the brain, but its origin is often of microscopic size. It is diagnosed by the clinical symptoms based on the observations of witnesses. Its cause can sometimes be established by laboratory tests, and brain scanning. Fits can be the ?rst sign of a tumour, or follow a stroke, brain injury or infection, but in the large majority no underlying cause is found – so-called idiopathic epilepsy.

A single epileptic ?t is not epilepsy. Of those people who have a single seizure, a signi?cant minority (20 per cent) have no further attacks.

Major (generalised) seizures have a sudden, often unprovoked onset; the patient emits a cry, then falls to the ground, rigid, blue, and then twitching or jerking both sides of the body: the tonic-clonic convulsion. Drowsiness and confusion may last for some hours after recovering consciousness. Some experience a momentary warning (AURA): a smell, or sensation in the head or abdomen, vision, or déjà vu.

Partial seizures: focal motor (Jacksonian) begin with twitching of the angle of the mouth, the thumb, or the big toe. If the seizure discharge then spreads, the twitching or jerking spreads gradually through the limbs. Consciousness is preserved unless the seizure spreads to produce a secondary generalised ?t. In some attacks the eyes and head may turn, the arm may rise, and the body may turn, while some patients feel tingling in the limbs.

Complex partial seizures (temporal lobe epilepsy) The patient usually appears blank, vacant and may be unable to talk, or may mumble or chatter – though later they often have no memory of this period. They may be able to carry out complex tasks, taking o? gloves or clothes, and may smack their lips or rub repeatedly on one limb (automatisms). A sense of strangeness supervenes: unreality, or a feeling of having experienced it all before (déja vu). There may be a sense of panic. Strange unpleasant smells and tastes are olfactory and gustatory hallucinations. The visual hallucinations evoke complex scenes. An initial rising sense of warmth or discomfort in the stomach, or ‘speeding-up’ of thoughts are common psychomotor symptoms. All these strange symptoms are brief, disappearing within a few seconds or up to 3–4 minutes.

Minor seizures (petit mal) Attacks start in childhood. They last a few seconds. The child ceases what he or she is doing, stares, looks a little pale, and may ?utter the eyelids. The head may drop forwards. Attacks are commonly provoked by overbreathing. The child and parents may be unaware of the attacks

– ‘just daydreaming’. Major ?ts develop in one-third of subjects. By contrast with other types of epilepsy, the ELECTROENCEPHALOGRAM (EEG) is diagnostic.

Precautions Children with epilepsy should take normal school exercises and games, and can swim under supervision. Adults must avoid working at heights, with exposed dangerous machinery, and driving vehicles on public roads. Current legislation allows driving after two years of complete freedom from attacks during waking hours; those who for more than three years have had a history of attacks only while asleep may also drive.

Treatment identi?es, and avoids where possible, any factors (such as shortage of sleep or excessive ?uids) which aggravate or trigger attacks. If ?ts are very infrequent, treatment may not be recommended. However, frequent ?ts may be embarassing, may cause injury or may cause long-term brain damage so treatment is advisable. Anti-epileptic drugs are usually necessary for several years under medical supervision. Carbamazepine and sodium valproate are the most frequently prescribed. The dose is governed by the degree of control of ?ts and sometimes drug levels can be monitored by blood tests to check on dosage. Strict adherence to the drug schedule gives a reasonable chance of total suppression of ?ts, especially in younger patients whose ?ts have started recently. The table summarises anticonvulsant drugs in use. Interactions can occur between anti-epileptics and, if drug treatment is changed, the patient needs careful monitoring. In particular, abrupt withdrawal of a drug should be avoided as this may precipitate severe rebound seizures.

Indications First-choice drugs: Ethosuximide PM, JME Phenobarbitone M, P Phenytoin M, P, CP Carbamazepine M, P, CP Valproate M, PM, JME Second-line drugs: Primidone M, P, CP Clobazam M, CP Vigabatrin M, P, CP Lamotrigine M, P, CP Gabapentin M, P, CP Topirimate P

M = major generalised tonic-clonic; P = partial or focal; CP = complex partial (temporal lobe); PM = petit mal; JME = juvenile myoclonic epilepsy.

Anticonvulsant drugs

As all anticonvulsant drugs have an e?ect on the brain, it is not surprising that there may be side-effects, especially inolving alertness or behaviour. In each case careful assessment is necessary for doctor and patient to agree on the best compromise between stopping ?ts and avoiding ill-effects of medication.

Patients who have an epileptic seizure should not be restrained or have a gag or anything else placed in their mouths; nor should they be moved unless in danger of further injury. Any tight clothing around the neck should be loosened and, when the seizure has passed, the person should be placed in the recovery position to facilitate a return to consciousness (see APPENDIX 1: BASIC FIRST AID).

Patients with epilepsy and their relatives can obtain further advice and information from the British Epilepsy Association or Epilepsy Action Scotland.... epilepsy

Abnormal electrical waves observed in the electroencephalogram (see ELECTROENCEPHALOGRAPHY (EEG)). The frequency of the normal alpha waves is 10 per second; that of the delta waves is 7 or fewer per second. They occur in the region of tumours of the brain, and in the brains of patients with EPILEPSY.... delta waves

In the BRAIN there is a regular, rhythmical change of electric potential, due to the rhythmic discharge of energy by nerve cells. These changes can be recorded graphically and the ‘brain waves’ examined – a procedure introduced to medicine in the 1920s. These records

– electroencephalograms – are useful in DIAGNOSIS: for example, the abnormal electroencephalogram occurring in EPILEPSY is characteristic of this disease. The normal waves, known as alpha waves, occur with a frequency of 10 per second. Abnormal waves, with a frequency of 7 or fewer per second, are known as delta waves and occur in the region of cerebral tumours and in the brains of epileptics. An electroencephalogram can assess whether an individual is awake, alert or asleep. It may also be used during surgery to monitor the depth of unconsciousness in anaesthetised patients.... electroencephalography (eeg)

Also known as salaam attacks, these are a rare but serious type of EPILEPSY, usually starting in the ?rst eight months of life. The spasms are short and occur as involuntary ?exing of the neck, arms, trunk and legs. They may occur several times a day. If the baby is sitting, it may collapse into a ‘salaam’ position; more usually there is a simple body jerk, sometimes accompanied by a sudden cry. An electroencephalogram (see ELECTROENCEPHALOGRAPHY (EEG)) shows a picture of totally disorganised electrical activity called hypsarrhythmia. The condition results from any one of many brain injuries, infections or metabolic insults that may have occurred before, during, or in the ?rst few months after birth. Its importance is that in most cases, the baby’s development is seriously affected such that they are likely to be left with a profound learning disability. Consequently, prompt diagnosis is important. Treatment is with CORTICOSTEROIDS or with certain anti-convulsants – the hope being that prompt and aggressive treatment might prevent further brain damage leading to learning disability.... infantile spasms

n. a state of natural unconsciousness, during which the brain’s activity is not apparent (apart from the continued maintenance of basic bodily functions, such as breathing) but can be detected by means of an electroencephalogram (EEG). Different stages of sleep are recognized by different EEG wave patterns. Drowsiness is marked by short irregular waves; as sleep deepens the waves become slower, larger, and more irregular. This slow-wave sleep is periodically interrupted by episodes of paradoxical, or *REM (rapid-eye-movement), sleep, when the EEG pattern is similar to that of an awake and alert person. Dreaming occurs during REM sleep. The two states of sleep alternate in cycles of from 30 to 90 minutes, REM sleep constituting about a quarter of the total sleeping time.... sleep

see enhanced external counterpulsation.

EEG (electroencephalogram) see electroencephalography.... eecp

n. the technique for recording the electrical activity from different parts of the brain and converting it into a tracing called an electroencephalogram (EEG). The machine that records this activity is known as an encephalograph. The pattern of the EEG reflects the state of the patient’s brain and his level of consciousness in a characteristic manner. Electroencephalography is mostly used in the diagnosis and management of epilepsy and sleep disorders.... electroencephalography

n. the branch of psychology that records physiological measurements, such as the electrical resistance of the skin, the heart rate, the size of the pupil, and the electroencephalogram, and relates them to psychological events. —psychophysiological adj.... psychophysiology