The main use of electroencephalography (EEG) is in the investigation of the epilepsies and the monitoring of cerebral function eg neonates/coma/encephalopathy/paralysed patients.
Use in epilepsy
- To support the clinical diagnosis of epilepsy on the basis of epileptiform abnormalities or recorded seizures.
- To help classify the epilepsy syndrome, (identified on the basis of age onset of seizures, the clinical seizure type(s), EEG and neuro-imaging findings).
The routine EEG is a twenty-minute recording, usually performed with activation procedures such as hyperventilation and photic stimulation.
A first routine EEG will identify abnormalities in about 50 per cent of children with epilepsy. If normal, a sleep EEG may be indicated to improve the detection of epileptiform abnormalities. A sleep EEG may be achieved spontaneously, by a period of sleep deprivation or by the administration of melatonin.
Use in monitoring cerebral function
The EEG can be used to assess the presence or absence of normal brain activity. This can be used to give an indication of cerebral dysfunction, particularly where neurological assessment is difficult, eg paralysed, coma, encephalopathy, or particularly in the neonates.
An EEG is normally indicated in the following situations:
- In children in whom epilepsy has been diagnosed clinically to help classify the epilepsy syndrome.
- To confirm the diagnosis of non-convulsive status.
- In a child who shows definite unexplained developmental plateau or regression, or with an apparent acquired impairment of speech and language function.
- In a comatose child on the Intensive Care Unit, a child with an encephalopathy, or in status epilepticus.
- In specific situations:
- To monitor the EEG response to treatment.
- The development of new seizure type(s) (eg West syndrome, non-convulsive status epilepticus and electrical status epilepiticus of sleep – ESES).
An EEG is not normally indicated in the following situations:
- In a child who has ‘funny turns’, dizzy spells, temper tantrums/outbursts of rage or strange behaviour.
- In a child with definite non-epileptic attacks, specifically syncopal episodes, reflex anoxic seizures or breathholding attacks.
- In a child with simple or complicated febrile seizures.
- In a child who has had only one brief and uncomplicated afebrile tonic/clonic seizure.
- In a child who has global developmental delay unless characteristic signs are sought to support a particular syndromic diagnosis (eg Angelman’s or Rett’s syndrome).
- In a child before an anti-epileptic drug is to be withdrawn.
- In a child with autism including those with autistic regression who do not have a history of seizures.
A repeat EEG may be considered in the following situations:
In a child with epilepsy:
- Where the diagnosis of non-convulsive status is suspected.
- To assess response to treatment (eg West syndrome, non-convulsive status).
- In the development of new seizure type(s), or clarification of syndrome.
A sleep EEG may be considered in the following situations:
- In a child in whom epilepsy has been diagnosed clinically and seizures persist and where a routine EEG has failed to show an abnormality.
- In a child with epilepsy who shows a global or focal deterioration or plateau in cognitive function.
- In a child who has not been diagnosed with epilepsy who shows a global or focal deterioration or plateau in cognitive function.
- In a child where a specific epilepsy syndrome diagnosis is suspected in which there are characteristic or particular sleep EEG findings.
- To assess response to treatment in a child with specific epilepsy syndrome (eg Landau-Kleffner, ESES).
- In the diagnosis of narcolepsy (a prolonged multiple sleep latency test is indicated).
If there is doubt about whether an EEG should be undertaken, or repeated, please discuss with a paediatric neurologist.
National Institute for Health and Clinical Excellence (NICE) (2004) Epilepsy in adults and children, CG20
. Viewed on: 01/07/2006
Markand ON (2003) Pearls, perils, and pitfalls in the use of the electroencephalogram
. Semin Neurol 23 (1): 7-46.
This guideline was written by the North Central London (NCL) Epilepsy Network.
Document control information Lead author(s)
NCL epilepsy network Document owner
Stewart Boyd, Consultant, Neurology Approved by
NCL epilepsy network First introduced:
1 July 2006
6 July 2012
6 July 2014