Patient guide · Neurophysiology
EEG (electroencephalogram), the brain-wave test for epilepsy, encephalopathy and sleep disorders.
An EEG records the electrical activity of the brain through scalp electrodes. Used to investigate seizures, encephalopathy, coma prognosis and sleep disorders. Modern options include standard EEG, sleep-deprived EEG, ambulatory EEG and video-EEG.
Key facts
- 01
Definition
A scalp-recording of the brain’s electrical activity.
- 02
Painless, 30–60 minutes
A comfortable, non-invasive test - no needles, no radiation.
- 03
Photic and hyperventilation
Standard provocations to uncover latent epileptiform activity.
- 04
Complements MRI
EEG shows electrical function; MRI shows structure - together they answer the epilepsy question.
- 05
Consultant neurophysiologist
Every trace reported by a consultant clinical neurophysiologist.
- 06
Ambulatory and video-EEG
Extended recording or video correlation for complex or infrequent events.
Preparation
From referral to report - what to expect, in order.
Seven steps, from the neurology consultation to the follow-up plan.
Phase 1 · Before the EEG
Consultation and preparation
Phase 2 · On the day
30–60 minutes in the department
Phase 3 · After
Report and follow-up
- 01
Before
Neurology consultation
A consultant neurology assessment establishes the clinical question the EEG needs to answer.
- 02
Before
Wash hair, no oil or conditioner
Clean, product-free hair ensures reliable electrode contact and a clean trace.
- 03
Before
Sleep-deprived if requested
For a sleep-deprived EEG, stay awake through the night beforehand to increase yield.
- 04
On the day
Scalp electrodes applied
Around 20 electrodes are positioned on the scalp with conductive paste - comfortable and reversible.
- 05
On the day
Recording during rest, photic and HV
Baseline recording, then photic (strobe) stimulation and three minutes of hyperventilation.
- 06
After
Report by neurophysiologist
A consultant clinical neurophysiologist reads the trace and issues a written report.
- 07
After
Neurology follow-up plan
Your neurologist explains the findings and sets the next diagnostic or treatment step.
What it shows
The patterns an EEG can capture.
EEG answers a specific question - is the brain’s electrical activity organised, disorganised, or actively seizing. These are the findings we see most.
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Epileptiform discharges
Spikes, sharp waves and spike-and-wave complexes that support an epilepsy diagnosis.
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Focal or generalised slowing
Regional or diffuse slow-wave activity pointing to focal lesion or diffuse dysfunction.
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Encephalopathy pattern
Diffuse background slowing and triphasic waves seen in metabolic or toxic encephalopathy.
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Photic-induced abnormality
Photoparoxysmal response - activity provoked by intermittent photic stimulation.
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Nocturnal seizure activity (video-EEG)
Overnight video-EEG captures sleep-related seizures and parasomnias.
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Coma prognosis pattern
Burst-suppression, alpha-coma or reactivity patterns that inform prognosis in the ICU.
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Non-epileptic events (video-EEG)
Video correlation distinguishes epileptic seizures from non-epileptic attack disorder.
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Red flag: status epilepticus on EEG - urgent admission
Continuous or evolving seizure activity on EEG is a neurological emergency.
Next steps
After the EEG - what typically follows.
The pathways your neurologist may recommend, matched to your EEG result and clinical picture.
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Anti-seizure medication
A neurologist-led decision, matched to seizure type and EEG signature.
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Video-EEG for pre-surgical planning
Prolonged inpatient recording to localise the seizure focus before epilepsy surgery.
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Sleep-medicine referral
Onward route when nocturnal events point to a primary sleep disorder.
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Ambulatory EEG for infrequent events
24–72 hour outpatient recording to capture events a routine EEG will miss.
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MRI brain
Structural imaging to exclude a lesion when the EEG suggests a focal onset.
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Neurology follow-up
A dedicated review to explain results, adjust treatment and set the monitoring plan.
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Multi-disciplinary team review
Complex or drug-resistant epilepsy is discussed by an epilepsy MDT before intervention.
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Driving-restrictions advice
Formal DVLA guidance on driving after a seizure or an abnormal EEG.
Red flags
When an EEG demands urgent action.
Findings that escalate a patient from an outpatient pathway to same-day neurology review or hospital admission.
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Status epilepticus
A continuous seizure or repeated seizures without recovery - emergency admission.
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Non-convulsive status
Altered consciousness with continuous EEG seizure activity but few motor signs.
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Sub-clinical seizures
Electrographic seizures without a clinical correlate - treatment usually indicated.
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New-onset focal seizures
First focal seizure in an adult mandates urgent MRI and neurology review.
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Post-traumatic epilepsy
Seizures following head injury - an EEG guides treatment and prognosis.
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Encephalitis pattern
Focal slowing or periodic discharges suggesting acute encephalitis - admit.
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Creutzfeldt–Jakob triphasic waves
Periodic sharp-wave complexes in a rapidly progressive dementia - refer urgently.
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Coma with poor prognostic features
Burst-suppression, non-reactive background or generalised periodic discharges after arrest.
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SUDEP risk features
Frequent generalised tonic-clonic seizures - counselling and treatment escalation.
Sources
The evidence behind this guide.
Every statement on this page is anchored to a named guideline or professional body.
Editorial standard
Written by our editorial team, clinically reviewed by Pulse Atlas Editorial Board ().
Published 2026-07-30. Next scheduled review 2027-07-30.
- 01 Source
NICE. Epilepsies in children, young people and adults (NG217).
NICE. Epilepsies in children, young people and adults (NG217). - 02 Source
British Society for Clinical Neurophysiology. Standards for EEG recording.
British Society for Clinical Neurophysiology. Standards for EEG recording. - 03 Source
International League Against Epilepsy. Classification and diagnostic guidance.
International League Against Epilepsy. Classification and diagnostic guidance. - 04 Source
American Clinical Neurophysiology Society. EEG guidelines and terminology.
American Clinical Neurophysiology Society. EEG guidelines and terminology.
Frequently asked
Everything patients ask us about the EEG.
Quick answers on what the test shows, whether it hurts, sleep-deprived and ambulatory recordings, and what a normal EEG means.
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What does an EEG show?
An EEG records the brain’s electrical activity through scalp electrodes. It shows epileptiform discharges, focal or generalised slowing, encephalopathy patterns, and - with video correlation - the electrical signature of a captured event.
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Is an EEG painful?
No. It’s entirely painless. Around 20 electrodes are positioned on the scalp with conductive paste, the recording lasts 30–60 minutes, and there are no needles and no radiation.
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What is a sleep-deprived EEG?
A standard EEG performed after a night of sleep deprivation. Reduced sleep lowers the seizure threshold and increases the yield of epileptiform abnormalities, particularly in suspected juvenile-onset epilepsy.
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When is ambulatory or video-EEG needed?
Ambulatory EEG (24–72 hours at home) is used when events are too infrequent for a routine EEG. Video-EEG, either overnight or as an inpatient admission, is used to correlate events with the trace - essential for pre-surgical planning and for distinguishing epileptic from non-epileptic attacks.
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A normal EEG - does that exclude epilepsy?
No. A single normal EEG doesn’t exclude epilepsy: routine interictal recordings are often normal between events. Repeat, sleep-deprived, ambulatory or video-EEG may be indicated when clinical suspicion remains high.
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How quickly will I get the report?
A consultant clinical neurophysiologist typically reports the trace within a few working days. Urgent inpatient recordings are read the same day.
Related tests
Looking for a different test?
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Combined video-EEG PSG
Overnight video-EEG with polysomnography - nocturnal events and sleep architecture together.
Learn more -
Brain MRI
Structural imaging of the brain - the anatomical counterpart to the EEG.
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Electromyography
Electrical recording of muscle and peripheral nerve activity.
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In practice, in London
Booking EEG privately in London - what actually happens
With EEG, the London question is usually about report turnaround and the radiologist reading it - not whether the scan is available. On the NHS, EEG typically sits behind a triage step and a wait that can stretch from a few weeks into months. In London’s private sector, the same appointment often lands within days. That speed matters when symptoms are disrupting work, sleep, or a plan you’d already committed to - and it’s the single most common reason people call us in the first place.
A private EEG pathway in London usually looks like this: an initial consultation, any diagnostics booked at a nearby facility (most within Zone 1 or 2), and a written report sent to you and your GP within a few days. The consultants we work with hold NHS posts alongside their private lists, which keeps the standards consistent across both settings. For EEG specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
Fit matters more than people expect. For EEG, the right consultant depends on what you actually need - a second opinion, a definitive diagnosis, a bridge into treatment, or reassurance that nothing’s being missed. We match on that, not on who has the biggest brochure. If a test isn’t the right next step, we’ll say so before you book anything.