At a glance
An electroencephalogram (EEG) is a test that records the electrical activity of the brain by picking up tiny signals through sensors placed on the scalp. It does not send electricity into the body; it only listens.
Brain cells communicate by firing electrical impulses. The EEG captures these impulses as wave patterns on a graph. Doctors read the shape, speed, and rhythm of those waves to judge whether the brain is working normally or showing signs of a problem.
Medical Condition
Neurologists order an EEG whenever they need to see how the brain's electrical activity looks at a given moment or over a period of time. It is most often used to investigate seizures (sudden bursts of abnormal electrical activity in the brain), but it serves several other purposes.
- Epilepsy: confirming the diagnosis, identifying where in the brain seizures start, and helping choose the right treatment.
- Unexplained blackouts or loss of consciousness, to check whether a seizure caused them.
- Sleep disorders such as narcolepsy (a condition causing sudden, uncontrollable sleepiness) or sleepwalking.
- Encephalopathy (a general term for brain dysfunction) caused by infection, liver or kidney failure, or toxic substances.
- Monitoring brain activity in patients who are in a coma or under heavy sedation in the ICU.
- Evaluating patients before epilepsy surgery to map the area of the brain that will be operated on.
- Detecting unusual brain wave patterns linked to certain dementias (brain conditions that affect memory and thinking).
An EEG is generally not the right tool when the doctor is looking for structural problems, such as a tumour or a bleed, because it shows electrical signals, not images of brain tissue. In those cases a CT or MRI scan is used instead.
Risks & Complications
A standard EEG is one of the safest procedures in medicine. The sensors record electrical signals; they do not deliver any current, radiation, or chemicals into the body.
- Skin irritation or mild redness under the electrode sites, which fades within hours.
- Gel or paste used to attach the electrodes can be difficult to wash out of the hair, causing temporary tangles or scalp discomfort.
- During activation tests, the technician may ask you to breathe rapidly (hyperventilation) or look at a flashing light; in very rare cases, this can trigger a seizure in someone already prone to them. This is done in a controlled setting precisely so the team can respond immediately.
- For prolonged or video EEG recordings done over many hours or days, the patient stays in hospital and there is a very small risk of a fall during a monitored seizure event.
Preparation & Procedure
Fasting is not required for a routine EEG. However, it is wise to avoid caffeine (coffee, tea, energy drinks) for at least 24 hours beforehand, because caffeine changes brain wave patterns and can make the recording harder to read.
Hair must be clean and completely free of oils, conditioner, sprays, or styling products on the day of the test. These substances interfere with electrode contact. Some hospitals ask patients to arrive with slightly damp, product-free hair.
Most neurologists advise continuing regular medications unless specifically told otherwise, because stopping anti-seizure drugs abruptly can be dangerous. Your prescribing doctor will give clear guidance on this point.
A sleep-deprived EEG is sometimes ordered, meaning the patient is asked to sleep much less than usual the night before. This makes the brain more likely to show abnormal patterns that only appear during drowsiness or sleep. The care team will explain if this applies.
There are usually no pre-procedure blood tests or imaging scans required solely for an EEG. If tests are ordered beforehand, they relate to the underlying condition being investigated, not to the EEG itself.
The procedure itself typically follows these steps:
- The patient sits in a reclining chair or lies on a bed in a quiet room.
- A technician measures the head and marks positions on the scalp using a soft pencil.
- Small metal discs called electrodes are attached to the scalp, usually with a water-soluble gel or paste. No needles are used.
- Wires from the electrodes connect to the EEG machine, which amplifies and records the brain signals.
- The patient rests quietly with eyes closed for the baseline recording, which usually lasts around 20 minutes for a routine study.
- Activation tests may follow: the technician may ask the patient to breathe deeply and rapidly for a few minutes, or to look at a strobe light flickering at different speeds.
- If a sleep recording is needed, the room is darkened and the patient is allowed to doze.
- Once recording is complete, the electrodes are removed and the gel is cleaned from the scalp. The patient can go home and resume normal activities straight away in most cases.
Aftercare
Recovery from a routine EEG requires no special care. The patient leaves the recording room with no restrictions in most cases, and the gel residue on the scalp washes out easily with normal shampooing.
- If a sleep-deprived EEG was done, the patient may feel very drowsy afterward. Arranging a companion to drive home is advisable.
- If a seizure occurred during the recording, the hospital team will assess the patient before discharge and advise on when it is safe to drive or operate machinery.
- Medications are restarted or continued exactly as the doctor instructed before the test.
- The neurologist usually reviews the EEG recording within a few days to a week and then discusses the findings at a follow-up appointment.
- If the EEG is part of ongoing epilepsy monitoring, the doctor will outline a schedule for repeat recordings.
- No wound care, dressings, or activity limits apply after a standard outpatient EEG.
Cost & What Determines It
The price of an EEG varies widely depending on the type of recording ordered, where it is performed, and what additional services surround it. A brief routine recording in a clinic costs far less than a multi-day video EEG done in a hospital epilepsy monitoring unit.
- Type of EEG: a standard 20-to-40-minute outpatient recording, a sleep-deprived EEG, an ambulatory EEG (where the device is worn at home for 24 hours or more), or a prolonged video EEG in hospital each fall into different cost brackets.
- Hospital class and country: private specialist centres, university hospitals, and general hospitals charge differently, and costs differ substantially between countries.
- Length of inpatient stay: video EEG monitoring that requires an admission of one or more nights adds ward fees, nursing costs, and daily monitoring charges.
- Neurologist's interpretation fee: the reading of the EEG by a specialist is sometimes billed separately from the technical recording itself.
- Additional tests ordered at the same visit: an MRI, blood tests, or neuropsychological assessments run alongside the EEG add to the total.
- Sedation: if mild sedation is used to help a child or an anxious adult remain still, anaesthesia fees apply.
- Complexity of the case: patients with medically refractory epilepsy (epilepsy that does not respond to medication) often need longer or more sophisticated monitoring, which increases cost.
A hospital package for an inpatient video EEG typically includes the room, nursing care, electrode setup, and the recording itself. The neurologist's interpretation report, follow-up consultation, and any imaging or blood tests are usually billed as separate line items. For outpatient EEGs, the package is simpler and usually covers the technician's time and the machine fee, with the specialist's reading fee added on top.
BPJS Kesehatan and most Indonesian private insurance policies do not cover medical procedures performed abroad, so patients who travel for an EEG typically pay out of pocket or rely on international private health insurance that explicitly includes overseas treatment. Before booking, ask the hospital for a written cost estimate that lists each item separately. This protects against unexpected charges on the day of discharge and makes it easier to compare offers from different facilities.
Frequently Asked Questions
Does an EEG hurt?
An EEG is painless. Small sensors called electrodes are placed on the scalp with a mild gel or paste, and they only record electrical signals from the brain without sending anything into it.
How do I prepare for an EEG?
Your doctor will usually ask you to wash your hair the night before and avoid putting in any products such as hairspray or conditioner on the day of the test. Depending on why the EEG is ordered, you may also be asked to sleep less than usual the night before, or to avoid caffeine, so follow any specific instructions given to you at the time of booking.
How long does an EEG take?
A standard EEG usually takes between 45 minutes and one hour from setup to finish. Some types, such as a sleep EEG or a prolonged monitoring EEG, can take several hours or even run overnight, depending on what your neurologist needs to observe.
How much does an EEG cost?
The cost depends mainly on the type of EEG ordered, since a short routine recording is priced differently from a sleep study or a full-day monitoring session, and hospital class also affects the final figure. Requesting a written cost estimate directly from the hospital before your appointment is the clearest way to know what you will be charged.
This page is general information, not a substitute for medical advice. Every case is different. Your doctor decides what is right for you.
