Electroencephalogram (EEG) – NHS

An electroencephalogram (EEG) is a recording of brain activity.

During this painless test, small sensors are attached to the scalp to pick up the electrical signals produced by the brain.

These signals are recorded by a machine and are looked at by a doctor.

The EEG procedure is usually carried out by a highly trained specialist, called a clinical neurophysiologist, during a short visit to hospital.

When an EEG is used

An EEG can be used to help diagnose and monitor a number of conditions affecting the brain.

It may help identify the cause of certain symptoms – such as seizures (fits) or memory problems – or find out more about a condition you’ve already been diagnosed with.

The main use of an EEG is to detect and investigate epilepsy, a condition that causes repeated seizures. An EEG will help your doctor identify the type of epilepsy you have, what may be triggering your seizures and how best to treat you.

Less often, an EEG may be used to investigate other problems, such as:

• dementia
• head injury and concussion
• brain tumours
• encephalitis (brain inflammation)
• sleep disorders, such as sleep apnoea.

Preparing for an EEG

Your appointment letter will mention anything you need to do to prepare for the test.

Unless told otherwise, you can usually eat and drink beforehand and continue to take all your normal medication.

To help the sensors stick to your scalp more easily, you should make sure your hair is clean and dry before arriving for your appointment, and avoid using products such as hair gel and wax.

You might want to bring a hairbrush or comb with you, as your hair may be a bit messy when the test is finished. Some people bring a hat to cover their hair until they can wash it at home afterwards.

How an EEG is carried out

There are several different ways an EEG recording can be taken. The clinical neurophysiologist will explain the procedure to you and can answer any questions you have. 

You’ll also be asked whether you consent to treatment for the various parts of the test to be carried out. This may include video consent for some EEGs.

Before the test starts, your scalp will be cleaned and about 20 small sensors called electrodes will be attached using a special glue or paste. These are connected by wires to an EEG recording machine.

Sensors called electrodes are attached to the head (usually with glue or paste) and connect to an EEG recording machine. You’ll sit or lie down for an EEG.

Credit:

Phanie / Alamy Stock Photo https://www.alamy.com/stock-photo-woman-undergoing-an-electroencephalogram-eeg-limoges-hospital-france-72431574.html?pv=1&stamp=2&imageid=7AA22C91-664F-4D38-8619-582AA92C0168&p=218158&n=0&orientation=0&pn=1&searchtype=0&IsFromSearch=1&srch=foo%3dbar%26st%3d0%26pn%3d1%26ps%3d100%26sortby%3d2%26resultview%3dsortbyPopular%26npgs%3d0%26qt%3dE5RF5X%26qt_raw%3dE5RF5X%26lic%3d3%26mr%3d0%26pr%3d0%26ot%3d0%26creative%3d%26ag%3d0%26hc%3d0%26pc%3d%26blackwhite%3d%26cutout%3d%26tbar%3d1%26et%3d0x000000000000000000000%26vp%3d0%26loc%3d0%26imgt%3d0%26dtfr%3d%26dtto%3d%26size%3d0xFF%26archive%3d1%26groupid%3d%26pseudoid%3d%7bA883FDE5-7F3D-4472-81F5-B61111916852%7d%26a%3d%26cdid%3d%26cdsrt%3d%26name%3d%26qn%3d%26apalib%3d%26apalic%3d%26lightbox%3d%26gname%3d%26gtype%3d%26xstx%3d0%26simid%3d%26saveQry%3d%26editorial%3d1%26nu%3d%26t%3d%26edoptin%3d%26customgeoip%3d%26cap%3d1%26cbstore%3d1%26vd%3d0%26lb%3d%26fi%3d2%26edrf%3d0%26ispremium%3d1%26flip%3d0%26pl%3d

Routine EEG recordings usually take 20 to 40 minutes, although a typical appointment will last about an hour, including some preparation time at the beginning and some time at the end.

Other types of EEG recording may take longer.

Types of EEG

Routine EEG

A routine EEG recording lasts for about 20 to 40 minutes.

During the test, you’ll be asked to rest quietly. You will usually be asked to open or close your eyes from time to time. In most cases, you’ll also be asked to breathe in and out deeply (called hyperventilation) for a few minutes.

A flashing light may also be used to see if this affects your brain activity.

Sleep EEG or sleep-deprived EEG

A sleep EEG is carried out while you’re asleep. It may be used if a routine EEG does not give enough information, or to test for sleep disorders.

In some cases, you may be asked to stay awake the night before the test to help ensure you can sleep while it’s carried out. This is called a sleep-deprived EEG.

Ambulatory EEG

An ambulatory EEG is where brain activity is recorded throughout the day and night over a period of one or more days. The electrodes will be attached to a small portable EEG recorder that can be clipped onto your clothing.

You can continue with most of your normal daily activities while the recording is being taken, although you’ll need to avoid getting the equipment wet.

Video telemetry

Video telemetry, also called video EEG, is a special type of EEG where you’re filmed while an EEG recording is taken. This can help provide more information about your brain activity.

The test is usually carried out over a few days while staying in a purpose-built hospital suite.

The EEG signals are transmitted wirelessly to a computer. The video is also recorded by the computer and kept under regular surveillance by trained staff.

Invasive EEG-telemetry

This EEG is not common, but it may be used to check if surgery is possible for some people with more complex epilepsy.

It involves surgery to place electrodes directly on the brain to find out exactly where the seizures are coming from.

What happens after an EEG

When the test is finished, the electrodes will be removed and your scalp will be cleaned. Your hair will probably still be a bit sticky and messy afterwards, so you may want to wash it when you get home.

You can usually go home soon after the test is finished and return to your normal activities. You might feel tired after the test, particularly if you had a sleep or sleep-deprived EEG, so you may want someone to pick you up from hospital.

You normally will not get your results on the same day. The recordings will need to be analysed first and will be sent to the doctor who requested the test. They can discuss the results with you a few days or weeks later.

Are there any risks or side effects?

The EEG procedure is painless, comfortable and generally very safe. No electricity is put into your body while it’s carried out. Apart from having messy hair and possibly feeling a bit tired, you normally will not experience any side effects.

However, you may feel lightheaded and notice a tingling in your lips and fingers for a few minutes during the hyperventilation part of the test. Some people develop a mild rash where the electrodes were attached.

If you have epilepsy, there’s a very small risk you could have a seizure while the test is carried out, but you’ll be closely monitored and help will be on hand in case this happens.

Video: epilepsy research – EEG

This video covers the benefits of participating in EEG research.

Media last reviewed: 5 August 2022
Media review due: 5 August 2025

Page last reviewed: 05 January 2022
Next review due: 05 January 2025

Electroencephalogram (EEG) | Johns Hopkins Medicine

What is an EEG?

An EEG is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto your scalp. The electrodes detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen, or as a recording that may be printed out on paper. Your healthcare provider then interprets the reading.

During an EEG, your healthcare provider typically evaluates about 100 pages, or computer screens, of activity. He or she pays special attention to the basic waveform, but also examines brief bursts of energy and responses to stimuli, such as flashing lights.

Evoked potential studies are related procedures that also may be done. These studies measure electrical activity in your brain in response to stimulation of sight, sound, or touch.

Why might I need an EEG?

The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG.

People with lesions of their brain, which can result from tumors or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion.

The test can also be used to diagnose other disorders that influence brain activity, such as Alzheimer’s disease, certain psychoses, and a sleep disorder called narcolepsy.

The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures.

There may be other reasons for your healthcare provider to recommend an EEG.

What are the risks of an EEG?

The EEG has been used for many years and is considered a safe procedure. The test causes no discomfort. The electrodes record activity. They do not produce any sensation. In addition, there is no risk of getting an electric shock.

In rare instances, an EEG can cause seizures in a person with a seizure disorder. This is due to the flashing lights or the deep breathing that may be involved during the test. If you do get a seizure, your healthcare provider will treat it immediately.

Other risks may be present, depending on your specific medical condition. Be sure to discuss any concerns with your healthcare provider before the procedure.

Certain factors or conditions may interfere with the reading of an EEG test. These include:

• Low blood sugar (hypoglycemia) caused by fasting
• Body or eye movement during the tests (but this will rarely, if ever, significantly interfere with the interpretation of the test)
• Lights, especially bright or flashing ones
• Certain medicines, such as sedatives
• Drinks containing caffeine, such as coffee, cola, and tea (while these drinks can occasionally alter the EEG results, this almost never interferes significantly with the interpretation of the test)
• Oily hair or the presence of hair spray

How do I get ready for an EEG?

Ask your healthcare provider to tell you what you should do before your test. Below is a list of common steps that you may be asked to do.

• Your healthcare provider will explain the procedure to you and you can ask questions.
• You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
• Wash your hair with shampoo, but do not use a conditioner the night before the test. Do not use any hair care products, such as hairspray or gels.
• Tell your healthcare provider of all medicines (prescription and over-the-counter) and herbal supplements that you are taking.
• Discontinue using medicines that may interfere with the test if your healthcare provider has directed you to do so. Do not stop using medicines without first consulting your healthcare provider.
• Avoid consuming any food or drinks containing caffeine for 8 to 12 hours before the test.
• Follow any directions your healthcare provider gives you about reducing your sleep the night before the test. Some EEG tests require that you sleep through the procedure, and some do not. If the EEG is to be done during sleep, adults may not be allowed to sleep more than 4 or 5 hours the night before the test. Children may not be allowed to sleep for more than 5 to 7 hours the night before.
• Avoid fasting the night before or the day of the procedure. Low blood sugar may influence the results.
• Based on your medical condition, your healthcare provider may request other specific preparations.

What happens during an EEG?

An EEG may be done on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your healthcare provider’s practices. Talk with your healthcare provider about what you will experience during your test.

Generally, an EEG procedure follows this process:

1. You will be asked to relax in a reclining chair or lie on a bed.
2. Between 16 and 25 electrodes will be attached to your scalp with a special paste, or a cap containing the electrodes will be used.
3. You will be asked to close your eyes, relax, and be still.
4. Once the recording begins, you will need to remain still throughout the test. Your healthcare provider may monitor you through a window in an adjoining room to observe any movements that can cause an inaccurate reading, such as swallowing or blinking. The recording may be stopped periodically to let you rest or reposition yourself.
5. After your healthcare provider does the initial recording while you are at rest, he or she may test you with various stimuli to produce brain wave activity that does not show up while you are resting. For example, you may be asked to breathe deeply and rapidly for 3 minutes, or you may be exposed to a bright flashing light.
6. This study is generally done by an EEG technician and may take approximately 45 minutes to 2 hours.
7. If you are being evaluated for a sleep disorder, the EEG may be done while you are asleep.
8. If you need to be monitored for a longer period of time, you may also be admitted to the hospital for prolonged EEG (24-hour EEG) monitoring.
9. In cases where prolonged inpatient monitoring is not possible, your doctor may consider doing an ambulatory EEG.

What happens after an EEG?

Once the test is completed, the electrodes will be removed and the electrode paste will be washed off with warm water, acetone, or witch hazel. In some cases, you may need to wash your hair again at home.

If you took any sedatives for the test, you may be required to rest until the sedatives have worn off. You will need to have someone drive you home.

Skin irritation or redness may be present at the locations where the electrodes were placed, but this will wear off in a few hours.

Your healthcare provider will inform you when you may resume any medicines you stopped taking before the test.

Your healthcare provider may give you additional or alternate instructions after the procedure, depending on your particular situation.

Next steps

Before you agree to the test or the procedure make sure you know:

• The name of the test or procedure
• The reason you are having the test or procedure
• What results to expect and what they mean
• The risks and benefits of the test or procedure
• What the possible side effects or complications are
• When and where you are to have the test or procedure
• Who will do the test or procedure and what that person’s qualifications are
• What would happen if you did not have the test or procedure
• Any alternative tests or procedures to think about
• When and how will you get the results
• Who to call after the test or procedure if you have questions or problems
• How much will you have to pay for the test or procedure

Electroencephalography (EEG) in Perm.

Appointment for a consultation with a specialist doctor +7 (342) 234-03-03

If you have headaches, impaired memory, attention, meteorological dependence, high or low blood pressure, insomnia, anxiety, depression, fainting, epileptic seizures, traumatic brain injury, and if you consider yourself sick, but the doctors you have consulted so far since they haven’t diagnosed you and haven’t explained to you that the prescribed treatment does not help you and you, go through an electroencephalographic study yourself without a doctor’s prescription !!!

This study of brain function has no absolute contraindications to conduct. A relative contraindication is an acute infectious disease with a temperature rise above 38 degrees.

Conducting electroencephalography will give you a lot of necessary information and help to establish an accurate diagnosis, predict the course of your disease and draw up a plan of measures for recovery.

When you pass an electroencephalographic study and receive a conclusion about the study in your hands, then in the conclusion you will have all the necessary information that you so lacked for an accurate diagnosis and proper treatment:

• Whether there is a violation of the functions of your brain or not.
• Is there a pathological focus in your brain or not?
• Does your brain tend to have seizures and fainting?
• Is your brain function appropriate for your age?
• How does your brain handle stress?
• What causes brain dysfunction – congenital or acquired causes during your life
• In conclusion, you will receive an answer to the question what is the degree and severity of brain dysfunction.
• After the study, you will be recommended the main directions of therapeutic measures for your condition.

Electroencephalography (EEG) is one of the most informative instrumental studies in neurology, which serves to record the electrical activity of brain neurons and determine its functional activity.

Who can be tested?

The study can be performed on children of any age, pregnant women and the elderly an unlimited number of times, being safe and painless.

When conducting an EEG for a child, a specialist takes into account the individual characteristics associated with age: what may be a pathology for an adult is the norm for a child, and vice versa, depending on the stage of maturation of the nervous system. In this regard, when conducting an EEG on a child, the researcher, as a rule, spends more time interpreting the results, as well as the study itself.

Indications and contraindications

Indications and the study itself, as a rule, are prescribed by the attending physician. However, with an already established diagnosis, for example, epilepsy, it is possible to undergo an EEG without a doctor’s referral to assess the dynamics of the disease or in case of apparent deterioration. Then, with the existing results of the study, you can contact your doctor, which will significantly speed up the process and increase the effectiveness of the consultation.

Indications:

• epileptic seizures;
• epileptic-like seizures, with or without convulsions;
• assessment of the dynamics of treatment with an established diagnosis of epilepsy, control of the effectiveness of the dosage of antiepileptic drugs;
• sleep disorders;
• brain tumors;
• neuroses, psychopathy;
• vascular diseases of the brain;
• degenerative changes in the brain;
• inflammatory diseases of the brain, consequences of neuroinfections;
• consequences of traumatic brain injury;
• effects of neurotoxic poisoning;
• various organic lesions of the brain;
• diencephalic syndrome;
• during surgery: assessment of the depth of anesthesia;
• in children: evaluation of the functional maturity of the brain;
• autism;
• study in ICU conditions.

Contraindications: none.

Diagnostic principle

The work of brain cells is organized and synchronized thanks to pacemakers. Such organization allows us to know a certain order of the functioning of the brain, necessary for recording and interpreting the results. The brain, in the course of its life, makes many electrical connections that allow nerve cells to communicate with each other. There is a difference in electrical potentials, which is recorded on the electroencephalogram.

Preparation for the test

• For the test, the scalp must be clean, without varnish, gel, etc. – this is necessary for good contact between the electrodes and the scalp;
• If there is hair, dreadlocks, pigtails must be unbraided;
• Earrings must be removed before examination;
• The scalp must not be damaged;
• The child, if research is being carried out on him, must be explained in advance that the procedure will be painless, and you will be able to be with him all the time, play with him with a cap and with ropes that look like wires;
• Examination is not performed during a cold;
• Only on the recommendation of a doctor, anticonvulsants can be stopped within 3 days.

How is the study carried out?

Before the examination, a special cap with built-in electrodes is put on the head, presented in the form of plates connected by wires to the researcher’s apparatus. Before that, a special gel is applied to the scalp, which does not give any unpleasant sensations, similar to ultrasound gel, which serves to improve contact with the electrodes, improve electrical conductivity and increase the reliability of the study. The electrodes are located on the surface of the scalp so that it is possible to simultaneously register the activity of all parts of the brain. The electrodes register the potential difference, this data is then converted into digital form and transferred to the computer of the researcher.

The study is carried out in a darkened room, without annoying extraneous sounds. In this case, the subject can sit on a special couch or lie with his eyes closed. Thus, excessive activity of the nervous system, which may incorrectly affect the results of the study, is excluded. During the study, periodic exposure to a sound or light stimulus is carried out to identify the response of the brain to a specific stimulus. Also, for a similar purpose, it is possible to conduct an EEG with the addition of a mental load.

How are results and conclusions formed?

Already during the procedure, the researcher notes certain trends, but the doctor can draw up a final picture only at the end of the study after processing the results. The specialist processes and deciphers the results and then makes a conclusion, which can be used to suggest, confirm or reject the diagnosis with a high probability. The results are processed on a computer provided with the Neuron-Spectrum 5, Neurosoft software package. This complex allows you to receive a bioelectric impulse through 8–23 channels. The frequency, amplitude and types of waves, their distribution in time and space, deviation from the age and gender individually established norms (spectral analysis), the activity of various centers of the brain and their interaction and response to various stimuli (coherent analysis) are assessed. All results are recorded on a DVD / CD disc, which is given to the subject.

After the conclusion is made, the doctor explains the results and gives certain recommendations. You should always remember that the conclusion is not a diagnosis, and sometimes one study is not enough to make a diagnosis, then you can turn to additional diagnostics.

Additional diagnostic methods

If EEG abnormalities are not detected, but symptoms are present, if it is necessary to make a final diagnosis between epilepsy and other diseases with similar symptoms, a highly effective method is video-EEG sleep monitoring, during which the electrical activity of the brain, motor and behavioral activity of the patient under study is recorded simultaneously. sleep time for several hours. In this study, the diagnosis occurs continuously for several hours, while the EEG can be recorded outside the attacks and not provide enough information.

Also, the most informative type of study with the registration of electrical activity of the brain is a polysomnographic study.

An EEG study in the medical and diagnostic center “< NEURO + Clinic" is carried out by:

• neurologist, neurophysiologist, doctor of functional diagnostics Lysichenkova OV;
• neurologist, somnologist, MD Shevchenko K.V.

Electroencephalography, price.

EEG – electroencephalography

To date, EEG is one of the most widely used and available in neurology and neurosurgery for diagnosing changes in the functional state of brain cell activity.

The use of modern equipment in a specially equipped room provides high accuracy in obtaining diagnostic information and data analysis capabilities with minimal time costs.

Electroencephalogram – a curve obtained by recording fluctuations in the electrical potential of the brain through the integument of the head. The EEG reflects the mosaic of activity of the cerebral cortex, which in a healthy person is distinguished by a certain pattern corresponding to the harmony of the course of the main nervous processes in the brain. With organic pathology of the brain, this harmony of processes is disturbed.

EEG can show one of the main parameters of the nervous system – the property of rhythm, which reflects the consistency of the work of different brain structures. Therefore, when recording an encephalogram, the neurophysiologist has access to the actual information processing mechanisms of the brain. This helps to reveal the blueprint of the processes involved in the brain, showing not only “where”, but also “how” information is processed in the brain. It is this possibility that makes the EEG a unique and undoubtedly valuable diagnostic method. Electroencephalographic examinations reveal how the human brain uses its functional reserves.

EEG method:

completely harmless
painless
safe
non-invasive (no effect on the patient).
highly sensitive How to prepare for an EEG:
After midnight before the examination, avoid drinking caffeinated drinks: coffee, tea or soft drinks (energy tonics). Hair must be clean and dry and free of oils, sprays or lotions.

If the examination is for a child:
Explain what will happen to the child during the examination. Make sure it’s pain free. With preschool children, it is necessary to practice putting on a “helmet” and staying still with your eyes closed (playing astronaut, tanker, etc.), as well as teaching you to breathe deeply and often (like blowing up a balloon).

How the EEG is performed:
The patient sits in a comfortable chair during the examination, relaxed with his eyes closed (passive wakefulness state).
To perform an EEG, small pads called electrodes will be placed on the scalp. The pads read the electrical activity of the brain and transmit this data to a computer. There are no pain sensations during the procedure. What the EEG examination procedure consists of:
sit quietly with your eyes closed.
may be asked to open and close their eyes
may be asked to breathe deeply and frequently through their mouth.
may show a flashing light for a short time.
after electroencephalography: the electrodes will be removed from the scalp.
the results of the examination will be explained by the doctor and given immediately to the hands. Under what conditions should a person think about going to the doctor and conducting electroencephalography?
These are syncope, attacks of involuntary movements, unusual sensations or emotions, in addition, these are attacks of inexplicable behavior and episodes of freezing. One of the causes of all these conditions may be epilepsy. If the diagnosis of epilepsy has already been made, then the selection of treatment is necessarily accompanied by repeated recordings of electroencephalography. In some cases, electroencephalography can predict the course of the disease. Recording of electroencephalography is carried out not only with suspicion of epilepsy.
Electroencephalography is prescribed after brain injuries. This method with a certain accuracy allows you to specify the location of the main damage, as well as to identify the severity of cerebral changes, which is extremely important for predicting the condition in the long-term period of injury.

Established indications for EEG:

Epilepsy. establish the brain regions involved in the triggering of seizures, monitor the effect of drugs, decide on the termination of drug therapy, determine the degree of brain dysfunction during periods when there are no seizures.
Convulsive seizures of unknown origin.
Sleep disorders of a paroxysmal nature.
Fainting (syncope).
If a neoplasm is suspected. By modern standards, an EEG study can be recommended as a screening study. Due to the harmlessness, relative availability and speed of the EEG, the doctor can tell whether it is worth sending the patient for an additional (more often tomographic) study or not.
To clarify the diagnosis of patients with: headaches.
dizziness.
unstable blood pressure, hypertension.
vegetovascular dystonia.
vertebrobasilar insufficiency in cervical osteochondrosis.
neurotic disorders.
Traumatic brain injury (assessment of the severity and effectiveness of the restoration of brain function after an injury). With repeated studies, the EEG helps to assess the speed and completeness of the disappearance of signs of brain dysfunction. Further treatment depends on this.
Conditions after neurosurgical interventions.
Dyscirculatory encephalopathy,
Investigate the functional state of the brain in people whose structural research methods (for example, MRI: magnetic resonance imaging method) show that the brain structure is without pathology, but there is a violation of brain functions in the clinic (for example, with metabolic encephalopathy) .
Acute disorders of cerebral circulation (early and long-term consequences of strokes).
Inflammatory diseases of the central nervous system (cerebral arachnoiditis, meningitis, encephalitis).
Perinatal pathology of the nervous system (PP CNS in children of early and younger childhood)
Delayed psycho-speech development of unclear origin.
Behavioral disorders of a paroxysmal nature (including without impaired consciousness).
Endocrine pathology.
Contraindications for EEG – none

EEG in epilepsy:
this is the most important test in the diagnosis of epilepsy.
is carried out immediately after the first seizures appear. Based on the examination data, a specialist can determine what changes have occurred in the brain, clarify the type of seizures, and, based on this, determine which drugs will be most effective in treatment. The effectiveness of the treatment is also monitored and the issue of stopping treatment is decided.

How often to do an EEG in epilepsy: The number of EEG examinations and their frequency depends on what the attending physician needs to identify. If there are no seizures (for example, in the case of successful treatment), then the EEG can be done about 1-2 times a year. In the presence of seizures, changes in treatment or dose of drugs, the frequency of EEG increases.

The best time to conduct an EEG during an attack is not earlier than a week after an attack.