Electroencephalography with computer processing and functional tests. What does the EEG (electroencephalogram) of the brain show

For convenience, both doctors and patients replace the long word “electroencephalography” with an abbreviation and simply call this diagnostic method EEG. It should be noted here that some (probably to enhance the significance of the study) talk about the EEG of the brain, but this is not entirely correct, since the Latinized version of the ancient Greek word "encephalon" is translated into Russian as "brain" and in itself is already part of the medical term is encephalography.

Electroencephalography or EEG is a method of studying the brain (GM) in order to identify foci of increased convulsive readiness of its cortex, which is typical for (main task), tumors, conditions after a stroke, structural and metabolic, sleep disorders and other diseases. Encephalography is based on recording the electrical activity of the GM (frequency, amplitude), and this is done with the help of electrodes attached in different places on the surface of the head.

What kind of study is an EEG?

Periodically coming convulsive seizures, occurring in most cases with a complete loss of consciousness, are popularly called epilepsy, which official medicine calls epilepsy.

The very first and main method for diagnosing this disease, serving humanity for many decades (the first EEG taken dates back to 1928), is encephalography (electroencephalography). Of course, the research apparatus (encephalograph) has significantly changed and improved by now, its capabilities with the use of computer technology have significantly expanded. However, the essence of the diagnostic method remained the same.

The electrodes (sensors) are connected to the electroencephalograph, which are placed in the form of a cap on the surface of the subject's head. These sensors are designed to capture the slightest electromagnetic bursts and transmit information about them to the main equipment (device, computer) for automatic processing and analysis. The encephalograph processes the received impulses, amplifies them and fixes them on paper in the form of a broken line, very reminiscent of an ECG.

The bioelectrical activity of the brain is created mainly in the cortex with the participation of:

• Thalamus, which oversees and redistributes information;
• ARS (activating reticular system), the nuclei of which, settled in various parts of the GM (medulla oblongata and midbrain, pons, diencephalic system), receive signals from many pathways and transmit them to all parts of the cortex.

The electrodes read these signals and deliver them to the apparatus where the recording takes place (a graphic image is an encephalogram). Information processing and analysis are the tasks of computer software that “knows” norms of biological activity of the brain and the formation of biorhythms depending on age and a certain situation.

For example, routine EEG captures the formation of pathological rhythms during an attack or in the period between seizures, sleep EEG or nighttime EEG monitoring shows how the biopotentials of the brain change during immersion in the world of dreams.

Thus, electroencephalography shows the bioelectrical activity of the brain and the coordination of the activity of brain structures during wakefulness or during sleep and answers the questions:

1. Are there foci of increased convulsive readiness of GM, and if they are, in what area are they located;
2. At what stage is the disease, how far has it gone or, on the contrary, has begun to regress;
3. What effect does the chosen medicine give and whether its dose is correctly calculated;

Of course, even the most "smart" machine will not replace a specialist (usually a neurologist or neurophysiologist) who receives the right to decipher the encephalogram after passing special training.

Features of the EEG in children

What can we say about babies, if some adults, having received an EEG referral, begin to ask what and how, because they doubt the safety of this procedure. Meanwhile, it actually cannot bring any harm to the child, but it is really difficult to make an EEG for a small patient. Babies under one year of age measure the bioelectrical activity of the brain during sleep, before that they wash their hair, feed the baby and, without deviating from the usual schedule (sleep / wakefulness), adjust the procedure to the child's sleep.

But if in children under one year old it is enough to wait for falling asleep, then a child from one to three years old (and some even older) still needs to be persuaded, therefore, up to 3 years old, the study is carried out in a waking state only for calm and contact children, giving preference in other cases to EEG sleep.

Preparations for visiting the appropriate office should be started a few days in advance, turning the future trip into a game. You can try to interest the baby in a pleasant journey, where he can go with his mother and his favorite toy, come up with some other options (usually parents are more aware of how to convince the child to sit quietly, not move, do not cry or talk). Unfortunately, such restrictions are very difficult for young children to endure, because they still cannot understand the seriousness of such an event. Well, in such cases, the doctor is looking for an alternative ...

Indications for daytime sleep encephalography or nocturnal EEG in a child are:

• Identification of paroxysmal conditions of various origins - epileptic seizures, convulsive syndrome against the background of high body temperature (febrile convulsions), epileptiform seizures that are not associated with true epilepsy and are differentiated from it;
• Monitoring the effectiveness of antiepileptic therapy in case of an established diagnosis of epilepsy;
• Diagnosis of hypoxic and ischemic lesions of the central nervous system (presence and severity);
• Determining the severity of brain lesions for prognostic purposes;
• The study of the bioelectrical activity of the brain in young patients to study the stages of its maturation and the functional state of the central nervous system.

In addition, it is often suggested to do an EEG with frequent and, with a delay in the acquisition of speech skills and stuttering. This method should not be neglected in other cases that require the study of the reserves of the functional capabilities of the brain, because the procedure is harmless and painless, but it can provide maximum information for diagnosing a certain pathology. Electroencephalography is very useful if there are episodes of disturbances of consciousness, but their cause has not been elucidated.

Various Recording Methods

Registration of bioelectric potentials of the brain is carried out in different ways, for example:

1. At the beginning of a diagnostic search that identifies the causes of paroxysmal conditions, a short time (≈ 15 min) is used. routine method of recording an encephalogram, which, to identify hidden disorders, involves the use of provocative tests - the patient is asked to breathe deeply (hyperventilation), open and close his eyes, or give light stimulation (photostimulation);
2. If the routine EEG did not provide the necessary information, then the doctor prescribes encephalography with deprivation(deprivation of sleep at night in whole or in part). In order to conduct such a study and obtain reliable results, a person is either not allowed to sleep at all, or they wake him up 2-3 hours before the subject’s “biological alarm clock rings”;
3. Long-term EEG recording with the registration of the bioelectrical activity of the GM cortex during the "quiet hour" (EEG of sleep) occurs if the doctor suspects that changes in the brain occur during the stay in the "sleep mode";
4. Experts consider the most informative nocturnal EEG, the recording of which is carried out in a hospital. They begin the study while still awake (before going to bed), continue when immersed in a nap, capture the entire period of night sleep and end after a natural awakening. If necessary, the registration of the bioelectrical activity of the GM is supplemented by the application of supernumerary electrodes and the use of video recording equipment.

Long-term recording of electrical activity for several hours during sleep and nighttime EEG recording is called EEG monitoring. Naturally, such methods require the involvement of additional equipment and material resources, as well as the patient's stay in a hospital.

Time and equipment form the price

In other cases, there is a need to measure the GM biopotentials at the time of an attack. In pursuit of such goals, the patient, as well as for conducting a night EEG, is sent to a hospital for hospitalization, where daily EEG monitoring is carried out using audio and video equipment. Continuous EEG monitoring with video recording during the day makes it possible to verify the epileptic origin of paroxysmal memory disorders, isolated auras, as well as episodically occurring psychomotor phenomena.

Electroencephalography is one of the most accessible methods for studying the brain. And for the price too. In Moscow, you can find this study for 1,500 rubles, and for 8,000 rubles (EEG sleep monitoring for 6 hours), and for 12,000 rubles (night EEG).

In other cities of Russia, you can get by with a smaller amount, for example, in Bryansk the price starts from 1200 rubles, in Krasnoyarsk - from 1100 rubles, and in Astrakhan it starts from 800 rubles.

Certainly, it is better to do an EEG in a specialized neurological clinic, where in doubtful cases there is the possibility of a collegial diagnosis (in such institutions, many specialists can encrypt the EEG), as well as get a doctor's consultation immediately after the test or quickly resolve the issue regarding other methods of brain research.

About the main rhythms of the electrical activity of the GM

When deciphering the results of the study, various factors are taken into account: the age of the subject, his general condition (presence of tremor, weakness in the limbs, visual impairment, etc.), anticonvulsant therapy at the time of registration of the bioelectrical activity of the brain, the approximate time (date) of the last seizure, and others

The electroencephalogram is composed of various complex biorhythms emanating from the electrical activity of the GM in different periods of time, depending on specific situations.

When deciphering the EEG, first of all, attention is paid to the main rhythms and their characteristics:

• alpha rhythm(frequency - in the range from 9 to 13 Hz, amplitude of oscillations - from 5 to 100 μV), which is present in almost all persons who do not make claims to their health during the period of inactive wakefulness (relaxation during rest, relaxation, shallow meditation) . As soon as a person opens his eyes and tries to visualize any picture, α-waves decrease and may disappear altogether if the functional activity of the brain continues to increase. When deciphering the EEG, the following parameters of the α-rhythm are important: amplitude (μV) over the left and right hemispheres, dominant frequency (Hz), dominance of certain leads (frontal, parietal, occipital, etc.), interhemispheric asymmetry (%). Depression of the α-rhythm is caused by anxiety, fear, activation of autonomic nervous activity;
• beta rhythm(the frequency is in the range from 13 to 39 Hz, the amplitude of oscillations is up to 20 μV) - this is not only the mode of our wakefulness, the β-rhythm is characteristic of active mental work. In the normal state, the severity of β-waves is very weak, their excess indicates an immediate reaction of the GM to stress;
• Theta rhythm(frequency - from 4 to 8 Hz, the amplitude is in the range of 20-100 μV). These waves do not reflect a pathological change in consciousness, for example, a person is dozing, is in a half-sleep, in the stage of superficial sleep, he already sees some dreams, and then θ-rhythms are detected. In a healthy person, falling into sleep is accompanied by the appearance of a significant number of θ-rhythms. An increase in theta rhythm is observed with prolonged psycho-emotional stress, mental disorders, twilight states characteristic of some neurological diseases, asthenic syndrome, concussion of the brain;
• delta rhythm(frequency is in the range from 0.3 to 4 Hz, amplitude - from 20 to 200 μV) - is typical for deep immersion in sleep (natural falling asleep and artificially created sleep - anesthesia). With various neurological pathologies, an increase in the δ-wave is observed;

In addition, other electrical oscillations pass through the cerebral cortex: gamma rhythms that reach a high frequency (up to 100 Hz), kappa rhythms that form in the temporal leads during active mental activity, and mu rhythms associated with mental stress. These waves are not particularly interesting in the diagnostic sense, since they occur with a significant mental load and intense "thought work" that requires a high concentration of attention. The electroencephalogram, as you know, is recorded, although during wakefulness, but in a calm state, and in some cases night monitoring of the EEG or EEG of sleep is generally prescribed.

Video: alpha and beta rhythms on the EEG

EEG decoding

main EEG leads and their designations

A bad or good EEG can only be judged after the final interpretation of the results of the study. In this way, a good EEG will be discussed if, during the period of wakefulness, the following were recorded on the encephalogram tape:

• In the occipito-parietal leads - sinusoidal α-waves with an oscillation frequency ranging from 8 to 12 Hz and an amplitude of 50 μV;
• In the frontal areas - β-rhythms with an oscillation frequency of more than 12 Hz and an amplitude not exceeding 20 μV. In some cases, β-waves alternate with θ-rhythms with a frequency of 4 to 7 Hz, and this is also referred to as normal variants.

It should be noted that individual waves are not specific to any particular pathology. An example is epileptiform sharp waves, which, under certain circumstances, can appear in healthy people who do not suffer from epilepsy. And, conversely, peak-wave complexes (frequency 3 Hz) clearly indicate epilepsy with small convulsive seizures (petit mal), and sharp waves (frequency 1 Hz) indicate a progressive degenerative disease of the GM - Creutzfeldt-Jakob disease, therefore, these waves at decoding are among the important diagnostic features.

In the period between attacks, epilepsy may not be noticed, since the peaks and sharp waves characteristic of this disease are not observed in all patients, showing all the clinical symptoms of the pathology at the time of a convulsive seizure. Moreover, paroxysmal manifestations in other cases can be recorded in people who are absolutely healthy, who do not have any signs and prerequisites for the development of a convulsive syndrome.

In connection with the above, having conducted a single study and not finding epileptic activity on the background EEG (“good EEG”), one cannot completely exclude epilepsy from the results of a single test if there are clinical signs of the disease. It is necessary to examine the patient for this unpleasant disease by other methods.

Recording an EEG during a seizure in a patient with epilepsy can provide the following options:

1. Frequent electrical discharges of high amplitude, which indicate that the peak of the seizure has come, slowing down activity - the attack has passed into the attenuation phase;
2. Focal epiactivity (it indicates the location of the focus of convulsive readiness and the presence of partial seizures - you will have to look for the cause of the focal lesion of the GM);
3. Manifestations of diffuse changes (registration of paroxysmal discharges and peak-wave) - such indicators indicate that the attack is of a generalized nature.

As for other diseases in which pathological electrical activity has nothing to do with epilepsy, they can be recorded in the form of focal brain lesions and diffuse changes. For example, a slow rhythm with a predominance of θ- and δ-waves is considered a generally significant identifier of twilight consciousness of various origins ( , ), which, in the case of focal brain damage, manifests itself more noticeably on the suffering side of the GM than on the healthy side.

If the origin of the GM lesion is established, and diffuse changes are recorded on the EEG, then the diagnostic value of this study, although not so significant, still allows you to find a particular disease, far from epilepsy:

• Meningitis (especially those caused by herpes infection) - on the EEG: periodic formation of epileptiform discharges;
• Metabolic encephalopathy - on the encephalogram: the presence of "three-phase" waves or diffuse slowdowns in rhythm and outbreaks of symmetrical slow activity in the frontal areas.

Diffuse changes on the encephalogram can be recorded in patients who have suffered a brain injury or concussion, which is understandable - with severe head injuries, the entire brain suffers. However, there is another option: diffuse changes are found in people who do not present any complaints and consider themselves absolutely healthy. It also happens, and if there are no clinical manifestations of pathology, then there is no reason for concern either. Perhaps at the next examination, the EEG record will reflect the full norm.

When is an EEG helpful in making a diagnosis?

Electroencephalography, revealing the functional capabilities and reserves of the central nervous system, has become the standard for studying the brain; doctors consider it appropriate to conduct it in many cases and under various conditions:

1. To assess the degree of functional immaturity of the brain in young patients (in a child under one year old, the study is always carried out during sleep, in older children - according to the situation);
2. With various sleep disorders (, frequent nocturnal awakenings, etc.);
3. In the presence of epileptic seizures;
4. To confirm or exclude complications of inflammatory processes caused by neuroinfection;
5. At, );
6. Patients who are in a coma need an assessment of the state of the brain;
7. In some cases, the study requires surgery (determination of the depth of anesthesia);
8. How far neuropsychiatric disorders have gone in hepatocellular insufficiency (hepatic encephalopathy), as well as in other forms of metabolic encephalopathies (renal, hypoxic), encephalography will help to recognize;
9. All drivers (future and current) when passing a medical examination to obtain / replace rights are offered to pass an EEG for a certificate provided by the traffic police. The survey is available in use and easily reveals those who are completely unfit to drive vehicles, therefore it was adopted;
10. Assign electroencephalography to conscripts with a history of convulsions (based on medical records) or in case of complaints of seizures with loss of consciousness accompanied by convulsions;
11. In some cases, such a study as EEG is used to ascertain the death of a significant part of nerve cells, that is, brain death(we are talking about situations when they say that “a person most likely turned into a plant”).

Video: EEG and epilepsy detection

The study does not require special preparation

EEG does not require special preparation, however, some patients are frankly afraid of the upcoming procedure. It's no joke - sensors with wires are placed on the head, which read "everything that happens inside the skull" and transmit the full amount of information to the "smart" device (in fact, the electrodes record changes in the potential difference between two sensors in different leads). Adults are provided with symmetrical attachment to the surface of the head of 20 sensors + 1 unpaired one, which is superimposed on the parietal region, 12 are enough for a small child.

Meanwhile, I would like to reassure especially suspicious patients: the study is absolutely harmless, has no restrictions on the frequency of conduct and age (at least several times a day and at any age - from the first days of life to extreme old age, if circumstances so require).

The main preparation is to ensure the cleanliness of the hair, for which the day before the patient washes his head with shampoo, rinses well and dries, but does not use any chemical styling products (gel, foam, varnish). Metal objects used for decoration (clips, earrings, barrettes, piercings) are also removed before an EEG is taken. Besides:

• For 2 days they refuse alcohol (strong and weak), do not use drinks stimulating the nervous system, do not regale themselves with chocolate;
• Before the study, they receive advice from a doctor regarding the medications taken (hypnotics, tranquilizers, anticonvulsants, etc.). It is possible that individual drugs, having agreed with the attending doctor, will have to be canceled, and if this cannot be done, then you should inform the doctor who will decipher the encephalogram (mark in the referral form) so that he has in mind these circumstances and takes them into account when drawing up the conclusion.
• 2 hours before the examination, patients should not allow themselves a hearty meal and relaxation with a cigarette (such activities can distort the results);
• It is not recommended to do an EEG in the midst of an acute respiratory illness, as well as with coughing and nasal congestion, even if these signs do not belong to an acute process.

When all the rules of the preparatory stage are observed, some moments are taken into account, the patient is seated in a comfortable chair, the points of contact of the head surface with the electrodes are lubricated with gel, sensors are attached, a cap is put on or dispensed with, the device is turned on - the recording has begun ... Provocative tests are used as needed during time of registration of bioelectrical activity of the brain. As a rule, this need arises when routine methods do not provide adequate information, that is, when epilepsy is suspected. Techniques provoking epileptic activity (deep breathing, opening and closing of the eyes, sleep, light irritation, sleep deprivation) activate the electrical activity of the GM cortex, the electrodes pick up the impulses sent by the cortex and transmit it to the main equipment for processing and recording.

In addition, if epilepsy is suspected (especially temporal epilepsy, which in most cases presents difficulties in diagnosis), special sensors are used: temporal, sphenoidal, nasopharyngeal. And, it should be noted, doctors officially recognized that in many cases it is the nasopharyngeal abduction that detects the focus of epileptic activity in the temporal region, while other leads do not react to it in any way and send normal impulses.

Video: EEG experts - information for patients

Video: conducting an EEG - a medical film

Electroencephalography (EEG)- a method of studying the activity of the brain, by registering its bioelectrical activity.

During the examination, bioelectrical activity is recorded in the form of a curve, the readings are recorded on paper (computer). By the nature of the signals, experts judge the consistency of the work of all brain structures.

Why do we need electroencephalography of the brain

EEG has a high diagnostic value, especially when it comes to a medical examination of a person who is going to get a license. In particular, the removal of an electroencephalogram is the only method that can reliably distinguish epilepsy from similar disorders (paroxysmal conditions).

Indications for brain electroencephalography

• to assess the consequences of traumatic brain injury;
• with epilepsy (before prescribing drug therapy, against the background of taking medications - to assess their effectiveness - and, of course, before canceling therapy or before reducing the dose of anticonvulsants);
• with brain tumors;
• with disorders of cerebral circulation;
• after neurosurgical operations;
• after perinatal damage to the central nervous system;
• with neurosis (stuttering, sleep disturbances, obsessive movements, tics, nocturnal enuresis);
• with a delay in psychomotor, psychoverbal or mental development in children;
• with cerebral palsy;
• within the framework of various medical examinations.

How is the EEG procedure performed?

There is daytime EEG monitoring, nighttime EEG video monitoring and daily EEG monitoring.

An EEG is a completely harmless and painless examination. The patient with his eyes closed sits in a comfortable chair, as relaxed as possible. On the skin of his head, electrodes are fixed that record the bioelectric activity of the brain.

Their readings are recorded by an electroencephalograph, and the doctor eventually receives a graph - an electroencephalogram. The type of graph also makes it possible to judge the presence of certain deviations from the norm.

Separately, it is worth mentioning the EEG in a dream - this significantly increases the information content of the diagnosis, since in a dream the brain activity characteristic of epilepsy increases dramatically. For children under 3 years of age, an EEG is done only while they are sleeping.

EEG preparation

Special preparation for the examination is not required, it is enough to avoid the use of caffeine for 12 hours: tea, coffee, energy drinks. You need to come to the procedure with clean and dry hair, on which there are no oils, lotions, aerosols, etc. cosmetics.

In our clinic, you can pass an EEG in one day, get a transcript and get a certificate for the traffic police (new sample).

Causeless headaches, poor sleep, fatigue, irritability - all this can be the result of poor blood circulation in the brain or abnormalities in the nervous system. For the timely diagnosis of negative disorders in the vessels, an EEG is used - an electroencephalogram of the brain. This is the most informative and accessible examination method that does not harm the patient and can be safely used in childhood.

An electroencephalogram is used to examine the blood vessels of the brain.

EEG of the brain - what is it?

An encephalogram of the head is a study of a vital organ by exposing its cells to electrical impulses.

The method determines the bioelectrical activity of the brain, is very informative and most accurate, as it shows the complete clinical picture:

• the level and spread of inflammatory processes;
• the presence of pathological changes in the vessels;
• early signs of epilepsy;
• tumor processes;
• the degree of impaired brain functioning due to pathologies of the nervous system;
• consequences of a stroke or surgery.

EEG helps detect signs of epilepsy

The EEG helps monitor changes in the brain, both structural and reversible. This allows you to monitor the activity of a vital organ during therapy, and adjust the treatment of identified diseases.

Where can I do and the price of the survey

Electroencephalography can be done at any specialized medical center. Institutions can be either public or private. Depending on the form of ownership, the level of qualification of the clinic, as well as the equipment used, the prices for the procedure differ significantly.

In addition, the following factors influence the cost of an encephalogram:

• the duration of the diagnostic procedure;
• carrying out functional tests;
• the use of special programs (for mapping, studying epileptic impulses, comparing zones of symmetrical zones of the brain).

Indications for an electroencephalogram

Before prescribing encephalography to a patient, a specialist examines a person and analyzes his complaints.

The following conditions may be the reason for the EEG:

• sleep problems - insomnia, frequent awakenings, sleepwalking;
• regular dizziness, fainting;
• fatigue and constant feeling of fatigue;
• causeless headaches.

Do not eat chocolate the day before the test.

How is an electroencephalogram performed?

Assessment of the electrical activity of brain cells is carried out using an encephalograph. It consists of sensors (electrodes) that resemble a cap for a pool, a block and a monitor to which the monitoring results are transmitted. The study is conducted in a small room that is isolated from light and sound.

The EEG method takes a little time and includes several steps:

1. Training. The patient takes a comfortable position - sits on a chair or lie down on the couch. Then the electrodes are applied. A specialist puts on a “cap” with sensors on the head of a person, the wiring of which is connected to the device, which captures the bioelectric impulses of the brain.
2. Study. After turning on the encephalograph, the device begins to read information, transferring it to the monitor in the form of a graph. At this time, the power of electric fields and its distribution by different parts of the brain can be recorded.
3. Use of functional tests. This is the implementation of simple exercises - blinking, looking at light flashes, breathing rarely or deeply, listening to sharp sounds.
4. Completion of the procedure. The specialist removes the electrodes and prints the results.

The importance of the normal functioning of the parts of the brain is undeniable - any deviation will certainly affect the health of the whole organism, regardless of the age and gender of the person. Therefore, at the slightest signal about the occurrence of violations, doctors immediately recommend an examination. Currently, medicine successfully uses a fairly large number of different methods for studying the activity and structure of the brain.

But if it is necessary to find out the quality of the bioelectrical activity of its neurons, then the electroencephalogram (EEG) is clearly considered the most suitable method for this. The doctor performing the procedure must be highly qualified, since, in addition to conducting the study, he will need to correctly read the results. Competent decoding of the EEG is a guaranteed step towards establishing the correct diagnosis and subsequent appointment of appropriate treatment.

More about the encephalogram

The essence of the survey is to fix the electrical activity of neurons in the structural formations of the brain. An electroencephalogram is a kind of recording of neural activity on a special tape when using electrodes. The latter are fixed on parts of the head and record the activity of a certain part of the brain.

The activity of the human brain is directly determined by the work of its median formations - the forebrain and the reticular formation (connecting neural complex), which determine the dynamics, rhythm and construction of the EEG. The linking function of the formation determines the symmetry and relative identity of signals between all brain structures.

The structure of the brain, on the basis of these data, the specialist deciphers the diagnosis

The procedure is prescribed for suspected various disorders of the structure and activity of the central nervous system (central nervous system) - neuroinfections, such as meningitis, encephalitis, poliomyelitis. With these pathologies, the activity of brain activity changes, and this can be immediately diagnosed on the EEG, and in addition, the localization of the affected area can be established. EEG is carried out on the basis of a standard protocol, which records the removal of indicators during wakefulness or sleep (in infants), as well as using specialized tests.

The main tests include:

• photostimulation - exposure to closed eyes with bright flashes of light;
• hyperventilation - deep rare breathing for 3-5 minutes;
• opening and closing of the eyes.

These tests are considered standard and are used for brain encephalograms in both adults and children of any age, and in various pathologies. There are several additional tests that are prescribed in individual cases, such as: clenching your fingers into a so-called fist, being in the dark for 40 minutes, sleep deprivation for a certain period, monitoring night sleep, passing psychological tests.

These tests are determined by the neurologist and are added to the main ones conducted during the examination, when the doctor needs to evaluate specific brain functions.

What can be assessed with an EEG?

This type of examination allows you to determine the functioning of the parts of the brain in different states of the body - sleep, wakefulness, active physical, mental activity, and others. EEG is a simple, absolutely harmless and safe method that does not require violation of the skin and mucous membranes of the organ.

Currently, it is widely in demand in neurological practice, since it makes it possible to diagnose epilepsy, to detect inflammatory, degenerative and vascular disorders in the brain regions with a high degree. The procedure also provides for the determination of the specific location of neoplasms, cystic growths and structural damage as a result of trauma.

EEG with the use of light and sound stimuli makes it possible to distinguish hysterical pathologies from true ones, or to reveal the simulation of the latter. The procedure has become almost indispensable for intensive care units, providing dynamic monitoring of comatose patients.

The disappearance of eclectic activity signals on the EEG indicates the onset of a lethal outcome.

The process of studying the results

The analysis of the results obtained is carried out in parallel during the procedure, and during the fixation of indicators, and continues after its completion. When recording, the presence of artifacts is taken into account - the mechanical movement of the electrodes, electrocardiograms, electromyograms, induction of mains current fields. The amplitude and frequency are estimated, the most characteristic graphic elements are distinguished, their temporal and spatial distribution is determined.

At the end, a patho- and physiological interpretation of the materials is made, and on its basis an EEG conclusion is formulated. Upon completion, the main medical form for this procedure is filled in, which has the name "clinical-electroencephalographic conclusion", compiled by the diagnostician on the analyzed data of the "raw" record.

The interpretation of the EEG conclusion is formed on the basis of a set of rules and consists of three sections:

• Description of the leading types of activity and graphic elements.
• Conclusion after description with interpreted pathophysiological materials.
• Correlation of indicators of the first two parts with clinical materials.

The main descriptive term in EEG is "activity", it evaluates any sequence of waves (acute wave activity, alpha activity, etc.).

Types of human brain activity recorded during EEG recording

The main types of activity that are recorded during the procedure and subsequently subjected to interpretation, as well as further study, are wave frequency, amplitude and phase.

Frequency

The indicator is estimated by the number of wave oscillations per second, fixed in numbers, and expressed in the unit of measurement - hertz (Hz). The description indicates the average frequency of the studied activity. As a rule, 4-5 sections of the recording are taken with a duration of 1 s, and the number of waves in each time interval is calculated.

Amplitude

This indicator is the range of wave fluctuations of the eclectic potential. It is measured by the distance between wave peaks in opposite phases and is expressed in microvolts (µV). A calibration signal is used to measure the amplitude. If, for example, a calibration signal at a voltage of 50 µV is detected on a record 10 mm high, then 1 mm will correspond to 5 µV. In deciphering the results, interpretations are given to the most frequent values, completely excluding rare ones.

Phase

The value of this indicator evaluates the current state of the process and determines its vector changes. On the electroencephalogram, some phenomena are estimated by the number of phases they contain. Oscillations are divided into monophasic, two-phase and polyphasic (containing more than two phases).

Rhythms of brain activity

The concept of "rhythm" on the electroencephalogram is considered to be a type of electrical activity related to a certain state of the brain, coordinated by appropriate mechanisms. When deciphering the indicators of the EEG rhythm of the brain, its frequency corresponding to the state of the brain area, amplitude, and its characteristic changes during functional changes in activity are entered.

Characteristics of brain rhythms depend on whether the subject is awake or asleep.

Rhythms of a waking man

Brain activity, recorded on the EEG in an adult, has several types of rhythms, characterized by certain indicators and conditions of the body.

• Alpha rhythm. Its frequency adheres to the interval of 8-14 Hz and is present in most healthy individuals - more than 90%. The highest amplitude values ​​are observed in the state of rest of the subject, who is in a dark room with his eyes closed. It is best defined in the occipital region. Fragmentally blocked or completely subsides during mental activity or visual attention.
• Beta rhythm. Its wave frequency fluctuates in the range of 13–30 Hz, and the main changes are observed when the subject is active. Pronounced fluctuations can be diagnosed in the frontal lobes with the obligatory condition of the presence of vigorous activity, for example, mental or emotional arousal and others. The amplitude of beta oscillations is much less than alpha.
• Gamma rhythm. The oscillation interval is from 30, can reach 120–180 Hz and is characterized by a rather reduced amplitude - less than 10 μV. Exceeding the limit of 15 μV is considered a pathology that causes a decrease in intellectual abilities. Rhythm is determined when solving problems and situations that require increased attention and concentration.
• Kappa rhythm. It is characterized by an interval of 8–12 Hz, and is observed in the temporal part of the brain during mental processes by suppressing alpha waves in other areas.
• Lambda rhythm. It has a small range - 4-5 Hz, starts in the occipital region when it is necessary to make visual decisions, for example, searching for something with open eyes. Fluctuations completely disappear after focusing the gaze at one point.
• Mu rhythm. Determined by the interval 8–13 Hz. It starts in the back of the head, and is best observed when at rest. It is suppressed at the start of any activity, not excluding the mental one.

Rhythms in sleep

• Delta rhythm. It is characteristic of the phase of deep sleep and for comatose patients. It is also recorded when recording signals from areas of the cerebral cortex located on the border with areas affected by oncological processes. Sometimes it can be recorded in children 4–6 years old.
• Theta rhythm. The frequency interval is within 4–8 Hz. These waves are triggered by the hippocampus (information filter) and appear during sleep. Responsible for the qualitative assimilation of information and underlies self-learning.
• Sigma rhythm. It differs in frequency of 10–16 Hz, and is considered one of the main and noticeable oscillations of the spontaneous electroencephalogram, which occurs during natural sleep at its initial stage.

Based on the results obtained when recording the EEG, an indicator is determined that characterizes a complete comprehensive assessment of the waves - the bioelectrical activity of the brain (BEA). The diagnostician checks the EEG parameters - frequency, rhythm and the presence of sharp flashes that provoke characteristic manifestations, and on these grounds makes a final conclusion.

Deciphering the indicators of the electroencephalogram

In order to decipher the EEG, and not to miss any of the smallest manifestations on the record, the specialist needs to take into account all the important points that may affect the parameters under study. These include age, the presence of certain diseases, possible contraindications and other factors.

Upon completion of the collection of all the data of the procedure and their processing, the analysis is being completed and then a final conclusion is formed, which will be provided for making a further decision on the choice of the method of therapy. Any disturbance of activities can be a symptom of diseases caused by certain factors.

alpha rhythm

The norm for the frequency is determined in the range of 8–13 Hz, and its amplitude does not go beyond 100 μV. Such characteristics indicate a healthy state of a person and the absence of any pathologies. Violations are considered:

• permanent fixation of the alpha rhythm in the frontal lobe;
• excess of the difference between the hemispheres up to 35%;
• permanent violation of wave sinusoidality;
• the presence of frequency spread;
• amplitude below 25 µV and over 95 µV.

The presence of violations of this indicator indicates a possible asymmetry of the hemispheres, which may be the result of oncological neoplasms or pathologies of the blood circulation of the brain, for example, stroke or hemorrhage. A high frequency indicates brain damage or TBI (traumatic brain injury).

Stroke or hemorrhage is one of the possible diagnoses for functional changes in the alpha rhythm.

The complete absence of the alpha rhythm is often observed in dementia, and in children, deviations from the norm are directly related to mental retardation (MPD). Such a delay in children is evidenced by: disorganization of alpha waves, a shift in focus from the occipital region, increased synchrony, a short activation reaction, and an overreaction to intense breathing.

These manifestations may be due to inhibitory psychopathy, epileptic seizures, and a short reaction is considered one of the primary signs of neurotic disorders.

beta rhythm

In the accepted norm, these waves are clearly defined in the frontal lobes of the brain with a symmetrical amplitude in the range of 3–5 μV, which is recorded in both hemispheres. A high amplitude leads doctors to think about the presence of a concussion, and when short spindles appear, encephalitis occurs. An increase in the frequency and duration of spindles indicates the development of inflammation.

In children, pathological manifestations of beta oscillations are considered to be a frequency of 15-16 Hz and a high amplitude present - 40-50 μV, and if its localization is the central or anterior part of the brain, then this should alert the doctor. Such characteristics indicate a high probability of a delay in the development of the baby.

Delta and Theta Rhythms

An increase in the amplitude of these indicators over 45 μV on an ongoing basis is characteristic of functional disorders of the brain. If the indicators are increased in all brain regions, then this may indicate severe violations of the functions of the central nervous system.

If a high amplitude of the delta rhythm is detected, a neoplasm is suspected. The overestimated values ​​of theta and delta rhythm, recorded in the occipital region, indicate the inhibition of the child and a delay in his development, as well as a violation of the circulatory function.

Deciphering values ​​in different age intervals

The EEG recording of a premature baby at 25–28 gestational weeks looks like a curve in the form of slow flashes of delta and theta rhythms, periodically combined with sharp wave peaks 3–15 seconds long with a decrease in amplitude to 25 μV. In full-term infants, these values ​​are clearly divided into three types of indicators. During wakefulness (with a periodic frequency of 5 Hz and an amplitude of 55-60 Hz), active phase of sleep (with a stable frequency of 5-7 Hz and a fast low amplitude) and restful sleep with flashes of delta oscillations at high amplitude.

Over the course of 3-6 months of a child's life, the number of theta oscillations is constantly growing, while the delta rhythm, on the contrary, is characterized by a decline. Further, from 7 months to a year, the child has the formation of alpha waves, and the delta and theta gradually fade away. Over the next 8 years, the EEG shows a gradual replacement of slow waves with fast ones - alpha and beta oscillations.

Rhythm indicators undergo regular changes depending on age

Until the age of 15, alpha waves predominate, and by the age of 18, the BEA transformation is completed. Over a period of 21 to 50 years, stable indicators hardly change. And from 50, the next phase of rhythmic restructuring begins, which is characterized by a decrease in the amplitude of alpha oscillations and an increase in beta and delta.

After 60 years, the frequency also begins to gradually fade away, and in a healthy person, delta and theta oscillations are noticed on the EEG. According to statistical data, age indicators from 1 to 21 years old, considered "healthy", are determined in the examined 1-15 years old, reaching 70%, and in the range of 16-21 years - about 80%.

The most common diagnosed pathologies

Thanks to the electroencephalogram, diseases such as epilepsy, or various types of traumatic brain injury (TBI) are quite easily diagnosed.

Epilepsy

The study allows you to determine the localization of the pathological area, as well as the specific type of epileptic disease. At the time of the convulsive syndrome, the EEG recording has a number of specific manifestations:

• pointed waves (peaks) - suddenly rising and falling can appear in one or several areas;
• the set of slow pointed waves during an attack becomes even more pronounced;
• sudden increase in amplitude in the form of flashes.

The use of stimulatory artificial signals helps in determining the form of epileptic disease, as they provide the visibility of hidden activity, which is difficult to diagnose by EEG. For example, intense breathing, requiring hyperventilation, leads to a decrease in the lumen of the vessels.

Photostimulation is also used, carried out using a stroboscope (a powerful light source), and if there is no reaction to the stimulus, then most likely there is a pathology associated with the conduction of visual impulses. The appearance of non-standard fluctuations indicates pathological changes in the brain. The doctor should not forget that exposure to powerful light can lead to an epileptic seizure.

TBI

If it is necessary to establish the diagnosis of TBI or concussion with all the inherent pathological features, EEG is often used, especially in cases where it is required to establish the location of the injury. If the TBI is mild, then the recording will record insignificant deviations from the norm - asymmetry and instability of rhythms.

If the lesion turns out to be serious, then, accordingly, the deviations on the EEG will be pronounced. Atypical changes in the recording, worsening during the first 7 days, indicate a massive brain lesion. Epidural hematomas are most often not accompanied by a special clinic, they can only be determined by slowing down alpha fluctuations.

But subdural hemorrhages look completely different - they form specific delta waves with flashes of slow oscillations, and at the same time, alpha is upset. Even after the disappearance of clinical manifestations, cerebral pathological changes may still be observed on the record for some time, due to TBI.

Restoration of brain function directly depends on the type and extent of the lesion, as well as on its localization. In areas subjected to disturbances or injuries, pathological activity may occur, which is dangerous for the development of epilepsy, therefore, in order to avoid complications of injuries, one should regularly undergo an EEG and monitor the state of the indicators.

Regular examination of the brain after a TBI will allow timely detection of complications

An encephalogram is an easy way to keep many brain disorders under control.

Despite the fact that the EEG is a fairly simple research method that does not require intervention in the patient's body, it has a fairly high diagnostic ability. Identification of even the smallest disturbances in the activity of the brain provides a quick decision on the choice of therapy and gives the patient a chance for a productive and healthy life!

EEG of the brain is a non-invasive method for studying an organ in order to identify foci of increased convulsive readiness of its cortex. This diagnostic method allows you to determine pathological changes in adults and children that can affect the functionality of individual parts of the hemisphere.

Electroencephalography (EEG) is a study of the functional state of the brain by recording its bioelectrical activity. For the procedure, an electroencephalograph is used, then computer data processing is carried out.

The result of the EEG is an electroencephalogram - a graphic recording of brain rhythms in the form of curved lines.

What does it show?

This study shows:

• rhythms of electrical activity of the brain, their characteristics;
• the presence or absence of foci of increased convulsive readiness and their localization;
• the effects of brain surgery or strokes;
• tumor processes in the brain and their impact on functional activity;
• effectiveness of drug treatment in epilepsy.

Advantages

The main advantages of the EEG method in medicine:

• high accuracy and efficiency;
• no need for complex preparation;
• not only diagnoses diseases, but also helps to distinguish true disorders from simulations or hysteria;
• allows you to conduct a study when the patient is in serious condition or in a coma;
• passes safely and painlessly for patients of different ages;
• the procedure is inexpensive, the equipment is available in almost all hospitals;
• detects brain disorders in the early stages, before the onset of clinical symptoms.

disadvantages

The study also has disadvantages:

1. The high sensitivity of the device to movements and tremors caused by the patient's psycho-emotional stress causes interference in operation, which can make diagnosis difficult.
2. It is necessary to remain calm and immobile throughout the study.
3. Particular difficulties arise with children, since it is difficult for young patients to explain the importance of the procedure.

The main indications for carrying out

An encephalogram is performed in such cases:

• complaints of insomnia, problems falling asleep, nocturnal awakenings;
• frequent dizziness, fainting;
• severe causeless headaches;
• epileptic seizures;
• psychopathy, psychoses, nervous breakdowns;
• poisoning with neurotoxic substances (lead, mercury, manganese, pesticides, carbon monoxide and others);
• infectious and viral diseases affecting the brain (encephalitis, meningitis);
• suspicion of a tumor;
• coma of the patient;
• lag in speech or mental development in children;
• head and neck injuries;
• all types of strokes;
• diseases of the endocrine system;
• studying the cycle of sleep and wakefulness;
• before, after and during brain surgery.

Contraindications for EEG

There are no absolute contraindications for the EEG of the brain, however, you can undergo the procedure on another day if you have:

• open injuries on the head;
• postoperative wounds;
• colds or SARS, flu.

With caution, studies should be carried out in patients with acute mental disorders, as well as violent patients. Exercise tests (sounds, flashing lights), and even the very sight of a cap with electrodes can trigger an attack. If the benefit of the study outweighs the possible risk, then the EEG is performed in such patients with preliminary medical sedation in the presence of an anesthesiologist.

Varieties of research methods

Several EEG methods are used:

• routine;
• with deprivation;
• long;
• night.

Depending on the duration and purpose, computed encephalography is divided into types:

1. An electroencephalogram of the brain is used at the initial stages of the examination. Both background activity and exercise tests (hyperventilation, harsh sounds, flashes of light) are recorded.
2. EEG monitoring is a continuous recording of brain activity. It is used when it is necessary to cover all possible physiological states of the central nervous system (sleep, wakefulness, mental work, emotions).
3. Rheoencephalography - a study of the vessels of the brain. Diagnostics is based on recording the changing electrical resistance of tissues when a weak high-frequency current is passed through them. Gives information about the tone and elasticity of the vascular wall, the value of pulse blood filling.

routine method

The routine method consists in short-term (approximately 15 minutes) recording of brain biopotentials. This is necessary to investigate and evaluate the dominant rhythms, the presence of pathological potentials and paroxysmal activity.

Functional tests are also carried out, in which the reaction to:

• opening - closing eyes;
• clenching a fist;
• hyperventilation - forced breathing;
• photostimulation - blinking of LEDs with closed eyes;
• harsh sounds.

The video shows an EEG with functional tests. Shot by the channel "Clinic doctor SAN".

Encephalography with deprivation

Encephalography with deprivation is performed with complete or partial sleep deprivation. Determines epileptic activity in situations that did not occur during provocative tests.

The patient either stays up all night or wakes up 2-3 hours earlier than usual. Not earlier than one day after the initial awakening, a routine EEG will be performed.

Long-term EEG recording

Long-term recording of indicators during sleep is often performed after EEG with deprivation, since sleep is a powerful activator for detecting epiactivity.

Only when performing a sleep EEG can differential diagnosis of epilepsy with cognitive impairment be made. Therefore, this type of examination is prescribed if the doctor suspects that changes in the brain occur while the patient is sleeping.

Nighttime EEG

Night EEG is recorded in a hospital in the following way:

• starts a few hours before bedtime;
• covers the period of falling asleep and the entire night's sleep;
• ends after natural awakening.

If necessary, additionally carried out:

• video monitoring;
• electrooculography (EOG);
• cardiogram recording (ECG);
• electromyograms (EMG);

How to prepare for the study

Basic preparation rules:

1. Wash your hair thoroughly with shampoo the night before. Do not use styling products (varnishes, foams). Hair must be loose.
2. Remove earrings, hairpins and all metal objects.
3. Before the examination, discuss with the doctor the use of medications (sleeping pills, tranquilizers, anticonvulsants, etc.). Some may have to be temporarily cancelled. If this is not possible, be sure to warn the specialist who will conduct the EEG so that he takes these circumstances into account when deciphering the results.
4. Give up alcohol, caffeinated and energy drinks (coffee, tea, Pepsi) within 24 hours. Avoid chocolate and cocoa. The same is true for anti-anxiety products and preparations.
5. 2 hours before the procedure, you need to eat, but without frills.
6. It is advisable not to smoke on this day or at least 2-3 hours before the study.
7. Remain calm before and during the procedure. Avoid stress the day before.
8. Get good sleep (except in deprivation studies).

Methodology

The EEG technique is as follows:

1. The electroencephalograph is connected to the electrodes, which are placed in the form of a cap on the surface of the subject's head. The standard scheme provides for the establishment of 21 electrodes. These sensors are designed to capture the potential difference between the electrodes in different leads and transfer information about them to the main equipment (device, computer) for automatic processing and analysis. Make a record with a certain frequency - 5-10 pulses per second.
2. The encephalograph processes the received signals, amplifies them and fixes them on paper in the form of a broken line, very reminiscent of an ECG. During the recording, the patient is asked not to move and to lie down with their eyes closed.
3. After a resting EEG, exercise tests are performed to assess the brain's response to stress.
4. A neurologist or neurophysiologist must decipher the results and issue a conclusion.

The study is carried out in a specially equipped room, protected from noise and light.

How long does the procedure take

The time it takes to complete an EEG depends on the type of study:

Stages

Routine EEG algorithm:

1. The patient sits on a chair or lays down on a couch, relaxes, closes his eyes.
2. Electrodes are placed on the head. Places of contact with the skin are lubricated with a gel or isotonic solution.
3. After switching on, the device starts reading information and transmitting it to the monitor in the form of a graph. This is how background activity is recorded.
4. Carrying out functional tests necessary to assess the reaction of the brain to stressful situations for it.
5. Completion of the procedure. The electrodes are removed, the doctor makes a description and printout of the results.

EEG monitoring

EEG monitoring is carried out to record and recognize brain activity during an epileptic attack.

The patient is hospitalized in a hospital for several days, all anticonvulsants are canceled for provocation. Monitoring is carried out with parallel sound and video recording for a day or more.

The method is more effective than conventional EEG for localizing areas of increased seizure activity, as well as for prescribing and monitoring the effectiveness of drug therapy.

Features of the conduct in children

For children under one year old, an EEG is done during sleep: according to the regimen, the duration of the procedure is adjusted.

Before research:

• wash your hair with shampoo;
• fed;
• put to sleep on schedule.

After a year, the child can be examined in a state of wakefulness. The task of parents is to psychologically prepare the baby, to talk about the procedure and its importance. You can come up with a game of astronauts or superheroes so that the child adapts faster.

EEG for children is carried out without stress tests.

What do EEG results show and their interpretation

The decoding of the electroencephalogram shows many types of waves in one or more diagrams. Each of them has its own characteristic and will display a certain type of activity.

Deciphering the EEG graph

You can decipher the EEG based on the following parameters:

1. Alpha wave - will show the work of the brain in a state of inactive wakefulness. Depression of the α-rhythm is caused by anxiety, fear, activation of autonomic nervous activity.
2. Beta wave - wakefulness mode, active mental work. In the normal state, it is weakly expressed.
3. Theta wave - natural sleep and falling asleep. An increase in theta rhythm is observed with prolonged psychoemotional stress, mental disorders, twilight states characteristic of some neurological diseases, asthenic syndrome, and concussion of the brain.
4. Delta wave - phase of deep sleep. As in the case of theta rhythm, the appearance during wakefulness indicates neurological disorders.

When describing the EEG, the following are taken into account:

• patient's age;
• general condition (tremor, visual disturbances, weakness in the limbs);
• medication, anticonvulsant therapy;
• date of the last attack;
• symmetry of rhythm amplitudes in different hemispheres;
• rhythm frequency;
• the presence or absence of paroxysm;
• rhythm synchrony.

Coherence analysis is used to assess the synchrony of the functional activity of brain regions. One of its main advantages is its independence from the amplitude of signal fluctuations in different areas of the brain. This makes it possible to show and evaluate the participation of different areas of the cortex in the performance of certain brain functions.