Electroencephalogram of the brain, what the transcript shows. What is electroencephalography, what does it detect and how is the brain examined. Types of activities that are pathological for an adult awake person

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The activity of the brain, the state of its anatomical structures, the presence of pathologies are studied and recorded using various methods– electroencephalography, rheoencephalography, computed tomography, etc. A huge role in identifying various abnormalities in the functioning of brain structures belongs to methods of studying its electrical activity, in particular electroencephalography.

Electroencephalogram of the brain - definition and essence of the method

Electroencephalogram (EEG) is a recording of the electrical activity of neurons in various brain structures, which is made on special paper using electrodes. Electrodes are placed on different parts of the head and record the activity of a particular part of the brain. We can say that an electroencephalogram is a recording of the functional activity of the brain of a person of any age.

The functional activity of the human brain depends on the activity of the median structures - reticular formation And forebrain, which determine the rhythm, general structure and dynamics of the electroencephalogram. A large number of connections of the reticular formation and forebrain with other structures and the cortex determine the symmetry of the EEG, and its relative “sameness” for the entire brain.

An EEG is taken to determine the activity of the brain in case of various lesions of the central nervous system, for example, with neuroinfections (poliomyelitis, etc.), meningitis, encephalitis, etc. Based on the EEG results, it is possible to assess the degree of brain damage due to various causes, and clarify specific location that has been damaged.

The EEG is taken according to a standard protocol, which takes into account recordings in a state of wakefulness or sleep (infants), with special tests. Routine tests for EEG are:
1. Photostimulation (exposure to flashes of bright light on closed eyes).
2. Opening and closing eyes.
3. Hyperventilation (rare and deep breathing for 3 to 5 minutes).

These tests are performed on all adults and children when taking an EEG, regardless of age and pathology. In addition, additional tests may be used when taking an EEG, for example:

• clenching your fingers into a fist;
• sleep deprivation test;
• stay in the dark for 40 minutes;
• monitoring the entire period of night sleep;
• reception medicines;
• performing psychological tests.

Additional tests for EEG are determined by a neurologist who wants to evaluate certain functions of a person's brain.

What does an electroencephalogram show?

An electroencephalogram reflects the functional state of brain structures in various human states, for example, sleep, wakefulness, active mental or physical work, etc. An electroencephalogram is an absolutely safe method, simple, painless and does not require serious intervention.

Today, the electroencephalogram is widely used in the practice of neurologists, since this method makes it possible to diagnose epilepsy, vascular, inflammatory and degenerative lesions of the brain. In addition, EEG helps to determine the specific location of tumors, cysts and traumatic damage to brain structures.

An electroencephalogram with irritation of the patient by light or sound makes it possible to distinguish true visual and hearing impairments from hysterical ones, or their simulation. EEG is used in intensive care units for dynamic monitoring of the condition of patients in a coma. The disappearance of signs of electrical activity of the brain on the EEG is a sign of human death.

Where and how to do it?

An electroencephalogram for an adult can be taken in neurological clinics, in departments of city and regional hospitals, or at a psychiatric clinic. As a rule, electroencephalograms are not taken in clinics, but there are exceptions to the rule. It's better to contact mental asylum or the neurology department, where specialists with the necessary qualifications work.

Electroencephalograms for children under 14 years of age are taken only in specialized children's hospitals where pediatricians work. That is, you need to go to the children's hospital, find the neurology department and ask when the EEG is taken. Psychiatric clinics, as a rule, do not take EEGs for young children.

In addition, private medical centers specializing in diagnostics and treatment of neurological pathology, also provide EEG services for both children and adults. You can contact a multidisciplinary private clinic, where there are neurologists who will take an EEG and decipher the recording.

An electroencephalogram should be taken only after a full night's rest, in the absence of stressful situations and psychomotor agitation. Two days before the EEG is taken, it is necessary to exclude alcoholic beverages, sleeping pills, sedatives and anticonvulsants, tranquilizers and caffeine.

Electroencephalogram for children: how the procedure is performed

Taking an electroencephalogram in children often raises questions from parents who want to know what awaits the baby and how the procedure goes. The child is left in a dark, sound- and light-proof room, where he is placed on a couch. Children under 1 year of age are kept in their mother's arms during EEG recording. The whole procedure takes about 20 minutes.

To record an EEG, a cap is placed on the baby's head, under which the doctor places electrodes. The skin under the electrodes is wetted with water or gel. Two inactive electrodes are placed on the ears. Then, using alligator clips, the electrodes are connected to the wires connected to the device - the encephalograph. Because the electric currents are very small, then an amplifier is always necessary, otherwise brain activity will simply be impossible to register. It is the small current strength that is the key to the absolute safety and harmlessness of EEG, even for infants.

To begin the examination, the child's head should be placed flat. Anterior tilt should not be allowed as this may cause artifacts that will be misinterpreted. EEGs are taken for infants during sleep, which occurs after feeding. Wash your child's hair before taking the EEG. Do not feed the baby before leaving the house; this is done immediately before the test so that the baby eats and falls asleep - after all, it is at this time that the EEG is taken. To do this, prepare formula or express breast milk into a bottle that you use in the hospital. Up to 3 years of age, EEG is taken only in a state of sleep. Children over 3 years old can stay awake, but to keep your baby calm, take a toy, book, or anything else that will distract the child. The child should be calm during the EEG.

Typically, the EEG is recorded as a background curve, and tests with opening and closing the eyes, hyperventilation (slow and deep breathing), and photostimulation are also performed. These tests are part of the EEG protocol, and are performed on absolutely everyone - both adults and children. Sometimes they ask you to clench your fingers into a fist, listen to various sounds, etc. Opening the eyes allows us to assess the activity of inhibition processes, and closing them allows us to assess the activity of excitation. Hyperventilation can be carried out in children after 3 years of age in the form of a game - for example, asking the child to inflate a balloon. Such rare and deep inhalations and exhalations last for 2–3 minutes. This test allows you to diagnose latent epilepsy, inflammation of the structures and membranes of the brain, tumors, dysfunction, fatigue and stress. Photostimulation is carried out with the eyes closed and the light blinking. The test allows you to assess the degree of delay in the child’s mental, physical, speech and mental development, as well as the presence of foci of epileptic activity.

Electroencephalogram rhythms

The electroencephalogram must show a regular rhythm of a certain type. The regularity of rhythms is ensured by the work of the part of the brain - the thalamus, which generates them and ensures the synchronization of the activity and functional activity of all structures of the central nervous system.

The human EEG contains alpha, beta, delta and theta rhythms, which have different characteristics and reflect certain types of brain activity.

Alpha rhythm has a frequency of 8 – 14 Hz, reflects a state of rest and is recorded in a person who is awake, but with his eyes closed. This rhythm is normally regular, the maximum intensity is recorded in the area of ​​the back of the head and the crown. The alpha rhythm ceases to be detected when any motor stimuli appear.

Beta rhythm has a frequency of 13 – 30 Hz, but reflects the state of anxiety, restlessness, depression and the use of sedative medications. The beta rhythm is recorded with maximum intensity over the frontal lobes of the brain.

Theta rhythm has a frequency of 4–7 Hz and an amplitude of 25–35 μV, reflecting the state of natural sleep. This rhythm is a normal component of the adult EEG. And in children this type of rhythm on the EEG predominates.

Delta rhythm has a frequency of 0.5 - 3 Hz, it reflects the state of natural sleep. It can also be recorded in a limited amount during wakefulness, a maximum of 15% of all EEG rhythms. The amplitude of the delta rhythm is normally low - up to 40 μV. If there is an excess of amplitude above 40 μV, and this rhythm is recorded for more than 15% of the time, then it is classified as pathological. Such a pathological delta rhythm indicates a dysfunction of the brain, and it appears precisely over the area where pathological changes develop. The appearance of a delta rhythm in all parts of the brain indicates the development of damage to the structures of the central nervous system, which is caused by liver dysfunction, and is proportional to the severity of the disturbance of consciousness.

Electroencephalogram results

The result of the electroencephalogram is a recording on paper or in computer memory. The curves are recorded on paper and analyzed by the doctor. The rhythm of EEG waves, frequency and amplitude are assessed, characteristic elements are identified, and their distribution in space and time is recorded. Then all the data is summarized and reflected in the conclusion and description of the EEG, which is pasted into the medical record. The EEG conclusion is based on the type of curves, taking into account the clinical symptoms present in a person.

Such a conclusion must reflect the main characteristics of the EEG, and includes three mandatory parts:
1. Description of the activity and typical affiliation of EEG waves (for example: “The alpha rhythm is recorded over both hemispheres. The average amplitude is 57 μV on the left and 59 μV on the right. The dominant frequency is 8.7 Hz. The alpha rhythm dominates in the occipital leads.”).
2. Conclusion according to the description of the EEG and its interpretation (for example: “Signs of irritation of the cortex and midline structures of the brain. Asymmetry between the hemispheres of the brain and paroxysmal activity were not detected”).
3. Determining the correspondence of clinical symptoms with EEG results (for example: “Objective changes in the functional activity of the brain were recorded, corresponding to manifestations of epilepsy”).

Decoding the electroencephalogram

Decoding an electroencephalogram is the process of interpreting it taking into account the clinical symptoms present in the patient. In the process of decoding, it is necessary to take into account the basal rhythm, the level of symmetry in the electrical activity of brain neurons of the left and right hemispheres, the activity of the commissure, EEG changes against the background of functional tests (opening - closing the eyes, hyperventilation, photostimulation). The final diagnosis is made only taking into account the presence of certain clinical signs that concern the patient.

Decoding the electroencephalogram involves interpreting the conclusion. Let's consider the basic concepts that the doctor reflects in the conclusion and their clinical significance (that is, what these or those parameters can indicate).

Alpha - rhythm

Normally, its frequency is 8–13 Hz, the amplitude ranges up to 100 μV. It is this rhythm that should prevail over both hemispheres in healthy adults. Alpha rhythm pathologies are the following:

• constant registration of the alpha rhythm in the frontal parts of the brain;
• interhemispheric asymmetry above 30%;
• violation of sinusoidal waves;
• paroxysmal or arc-shaped rhythm;
• unstable frequency;
• amplitude less than 20 μV or more than 90 μV;
• rhythm index less than 50%.

What do common alpha rhythm disturbances indicate?
Severe interhemispheric asymmetry may indicate the presence of a brain tumor, cyst, stroke, heart attack or scar at the site of an old hemorrhage.

High frequency and instability of the alpha rhythm indicate traumatic brain damage, for example, after a concussion or traumatic brain injury.

Disorganization of the alpha rhythm or its complete absence indicates acquired dementia.

About delayed psycho-motor development in children they say:

• alpha rhythm disorganization;
• increased synchrony and amplitude;
• moving the focus of activity from the back of the head and crown;
• weak short activation reaction;
• excessive response to hyperventilation.

A decrease in the amplitude of the alpha rhythm, a shift in the focus of activity from the back of the head and crown, and a weak activation reaction indicate the presence of psychopathology.

Excitable psychopathy is manifested by a slowdown in the frequency of the alpha rhythm against the background of normal synchrony.

Inhibitory psychopathy is manifested by EEG desynchronization, low frequency and alpha rhythm index.

Increased synchronization of the alpha rhythm in all parts of the brain, a short activation reaction - the first type of neuroses.

Weak expression of the alpha rhythm, weak activation reactions, paroxysmal activity - the third type of neuroses.

Beta rhythm

Normally, it is most pronounced in the frontal lobes of the brain and has a symmetrical amplitude (3–5 μV) in both hemispheres. Pathology of the beta rhythm is the following signs:

• paroxysmal discharges;
• low frequency, distributed over the convexital surface of the brain;
• asymmetry between hemispheres in amplitude (above 50%);
• sinusoidal type of beta rhythm;
• amplitude more than 7 μV.

What do beta rhythm disturbances on the EEG indicate?
The presence of diffuse beta waves with an amplitude no higher than 50-60 μV indicates a concussion.

Short spindles in the beta rhythm indicate encephalitis. The more severe the inflammation of the brain, the greater the frequency, duration and amplitude of such spindles. Observed in a third of patients with herpes encephalitis.

Beta waves with a frequency of 16–18 Hz and high amplitude (30–40 μV) in the anterior and central parts of the brain are signs of delayed psychomotor development of a child.

EEG desynchronization, in which the beta rhythm predominates in all parts of the brain, is the second type of neurosis.

Theta rhythm and delta rhythm

Normally, these slow waves can only be recorded on the electroencephalogram of a sleeping person. In a state of wakefulness, such slow waves appear on the EEG only in the presence of degenerative processes in the tissues of the brain, which are combined with compression, high blood pressure and lethargy. Paroxysmal theta and delta waves in a person in a state of wakefulness are detected when the deep parts of the brain are damaged.

In children and young people under 21 years of age, the electroencephalogram may reveal diffuse theta and delta rhythms, paroxysmal discharges and epileptoid activity, which are normal variants and do not indicate pathological changes in brain structures.

What do disturbances of theta and delta rhythms on the EEG indicate?
Delta waves with high amplitude indicate the presence of a tumor.

Synchronous theta rhythm, delta waves in all parts of the brain, bursts of bilateral synchronous theta waves with high amplitude, paroxysms in the central parts of the brain - indicate acquired dementia.

The predominance of theta and delta waves on the EEG with maximum activity in the occipital region, flashes of bilateral synchronous waves, the number of which increases with hyperventilation, indicates a delay in the psychomotor development of the child.

A high index of theta activity in the central parts of the brain, bilateral synchronous theta activity with a frequency of 5 to 7 Hz, localized in the frontal or temporal regions of the brain indicate psychopathy.

Theta rhythms in the anterior parts of the brain as the main ones are an excitable type of psychopathy.

Paroxysms of theta and delta waves are the third type of neuroses.

The appearance of high-frequency rhythms (for example, beta-1, beta-2 and gamma) indicates irritation (irritation) of brain structures. This may be due to various cerebrovascular accidents, intracranial pressure, migraines, etc.

Bioelectric activity of the brain (BEA)

This parameter in the EEG conclusion is a complex descriptive characteristic regarding brain rhythms. Normally, the bioelectric activity of the brain should be rhythmic, synchronous, without foci of paroxysms, etc. At the conclusion of the EEG, the doctor usually writes what specific disturbances in the bioelectrical activity of the brain were identified (for example, desynchronized, etc.).

What do various disturbances in the bioelectrical activity of the brain indicate?
Relatively rhythmic bioelectrical activity with foci of paroxysmal activity in any area of ​​the brain indicates the presence of some area in its tissue where excitation processes exceed inhibition. This type of EEG may indicate the presence of migraines and headaches.

Diffuse changes in the bioelectrical activity of the brain may be normal if no other abnormalities are detected. Thus, if in the conclusion it is written only about diffuse or moderate changes in the bioelectrical activity of the brain, without paroxysms, foci of pathological activity, or without a decrease in the threshold of convulsive activity, then this is a variant of the norm. In this case, the neurologist will prescribe symptomatic treatment and put the patient under observation. However, in combination with paroxysms or foci of pathological activity, they speak of the presence of epilepsy or a tendency to seizures. Reduced bioelectrical activity of the brain can be detected in depression.

Other indicators

Dysfunction of midbrain structures – this is a mildly expressed disturbance in the activity of brain neurons, which is often found in healthy people, and indicates functional changes after stress, etc. This condition requires only a symptomatic course of therapy.

Interhemispheric asymmetry may be a functional disorder, that is, not indicate pathology. In this case, it is necessary to undergo examination by a neurologist and a course of symptomatic therapy.

Diffuse disorganization of the alpha rhythm, activation of diencephalic-stem structures of the brain against the background of tests (hyperventilation, closing-opening of eyes, photostimulation) is the norm, if the patient has no complaints.

Center of pathological activity indicates increased excitability of this area, which indicates a tendency to seizures or the presence of epilepsy.

Irritation of various brain structures (cortex, middle sections, etc.) is most often associated with impaired cerebral circulation due to various reasons (for example, atherosclerosis, trauma, increased intracranial pressure, etc.).

Paroxysms They talk about increased excitation and decreased inhibition, which is often accompanied by migraines and simple headaches. In addition, there may be a tendency to develop epilepsy or the presence of this pathology if a person has had seizures in the past.

Reducing the threshold for seizure activity indicates a predisposition to seizures.

The following signs indicate the presence of increased excitability and a tendency to convulsions:

• changes in electrical potentials of the brain according to the residual-irritative type;
• enhanced synchronization;
• pathological activity of the midline structures of the brain;
• paroxysmal activity.

In general, residual changes in brain structures are the consequences of damage of various types, for example, after injury, hypoxia, viral or bacterial infection. Residual changes are present in all brain tissues and are therefore diffuse. Such changes disrupt the normal passage of nerve impulses.

Irritation of the cerebral cortex along the convexial surface of the brain, increased activity of the median structures at rest and during tests can be observed after traumatic brain injuries, with a predominance of excitation over inhibition, as well as with organic pathology of brain tissue (for example, tumors, cysts, scars, etc.).

Epileptiform activity indicates the development of epilepsy and an increased tendency to seizures.

Increased tone of synchronizing structures and moderate dysrhythmia are not pronounced disorders or pathologies of the brain. In this case, resort to symptomatic treatment.

Signs of neurophysiological immaturity may indicate a delay in the child’s psychomotor development.

Pronounced changes in residual organic type with increasing disorganization during tests, paroxysms in all parts of the brain - these signs usually accompany severe headaches, increased intracranial pressure, attention deficit hyperactivity disorder in children.

Disturbance of brain wave activity (appearance of beta activity in all parts of the brain, dysfunction of midline structures, theta waves) occurs after traumatic injuries, and can manifest itself as dizziness, loss of consciousness, etc.

Organic changes in brain structures in children are a consequence infectious diseases, such as cytomegalovirus or toxoplasmosis, or hypoxic disorders that arose during childbirth. A comprehensive examination and treatment is necessary.

Regulatory cerebral changes are registered in hypertension.

The presence of active discharges in any part of the brain , which intensify with exercise, means that in response to physical stress a reaction may develop in the form of loss of consciousness, visual impairment, hearing loss, etc. The specific reaction to physical activity depends on the location of the source of active discharges. In this case, physical activity should be limited to reasonable limits.

In case of brain tumors, the following are detected:

• the appearance of slow waves (theta and delta);
• bilateral synchronous disorders;
• epileptoid activity.

Changes progress as the volume of education increases.

Desynchronization of rhythms, flattening of the EEG curve develops in cerebrovascular pathologies. A stroke is accompanied by the development of theta and delta rhythms. The degree of electroencephalogram abnormalities correlates with the severity of the pathology and the stage of its development.

Theta and delta waves in all parts of the brain; in some areas, beta rhythms are formed during injury (for example, with a concussion, loss of consciousness, bruise, hematoma). The appearance of epileptoid activity against the background of brain injury can lead to the development of epilepsy in the future.

Significant slowing of alpha rhythm may accompany parkinsonism. Fixation of theta and delta waves in the frontal and anterior temporal parts of the brain, which have different rhythms, low frequencies and high amplitudes, is possible in Alzheimer's disease

Under the complex name lies a safe, easy-to-perform method of studying the brain that captures electrical impulses and records their rhythm and frequency. An electroencephalogram of the brain provides information about the functional characteristics of this organ.

EEG is a test that can be performed on patients of all ages and in any condition. An electroencephalograph, a research device, is indispensable in intensive care wards. This is what is connected to patients in a coma to monitor the slightest changes in the electrical activity of the brain.

Electroencephalography can be carried out in parallel with the patient's exposure to irritating factors: sounds, light, sleep deprivation. This gives a clearer picture of the nature of the disorder and areas of epileptic activity.

Indications

After an EEG, it is more likely to exclude or confirm the presence of such pathologies in a person as:

• vegetative-vascular dystonia;
• brain inflammation;
• neoplasms;
• epilepsy;
• hypertonic disease;
• nervous disorders;
• cervical osteochondrosis;
• traumatic brain injury.

The electroencephalogram of the brain reflects the state of the organ in postoperative period, after a stroke, the dynamics of changes after treatment. It is required when passing a medical examination to obtain a driving category C and D.

How to prepare

You need to prepare for the examination. Tell your doctor if you are taking certain medications. Some of them affect brain activity and should be discontinued 3-4 days before the examination. These medications include anticonvulsants and tranquilizers.

On the eve of the EEG and on the day of the test, you should not consume caffeine-containing products and energy drinks: coffee, tea, chocolate, energy drinks. You can't drink alcohol. These foods have a stimulating effect on the brain, and the brain's encephalogram will be distorted.

It is advisable to eat a few hours before the examination.

It is recommended to wash your hair, but do not apply hairspray, styling foam, etc. cosmetical tools. The fats and other components they contain can worsen the contact of the electrodes with the scalp. Braids and dreadlocks will have to be unbraided, and earrings and jewelry removed.

During the procedure, you need to remain calm and not be nervous. Nothing bad happens, and the procedure is completely harmless.

Carrying out an EEG

Typically, electroencephalography is carried out in a specially equipped room, protected from noise and bright light, in which there is a stationary electroencephalograph. If it is necessary to conduct an EEG on site, mobile devices are used.

The patient is asked to lie down on a couch or sit comfortably in a chair. A helmet or cap with electrodes is placed on the head, the number of which depends on the age of the patient. For a small child, 12 electrodes are enough; for adults, 21 are used. The electrode cavity is filled with a special substance that facilitates the rapid transmission of electrical impulses. Signals coming from the area next to the electrode have the greatest clarity and strength. Signals received from remote areas are weak.

The cap is connected to an encephalograph, which is capable of detecting vibration frequencies of 0.5 - 100 Hz and serves as an amplifier. The electrical signal is amplified by the encephalograph millions of times and transmitted for subsequent processing to a computer. Here, a huge number of signals are converted into a graph - an encephalogram, which is analyzed by the doctor.

The patient must remain calm and not move during the examination. Only at the very beginning may the doctor ask him to blink several times to assess the nature of the technical errors. If the patient urgently needs to change body position or go to the toilet, the study is stopped. In a situation where he made an involuntary movement, moved, the doctor makes an appropriate note so that during further analysis false information does not appear.

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An encephalogram of the brain is recorded for about 15-20 minutes.

EEG with provocative tests

If necessary, after the main recording, provocative tests are done:

1. With hyperventilation - the patient is asked to breathe deeply for several minutes.
2. Test with bright light. It uses a special device capable of reproducing repeating light pulses. An electroencephalogram of the brain records the patient's reaction.
3. Test with an unexpected sound.

Tests help to find out the real cause of the disorder - whether it is a manifestation of a pathological process, mental disorder or simulation. If there is a real pathology, testing may provoke an epileptic attack or convulsion. Therefore, the doctor conducting the diagnosis has the experience and knowledge necessary to provide urgent care. The time required for the sample procedure increases.

EEG with sleep deprivation

If there is a suspicion that a conventional EEG did not provide complete and reliable information, electroencephalography with sleep deprivation is prescribed. Some sources indicate that only in 20-30% of cases, when performed in a standard manner, an encephalogram of the head shows signs of epilepsy. Data obtained during sleep is considered more accurate. Before the study, an adult should not sleep for 18 hours. In some cases, if the examination is carried out in a hospital, the patient is woken up in the middle of the night and forced to undergo diagnostics.

If the patient was able to fall asleep quickly, the procedure takes about an hour. The doctor or nurse makes notes regarding any changes in the patient: flinching, movements of the eyes, arms, legs. In the future, the encephalogram of the brain will be interpreted with their help.

At the end of the procedure, the patient is woken up, his condition is checked and sent home or to the ward. After the diagnosis, rest is recommended.

Features of EEG in children

It is not easy to conduct an EEG of the brain in a small child. It scares him a large number of wires, a strange cap, unfamiliar surroundings, people, devices. It is quite difficult to convince your baby that he will have to lie still for some time. Young children are examined during sleep. Before the study, they need to limit the rest time so that he is tired and wants to sleep before the study. On the day of the examination, babies are woken up 4-6 hours before the usual wake-up time. Younger children school age- in 6-8 hours, and children over 12 years old are not allowed to fall asleep at night at all.

Electroencephalography (EEG) is a modern method for diagnosing brain diseases in children and adult patients. This procedure is based on recording the electrical activity of individual parts of the central nervous system (CNS), which makes it possible to assess their condition and functional activity. When conducting an EEG of the brain, deciphering the indicators is the most important step, since the diagnosis and the prescription of subsequent treatment depend on this. The data obtained from the electroencephalogram must be interpreted by a neurologist who has undergone special training. Otherwise, it is possible to use inappropriate medications, which can lead to various complications and side effects medicines.

When performing an EEG, the patient must be in a calm state

About method

EEG is a diagnostic procedure based on recording the activity of parts of the brain. This becomes possible thanks to the use of precise electrodes that make it possible to record the functional state various groups neurons. At the same time, the procedure can be performed at different ages for a wide range of diseases, including neuroinfections, infectious and non-infectious encephalitis and meningitis, epilepsy, etc. The technique allows us to identify the presence and extent of brain damage.

The procedure is carried out in accordance with a special protocol, which includes various functional tests:

• Exposure to flashes of bright light, or photostimulation. It is important to note that at this moment the patient must keep his eyes closed.
• Alternating eye opening and closing test.
• Breathing test assessing the state of the central nervous system during hyperventilation.

Special tests allow for a more complete study of the functions of various parts of the brain. At the same time, a number of doctors, to obtain accurate results, use additional actions on the part of the patient, for example, squeezing the fingers or staying in the dark for a long time. In addition, drug tests, daily monitoring of brain activity, etc. are possible. All this is necessary for the subsequent interpretation of the EEG of the brain in order to make a correct diagnosis.

Conducting research

When conducting a diagnostic analysis of brain activity, an EEG must be performed in a special room that excludes any external stimuli to the patient, including visual and sound stimuli. The patient can sit or lie down while the encephalogram is being taken. Analysis of neuron activity occurs thanks to a special cap with several dozen electrodes, which are sensors.

These sensors are lubricated with a special electrically conductive gel, which allows one to obtain clearer results, facilitating the subsequent interpretation of the EEG. Depending on the need for additional tests, the duration of the study can vary from 15 minutes to twenty-four hours.

Correct interpretation of the EEG in an adult requires compliance with the standard protocol of the procedure. To do this, before starting the study, the doctor must talk with the patient and explain to him the essence of the upcoming procedure, as well as possible indicators that reflect the normality or pathology of the brain.

During the process of taking an EEG, the patient should not move, keep his eyes closed at all times and follow all incoming doctor’s instructions.

EEG rhythms in a healthy person

The main types of rhythms observed during EEG

The activity of brain neurons is recorded in the form of a certain rhythm, which depends on the work of the subcortical and cortical parts of the central nervous system. As a rule, four types of rhythms can be detected in a healthy person:

1. The alpha rhythm corresponds to the state of rest during wakefulness. It is important to note that in this case, the person must have his eyes closed. The average frequency of such a rhythm is 8-14 Hz. With any physical activity, the alpha rhythm changes.
2. The beta rhythm is characteristic of a state of excitement when a person experiences fear, anxiety and any other negative emotions. The pulse frequency ranges from 13 to 30 Hz.
3. The theta rhythm is associated with rare impulses (4-7 Hz) and is low-amplitude. It corresponds to natural sleep and is most common in children.
4. The delta rhythm has an even lower frequency (up to 3 Hz) and is also characteristic of the sleep period. A similar form of activity occurs during the waking period, however, quite rarely.

The picture of the resulting rhythms should only be deciphered by a neurologist. When trying to interpret it yourself, mistakes and incorrect conclusions are possible, which can cause harm to the patient.

Decoding the results

Patients often wonder: did they undergo an electroencephalogram of the brain, what does the transcript of this study show? Such an analysis allows the doctor to assess the condition and activity of various parts of the brain, which is necessary to identify diseases.

To decipher the electroencephalogram, the doctor must have certain qualifications

It becomes possible to identify changes and disturbances in the activity of the central nervous system by assessing the rhythm of excitation, comparing data obtained from symmetrical areas of the brain, as well as by analyzing the results of special functional tests with photostimulation, hyperventilation, etc.

If EEG interpretation is required in children (suspected autism, epilepsy, etc.), then, due to the insufficient maturity of the structures of the central nervous system, a number of studies are required to compare the results with each other. This approach makes it possible to suspect diseases at an early age.

Various characteristics of the patient’s body or external influences can change the results obtained, affecting the conclusion of the EEG. These include:

• Patient's age.
• Presence of concomitant diseases.
• Tremor and other changes in the motor sphere.
• Visual impairment.
• Taking medications that affect the nervous system. Similar changes are observed when drinking drinks containing caffeine.
• Any changes in the electrical conductivity of the skin, which can be observed with increased oiliness, etc.

The attending physician must take these factors into account when drawing up the results and conclusion of the EEG. If you suspect errors during the research process, it is better to repeat it.

Possible deviations in results

The final diagnosis is made only taking into account the clinical symptoms that concern the patient

Doctors know well how to decipher an EEG and what changes this technique can show. It is important to note that not every doctor is able to provide the correct interpretation of the results, and therefore patients should only contact specialists.

There is a large number possible options deviations that can be moderate or severe, depending on the degree of damage to the central nervous system. The main changes in the electroencephalogram include:

• Impaired coordination of the central nervous system structures located in different hemispheres. This can be observed with damage to pathways or local effects on a group of neurons.
• The appearance of sharp bursts of activity or their suppression may indicate an infectious lesion of the nervous system, the development of a tumor process, traumatic brain injury or various types of stroke.
• The appearance of rhythms with high amplitude, irregular shape, and also in the form of multiple repetitions, reflects diffuse disturbances in neuronal activity, which can occur in epilepsy.
• When awake, delta and theta rhythms should not be detectable in a normal person. If they are detected, then this indicates a disruption of the central nervous system.
• A significant decrease in brain activity is observed in patients in a coma.

In addition to these obvious deviations, the doctor can indicate in his conclusion changes in individual rhythms that are observed in healthy people. Such deviations are characterized by an increase in the frequency or amplitude of individual rhythms and reflect damage to the structures of the central nervous system of an organic or functional nature.

Electroencephalograms in normal conditions and during epileptic seizures

In some patients, the medical report form on EEG interpretation contains additional signs of impaired brain function:

• Paroxysmal changes, mainly indicating a severe headache that persists constantly. There is also evidence that such paroxysms may reflect the patient’s predisposition to epileptic seizures.
• When the EEG is deciphered, the doctor can pay attention to foci of constant excitation of neurons - they can become the site of the onset of epileptic activity in a patient at any age.
• A decrease in activity, even to the point of disappearance, of neurons in individual brain structures indicates their serious damage, which can occur with strokes, traumatic brain injuries, etc.

The obtained electroencephalogram values ​​make it possible to make an accurate diagnosis of central nervous system damage, which is necessary for choosing further diagnostic and therapeutic tactics. Possible deviations should be carefully analyzed, comparing, if possible, the picture of changes with previous survey results.

Electroencephalography is an indispensable diagnostic method for many neurological diseases, for example, epilepsy. A neurologist can interpret the results and determine the presence and extent of brain damage without using invasive diagnostic methods. The procedure can be performed at any age, including infants.

The importance of the normal functioning of parts of the brain is undeniable - any deviation will certainly affect the health of the entire body, regardless of the person’s age and gender. Therefore, at the slightest signal of a violation, doctors immediately recommend undergoing 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 interpretation of the EEG is a guaranteed step towards establishing the correct diagnosis and subsequent prescription of appropriate treatment.

More about the encephalogram

The essence of the examination is to record the electrical activity of neurons in the structural formations of the brain. An electroencephalogram is a kind of recording of neural activity on special tape when using electrodes. The latter are attached to areas of the head and record the activity of a certain area of ​​the brain.

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

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

The procedure is prescribed if there are suspicions of 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 the brain changes, and this can be immediately diagnosed on the EEG, and in addition, the localization of the affected area can be established. An EEG is carried out on the basis of a standard protocol, which records measurements taken while awake or asleep (in infants), as well as using specialized tests.

The main tests include:

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

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

These tests are determined by a neurologist and are added to the main tests performed 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 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 disruption skin and the mucous membrane of the organ.

Currently, it is widely in demand in neurological practice, since it makes it possible to diagnose epilepsy and highly identify inflammatory, degenerative and vascular disorders in the brain. The procedure also provides identification of the specific location of tumors, cystic growths and structural damage as a result of trauma.

EEG using light and sound stimuli makes it possible to distinguish hysterical pathologies from true ones, or to identify 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 death

Process of studying the results

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

Upon completion, 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 out, called a “clinical electroencephalographic report”, compiled by a diagnostician based on the analyzed data from the “raw” recording.

The transcript 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 (sharp 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 and further study are wave frequency, amplitude and phase.

Frequency

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

Amplitude

This indicator is the range of wave oscillations of the eclectic potential. It is measured by the distance between the peaks of waves 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 determined on a record with a height of 10 mm, then 1 mm will correspond to 5 µV. In deciphering the results, interpretations are given to the most common meanings, completely excluding rare ones.

Phase

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

Rhythms of brain activity

The concept of “rhythm” in 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 EEG rhythm indicators of the brain, its frequency corresponding to the state of the brain region, 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 person

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

• Alpha rhythm. Its frequency remains in the range of 8–14 Hz and is present in most healthy individuals – more than 90%. The highest amplitude values ​​are observed in the resting state of the subject, who is in dark room with eyes closed. It is best identified in the occipital region. It is fragmentarily 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 under the obligatory condition of active 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 causing 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, and is triggered in the occipital region when it is necessary to make visual decisions, for example, when searching for something with open eyes. The vibrations disappear completely after concentrating your gaze on one point.
• Mu rhythm. Defined by the interval 8–13 Hz. It starts in the back of the head, and is best observed in a calm state. Suppressed when starting any activity, not excluding mental activity.

Rhythms in sleep

• Delta rhythm. Characteristic of the deep sleep phase 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 high-quality assimilation of information and forms the basis of self-learning.
• Sigma rhythm. It has a 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 during EEG recording, an indicator is determined that characterizes a complete all-encompassing assessment of the waves - 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.

Decoding of electroencephalogram indicators

In order to decipher the EEG and not miss any of the smallest manifestations in the recording, the specialist needs to take into account everything important points, which may affect the studied indicators. These include age, the presence of certain diseases, possible contraindications and other factors.

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

Alpha rhythm

The normal 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. The following are considered violations:

• constant fixation of the alpha rhythm in the frontal lobe;
• exceeding the difference between the hemispheres by up to 35%;
• constant violation of wave sinusoidality;
• presence of frequency dispersion;
• amplitude below 25 μV and above 95 μV.

The presence of disturbances in this indicator indicates a possible asymmetry of the hemispheres, which may be the result of oncological tumors or pathologies of cerebral circulation, 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

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

These manifestations can be caused by 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 detected in the frontal lobes of the brain with a symmetrical amplitude in the range of 3–5 μV, recorded in both hemispheres. A high amplitude leads doctors to think about the presence of a concussion, and when short spindles appear, to the occurrence of encephalitis. An increase in the frequency and duration of spindles indicates the development of inflammation.

In children, the 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 delayed development of the baby.

Delta and theta rhythms

An increase in the amplitude of these indicators above 45 μV on a constant basis is characteristic of functional brain disorders. If the indicators are increased in all brain regions, then this may indicate severe dysfunction of the central nervous system.

If a high amplitude of the delta rhythm is detected, a tumor is suspected. Inflated values ​​of the theta and delta rhythm recorded in the occipital region indicate a child’s lethargy and a delay in his development, as well as impaired circulatory function.

Decoding values ​​in different age intervals

An 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), the active phase of sleep (with a stable frequency of 5–7 Hz and a fast low amplitude) and quiet sleep with flashes of delta oscillations at a 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 develops alpha waves, and 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 complete. Over the period from 21 to 50 years, stable indicators remain almost unchanged. And from 50, the next phase of rhythmicity 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, and in a healthy person, manifestations of delta and theta oscillations are noticed on the EEG. According to statistics, age indicators from 1 to 21 years, considered “healthy,” are determined in subjects 1–15 years old, reaching 70%, and in the range of 16–21 – 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 a 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 combination of slow pointed waves during an attack becomes even more pronounced;
• sudden increase in amplitude in the form of flashes.

The use of stimulating artificial signals helps in determining the form of epileptic disease, since they provide visibility of hidden activity that is difficult to diagnose with EEG. For example, intense breathing, requiring hyperventilation, leads to a decrease in the lumen of blood vessels.

Photostimulation is also used, carried out using a strobe (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 vibrations 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 a diagnosis of TBI or concussion with all its inherent pathological features, EEG is often used, especially in cases where it is necessary 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, deviations in the EEG will be pronounced. Atypical changes in recordings that worsen over the first 7 days indicate extensive brain damage. Epidural hematomas are most often not accompanied by a special clinical picture; they can only be identified by a slowdown in alpha oscillations.

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

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

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

An encephalogram is a simple way to keep many brain disorders under control.

Despite the fact that 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 brain activity ensures a quick decision on the choice of therapy and gives the patient a chance for productive and healthy life!

] are taken into account when diagnosing disorders and pathologies of the central nervous system. This is a study of brain functionality based on passive recording of frequency signals. What is EEG decoding, what parameters are used to perform it? What do the phrases and conclusions written in the conclusion mean? We explain it simply and in detail in this article.

Diagnosis of brain functions using EEG is based on recording signals and comparing them with indicators of bioelectrical activity of the brain (BEA) of a conditionally healthy person. Of course, there is no single sample or standard for comparison. Neurophysiologists know the normal parameters of BEA for humans different ages, there are observations for certain pathologies. Based on these data, it is possible to decipher the encephalogram, taking into account the developmental characteristics and health status of the patient.

The norm in the EEG results - what is the picture in a healthy person

The normal functioning of the brain is based on a frequency pattern of a combination of several rhythms. They have a certain localization, frequency and amplitude (maximum value), and can overlap and be suppressed by each other. For an examination, it is enough to record four types of signals, but sometimes there is a need to monitor all indicators.

Rhythms of bioelectrical activity of the brain during wakefulness

Let us briefly describe these frequency characteristics for a person in a state of normal rest, but not in sleep.

1. Alpha rhythm is inherent in most healthy people. It is defined as a signal with a frequency of 8 to 14 Hz when the subject is in a dark room, at rest, with his eyes closed. Localized in the back of the head and closer to the crown, evenly distributed (symmetrical) across the hemispheres of the brain. When visual signals appear and thinking (problem solving) may partially fade or be blocked.

2. The beta rhythm of brain activity manifests itself at a frequency of 13 to 30 Hz with obvious activity, attention and anxiety, and the receipt of external information. This is the rhythm of attention and activity, it is found in the frontal region of the brain. The amplitude is significantly inferior to the alpha rhythm. In a state of rest and absence of external signals, it calms down.

3. The gamma rhythm on the encephalogram is recorded with a significant frequency range from 30 to 120-180 Hz, which is fully explained by its purpose - this frequency occurs when solving mental problems, if necessary, to concentrate, to achieve concentration. The amplitude of gamma rhythm oscillations is very small, and when it reaches a value of 15 μV, doctors talk about pathology, a sharp loss of intellectual potential, and a disorder of mental function.

4. The kappa rhythm is interesting because it is actually a blocking signal for the alpha rhythm, when a person needs to move from a state of rest to mental work. A signal with a frequency of 8 - 12 Hz occurs in the temporal part. Its shape and frequency are such that when applied to the alpha rhythm, the latter’s oscillations fade away.

5. The lambda rhythm or “visually active” signal of medium frequency and a very narrow range occurs in the back of the head when a person activates the connection between vision and mental activity and attention - it is maintained when solving the task of searching for an object or image and fades away when fixing the gaze. During the search period, it partially extinguishes the alpha rhythm in the visual zone.

6. The mu rhythm signal is very similar to the alpha rhythm - it arises in the back of the head, has the same frequency range and actually maintains the alpha rhythm at rest, serving as a kind of frequency stabilizer that prevents the brain from losing balance too quickly with minor stimuli. The mu rhythm disappears as soon as any type of activity begins.

Rhythms of brain signals during sleep

In a state of sleep and transition to sleep, during blackout and coma, other BEA rhythms operate. Their appearance during wakefulness is alarming, as it is considered a sign of pathological processes, including cancer and epileptic nature.

1. The delta rhythm occurs during deep sleep and in coma. In children, it can manifest itself both at rest and during activity, and registration of delta oscillations while an adult is awake may mean that the encephalograph has “caught” the border of the oncological process.

2. The theta rhythm plays the role of a filtering agent, which is provoked by the hippocampus during sleep to process previously received information. Self-learning and filtering of data that the brain must process and remember depend on its stability. Its appearance outside sleep can be a sign of latent epilepsy, pre-epileptic aura.

3. The sigma rhythm is fixed in the initial stage of sleep, during the transition between phases of sleep, when the theta rhythm changes to the delta rhythm. It is considered an important diagnostic indicator in identifying problems with sleep and attention.

Based on the recorded signals, the overall BEA indicator of the brain is derived. Next, specialists begin to decipher the EEG according to the main signs and criteria. Attention is paid to frequency and amplitude indicators, pulse modulation, smoothness of graphs, localization and symmetry of their distribution. How to understand where is the norm and where is the violation?

Before evaluating the decryption results, you need to understand. This study is functional, which means that its results can be used to judge the functioning of the brain. A full diagnosis is not made on the basis of an EEG, but it is possible to assume the presence of pathologies, confirm or exclude some disorders. This can be explained something like this: if a person has signs of epilepsy, hidden seizures, then the EEG decoding of the theta rhythm will show the frequency value even when awake. But you will have to order a series of examinations to understand what is causing the attacks - a tumor, a scar from a stroke, inflammation in a separate part of the cerebral cortex.

What is interpretation of EEG results?

Is it possible to decipher EEG results yourself? This is impossible without knowledge of neurophysiology. There are many specific factors that need to be taken into account. If such a decoding is made without taking into account the individual characteristics of the patient, the result will be at least vague. In the worst case, you will find signs of terrible diseases, get neurosis and depression, but in reality it turns out that the result is not terrible.

What do doctors look at when deciphering encephalogram data?

After receiving the result in the form of recording signals on paper tape, the neurophysiologist studies them according to the main criteria:

• frequency and amplitude of oscillations - deviations from the norm may be within acceptable values ​​or deviate from them;

• the shape of the overall signal graph - it should be correct, smooth, without jumps and dips;

• distribution of rhythms across hemispheres and zones - knowing where the reading electrode is located, you can determine the localization of a specific rhythm;

• symmetry of signals - in most cases, uniform distribution between the hemispheres is considered the norm;

• dependence of the rhythm on the patient’s condition - in sleep, at rest, when stimulated by light, sound, activity;

• the presence of paroxysms - repeated short interruptions in frequency and rhythm.

Violations of the BEA of the brain in the recording are identified and recorded initially in order to subsequently determine their connection with pathologies.

Examples of violations of BEA and rhythms on the encephalogram

For alpha brain activity, pathology is considered to be a constant presence in the frontal lobes, an asymmetry between the hemispheres exceeding 35%, a non-sinusoidal graph, scatter and instability of frequency, increased and decreased amplitude. Based on the combination of signs of alpha rhythm disturbance, one can assume cancer and circulatory disorders in the brain.

Deviations in the amplitude of beta brain activity towards consistently high levels indicate the likelihood of a concussion. If spindle-shaped signals appear, encephalitis may be suspected. In children, a high amplitude of oscillations in the center and front of the brain can serve as a signal of delayed mental and mental development.

High amplitude sleep rhythms (delta and theta) indicate functional disorders. If a signal with such deviations is widely distributed throughout the brain and is recorded in all parts, then there is a high probability of severe disorders in the central nervous system.

Important! - indicators of normality and abnormalities on the EEG depend on age! Features of brain development must be taken into account when deciphering!

Decoding the encephalogram for some diseases

Specific diseases can give a well-described picture on the EEG. Thus, when taking data during an epileptic attack, you can quite accurately determine the place of its origin by the peaks on the encephalogram. During an attack, pointed waves appear especially clearly. Burst-like increases in signal amplitude may be present.

With traumatic brain injuries with minor consequences, EEG rhythms will be unstable and asymmetrical. If the pattern of rhythm disturbances increases during the week after the injury, alpha oscillations slow down, then a conclusion is drawn about the serious consequences of the injury.

Hemorrhages give a picture of a disorder of alpha waves and clearly visible flashes of the delta rhythm in a slow state. In this case, the picture may persist even after the disappearance of external signs of TBI. A desynchronized type of EEG can occur in irritative disorders and diffuse disorders of various origins.

What should not frighten the patient in deciphering the EEG?

Complex terms in EEG decoding do not always indicate real danger. You should not injure yourself with fears if a neurophysiologist has discovered an inconsistent asymmetry of signals between the hemispheres, diffuse disorganization of the alpha rhythm, moderate dysrhythmia and increased tone of the middle structures. Dysfunction of the middle structures can develop against a background of stress and is fully recoverable.

Only a doctor can interpret the EEG conclusion. And to make a diagnosis, an additional one is prescribed. When scars and tumor-like structures are detected, the picture of the vessels near them is determined using methods. Only based on the results of an encephalogram, a full diagnosis with the causes and picture of the development of the disease is not made. We should not forget that there is a set of diagnostic criteria that must converge in a certain combination - without this, the pathology is not considered confirmed.