Electroencephalogram of the brain that shows the transcript. What is electroencephalography, what reveals and how is the examination of the brain. Types of activity 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 is studied and recorded using various methods– electroencephalography, rheoencephalography, computed tomography, etc. A huge role in identifying various abnormalities in the work of brain structures belongs to the methods of studying its electrical activity, in particular electroencephalography.

Electroencephalogram of the brain - definition and essence of the method

Electroencephalogram (EEG) is a record of the electrical activity of neurons in various brain structures, which is done on special paper using electrodes. Electrodes are applied to various parts of the head and record the activity of one or another part of the brain. We can say that an electroencephalogram is a record 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 predetermine the rhythm, general structure and dynamics of the electroencephalogram. A large number of connections of the reticular formation and the forebrain with other structures and the cortex determine the symmetry of the EEG, and its relative "sameness" for the entire brain.

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

The EEG is taken according to the standard protocol, which takes into account the recording in the state of wakefulness or sleep (infants), with special tests. Routine EEG tests 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, when taking an EEG, additional tests may be used, for example:

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

Additional tests for EEG are determined by a neurologist who wishes to evaluate certain functions of the human 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.

To date, the electroencephalogram is widely used in the practice of neurologists, since this method allows diagnosing epilepsy, vascular, inflammatory and degenerative brain lesions. In addition, EEG helps to find out the specific position of tumors, cysts and traumatic injuries of brain structures.

An electroencephalogram with patient irritation by light or sound makes it possible to distinguish true visual and hearing impairments from hysterical ones, or their simulation. The 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 death of a person.

Where and how to do it?

An electroencephalogram for an adult can be taken in neurological clinics, in departments of city and district hospitals, or at a psychiatric dispensary. As a rule, an electroencephalogram is not taken in polyclinics, but there are exceptions to the rule. Better to contact mental asylum or the department of neurology, where specialists with the necessary qualifications work.

An electroencephalogram for children under 14 years of age is 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 usually do not take EEGs for young children.

In addition, private medical centers specializing in diagnostics and treatment of neurological pathology, they also provide an EEG service 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 good 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 insulated room, where he is laid on a couch. Children under 1 year of age are in the mother's arms during the EEG recording. The whole procedure takes about 20 minutes.

To record an EEG, a cap is put on the baby's head, under which the doctor places electrodes. The skin under the electrodes is urinated with water or gel. Two inactive electrodes are applied to the ears. Then, with crocodile 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 needed, otherwise the activity of the brain will simply be impossible to register. It is the small strength of the currents that is the key to the absolute safety and harmlessness of the EEG, even for infants.

To begin the study, you should lay the head of the child evenly. Anterior leaning should not be allowed as this may cause artifacts to appear that will be misinterpreted. An EEG is taken for babies during sleep, which occurs after feeding. Wash your child's head before taking an EEG. Do not feed the baby before leaving the house, this is done immediately before the study, 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 to use in the hospital. Up to 3 years, EEG is taken only in a state of sleep. Children over 3 years old can stay awake, and to keep the baby calm, take a toy, book, or anything else that will distract the child. The child should be calm during the EEG.

Usually, the EEG is recorded as a background curve, and tests are also performed with opening and closing the eyes, hyperventilation (rare and deep breathing), and photostimulation. These tests are part of the EEG protocol, and are carried out for absolutely everyone - both adults and children. Sometimes they are asked to clench their fingers into a fist, listen to various sounds, etc. Opening the eyes makes it possible 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 in the form of a game - for example, invite the child to inflate a balloon. Such rare and deep breaths and exhalations last 2-3 minutes. This test allows you to diagnose latent epilepsy, inflammation of the structures and membranes of the brain, tumors, dysfunction, overwork and stress. Photostimulation is carried out with the eyes closed, when the light is flashing. The test allows you to assess the degree of delay in the mental, physical, speech and mental development of the child, as well as the presence of foci of epileptic activity.

Electroencephalogram rhythms

The electroencephalogram should 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 synchronism of the activity and functional activity of all structures of the central nervous system.

On the human EEG, there are 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 the 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 region of the occiput and crown. The alpha rhythm ceases to be determined when any motor stimuli appear.

beta rhythm has a frequency of 13 - 30 Hz, but reflects the state of anxiety, anxiety, depression and the use of sedatives. 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, reflects the state of natural sleep. This rhythm is a normal component of the adult EEG. And in children, it is this type of rhythm that prevails on the EEG.

delta rhythm has a frequency of 0.5 - 3 Hz, it reflects the state of natural sleep. It can also be recorded in the state of wakefulness in a limited amount, 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 the amplitude above 40 μV, and this rhythm is recorded for more than 15% of the time, then it is referred to as pathological. Such a pathological delta rhythm indicates a violation of the functions of the brain, and it appears precisely above 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 impaired consciousness.

Electroencephalogram results

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

Such a conclusion should 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: "An 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 median structures of the brain. Asymmetry between the cerebral hemispheres and paroxysmal activity was not detected").
3. Determination of the correspondence of clinical symptoms with the results of the EEG (for example: "Objective changes in the functional activity of the brain were recorded, corresponding to the manifestations of epilepsy").

Deciphering the electroencephalogram

Deciphering an electroencephalogram is the process of interpreting it, taking into account the clinical symptoms that the patient has. In the process of decoding, the basal rhythm, the level of symmetry in the electrical activity of brain neurons in the left and right hemispheres, spike activity, EEG changes against the background of functional tests (opening - closing the eyes, hyperventilation, photostimulation) must be taken into account. The final diagnosis is made only taking into account the presence of certain clinical signs that disturb the patient.

Deciphering the electroencephalogram involves interpreting the conclusion. Consider the basic concepts that the doctor reflects in the conclusion, and their clinical significance (that is, what certain parameters may indicate).

Alpha - rhythm

Normally, its frequency is 8 - 13 Hz, the amplitude varies up to 100 μV. It is this rhythm that should prevail over both hemispheres in healthy adults. Pathologies of the alpha rhythm are the following signs:

• constant registration of the alpha rhythm in the frontal parts of the brain;
• interhemispheric asymmetry above 30%;
• violation of sinusoidal waves;
• paroxysmal or arcuate 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?
Pronounced interhemispheric asymmetry may indicate the presence of a brain tumor, cyst, stroke, heart attack, or a scar at the site of an old hemorrhage.

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

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

About the delay in psycho-motor development in children they say:

• disorganization of the alpha rhythm;
• increased synchronicity and amplitude;
• moving the focus of activity from the nape 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 nape and crown of the head, 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 synchrony 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, has a symmetrical amplitude (3–5 μV) in both hemispheres. The pathology of the beta rhythm is the following signs:

• paroxysmal discharges;
• low frequency distributed over the convexital surface of the brain;
• asymmetry between the 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 of no higher than 50-60 μV indicates a concussion.

Short spindles in 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 a high amplitude (30 - 40 μV) in the anterior and central parts of the brain are signs of a delay in the child's psychomotor development.

EEG desynchronization, in which the beta rhythm predominates in all parts of the brain - 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 the waking state, such slow waves appear on the EEG only in the presence of dystrophic processes in the brain tissues, which are combined with compression, high blood pressure, and lethargy. Paroxysmal theta and delta waves in a person in the waking state are detected when the deep parts of the brain are affected.

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

What do violations 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, flashes of bilaterally synchronous theta waves with high amplitude, paroxysms in the central parts of the brain - speak of acquired dementia.

The predominance of theta and delta waves on the EEG with maximum activity in the back of the head, flashes of bilaterally synchronous waves, the number of which increases with hyperventilation, indicates a delay in the child's psychomotor development.

A high index of theta activity in the central parts of the brain, bilaterally synchronous theta activity with a frequency of 5 to 7 Hz, localized in the frontal or temporal regions of the brain, speak of 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 rhythms with a high frequency (for example, beta-1, beta-2 and gamma) indicates irritation (irritation) of brain structures. This may be due to various disorders of cerebral circulation, intracranial pressure, migraines, etc.

Bioelectrical activity of the brain (BEA)

This parameter in the EEG conclusion is a complex descriptive characteristic relating to brain rhythms. Normally, the bioelectrical activity of the brain should be rhythmic, synchronous, without foci of paroxysms, etc. In the conclusion of the EEG, the doctor usually writes what kind of violations of the bioelectrical activity of the brain were detected (for example, desynchronized, etc.).

What do various disorders of 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 a certain 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 a variant of the norm if no other abnormalities are detected. Thus, if the conclusion says only diffuse or moderate changes in the bioelectrical activity of the brain, without paroxysms, foci of pathological activity, or without lowering 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 convulsions. Reduced bioelectrical activity of the brain can be detected in depression.

Other indicators

Dysfunction of the middle structures of the brain - this is a mild violation of 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 indicative of pathology. In this case, it is necessary to undergo an examination by a neurologist and a course of symptomatic therapy.

Diffuse disorganization of the alpha rhythm, activation of the diencephalic-stem structures of the brain against the background of tests (hyperventilation, closing-opening of the eyes, photostimulation) is the norm, in the absence of complaints from the patient.

The focus of pathological activity indicates increased excitability of the specified area, which indicates a tendency to convulsions 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 causes (for example, atherosclerosis, trauma, increased intracranial pressure, etc.).

Paroxysms they talk about an increase in excitation and a decrease in inhibition, which is often accompanied by migraines and just headaches. In addition, a tendency to develop epilepsy or the presence of this pathology is possible if a person has had seizures in the past.

Decreased seizure threshold speaks of a predisposition to convulsions.

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

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

In general, residual changes in brain structures are the consequences of damage of a different nature, for example, after trauma, hypoxia, or a viral or bacterial infection. Residual changes are present in all brain tissues, therefore they are 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, it can be observed after traumatic brain injuries, with a predominance of excitation over inhibition, as well as with organic pathology of brain tissues (for example, tumors, cysts, scars, etc.).

epileptiform activity indicates the development of epilepsy and an increased tendency to convulsions.

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

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

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

Violation of the wave activity of the brain (the appearance of beta activity in all parts of the brain, dysfunction of the midline structures, theta waves) occurs after traumatic injuries, and can be manifested by dizziness, loss of consciousness, etc.

Organic changes in brain structures in children are the result infectious diseases such as cytomegalovirus or toxoplasmosis, or hypoxic disorders that occurred during childbirth. Comprehensive examination and treatment is required.

Regulatory cerebral changes recorded in hypertension.

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

Brain tumors are:

• 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 disorders 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 injuries (for example, during concussion, loss of consciousness, bruise, hematoma). The appearance of epileptoid activity against the background of a brain injury can lead to the development of epilepsy in the future.

Significant slowing of the 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 frequency and high amplitude, is possible with Alzheimer's disease

Beneath the complex name lies a safe, easy-to-use method for examining the brain, capturing electrical impulses and fixing their rhythm and frequency. The electroencephalogram of the brain provides information about the functional features of this organ.

EEG is a study that can be performed on patients of all ages in any condition. An electroencephalograph, a device for conducting research, is indispensable in intensive care units. It is he who is connected to patients in a coma to track the slightest changes in the electrical activity of the brain.

Electroencephalography can be performed in parallel with the patient's exposure to irritating factors: sounds, light, sleep deprivation. So they get a clearer picture of the nature of the violation, 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:

• vegetovascular dystonia;
• inflammation of the brain;
• neoplasms;
• epilepsy;
• hypertonic disease;
• nervous disorders;
• osteochondrosis of the cervical region;
• traumatic brain injury.

The electroencephalogram of the brain displays the state of the organ in postoperative period, after a stroke, the dynamics of changes after the treatment. It is necessary when passing a medical commission to obtain a driver's 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 canceled 3-4 days before the examination. These drugs include anticonvulsants, tranquilizers.

On the eve of the EEG and on the day of the EEG, you should not consume caffeinated products and energy drinks: coffee, tea, chocolate, energy drinks. You can't drink alcohol. These products have an exciting effect on the brain, and the encephalogram of the brain 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 varnish, styling foam, etc. cosmetical tools. The fats and other components they contain can impair the contact of the electrodes with the scalp. Braids, dreadlocks will have to be untangled, and earrings and jewelry removed.

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

Conducting an EEG

Usually, electroencephalography is carried out in a specially equipped room, protected from noise and bright light, in which there is a stationary electroencephalograph. If necessary, conduct an EEG on the road using mobile devices.

The patient is asked to lie down on a couch or sit comfortably in a chair. A helmet or cap with electrodes is put 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 cavity of the electrode is filled with a special substance that promotes the rapid transmission of electrical impulses. The 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 able to capture the oscillation frequency of 0.5 - 100 Hz and acts as an amplifier. The electrical signal is amplified millions of times by the encephalograph and transmitted to a computer for further processing. Here, a huge number of signals are converted into a graph - an encephalogram, which the doctor analyzes.

The patient during the study should be calm, do not move. Only at the very beginning, the doctor may ask him to blink several times in order to assess the nature of the technical errors. If the patient urgently needs to change the position of the body 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 false information does not appear during further analysis.

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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 made:

1. With hyperventilation, the patient is asked to breathe deeply for several minutes.
2. Test with bright light. For it, a special device is used that is capable of reproducing repetitive light pulses. An electroencephalogram of the brain captures the patient's reaction.
3. Test with an unexpected sound.

Samples help to find out the real cause of the violation - is it a manifestation of a pathological process, a mental disorder or a simulation. In the presence of a valid pathology, testing can provoke an epileptic seizure or convulsions. Therefore, the doctor conducting the diagnosis has the experience and knowledge necessary to provide urgent assistance. The time of the procedure with samples increases.

EEG with sleep deprivation

If there is a suspicion that the usual EEG did not provide complete and reliable information, electroencephalography with sleep deprivation is prescribed. Some sources indicate that only in 20-30% of cases, with a standard conduction, 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 a diagnosis.

If the patient was able to fall asleep quickly, the procedure takes about an hour. The doctor or nurse takes notes on any changes in the patient: shudders, 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 awakened, his condition is checked and sent home or to the ward. After the diagnosis, rest is recommended.

Features of the EEG in children

It is not easy for a small child to conduct an EEG of the brain. It scares him a large number of wires, a strange cap, an unfamiliar environment, people, devices. It is quite difficult to convince the baby that for some time he will have to lie still. Small children are examined during sleep. Before the study, they need to limit the rest time so that he is tired and sleepy by the time of 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- for 6-8 hours, and children over 12 years old are generally not allowed to fall asleep at night.

Electroencephalography (EEG) is a modern method for diagnosing brain diseases in children and adult patients. Such a procedure is based on recording the electrical activity of individual parts of the CNS (central nervous system), 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 appointment of subsequent treatment depend on this. A neurologist who has undergone special training should interpret the data obtained on the electroencephalogram. Otherwise, it is possible to use inappropriate drugs, which can lead to various complications and side effects medicines.

During the EEG, the patient should be in a calm state.

About method

EEG is a diagnostic procedure based on recording the activity of brain regions. This becomes possible due to the use of precise electrodes that allow recording the functional state. various groups neurons. At the same time, the procedure can be performed at different ages with a wide range of diseases, including neuroinfections, infectious and non-infectious encephalitis and meningitis, epilepsy, etc. The technique allows to identify the presence and degree 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 point the patient must keep his eyes closed.
• Alternate eye opening and closing test.
• A breath test that assesses 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, in order to obtain accurate results, use additional actions on the part of the patient, for example, squeezing the fingers on the hand 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 decoding of the EEG of the brain in order to make a correct diagnosis.

Conducting research

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

These sensors are lubricated with a special conductive gel, which allows you to get clearer results, facilitating the subsequent decoding 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 decoding 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 to the patient and explain to him the essence of the upcoming procedure, as well as possible indicators that reflect the norm or pathology of the brain.

In the process of taking the EEG, the patient should not move, keep his eyes constantly closed and follow all incoming instructions from the doctor.

EEG rhythms in a healthy person

The main types of rhythms observed during the EEG

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

1. The alpha rhythm corresponds to the state of rest during wakefulness. It is important to note that at the same time, the person's eyes must be 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 arousal, when a person experiences fear, anxiety, and any other negative emotions. The pulse frequency in this case ranges from 13 to 30 Hz.
3. Theta rhythm is associated with rare impulses (4-7 Hz) and is of 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 wakefulness, however, quite rarely.

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

Deciphering the results

Patients often ask themselves the question - they underwent an electroencephalogram of the brain, what does the decoding of this study show? Such an analysis allows the doctor to assess the state and activity of various parts of the brain, which is necessary to detect diseases.

To decipher an electroencephalogram, a doctor must have a certain qualification

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 parts of the brain, as well as by analyzing the results of special functional tests with photostimulation, hyperventilation, etc.

If EEG decoding 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 features 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 comorbidities.
• Tremor and other changes in the motor sphere.
• Visual disturbances.
• Taking medications that affect the nervous system. Similar changes are observed with the use of drinks containing caffeine.
• Any changes in the electrical conductivity of the skin, which can be observed with its increased fat content, etc.

The attending physician must take into account these factors when compiling the results and conclusion of the EEG. If you suspect errors in the process of conducting the study, it is better to repeat it.

Possible deviations in the results

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

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

There is a large number options deviations, which may be moderate or severe, depending on the degree of CNS damage. The main changes on the electroencephalogram include:

• Disturbances in the coordination of the work of the central nervous system structures located in different hemispheres. This can be observed with damage to the conduction pathways or local impact on a group of neurons.
• The appearance of sudden bursts of activity or their suppression may indicate an infectious lesion of the nervous system, the development of a tumor process, a traumatic brain injury, or various types of stroke.
• The appearance of rhythms with high amplitude, irregular shape, as well as 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 detected in a normal person. If they are detected, then this indicates a violation 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 and epileptic seizures

In some patients, in the form of a medical report on the decoding of the EEG, there are 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 the 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, up to the disappearance, of neurons in certain structures of the brain indicates their serious damage, which can occur with strokes, traumatic brain injuries, etc.

The obtained values ​​of the electroencephalogram make it possible to make an accurate diagnosis of the CNS lesion, which is necessary for the choice of 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 tool for many neurological diseases, such as epilepsy. A neurologist can interpret the results and determine the presence and extent of brain damage without the use of invasive diagnostic methods. The procedure can be performed at any age, including infants.

The importance of the normal functioning of the parts of the brain is undeniable - any deviation from it 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 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 readings 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, completely harmless and safe method that does not need to be disturbed. skin and mucous membrane of the body.

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 Current state 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 indicators are observed in the state of rest of the subject, who is in dark room with closed eyes. 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, it 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 that 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 miss any of the smallest manifestations on the record, the specialist needs to take into account all important points, which 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 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, 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 a permanent 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 that the child is lethargic and delayed in its 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 strobe (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 rather 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!

] are taken into account in the diagnosis of disorders and pathologies of the central nervous system. This is a study of the functionality of the brain, based on the passive recording of frequency signals. What is EEG decoding, what parameters is it used for? What do the phrases and conclusions recorded in the conclusion mean? Let's talk in detail in this article.

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

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

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

Rhythms of the bioelectrical activity of the brain during wakefulness

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

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, behind closed eyes. Localized in the back of the head and closer to the crown, evenly distributed (symmetrical) over the cerebral hemispheres. When visual signals appear and thinking (problem solving) may partially fade or be blocked.

2. The beta-rhythm of brain activity is manifested by 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. In amplitude, it is significantly inferior to the alpha rhythm. In a state of rest and the absence of external signals, it calms down.

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

4. The kappa rhythm is interesting in that 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 superimposed on the alpha rhythm, the oscillations of the latter 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 of vision with mental activity and attention - it is maintained when solving the problem of searching for an object or image and fades 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 occurs in the back of the head, has the same frequency range and actually maintains the alpha rhythm at rest, acting as a kind of frequency stabilizer that does not allow the brain to lose balance too quickly with minor stimuli. The mu rhythm disappears as soon as activity of any type begins.

Rhythms of brain signals in sleep

In the state of sleep and transition to sleep, when consciousness is turned off and in coma, other BEA rhythms work. Their appearance during wakefulness is alarming, as it is considered a sign of pathological processes, including oncological and epileptic ones.

1. Delta rhythm occurs during deep sleep and in a coma. In children, it can manifest itself both at rest and during activity, and the registration of delta oscillations during wakefulness of an adult may mean that the encephalograph has "caught" the border of the oncological process.

2. 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 depends on its stability. Its appearance outside of sleep can be a sign of latent epilepsy, a pre-epileptic aura.

3. The sigma rhythm is fixed in the initial stage of sleep, during the transition between sleep phases, 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 total BEA of the brain is displayed. Next, experts begin to decipher the EEG according to the main features and criteria. Attention is paid to frequency and amplitude indicators, pulse modulation, graph smoothness, localization and symmetry of their propagation. How to understand what is the norm and what is the violation?

Before evaluating the results of decryption, you need to understand, . This study is functional, which means that its results can be used to judge the work of the brain. A full diagnosis based on the EEG is not made, 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 on decoding the EEG, the theta rhythm will show the frequency value even when awake. But you will have to appoint a series of examinations to understand what caused the seizures - a tumor, a scar from a stroke, inflammation in a separate part of the cerebral cortex.

What is the interpretation of EEG results?

Is it possible to decipher the results of the EEG on your own? Without knowledge of neurophysiology, this is impossible. There are many specific factors to consider. If such a decoding is done 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 in yourself, get neurosis and depression, but in reality it turns out that the result is not terrible.

What do doctors look for when deciphering encephalogram data?

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

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

• the shape of the general signal graph - it must be correct, smoothed, without jumps and dips;

• distribution of rhythms over the hemispheres and zones - knowing where the reading electrode is located, it is possible to determine the localization of a particular rhythm;

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

• the dependence of the rhythm on the state of the patient - in a dream, at rest, during stimulation with light, sound, activity;

• the presence of paroxysms - repetitive short failures in frequency and rhythm.

Violations of the BEA of the brain on the record are identified and recorded initially in order to determine their relationship 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, asymmetry between the hemispheres exceeding 35%, a non-sinusoidal graph, frequency spread and instability, increased and decreased amplitude. Based on the combination of signs of alpha rhythm disturbance, one can assume an oncological disease and circulatory disorders in the brain.

Deviations in the amplitude of the beta activity of the brain towards consistently high rates indicate the likelihood of a concussion. When spindle signals appear, encephalitis can be suspected. In children, a high amplitude of oscillations in the center and front of the brain can serve as a signal of a delay in mental and mental development.

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

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

Deciphering the encephalogram in some diseases

Specific diseases can give a well-described picture on the EEG. So, when taking data during an epileptic seizure, one can quite accurately determine the place of its origin from the peaks on the encephalogram. During an attack, pointed waves appear especially brightly. Flash-like increases in signal amplitude may be present.

In traumatic brain injuries with minor consequences, EEG rhythms will be unstable and asymmetric. If the picture of rhythm disturbances increases within a week after the injury, alpha fluctuations slow down, then a conclusion is made about the severe consequences of the injury.

Hemorrhages give a picture of a disorder of alpha waves and well-distinguished flashes of a delta rhythm in a slow state. In this case, the picture can be preserved even after the disappearance of external signs of TBI. The desynchronized type of EEG can occur in irritative disorders and diffuse disorders of various origins.

What should not scare the patient in decoding the EEG

Far from always complex terms in deciphering the EEG speak of a real danger. You should not injure yourself with fears if a neurophysiologist has discovered a non-permanent asymmetry of signals between the hemispheres, diffuse disorganization of the alpha rhythm, moderate dysrhythmia and an increase in the tone of the middle structures. Dysfunction of the middle structures can develop against the background of stress and is quite subject to recovery.

Only a doctor can interpret the conclusion of the EEG. And for the diagnosis, an additional one is prescribed. When scars and tumor-like structures are detected, the picture of the vessels near them is determined by methods. Only according to the results of the encephalogram, a full diagnosis with the causes and picture of the development of the disease is not made. Do 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.