There is a wide variety of research on the brain. Some are based on the passage of X-rays through the body, others work on the basis of a magnetic field. But these examination methods can also be used to diagnose diseases of other organs and systems. However, there is an examination method that is used specifically for the diagnosis of brain pathologies. It's called an "electroencephalogram" (EEG) and it shows different EEG rhythms.
Working principle
Electroencephalogram is a method for diagnosing brain diseases, which is based on registering the potential difference between electrodes applied to the head. On the tape, which is printed during the EEG, curved lines of different frequency and amplitude are visible, which are called EEG rhythms.
Some rhythms are considered normal, or physiological, and some occur only in pathology. However, in children and the elderly, physiologicalrhythms that are pathological for people of other age groups.
So what does an adult brain EEG show? At its core, this method of examination makes it possible to see if different departments work together in a coordinated manner and if their neural activity is synchronized.
Key Benefits
What are the advantages of electroencephalography over other methods of diagnosing brain pathology?
- Absolutely harmless and painless - it has absolutely no side effects, and also does not cause discomfort.
- Safety - unlike other modern methods of diagnosing diseases of the nervous system, it has no contraindications. So, with computed tomography, the patient is exposed to X-rays, and with magnetic resonance imaging, the presence of metal objects in the body (vascular clips, pacemaker, prostheses) is contraindicated.
- Non-invasive - EEG does not require injections or other damage to the integrity of the skin.
- High sensitivity - can diagnose a wide range of diseases.
Indications
What conditions can be determined using this method of examination? What does the EEG of the brain show in an adult?
- The level of brain maturity in children.
- Sleep disorders such as insomnia, sleep-wake inversion.
- Voluminous formations of the brain.
- Tranio-cerebral injuries.
- Epileptic activity.
- Infectious diseases of the brain (encephalitis, encephalomyelitis).
- Poisoning with poisons that are toxic to the nervous system.
- Violation of consciousness: stupor, coma.
- Declaration of brain death.
- Neuroses.
- Sets the need for dose adjustments in the treatment of epilepsy.
For the diagnosis of diseases in which changes in the brain are unstable, for example, for epilepsy, it is important to record the EEG during an attack. Since in the interictal period, human EEG rhythms in 40-50% are absolutely normal, which can confuse the diagnosis.
Preparation for analysis and algorithm for conducting
No special manipulations are required to prepare for an electroencephalogram. The main thing is to tell the patient in detail about the procedure, about the algorithm for its implementation. This is especially important when conducting an EEG for a child. Since a large number of wires can frighten him, it is necessary to clearly explain that this procedure is absolutely safe and painless.
During the EEG recording, the person should be calm and relaxed.
Removal of electroencephalogram rhythms is carried out in a sitting or lying position, with eyes closed. The device itself is a cap with electrodes on it, which are lubricated with a contact agent and connected to the recording part of the device.
At the same time, the pulses picked up by the electrodes are registered and the patient's video is recorded. Thus, it is possible to compare convulsiveattack and change in EEG rhythms. With the help of video monitoring, it becomes possible to differentiate a real seizure from a simulation. So, if the video shows a change in the behavior of the patient, but the EEG shows the same activity as before, this means that the person is simulating. But there are also options when seizures are not associated with a change in brain activity, for example, with hysterical neurosis.
EEG characteristics
And now let's go directly to the decoding of the EEG. The main characteristic of the electroencephalogram is the frequency. Of course, the human eye is not able to capture and characterize absolutely all the frequencies present on the EEG tape. Therefore, they were classified according to the main frequency ranges. Each group corresponds to a letter of the Greek alphabet (alpha, beta, theta, delta and gamma).
Based on the frequency range, amplitude, waveform, EEG rhythms are formed, which are also denoted by Greek letters. For example, alpha rhythm. Each rhythm corresponds to a specific brain activity. A rhythm consists of EEG waves.
Basic Rhythms
The following basic EEG rhythms are distinguished:
- Alpha rhythm. Its characteristics: frequency - 8-12 Hz, wave duration - 75-125 ms, amplitude - 10-150 μV.
- Beta rhythm. Its characteristics: frequency - 13-30 Hz, wave duration - 40-75 ms, amplitude - 5-30 μV.
- Theta rhythm. Its characteristics: frequency - 4-7 Hz, wave duration - 130-250 ms, amplitude - 10-100 μV.
- Delta rhythm. Hischaracteristics: frequency - 3-4 Hz, amplitude - several hundred microvolts.
- Gamma rhythm. Its characteristics: frequency - 1-3 Hz.
Alpha Rhythm
Basic rhythm recorded in 90% of adults. Most pronounced in the occipital region of the brain. It is best visualized in the waking state, with eyes closed, in a room with the lights off. With the appearance of mental activity or with tension of attention, the amplitude (height) of the rhythm decreases.
Characteristic is the presence of amplitude inhomogeneity, it either increases or decreases. A so-called "spindle" is formed.
Beta Rhythm
Beta EEG rhythm is also observed during wakefulness. Most pronounced in the frontal regions of the brain. Unlike alpha waves, the amplitude of the beta rhythm sharply increases during mental activity and spreads to other parts of the brain. So, when attention is activated, especially visual, with emotional and mental stress, the height of beta waves increases sharply.
Theta Rhythm
This EEG rhythm is most clearly visualized in preschool children and in mentally unbalanced individuals with a tendency to aggression and with difficult adaptation in society. With an increase in mental activity, the amplitude of theta waves increases.
Delta Rhythm
This rhythm consists of delta waves, which have the largest amplitude among all waves on the electroencephalogram. This rhythm occurs when a person’s consciousness is disturbed, both during deep sleep andwith drug intoxication. In addition, the presence of delta waves is characteristic of a coma.
Also, using the visualization of this rhythm, you can determine the approximate localization of the traumatic focus or tumor, since this rhythm appears in areas that are on the border with brain damage.
Pathological rhythms
The above lists the EEG rhythms that a person normally has, depending on different states of the brain. However, there are special rhythms that can only appear in pathology:
- peaks - duration 10-75 ms and amplitude 10-100 uV;
- sharp waves - duration 75 ms, amplitude 20-200 uV, having a wide base and pointed tops;
- spikes - less than 10 ms long.
EEG in epilepsy
As noted above, electroencephalography is used in the diagnosis of many brain diseases. However, in most cases, EEG changes are nonspecific. For example, in order to differentiate a tumor from a brain injury, in addition to EEG, additional imaging methods (computed tomography, magnetic resonance imaging) should be performed.
But there is a disease in the diagnosis of which the EEG has not lost its relevance compared to more modern methods of examining the brain - epilepsy. In addition, this method allows not only to make a diagnosis, but also to determine the localization of the epileptic focus and the type of epilepsy.
Tagged in sectionhigher high-amplitude peak waves are the most characteristic sign of epilepsy on the EEG. They suddenly appear at the onset of a convulsive attack and also suddenly disappear after an attack. Here, video monitoring is of particular value, making it possible to compare EEG data with the clinical picture.
Also observed in epilepsy complexes "peak - slow wave", "peak - fast wave". They are manifested by the alternation of waves of different frequencies and amplitudes.
Stimulating signals are widely used for suspected epilepsy: hyperventilation (a series of deep slow breaths and exhalations), flashing bright light. These tests help to detect latent epileptic activity that is not displayed in peace.
EEG sleep monitoring
With the help of electroencephalography, it is possible to determine the phases of sleep and wakefulness in a child in the womb from the 28th week of pregnancy.
Separate REM and NREM sleep. When recording sleep, much attention is paid to the movements of the eyeballs and muscle activity, which are recorded in parallel with brain activity. According to these data, sleep is also divided into REM and Non-REM.
Non-REM sleep is divided into the following stages:
- The first stage continues while the person falls asleep. Its duration is up to 10 minutes. It is characterized by slow rotation of the eyeballs, predominantly the presence of theta waves on the EEG.
- Second stage - light sleep. The muscles are relaxed, the eyeballs do not move. The electroencephalogram shows thetarhythm, there are waves characteristic only of this stage: K-complexes and sleepy spindles. In time, this phase takes about half of all sleep.
- Third and fourth stages - non-REM sleep, or deep sleep. In the phase of deep sleep, a person sleeps most soundly. The eyeballs do not move. High-amplitude delta waves are observed on the electroencephalogram. When the delta rhythm exceeds half of the entire EEG tape, the transition from the third stage to the fourth begins. The duration of the first period of the deep sleep phase is 30 to 40 minutes.
REM sleep consists of only one phase. It is during REM sleep that a person sees vivid, memorable dreams. This stage is characterized by the rotation of the eyeballs, short-term muscle contractions, increased breathing and heart rate. The electroencephalogram consists of alpha and beta waves. The duration of this phase is about 20% of the total sleep period.
Where can I get an EEG?
We have already discussed how to prepare for the analysis, what conditions are indications for its implementation. In addition, we found out how the EEG is deciphered, and what rhythms are inherent in a person with different brain activity. Now it’s worth talking about where you can do an EEG.
EEG is available in a number of laboratories and private clinics in Russia, as well as in some state neuropsychiatric dispensaries.
Among laboratories, EEG diagnostics is presented in "Invitro", "EEG Lab" - a neurophysiological laboratory in Moscow.
Among private clinics, there is an opportunity to do an EEG in a medical"Ona" center, "Doctor Anna" family clinic, "Cardio-neurological center".
It can be concluded that although the electroencephalogram is not the most modern and sensitive method for diagnosing brain diseases, its absolute safety and availability ensure its widespread use in medical practice. And the use of EEG in the diagnosis of diseases accompanied by convulsive seizures completely displaces all other examination methods in terms of efficiency!
