Decoding of the parameters of the brain's electroencephalogram

1 The results of the

study Electroencephalography is effective for suspicions of brain tumors, epilepsy, and vascular diseases. It also reflects abnormalities in brain activity in cases of craniocerebral trauma and inflammatory processes. EEG is valuable in the case of certain mental and neurotic abnormalities and disorders. In addition, electroencephalography reflects the age-related changes in the functioning of the nervous system.

According to the results of the EEG, a neurologist's report is issued - usually a day or two after the examination. When diagnosing and prescribing treatment, not only electroencephalography data are taken into account, but also reactions when examined by a physician, clinical manifestations, and other studies.

The interpretation of the EEG includes an assessment of the constancy of the rhythms of the brain, the same activity of neurons in both hemispheres and the response to routine tests( open-close eyes, photostimulation, hyperventilation).

EEG in children is more difficult to decipher - this is due to the active growth and maturation of the entire nervous system, which can affect EEG results. Therefore, in children, any violations and changes should be analyzed in dynamics with a certain periodicity.

The interpretation of EEG parameters of the brain must take into account a number of factors, the influence of which can reduce the accuracy of the conducted study. These include:

• age;
• health status and concomitant diseases;
• active movement during the procedure;
• tremor;
• vision impairment;
• taking certain drugs that affect the nervous system;
• use of products that excite the nervous system( containing caffeine);
• carrying out EEG on an empty stomach;
• dirty hair, use of hair styling and treatment products;
• other factors that affect the activity of the brain and neurons.

The interpretation of the EEG with these conditions in mind will avoid errors in the conclusion.

2 Types of rhythms

Brain rhythms are one of the key parameters in the evaluation of EEG results. These are waves that differ in form, constancy, periods of oscillation and amplitude. Their regularity reflects the normal coordinated activity of various structures of the central nervous system.

There are several types of rhythms, each of which has its own set of characteristics and fixes the specific activity of the brain:

1. Alpha rhythm is revealed in a state of rest. Normally, when a person does not sleep with eyelids lowered, the frequency of the alpha-rhythm is 8-14 Hz, and the amplitude - up to 100 μV.The most intensive manifestation is in the occiput and crown. Alpha waves almost cease to be determined by mental activity, light flashes or opening of the eyes, nervous excitement or in a dream. The frequency of alpha rhythm can increase in women during menstruation.
2. Beta-rhythm is an indicator of active brain activity. In addition, it may reflect increased anxiety, nervousness, depression, or the administration of a large number of certain drugs. The normal frequency of beta-rhythm in both hemispheres is 14-30 Hz, the amplitude is 3-5 μV.The highest intensity of beta waves is recorded in the frontal lobes of the brain.
3. The delta rhythm has a normal frequency of 1-4 Hz at an amplitude of up to 40 μV and is reflected on the EEG when the person is asleep. At other times, its waves can not be more than 15% of all rhythms. In addition, the delta rhythm can reflect coma, drug effects, evidence of a tumor or brain damage.
4. Theta rhythm also characterizes the sleep of a healthy adult person. In children up to 4-6 years on the EEG it is the main one - it can be found in the central parts of the brain at the age of 3 weeks. The frequency of the theta rhythm is 4-8 Hz at an amplitude of about 30 μV.

Based on the results of the EEG, another parameter is derived, which is a comprehensive assessment of the rhythms of the brain, which is the bioelectrical activity of the brain( BEA).The doctor examines the rhythms for synchronism, rhythm and presence of sharp flares. Based on the analysis, the neurologist writes a conclusion that must necessarily contain the characteristics of the waves, a description of the disorders and their compliance with clinical manifestations.

3 Norms and deviations

Normally, the manifestations of brain rhythms in a healthy person correspond to the values ​​and functional states given above. In addition, the normal functioning of the nervous system is indicated by such signs:

• predominance of alpha and beta rhythms in the active state;
• synchronicity of rhythms in both hemispheres;
• absence of sharp peaks of electrical activity;
• stable brain activity even in the presence of short-term reactions to light exposure and other stimulation options.

In children at an early age, slow fluctuations are recorded, and the alpha rhythm is formed by 7 years. The EEG of adolescents 15-17 years old already corresponds to the study of an adult. After 50-60 years, the frequency decreases and the regularity of the delta rhythm is disturbed, the number of theta waves increases.

There are many abnormalities in the EEG of the brain. Determination of possible causes of brain rhythm disturbances is the task of an experienced specialist. Below are some variants of abnormal EEG results, which may be signs of neurological, mental or speech disorders.

1. Absence of synchronism and symmetry in the work of neurons of the right and left hemispheres.
2. Sudden changes in the frequency of rhythms: acute activity outbursts and sharp declines. This is the case with infections, tumors, injuries, stroke.
3. Alternation of peaks and falls, high amplitude oscillations at different frequencies, single or serial bursts of activity may be a sign of epilepsy. However, it should be borne in mind that between epileptic seizures of patients with epilepsy can show normal results.
4. The presence of delta and theta rhythms in the waking person indicates possible diseases or traumas of the brain.
5. A number of infections, poisoning and metabolic disorders can be characterized by changes in brain activity in several areas at once.
6. In the state of coma and in the suppression of the nervous system by potent drugs, zero electrical activity of the brain can be observed. This happens when the flow of blood to the brain is broken and it ceases to function.

4 Possible causes of violations of

1. Violations of alpha rhythm. The asymmetry of the alpha rhythms of the two hemispheres of the brain( a difference of more than 30%) may be a sign of tumors, a stroke or a heart attack. An unstable or high-frequency alpha-rhythm occurs with brain damage, in particular, as a result of CCT or concussion. In case of serious mental disorders, the amplitude can decrease to less than 20 μV, the rhythm index falls below 50%, the zone of the alpha rhythm development shifts from the occiput and the crown. With dementia, there may be no alpha waves or their arrhythmia. In a child, deviations from the norms of alpha rhythm can be evidence of a delay in psychomotor development.
2. Beta-rhythm disturbances. Concussion is usually characterized by the presence of high-amplitude( 50-60 μV) diffuse beta waves. With encephalitis, short spindles are recorded. The increase in the duration and frequency of occurrence of these spindles can speak of a developing inflammatory process. Children have abnormal beta waves with a frequency of 16-18 Hz and high amplitude( 30-40 μV) in the anterior and central parts of the brain - this is a sign of a lag in the development of the child.
3. Violations of theta and delta rhythm. Constant increase in the amplitude of delta rhythm - more than 40 μV - is an indicator of impaired brain functions. If the delta rhythm is recorded in all parts of the brain, then we can talk about serious diseases of the central nervous system. Large fluctuations of delta waves occur in the presence of tumors. Delay in development in children is characterized by maximum manifestations of theta and delta waves in the occiput. The increased frequency of these rhythms sometimes reflects impaired cerebral circulation and other neurological problems.

Timely EEG of the brain and competent interpretation of the results will help to establish a diagnosis in case of violations and to prescribe adequate therapy for brain diseases.