The human brain is a complex structure. It is here that the centralization of nervous activity is carried out, all impulses coming from the sense organs are processed and response signals are formed to perform this or that action.
Sometimes it happens that the brain starts to malfunction. It is not easy to suspect the presence of a pathological focus in the brain. Conventional diagnostic methods, such as ultrasound, MRI, do not always give a proper idea of its work. In such cases, it is necessary to take an electroencephalogram - a snapshot of the brain. Electroencephalography is the study of the formation of brain waves. What is it?
What is this method?
Electroencephalography is currently understood as a certain branch of electrophysiology that studies the electrical activity of the brain and its individual parts. The measurement is made using special electrodes applied to the scalp in various places. Electroencephalography of the brain is capable of recording the slightest changes in the activity of nerve cells, which puts itan order of magnitude higher than other methods for diagnosing neurological diseases.
As a result of the registration of brain activity, a “snapshot” or a curve is formed - an electroencephalogram. On it, you can determine all areas of brain activity, which is manifested by certain waves and rhythm. It is customary to designate these rhythms with the letters of the Greek alphabet (at least 10 such rhythms are distinguished). Each of them contains certain waves that characterize the activity of the brain or a certain part of it.
History of the creation of the study
The study of the electrical activity of the brain began in 1849, when it was proved that, like a muscle or nerve fiber, it is capable of generating electrical impulses.
In 1875, two independent scientists (Danilevsky in Russia and Caton in England) were able to provide measurements of the electrophysiological activity of the brain in animals (the study was conducted on dogs, rabbits and monkeys).
The foundations of electroencephalography were laid in 1913, when Vladimir Vladimirovich Pravdich-Neminsky was able to record the first electroencephalogram from a dog's brain. He was the first to propose the term “electrocerebrogram.”
The first human encephalogram was recorded in 1928 by the German scientist Hans Berger. He proposed to rename the term to electroencephalogram, and the method itself has been widely used since 1934, when the presence of Berger's rhythm was confirmed.
How is the procedure performed?
Recording of biopotentials from the brain is performed using a device called an electroencephalograph.
Normally, the biocurrents generated by the brain are rather weak, and it is difficult to fix them. And in this case, electroencephalography comes to the rescue. What is it, it was mentioned above. With the help of an electroencephalograph, these potentials are recorded and their amplification when passing through the apparatus.
Potentials are fixed by electrodes located on the surface of the head.
The received signal can either be recorded on paper or stored electronically (computed electroencephalography) for later study.
The recording itself is made relative to the so-called zero potential. It is usually taken as either the earlobe or the mastoid process of the temporal bone, which do not emit biocurrents.
Registration of impulses is carried out by electrodes placed on the surface of the head according to special schemes. The most widely used pattern is 10-20.
Scheme 10-20
This scheme is standard when placing electrodes. They are distributed on the scalp in the following sequence:
- First of all, the line connecting the bridge of the nose and the occiput is determined. It is divided into 10 equal segments. The first and last electrodes are superimposed respectively on the first and last, tenth, parts of the line. The other two electrodes are set relative to the first two electrodes at a distance,equal to 1/5 of the length of the line formed at the beginning. The fifth is placed in the middle between those already installed.
- One more line is conditionally formed between the external auditory canals. Sensors are installed two on each side (for each hemisphere) and one on the top of the head.
- Parallel to the midline between the back of the head and the bridge of the nose there are 4 more lines - right and left parasagittal and temporal. They pass through electrodes placed along the “ear” line. According to these lines, more electrodes are installed (5 - on the parasagittal, and 3 - on the temporal).
A total of 21 electrodes are placed on the surface of the head.
Interpretation of the obtained results
Computer electroencephalography usually involves recording the results on a computer to create a database of each patient. As a result of fixing the received data, rhythmic oscillations of two types are formed. Conventionally, they are called alpha and beta waves.
The first ones are usually fixed at rest. They are characterized by a voltage of 50 microvolts and a certain rhythm - up to 10 per second.
Electroencephalography of sleep is based on the definition of beta waves. Unlike alpha waves, they are smaller in size and occur in the waking state. Their frequency is about 30 per second, and the voltage is in the region of 15-20 microvolts. These waves usually indicate normal waking brain activity.
Clinical electroencephalography is based on fixationwave data. Any deviation from them (for example, the appearance of alpha waves in the waking state) indicates the presence of some pathological process. In addition, pathological waves may appear on the encephalogram - theta waves, peak waves - or a change in their nature - the appearance of peaked complexes.
Features of the study
A mandatory condition for the study is the immobility of the patient. When performing any activity on the electroencephalogram, interference occurs, which further prevents correct decoding. In children, the presence of such interference is inevitable.
In addition, electroencephalography itself has its own difficulties in carrying out in children. It is rather difficult to explain to a child what it is, and it is not always possible to persuade him to put on a helmet with electrodes. It can cause a feeling of panic in children, which is sure to distort the results. That is why parents should be warned that they need to somehow persuade the baby to put on the electrodes.
During the study, tests with hyperventilation and photostimulation are usually performed. They allow you to identify some disorders in the brain that are not fixed at rest.
Before the study, it is not recommended, and sometimes forbidden, to use any drugs that affect the functioning of the brain.
Indications for the procedure
When is this study recommended?
The electroencephalography method is shown in the followingcases:
- If there is a history of spontaneous syncope.
- Long-lasting headaches that do not respond to medication.
- In violation of memory and attention.
- Sleep disorders and trouble falling asleep and waking up.
- When children are suspected of mental retardation in development.
- Dizziness and fatigue.
In addition to the above, electroencephalography allows you to monitor the results of treatment in patients receiving one or another type of drug or physiotherapy.
The method allows you to determine the presence of diseases such as epilepsy, brain tumors, infectious lesions of the brain tissue, disorders of trophism and blood supply to the brain tissue.
Electroencephalography in children is performed in the diagnosis of Down syndrome, cerebral palsy, mental retardation.
Contraindications for the procedure
The procedure itself has practically no contraindications for use. The only thing that can limit its implementation is the presence of extensive injuries on the surface of the head, acute infectious processes or postoperative sutures that have not healed by the time of the study.
Electroencephalography of the brain is performed with caution in mentally violent patients, as the sight of the apparatus can infuriate them. To pacify such patients, it is necessary to introduce tranquilizers, which significantly reduce the information content of the procedure andresult in incorrect data.
If possible, the procedure should be avoided in severe patients with decompensated disorders of the cardiovascular system. If a portable electroencephalograph is available, then it is better to use it, rather than take the patient himself to the diagnostic room.
Need for research
Unfortunately, not every person knows that there is such a diagnostic method as electroencephalography. What it is - even fewer people know, which is why not everyone goes to the doctor about it. But in vain, because this method is quite sensitive when registering brain potentials. With a well-conducted study and an appropriate interpretation of the data obtained, it is possible to obtain an almost complete picture of the functionality of brain structures and the presence of a possible pathological process.
It is this technique that allows you to determine the presence of mental retardation in young children (although you should definitely make an allowance for the fact that the brain potentials in children are somewhat different from those in adults).
Even if there are no disorders of the nervous system, sometimes it is better to conduct a diagnostic examination with the mandatory inclusion of an EEG, as it can allow you to determine the beginning changes in the structure of the brain, and this is usually the key to successcure disease.
