Electroencephalography of the brain: a technique for conducting

Electroencephalography( EEG) is a method of studying the activity of the brain by recording electrical impulses emanating from its various regions. This diagnostic method is carried out by means of a special device, an electroencephalograph, and is highly informative for a variety of diseases of the central nervous system. On the principle of electroencephalography, indications and contraindications to its conduct, as well as the rules of preparation for the study and the methodology for its conduct, you will learn from our article.

What is EEG

Everyone knows that our brain consists of millions of neurons, each of which is capable of generating neural impulses andtransfer them to neighboring nerve cells. In fact, the electrical activity of the brain is very small and amounts to a millionths of a volt. Therefore, in order to evaluate it, it is necessary to use an amplifier, which is an electroencephalograph.

Normally, impulses coming from different parts of the brain are consistent within its small areas, under different conditions they weaken or reinforce each other. Amplitude and their strength also vary depending on the external conditions or the state of activity and health of the subject.

All these changes are quite possible to register the device with an electroencephalograph, which consists of a certain number of electrodes connected to a computer. The electrodes installed on the patient's scalp catch nerve impulses, transfer them to a computer, which in turn amplifies these signals and displays them on a monitor or on paper in the form of several curves, so-called waves. Each wave is a reflection of the functioning of a particular part of the brain and is indicated by the first letter of its Latin name. Depending on the frequency, amplitude and shape of the oscillations, the curves are divided into α-( alpha), β-( beta), δ-( delta), θ-( theta), and μ-( mu) waves.

Electroencephalographs are stationary( allowing to conduct research exclusively in a specially equipped office) and portable( allow diagnosis directly at the patient's bedside).Electrodes in turn are divided into plate( they look like metal plates 0.5-1 cm in diameter) and needles.

Why do EEG

Electroencephalography registers some conditions and gives the specialist the opportunity:

• to detect and evaluate the character of the brain functioning disorder;
• determine in which area of ​​the brain the pathological focus is located;
• detect epileptic activity in one or another part of the brain;
• assess the functioning of the brain in the period between seizures;
• find out the causes of fainting and panic attacks;
• to conduct differential diagnostics between organic brain pathology and functional disorders of the brain in case the patient has the symptoms characteristic of these conditions;
• to evaluate the effectiveness of therapy in the case of a previously established diagnosis by comparing the EEG before treatment and against it;
• assess the dynamics of the rehabilitation process after a disease.

Indications and contraindications

Electroencephalography makes it possible to clarify a lot of situations associated with the diagnosis and differential diagnosis of neurological diseases, therefore this method of research is widely used and positively evaluated by neurologists.

So, EEG is assigned with:

• disorders of falling asleep and sleep( insomnia, somnambulism, obstructive sleep apnea syndrome, frequent awakening in a dream);
• seizures;
• craniocerebral trauma;
• of neuro-circulatory dystonia;
• frequent headaches and dizziness;
• diseases of cerebral membranes: meningitis, encephalitis;
• acute disorders of cerebral circulation;
• brain tumors;
• recovery after neurosurgical operations;
• fainting( more than 1 episode in the anamnesis);
• panic attacks;
• a constant sense of fatigue;
• diencephalic crises;
• autism;
• speech development delay;
• delayed mental development;
• stuttering;
• tics in children;
• Down syndrome;
• cerebral palsy;
• suspicion of brain death.

As such, there are no contraindications to electroencephalography. Restricts the conduct of the diagnosis of the presence in the area of ​​the proposed installation of electrodes skin defects( open wounds), traumatic injuries, newly imposed, unhealed postoperative sutures, rashes, infectious processes.

Precautions should be taken in the study of people with mental illness, because they can not always follow the doctor's instructions( in particular, stay in the procedure with eyes closed and do not move), as well as violentpatients, because they themselves and the device, and the cap with electrodes can cause even a sense of rage. If it is necessary to conduct an EEG in these patients, they are previously given sedatives, which at the same time distort the results of the study, that is, make it less informative.

Not every diagnostic department has in its arsenal a portable electroencephalograph, so in such a situation, patients with cardiovascular pathology in the late stages, as well as patients with limited motor abilities, may become contraindicated to the study. Transporting them to the diagnostic department may have a higher risk than rejection of this method of investigation in the setting of a neurological diagnosis.

Is the preparation for the EEG of

necessary? In order for the study to proceed smoothly and the result is as informative as possible, the patient should observe several simple recommendations before the EEG.

• First of all, it is necessary to inform the attending physician about the medications that are on an ongoing basis or course, but it is during this time period that the patient is admitted. Some of them( in particular, tranquilizers, anticonvulsant drugs) can affect brain activity, thereby distorting the results, so the doctor is likely to ask the patient 3-4 days before the study to stop taking them.
• On the eve of the study and on the day of it, do not eat foods that include caffeine or energy substances - tea, coffee, chocolate, energy drinks and others. They will exert a stimulating effect on the nervous system of the patient, which will distort the result of the EEG.
• Before the procedure, thoroughly wash your head, clearing the hair of the rest of the foam for styling, varnish and other cosmetic products. Oils and hair masks should not be used, since the fat contained in them will worsen the contact of the electroencephalograph electrodes with the scalp.
• A few hours before the study is full to eat. Lack of food will lead to hypoglycemia( lowering blood sugar), which will also affect the EEG.
• During the diagnosis, you should not be nervous, but should be as calm as possible.
• If the patient is assigned EEG sleep, the night before the test should be for him sleepless. Immediately before the EEG, he receives a sedative, which will help him fall asleep during the recording of the electroencephalogram. EEG sleep, as a rule, is necessary for persons suffering from epilepsy.
• If the goal of electroencephalography is to confirm the patient's brain death, the physician should mentally prepare the relatives for a possible disappointing result and, if necessary, engage a psychologist or psychotherapist to work with them.

The greatest difficulty is the conduct of electroencephalography in children( especially early and preschool) patients. The kid is often frightened by the "cap" that a man in a white coat tries to put on his head. In addition, it is not easy to persuade a child to keep his eyes closed while studying and sit still - without moving. If the child still has an EEG, the doctor should explain to his parents what points to look for when preparing a son or daughter for the study( including psychological):

• to convince the child that an absolutely safe and painless procedure awaits him, explain it to himits available language is the essence;
• in the form of training to practice wearing a swimming cap( you can present it as a game, for example, in divers);
• on a personal example show the child how to breathe deeply, let him do it himself, negotiate with him to repeat the same thing in the doctor's office when he or you ask;
• it is good to wash your head, do not do complex hairstyles( to quickly get your hair dissolved), remove earrings, if any;
• fully feed before going out;
• do not forget to bring along your favorite toy and book, as well as some goodies - food and drink;in case you have to wait before the EEG, the child can be distracted so that he does not think about the forthcoming study and is not afraid of it.

Procedure for performing the

study The diagnostic time varies depending on the purpose. More often it is carried out in the morning or in the afternoon, but in some cases it is required to determine the electrical activity of the brain directly during sleep.

The study is conducted in a specially equipped room, protected from noise and light. Only the patient and the doctor are present in the room, but in some clinics even the doctor is outside of it, keeping in touch with the subject through a video camera and microphone. When conducting an EEG, the child in the study should have one of his parents.

The patient comfortably settles in an armchair or lays down on a couch. On his head they put on a special "cap": electrodes connected to each other by a network of wires. Begin the study.

First, to assess the nature of artifacts( technical errors) from blinking, the doctor asks the examinee to close and open his eyes several times. Considering this question completed, he suggests that the patient close his eyes and sit / lie still, without making any movements. The study is conducted for a short time, so an adult patient, as a rule, is not difficult to fulfill this condition of the diagnostician. If the subject well needs to change the position of the body or, for example, wants to go to the toilet, the EEG record is temporarily stopped. In the case when the patient still moved during the EEG recording, or blinked, or made a swallowing movement, the doctor makes an appropriate note on the film or in the computer - these actions of the subject may affect the character of the curve, and the doctor, in the absence of a note about them, mayit is wrong to interpret them, which will affect the conclusion.

When the EEG of rest is recorded, the patient is given the so-called stress tests to evaluate the brain's response to stressful situations for him:

• hyperventilation test: the specialist asks the examinee often to breathe deeply for 3 minutes;such actions in a predisposed patient can trigger both an attack of generalized seizures and seizures of the absense type;
• photostimulation: the sample is carried out using a stroboscopic light source that flashes at a frequency of 20 times per second;thus, the reaction of the brain to bright light is evaluated;In predisposed persons, in response to blinking, myoclonic cramps or epileptic seizures occur.

The specialist who conducts the study should be ready to develop the patient's pathological reaction to provocative tests and have the opportunity and relevant skills to provide him with emergency care.

At the end of the study, the patient should be reminded of the need to resume taking medications that were canceled before the EEG.

Concluding the article, I want to reiterate that electroencephalography is a painless and highly informative method for diagnosing diseases of the central nervous system. It is indicated for a variety of neurological conditions and choosing whether or not it is worthwhile to choose, it is more correct to stop your choice in favor of the former: if the pathology is absent, you will see this once again and calm down, and if any changes are detected on the EEGa correct diagnosis will be made quickly, and you will begin to receive the right treatment.

Clinic "Good Doctor", clinic specialist Yulia Krupnova talks about electroencephalography: