Electroencephalography (electroencephalogram, EEG) is a test aimed at assessing the bioelectrical activity of the brain, and thus - the functional state of the central nervous system. The electroencephalogram is helpful in the diagnosis of many diseases of the nervous system, especially epilepsy. Thanks to the EEG, it is also possible to determine the type of coma and assess the he alth status of patients with brain tumors. What is electroencephalography and what are the indications for its performance?

Electroencephalography( electroencephalogram, EEG ) is aelectrophysiological test,which uses the fact that brain cells communicate with each other using electrical impulses of low voltage and intensity. Its purpose is to assess whether this process is taking place properly. Therefore, the electroencephalogram is an important diagnostic method in patients with sleep disorders, coma, epilepsy and after craniocerebral trauma. EEG can also be performed in patients with encephalitis, diagnosed neoplasms and after strokes.

Electroencephalography - indications for the test

The indications for an electroencephalogram are symptoms of abnormal brain function (e.g. seizures), a condition after a head injury and after neurosurgery.

Electroencephalography - how to prepare for the test?

You should report to the electroencephalogram with washed hair (not covered with any styling agents, e.g. varnish, gel, etc.). In order to prevent a drop in blood sugar levels, it is advisable to eat a light meal before the test.

Important

During the day before the EEG, you should not take drugs that stimulate or inhibit the central nervous system (e.g. sedatives, sleep). It is also inadvisable to drink alcoholic or caffeinated drinks (coffee, strong tea, cola drinks or energy drinks).

Electroencephalography - what is the test?

A special mesh is put on the patient's head, in which 24 electrodes are inserted (for better electrical conductivity, the surface of the electrodes is covered with a special conductive gel or paste). Their task is to record the action currents produced by the nerve cells (neurons) of the brain andpassing these signals to an electroencephalograph, which converts them into a series of wavy lines. It is from them that the image of brain waves is formed.

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EEG - how to interpret the results?

The EEG recording consists of the so-called waves and rhythms of different frequencies and amplitudes. There are alpha, beta, theta, delta waves and rhythms, sharp waves and various complex elements such as spire assemblies.

EEG - correct result

Normal human EEG at rest and with eyes closed consists of the alpha rhythm (mainly in the occipital and parietal areas of the brain) and the beta rhythm (frontal areas of the brain). In addition, 15-20% of he althy people have theta waves in the recording, as well as flattening of the recording (low amount of alpha rhythm and its low amplitude).

EEG - incorrect result

Rhythm distortion, disappearance, significant asymmetry of the recording or the appearance of pathological waves (theta, delta, spikes and other complex elements) mean that the test result is abnormal.

The first stage of the research is to obtain the resting recording. For this purpose, the patient is lying or sitting down, motionless and with his eyes closed. Then, various stimulation methods are used - the patient opens his eyes and takes 30-40 deep breaths per minute (the so-called hyperventilation). Photostimulation is also used, i.e. the effect of light flashes of different frequency (then the patient's eyes are closed), less often physiological sleep and administration of pharmacological agents.

The test takes several dozen minutes.

The EEG resultis obtained immediately after completing the test in the form of a description with an attached graph (picture of the brain waves).

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