Technique of record of electroencephalogram

For reception of a high-grade picture of bioelectric activity of a brain careful installation of skin or needle electrodes is need. Thus observance of strict symmetry relatively of anterior a line is necessary, to try to install electrodes on identical distance from each other that they were above all basic departments of surfaces of a brain: frontal, central, parietal, cervical, temporal.

Fig. 6.

In applied medicine the international system of installation of electrodes is used "10-20 %" (Fig. 6). According to this system at each examinee precisely measure distancebetween the middle of nose bridge and external occipital protuberance (inion), and also between the left and right ear poles. Possible points of an arrangement of electrodes are divided by the intervals making 10 % or 20 % of these distances on a skull. Thus for convenience of registration all skull is broken into the areas designated by letters: F-frontal, About-occipital area, Р-parietal, Т-temporal, С-area central line.

Registration of EEG is made by special electrodes. Each electrode is connected to the amplifier.

Record of potentials from each electrode is carried out concerning zero potential of the reviewer to which is accepted lobe of the ear, or a tip of a nose.

Computer electroencephalograph «Компакт-нейро» - 16 channel device.

In electroencephalography two variants of taps subdivided on monopolar (referent) and bipolar are use.

Such tap is called monopolar when on one of entrance clamp of the amplifier the electric potential from an electrode which is above a brain moves, and on another clamp- potential from the electrode established on certain removal from a brain, or some average potential caused by any local source. The electrode located above a brain, is called active. The electrode removed from a brain tissue is called passive, referent, indifferent.

Referent electrode is located on lobe of the ear, on a chin or sometimes on a nose. An establishment of referent electrode on more removed parts of a body have a number of the difficulties partly connected with fixing of an electrode, but mainly, with handicapes from others электрически active bodies of a body - muscles and heart.

Tap is called bipolar at which to positive and negative to entrance clamp of the amplifier connect the electrodes which are above a brain.

For reception of qualitative EEG it is desirable to place the patient in an armchair, in the weakened pose, blindly. At first recording of EEG is made, then various tests are made: in the form of sound and light irritations, test with opening and closing of eyes with supervision over dynamics of the basic rhythms.

Now the test with hyperventilation is most widespread: the patient deeply and rhythmically breathes within 1 minutes; thus registration EEG is carried out not less than 3 minutes during and after carrying out of hyperventilation.

It is possible to apply pharmacological tests, entering during record EEG those or other preparations depending on the purpose of inspection.

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