**Abstract**

The method of electroencephalography is an accurate and objective method of recording the bioelectrical activity of the brain, used both in scientific research and in clinical practice. However, achieving a high-quality result requires a lot of preparatory work. This chapter describes the technology for conducting electroencephalographic studies, their subsequent analysis, and presentation of results that are understandable to both a specialist neurophysiologist and a practicing neurologist. You will also find a description of the organization of the EEG study, the choice of scenario, functional tests, and the basics of forming a medical report. We will also consider individual issues of organizing an EEG study in people who have had a stroke, and multichannel and functional EEG studies.

**Keywords:** electroencephalography, brainmapping, organization, clinical neurophysiology, clinical practice

### **1. Introduction**

Electroencephalography is an accessible method for objective diagnosis of the functional activity of the brain, widely used in modern neurology. The main reason for the modern use of electroencephalography in clinical diagnostics is the fact that there is no time delay between the level of nutrient supply to the nerve cell and changes in the total postsynaptic potential recorded using the electroencephalographic system, which is due to the absence of organelles in nerve cells that ensure the deposition of nutrients. This makes it possible to use the EEG for diagnosing brain processes with fast dynamics that are inaccessible to other technologies, in particular, fMRI. In practice, this makes it possible to observe the features of changes in cerebral hemoperfusion in the cortical regions of the cerebral hemispheres in real time. And taking into account the peculiarities of the EEG—technology to implement an economically accessible system of functional observation / control without significant risks of adverse effects on the subject.

However, the most significant issues limiting the use of EEG at present are the training of specialists who use in their daily work either primitive diagnostic

technologies in the form of visualization-phenomenological analysis or controversial mathematical methods introduced into the EEG technique back in the era of analog devices, thanks to their accessibility and ease of implementation, but lacking a convincing scientific justification [1].

To understand the place of EEG in modern neurological diagnostics, these issues need to be considered in more detail. The issue of localization of the EEG signal source and its connection with brain structures were solved as early as by Penfield in the 1940s of the last century [2], using the "10-20" system of electrode placement on the scalp, which is still used today, which made it possible to create a triangulation model for determining the basic signal, as which W. Penfield used a focal epileptic discharge. Currently, these ideas are actively used in the photogrammetric localization system, actively promoted by Magstim Corporation (USA) [3].

But due to a lack of understanding of the need to build a triangulation model, as well as attempts to revise the technology from the standpoint of other functional methods, a significant simplification of the EEG methodology was formed and the further development of electroencephalography went in two ways: The first was the use of a routine study in outpatient practice, the purpose of which was diagnostic search and active detection of epilepsy in workers of certain specialties and industries, and the purpose of the second was to scientifically search for the relationship between functional and behavioral reactions caused by various objective factors (especially those associated with the development of intracranial volumetric formations) and changes in the general nature of the EEG signal. These studies made it possible to make a number of significant observations about the nature of slow-wave rhythmic phenomena and from the connection with processes accompanied by swelling of the nervous tissue and disorders of cerebral hemoperfusion processes; however, the lack of localization technology and the search for alternative solutions led to a loss of interest in EEG in the late 1990s of the last century, with the advent of affordable radiological diagnostic systems that made it possible to obtain a two-dimensional image understandable to most specialists, comparable to traditional anatomical drawings and postmortem examination data.

At present, the creation of systems for accurate localization of the position of EEG electrodes in space [4–6], as well as the development of the latest EEG diagnostic systems with a large number of active electrodes presented in the developments (3), has revived interest in electroencephalography as an accessible a method that makes it possible to study the processes of brain activity that have fast dynamics, which are inaccessible to systems using technologies for recording the dynamics of changes in cerebral microcirculation (MRI, near-infrared spectroscopy), and the development of software products for combining the results of a spatial representation of the EEG potential distribution on the scalp with radio imaging data methods [7] made it possible to obtain information on functional changes, comparable in accuracy to the methods of X-ray neuroimaging.

This led the International Federation of the Clinical Neurophysiology (IFCN) guidelines in 2017 to adopt official recommendations for the use of advanced lead localization systems and also recommended a gradual transition from using the "10-20" system to the "10-10" system [8]. This approach makes it possible to develop new ideas for creating a system of brain mapping (brain mapping), which allows recording various functional changes in cerebral activity in real time and making their direct connection with anatomical data [9].

*Practical Recommendations for Conducting an EEG Study in a Neurophysiological Laboratory DOI: http://dx.doi.org/10.5772/intechopen.108879*

The development of such systems will improve the quality of life and stroke patients and accelerate their return to an active social life, which has already been shown by a number of authors [10–12].
