[Usefulness and limitation of clinical electroencephalography: from the clinical standpoint]

An electroencephalogram (EEG), is a visible record of the amplified electrical activity generated by the nerve cells of the brain. EEG has produced an abundance of useful information, though it shows only the activity of the immediately underlying cortex. From the beginning in the areas of convulsive disorder and tumor localization, electroencephalography has expanded to become useful not only in many organic brain disorders but also in many extracerebral conditions influencing the central nervous system (ie, metabolic, endocrine, and toxic). It has also shown some usefulness in sleep disorders. Sleep studies on humans are usually performed by using a polygraph to record three types of data: the EEG, the electrooculography (EOG), and the electromyogram (EMG). The EEG is the core measurement of polysomnography. Polysomnography is generally performed in diagnosing a variety of sleep disorders. Other measures used in polysomnography include: 1) Anterior tibialis EMG, 2) Nasal and oral flow, 3) Blood oxygen saturation, 4) Chest and abdominal movement, and 5) Electrocardiogram (EKG). Also different electronic apparatus and equipment for simultaneous and long-lasting observation and recording of varied physiological phenomena and behavioral manifestations (ie, video-electroencephalography with telemetry, topography, power spectrum) were used. However unless electroencephalography is organized and related to medicine and biology much of it will be disregarded and forgotten.