Electrodiagnostic study(NCS-EMG-EEG

ELECTRODIAGNOSTIC MEDICINE
Brain Waves
It is the electrical recording from the surface of the brain. Its intensity and patterns are determined to a great extent by the level of excitation of brain (sleep, wakefulness, diseases …etc). The entire recording is called EEG. Intensities range from 0-200 micro-volts and frequency from once every few seconds to 50 or more per second.
Types of Brain Waves
1.Alpha Waves: rhythmical waves of 8-13 /sec, frequency from an EEG of almost all normal adult people when they are awake in a quite, resting state of cerebration and closed eyes. When eyes are opened alpha waves change to beta waves. The voltage of alpha waves equals to 50 micro-volts and are easily recorded from occipital lobe, but also can be recorded from frontal and parietal regions of scalp.
1.Beta Waves: frequency from 14-25 /sec. It might reach to 80 /sec. Always recorded from parietal and frontal regions during activation or tension of CNS.
1.Theta Waves: frequency from 4-7 /sec. occur mainly in parietal and temporal regions in children, can be recorded in some adults during emotional stress (disappointment and frustration). It also occurs in many brain disorders (degenerative brain disease).
1.Delta Waves: frequency below 3.5 /sec. It reflects cortical activity. Can be recorded in deep sleep, in infancy and serious organic diseases.