EEG suppression occurs when neuronal activity decreases secondary to central nervous system damage, which may be associated with various diseases. Generally, more severe disease is associated with more pronounced EEG suppression. aEEG background activity is also used to assess the degree of this suppression. However, assessing chronic-stage abnormalities, such as disorganized patterns evident in a conventional EEG, is challenging in an aEEG, especially when relying on visual analysis. The primary purpose of an aEEG is to evaluate acute-stage abnormalities; i.e., whether there is a certain level of suppression of current brain activity. It is also important to know the limitations of aEEG.