Abnormal dynamic EEG is a waveform that would not be recorded under normal physiological conditions. The common ones are as follows: first, diffuse slow waves, which are mainly seen in diffuse encephalopathy, ischemic-hypoxic encephalopathy, as well as central nervous system degenerative diseases and demyelinating encephalopathy. The second type, focal slow waves, is caused by brain parenchymal dysfunction and is seen in focal epilepsy, brain abscesses, or epidural hematomas. The third type, triphasic waves, is usually of medium to high amplitude and is mainly seen in metabolic encephalopathies such as hepatic encephalopathy. The fourth type, epileptiform discharge, this waveform mainly includes spike, spike-wave, multi-spike, and spike-slow wave synthesis. This recording suggests that the patient has a seizure when it arrives, and different classifications of epilepsy can be determined depending on the waveform.