The appearance of the normal electroencephalogram (EEG) changes significantly from birth through the teenage years and remains relatively unchanged until at least age 80. Epileptiform abnormalities on the EEG may be either interictal or ictal. Status epilepticus (SE) is defined as a continuous seizure lasting 30 minutes or more, or the occurrence of two or more seizures without full recovery of the baseline level of consciousness. EEG abnormalities that are slower than expected for the age and behavioral state of the patient are referred to as slow-wave abnormalities. Focal slow-wave abnormalities imply a local disturbance of cortical and sometimes adjacent subcortical structures. Generalized intermittent slowing occurs most commonly in diverse encephalopathies. EEG is useful in establishing a diagnosis of brain death; it should be used only when the patient has met all clinical criteria for the absence of any brain or brainstem function due to a known and irreversible cause.