Affair With Triphasic Waves-Their Striking Presence, Mysterious Significance, and Cryptic Origins: What are They?

Triphasic waves, which have been recorded in the EEG of encephalopathy for more than 50 years, remain clearly identifiable but historically purportedly of uncertain significance. Initially described with liver failure and high serum ammonias, they came to be reported in an ever-expanding list of metabolic, toxic, and structural conditions. Often a dynamic finding (in which the occurrence of triphasic waves might increase or decrease with stimulation or arousal of the patient during EEG), there has been increasing insight into their correlation with multiple concurrent conditions, including subcortical white-matter disease, infections and metabolic disturbances, and their prognostic significance. There are sparse data, but there is active controversy into their confusion for, or occurrence in, nonconvulsive status epilepticus. This review and commentary discuss our current understanding of triphasic waves and the newer areas of contention surrounding this mysterious EEG morphology.