Are Triphasic Waves Different From Generalized Spike–Wave Discharges?

Summary: Generalized periodic discharges with triphasic morphology were previously referred to as triphasic waves but have now been subsumed into the ACNS classification as generalized periodic discharges. Although triphasic waves and generalized spike–wave complexes may resemble each other and hence may be incorrectly identified in comatose critically ill patients, many authors believe that there are different entities, with definable morphologic and clinical differences attributable to each waveform. The occurrence of both patterns in the same patient is extremely rare with only a single prior case report. Here the authors report a patient with typical triphasic waves and generalized spike–wave complexes and highlight the morphologic and EEG differences between the two patterns. The occurrence of both waveforms in the same EEG recording supports the notion of different cerebral generators and pathways, further differentiating rather than merging these morphologies.