Comparison of triphasic waves and epileptic discharges in one patient with genetic epilepsy.

Genetic epilepsies with generalized spike-wave complexes (GSWCs) and encephalopathy triphasic waves (TWs) may resemble each other and have three phases per complex. Electroencephalographic (EEG) interpretation is subjective, and EEGers have noted "TWs" in cases labeled nonconvulsive status epilepticus (NCSE). Direct comparison of both wave forms under the same conditions is rarely possible. In a single patient with generalized spike waves who developed hepatic TWs, morphologic characteristics of both were compared, and it was found that GSWCs have higher frequency first, second, and third phases; steeper phase 2 slope; and briefer after-going slow waves maximal at F3 to F4. Total complex duration was approximately 0.12 seconds. The TWs had dominant high-voltage phases 2 and 3 located more posteriorly, in the frontocentral region, lasting an average of approximately 0.32 seconds. These morphologic distinctions may help differentiate TWs from GSWCs.