Triphasic waves during post-ictal stupor.

BACKGROUND The term, "triphasic wave" originally described an EEG pattern believed to be a marker for a specific stage of hepatic coma. For 4 decades, the diagnostic and prognostic specificity of the pattern remains controversial. Its pathophysiology also continues to be elusive. METHODS EEG recordings were obtained in three patients known or suspected to have primary generalized epilepsy. In 2 patients, the EEGs were part of long-term monitoring using simultaneous video-EEG telemetry. For the third patient, the EEG was secured only during the post-ictal unconsciousness. These 3 patients were specifically selected because of the presence of triphasic waves in their EEGs. RESULTS Triphasic waves were observed in the EEG of the 3 patients only during post-ictal unconsciousness. The pattern was transient, being preceded by generalized suppression and delta slow waves and followed by theta activities. Alpha rhythms supervened when the patients became fully alert. CONCLUSION A post-ictal state should be considered in unconscious patients with triphasic EEG waves.