Triphasic waves during post-ictal stupor

Abstract

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.