triphasic waves
Pronunciation: TRY-faze-ick waves
Distinctive three-phase periodic discharges associated with metabolic encephalopathy, particularly hepatic failure.
Full Definition
Triphasic waves are characteristic periodic EEG discharges consisting of three distinct phases: an initial positive deflection, followed by a large negative wave, and concluding with a final positive component. These discharges typically occur at 1-2 Hz intervals and are most prominent over the frontal regions with an anterior-to-posterior phase lag. While originally described in hepatic encephalopathy, triphasic waves can occur in various metabolic disorders including uremia, hypoxia, and drug intoxication. The pattern indicates severe but potentially reversible brain dysfunction and is distinguished from other periodic patterns by its characteristic morphology and clinical context. The presence of triphasic waves often correlates with the degree of metabolic disturbance.
Usage
Usage note: Document frequency, distribution, and clinical context when reporting triphasic waves.
In Context
- "Generalized triphasic waves were present consistent with hepatic encephalopathy." — ICU EEG report
- "The triphasic waves resolved following correction of the metabolic abnormalities." — Follow-up neurophysiology report