What it looks like
Three phases, the second (positive) the largest: negative–positive–negative. Frontally predominant at 1.5–2.5 Hz, often with an anterior-to-posterior lag, increasing with stimulation. ACNS treats "triphasic morphology" as a modifier of GPDs. 1
What it means at the bedside
Classically hepatic or uraemic encephalopathy, also sepsis and drug toxicity (cefepime, lithium, baclofen). They are not specific: expert agreement on triphasic morphology is only fair, and it does not exclude an association with seizures. 22 Attenuation with a benzodiazepine without clinical improvement proves nothing.