Significance of triphasic waves in patients with acute encephalopathy: a nine-year cohort study

OBJECTIVE: Triphasic waves (TWs) are a frequent electroencephalography (EEG) finding in encephalopathy, yet their origin and prognostic significance are not well understood. The aim of this study was to determine the clinical and EEG characteristics in encephalopathic patients with TWs. We hypothesized that specific EEG characteristics are predictive of outcome. METHODS: Consecutive adult encephalopathic patients with TWs on EEG and neuroimaging were included. EEG analysis included semiquantitative evaluation of TWs, background activity, and EEG reactivity. The study endpoint was death. RESULTS: Over a nine-year period, 105 patients with TWs were included. Common abnormalities on neuroimaging were white matter lesions (60%) and cerebral atrophy (59%). Pathologic conditions included infections (56%), renal (50%) and liver insufficiency (12%), and respiratory failure (20%). Mortality was 20%. Absent EEG background reactivity and respiratory failure were independently associated with death (OR 3.73, 95%CI 1.08-12.80, p=0.037 and OR 6.47, 95%CI 1.98-21.12, p=0.02). CONCLUSIONS: These results suggest that TWs are a marker of structural brain disease coupled with toxic-metabolic perturbations, and that etiologies or underlying pathologies were not predictive for outcome while non-reactive EEG was independently associated with death. SIGNIFICANCE: In contrast to clinical, EEG and neuroimaging findings, non-reactive EEG patterns predicted death in encephalopathic patients with TWs.