Triphasic waves on electroencephalogram in patients with encephalopathy and their diagnosis significance. A review

Abstract

Triphasic waves are high-amplitude (>70 µV) positive sharp transients preceded and followed by relatively low-amplitude negative waves. The distribution is generalized and tends to have a repetition rate of approximately 1 to 2 Hz. This EEG-pattern is traditionally associated with hepatic encephalopathy, although they have been observed in a wide array of neurological disorders including subcortical white-matter disease, infections, metabolic disturbances and nonconvulsive status epilepticus.American Clinical Neurophysiology Society suggested Standardized Critical Care EEG Terminology (2012). One of the goals was to eliminate terms with clinical connotations, such as ‘triphasic waves’, a term that implies a metabolic encephalopathy with no relationship to seizures for many clinicians. The term ‘triphasic waves’ was replaced by ‘Generalized periodic discharges (GPDs) with triphasic morphology’. The clinical significance ofthese waveforms and their relationship with seizures and prognosis has been debated, and differentiation between interictal patterns, patternsassociated with seizures, and the patterns representing nonconvulsive status epilepticus have been concluded to be a challenge. In cases of uncertainty, the decision to treat should follow on a thorough evaluation with a continuous EEG monitoring and using a short-acting benzodiazepine or non-sedating antiepileptic drugs in order to discern the effects of the pattern on the patient’s clinical exam and EEG.