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Triphasic waves are abnormal electroencephalogram (EEG) waveforms seen with a multitude of clinical conditions including encephalopathy and structural brain lesions. They are non-specific, high amplitude, sharply contoured waves with a unique morphology. They were believed to be pathognomonic of hepatic encephalopathy. However, they can be seen with any metabolic encephalopathy and many other conditions. This activity reviews the evaluation and management of triphasic waves and highlights the role of the interprofessional team in evaluating and treating patients with this EEG finding. Objectives: Identify the significance and key concepts of triphasic waves on an EEG. Describe the differential diagnosis of triphasic waves. Outline the clinical significance of triphasic waves on an EEG and the management of potential underlying etiologies. Review interprofessional team strategies for improving care coordination and communication to advance the management of patients with triphasic waves and improve outcomes. Access free multiple choice questions on this topic.

Triphasic waves are abnormal electroencephalogram (EEG) waveforms observed in association with multiple clinical conditions, including encephalopathy and structural brain lesions. They are nonspecific, high-amplitude, sharp/sharply contoured waves with 3 distinctive phases. The main phase is surface-positive, with a high amplitude (greater than 70 microvolts), preceded by a low-amplitude negative deflection and followed by a slowly rising, broad negative deflection. They were initially believed to be pathognomonic of hepatic encephalopathy; however, they can be seen in any metabolic encephalopathy (in fact, more common with renal than hepatic conditions) and some other conditions. They may be considered a subset of generalized periodic discharges (GPDs).[1][2] This EEG pattern was first described by Foley in 1950. It was an EEG recording of a patient with hepatic encephalopathy. The author described the waveforms as "blunted and spike waves."[3] Literature is abundant in the 1950s on this topic, and most of it then suggested that this finding was specific to hepatic encephalopathy. It was felt to represent high mortality with severe liver conditions like portal cirrhosis, metastatic liver disease, and infective hepatitis.[4] At that time, EEG was used to diagnose early stages of hepatic encephalopathy and as a tool to guide treatment with medications like neomycin. The term triphasic waves was first coined in 1955 by Bickford and Butt, given the 3-phase morphology.[5]

Identification and management of patients with triphasic EEG activity require an interprofessional team approach involving EEG technicians, nurses, and physicians of different specialties (neurologists, intensivists, emergency physicians, and others). An interprofessional team approach could help improve patient outcomes by enabling accurate identification and treatment of underlying pathology. The education of the caregivers managing such patients is equally important. Adequate training in the interpretation of EEG and triphasic waves helps the clinical team to provide optimal care for these patients.