Triphasic Waves

Posted on
March 31, 2023
Let's learn all the facts about a brain pattern called

Triphasic Waves

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EEG Sample Credit: The Learning EEG (

Triphasic waves are a three-phase complex consisting of negative-positive-negative polarity in the delta/theta frequency ranges and a high amplitude. This pattern can be generalized or lateralized, often maximally frontal with an anterior to posterior lag (AP gradient). Triphasic waves appear synchronous with a periodic or pseudo periodic occurrence. Typically seen in obtunded or stuporous patients with impaired consciousness, associated with encephalopathy. The pattern was first reported as a specific pattern of hepatic encephalopathy, over time it has become a recognizable pattern metabolic, toxic and anoxic encephalopathies, reflective of a diffuse cerebral dysfunction. 

Text Resources: Greenfield, John, L. et al. Reading EEGs: A Practical Approach. Available from: Wolters Kluwer, (2nd Edition). Wolters Kluwer Health, 2020.

What degenerative central nervous system (CNS) disease is this EEG pattern indicative of, generally present after the first 2 months of clinical symptoms that include rapidly progressive dementia and myoclonus?
Parkinson with tremor
Alzheimer’s Disease
Creutzfeldt–Jakob disease (CJD)
Correct Answer: 

The classic clinical symptoms of CJD are rapidly progressing dementia and myoclonus. Ataxia, visual symptoms, and akinetic mutism are often present as well. 

Creutzfeldt-Jakob disease (CJD) is the most common human prion disease.  The EEG shows clinicians a key indicating pattern important in the diagnosis process. Typical EEG findings include bi-anterior dominant periodic triphasic sharp wave complexes, lasting 600-1000ms, occuring at a rate of 0.5 to 2Hz. These complexes can be purely unilateral in early stages of the disease of CJD. During the late stages of CJD myoclonus is common.

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