Abstracts

Rationale: Triphasic waves have a distinctive, but non-specific EEG pattern. It is associated with impaired consciousness although the severity varies. The most common etiologies reported are hepatic, renal failure, and anoxic injury. Although it is a common finding, there is not much reported in the literature of the specific etiologies of triphasic waves. Methods: This was a retrospective study which included all patients with triphasic waves seen on EEGs in the adult population at the University of Michigan from 2000 to 2009. Data was collected by chart reviews and included the age, reason for study, abnormal EEG pattern, and underlying etiology. Results: Sixty-eight patient had documented triphasic waves on EEG from 2000 to 2009. There were 52 females and 16 males between the ages of 25 and 86 years and the average age was 60.8 years. Sixty percent was due to metabolic causes while the remaining 40% was due to non-metabolic etiologies. The most common etiologies included infection (29.4%), acute renal failure (23.5%), liver toxicity (11.8%), multi-organ failure (5.9%), and anoxic injury (2.9%). In 20 cases (29.4%) the patient expired during the hospitalization or within 1 week after discharge. Nine patients had clinical seizures and 2 with documented subclinical electrographic seizures. Other concurrent diagnoses included focal sharp waves (13.2%), focal intermittent slowing (10.3%), and generalized slowing (10.3%). Conclusions: The most common etiologies included infection, acute renal failure, and liver toxicity. Infection alone was the most prevalent in this type of EEG pattern. Renal failure was seen associated with triphasic waves more frequently than hepatic failure. Interestingly, there was a relatively high risk of mortality with this EEG pattern.