TRIPHASIC WAVES IN A PSYCHIATRIC POPULATION - A RETROSPECTIVE STUDY

In a retrospective study of 15,326 EEGs performed from 1983 to 1992 in a psychiatric institute, 83 EEGs (62 patients-13 men and 49 women ran ging in age from 59 to 90 years, with a mean age of 74 years) had trip hasic waves (TWs). All 62 patients were awake, though they were often confused. Most (n = 56) had dementia, usually severe; 15 also had deli rium. There were six nondemented patients (age range, 59-79 years, wit h a mean age of 67 years). Infrequent etiologies included neuroleptic malignant syndrome (n = 1) and hepatic encephalopathy (n = 1); in four , the cause was uncertain, although all were receiving lithium. EEG fe atures analyzed included frequency of background rhythms, distribution of the TWs, periodicity, and epileptiform abnormalities. Background r hythms were slow in all but seven patients (mean. 6.2 +/- 1.7 [SD] Hz) . TWs were maximal posteriorly in 47 patients and anteriorly in six an d were diffuse in nine. Neuroimaging studies showed prominent posterio r abnormalities in only one case, Periodicity was prominent in four pa tients; in two the TWs were maximal anteriorly. Interictal epileptifor m activity was present in six, a history of seizures in eight, and myo clonus in four. TWs are uncommon in a psychiatric population: they occ ur primarily in elderly, severely demented patients. They are usually associated with background slowing, are often maximal posteriorly, and occasionally are periodic.