Triphasic waves in dementia syndromes

: Seventy-one EEGs (0.49%) of 53 patients, out of 14,458 recordings, contained triphasic waves: twenty-nine were patients with metabolic encephalopathies and 24 were demented patients (16 of these had a presumptive diagnosis of Alzheimer's disease and the other eight of mult-infarct dementia). Demented subjects with metabolic disorders are included in the metabolic encephalopathies group. In all of the cases of Alzheimer's disease, triphasic waves were atypical: in 14 they occurred singly or in short bursts, in 10 they had occipital predominance and in 2 they were bilateral but asymmetrical. In 5 cases, triphasic waves were associated with myoclonus and in 2 of them they occurred in long runs with a pseudo-periodic pattern. In these cases the distinction from Creutzfeldt-Jakob disease was based on neuropathologic findings.