Transient appearance of periodic EEG discharges in senile dementia.

We describe an elderly patient with probable Alzheimer's disease whose EEG and clinical status improved rapidly coincident with normalization of temperature. This finding suggests that her transient illness, of fever, pneumonia and confusional state, triggered the production of this periodic EEG pattern. With the increased prevalence of dementia in our aging population, we predict that the appearance of a multifocal periodic triphasic sharp wave pattern in the EEG of chronically demented patients (with superimposed infection) will become more common. Only when this pattern persists over time and the patient is not systemically ill, is this pattern a reliable discriminator for CJD. Serial EEGs in this setting (after treatment of the systemic illness) might reveal the transient nature of the periodic EEG change, thus avoiding the erroneous conclusion that the patient's dementia is a manifestation of CJD.