Electroencephalography and computerised tomography in vascular and non-vascular dementia in old age.

Nine normal elderly subjects and 81 patients with dementia have been studied by computerised tomography (CT) and electroencephalography (EEG). There was a broad relationship between slowing of the basic frequency of the EEG and the severity of mental impairment. Localised slow-wave activity was found in 19% of those with non-vascular dementia and 72% of those with dementia of vascular origin. The mean size of the ventricles, as determined from CT scans, was larger in the vascular than in the non-vascular group. Within the vascular group it was larger in those without than in those with visible infarcts. There was no relationship in either group between ventricular size and dominant EEG frequency.