Dominant frequency variability also differed between the AD (1.1 ± 0.4 Hz) and DLB groups (1.8 ± 1.2 Hz, P <0.001). Dominant frequencies were 8.3 ± 0.6 Hz for the AD group and 7.4 ± 1.6 Hz for the DLB group, in which most of the patients (88%) exhibited a frequency band of 5.6–7.9 Hz. The most relevant group differences were observed between the AD and DLB patients in EEGs from posterior derivations ( P <0.001). Initial diagnoses were confirmed in 36 DLB, 40 AD and 35 PDD patients. Patients’ initial diagnoses were revised at a 2-year follow-up visit with neuroimaging evaluation.
EEG variability was assessed by mean frequency analysis and compressed spectral arrays (CSA) in order to detect changes over time from different scalp derivations. To improve clinical diagnostic accuracy, special emphasis was placed on identifying cognitive fluctuations and REM-sleep behaviour disorder. The aim of this study was to evaluate whether EEG abnormalities can discriminate between DLB, AD and PDD in the earliest stages of dementia and to do this 50 DLB, 50 AD and 40 PDD patients with slight cognitive impairment at first visit (MMSE ≥ 20) were studied. No evidence is as yet available for Parkinson's disease with dementia (PDD). Although it has been suggested that variations in mean EEG frequency are greater in the former, the existence of meaningful differences remains controversial. EEG abnormalities have been reported for both dementia with Lewy bodies (DLB) and Alzheimer's disease (AD).