P2-217: A new approach to EEG analysis in dementia with Lewy bodies

Abstract

Background: Dementia with Lewy bodies (DLB) is claimed to be the second most common neurodegenerative dementia after Alzheimer’s disease (AD). The core clinical features are visual hallucinations, fluctuating cognition and parkinsonism. Fluctuating cognition is often difficult to evaluate in the clinic. In DLB, the EEG can show loss of alpha activity as the dominant rhythm and an increase in EEG power density in the delta and theta bands. One study by Walker et al (2000) correlated fluctuating cognition with greater variability in the delta domain of the quantitative EEG. In this study we aimed to investigate whether the EEG could be a way of visualising fluctuations in patients with DLB as well as if the EEG could be a useful way of distinguishing patients with DLB from patients with AD. Methods: We analysed the quantitative EEGs in 64 patients with Alzheimer’s disease, 20 patients with DLB and 54 controls from a clinical follow up programme. The parameters investigated were frequencies, variability and coherence. Results: The frequency analysis showed an increase in theta and delta activity in the DLB patients compared to both the AD patients and the controls. The variability in delta power was analysed between 2-sec intervals in parietal electrodes (P3 and P4). We found significantly greater variability even between these short epochs in the DLB patients compared to both the AD patients and the controls. The AD patients showed greater variability than the controls. (P3: p 0.001 DLB vs AD and DLB vs controls, p 0.001 AD vs controls; P4: p 0.001 DLB vs AD, DLB vs controls and AD vs controls.) The coherence analysis showed a significantly lower overall value in the alpha frequency band and a significantly higher overall value in the delta frequency band in the DLB group compared to the other two groups. (Delta: p 0.004 DLB vs AD, p 0.007 DLB vs controls; Alpha: p 0.011 DLB vs AD, p 0.016 DLB vs controls) Conclusions: In conclusion we suggest that this new approach to EEG analysis may visualise fluctuations in DLB on a second-to-second basis and might have clinical implications as guidance in the diagnosis of DLB.