Utility of quantitative EEG in early Lewy body disease

Introduction: The reduction of background activity and the increase of low-frequency powers on electroencephalogram (EEG) correlate with cognitive impairment and have been suggested to be underpinned by cholinergic deficit. We aimed to investigate the ratio between alpha and theta band power (alpha/theta ratio), as a synoptic index of quantitative EEG (qEEG) slowing-down, in a peculiar group of patients with mild cognitive impairment (MCI) due to an early-stage Lewy body disease (MCI-LBD), as compared to de novo PD patients without cognitive impairment (PD-MOT), to patients with MCI due to Alzheimer's disease (MCI-AD), and to healthy controls (HC). Methods: Twelve patients with MCI-LBD (8 males; mean age 74.8 +/- 3.6), 11 PD-MOT, 11 MCI-AD and 24 HC subjects undergoing qEEG were matched for gender, age, and education. Following logarithmic transformation, the alpha/theta ratio was compared among groups and brain regions by repeated measures ANOVA, also exploring group*regions interactions. Results: A significant effect of group (p = 0.0003), regions (p = 0.0001), and group*regions interaction (p = 0.0001) on the alpha/theta ratio was observed. At post-hoc analysis, alpha/theta ratio was significantly lower in MCI-LBD (p = 0.001) and in PD-MOT (p = 0.02) compared to HC, and in MCI-LBD than MCI-AD (p = 0.05). No significant differences were found between MCI-AD and HC, as well as between MCI-LBD and PD-MOT. Conclusion: The alpha/theta power ratio as a synoptic index of EEG background slowing-down could be a simple and easy-to-use qEEG index which might indirectly mirror a cholinergic failure, useful to pick-up those MCI patients at higher risk of developing a Lewy-body disease.