P122. Alpha1/theta ratio from quantitative EEG (qEEG) as a reliable marker for mild cognitive impairment (MCI) in patients with Parkinson’s disease (PD)

Abstract

Objective We investigated whether a combination of qEEG variables, in particular signal power in the alpha1 (8–10 Hz) and theta (4–8 Hz) bands, could represent a robust marker for MCI in patients with PD. Background MCI is diagnosed based on the results of a large standardized set of cognitive tests. Certain qEEG parameters are associated with dementia. Previous studies demonstrated a relation between MCI in PD patients and alpha1 power ( Bousleiman et al., 2014 ). Other studies introduced a ratio between alpha and theta powers and demonstrated its association with Alzheimer’s disease ( Schmidt et al., 2013 ). Methods High-resolution 256-channel EEG were recorded in 43 PD patients (MCI/non-MCI: 18/25 ∣age: 68.1 ± 7.9∣ female/male: 16/27). The data was pre-processed semi-automatically and global relative power in alpha1 and theta bands was calculated. Follow-up recordings at four weeks (4W) and six months (6 M) were collected for 32 patients (MCI/non-MCI: 13/19) to test the stability over time. Results were compared between groups using permutation tests on t-statistics to correct for multiple comparisons. Effect sizes (ES) and intra-class correlation (ICC) were calculated. Results An increase ( p = 0.017; ES = 0.789) in the theta and a decrease ( p = 0.042; ES = 0.782) in the alpha1 signal power were associated with MCI in PD patients. The ratio alpha1/theta showed a more robust negative association ( p = 0.012; ES = 1.04) than those calculated for each variable separately. Moreover, the ratio was stable over time (4 W: p = 0.002; ES = 1.082 – 6 M: p = 0.002; ES = 1.084 – ICC = 0.76). Patients whose baseline positive MCI diagnosis did not change at 6 M exhibited a higher ratio than those with a negative MCI diagnosis at 6 M. However, the difference was not statistically significant ( p = 0.1178). Conclusions Reduction of the alpha1/theta ratio is reliably associated with MCI in PD patients. This finding might be used as a robust marker for screening PD patients for early cognitive deficits.