Quantitative EEG Markers in Mild Cognitive Impairment: Degenerative versus Vascular Brain Impairment

Abstract

We evaluated the relationship between brain rhythmicity and both the cerebrovascular damage (CVD) and amygdalohippocampal complex (AHC) atrophy, as revealed by scalp electroencephalography (EEG) in a cohort of subjects with mild cognitive impairment (MCI). All MCI subjects underwent EEG recording and magnetic resonance imaging. EEGs were recorded at rest. Relative power was separately computed for delta, theta, alpha1, alpha2, and alpha3 frequency bands. In the spectral band power the severity of CVD was associated with increased delta power and decreased alpha2 power. No association of vascular damage was observed with alpha3 power. Moreover, the theta/alpha1 ratio could be a reliable index for the estimation of the individual extent of CV damage. On the other side, the group with moderate hippocampal atrophy showed the highest increase of alpha2 and alpha3 power. Moreover, when the amygdalar and hippocampal volumes are separately considered, within amygdalohippocampal complex (AHC), the increase of theta/gamma ratio is best associated with amygdalar atrophy whereas alpha3/alpha2 ratio is best associated with hippocampal atrophy. CVD and AHC damages are associated with specific EEG markers. So far, these EEG markers could have a prospective value in differential diagnosis between vascular and degenerative MCI.

Figure 1

Statistical ANOVA interaction among groups, factor and relative band power (delta, theta, alpha1, alpha2, and alpha3). In the diagram the difference in delta and alpha2 power among groups is also indicated, based on Duncan's post hoc testing. G1, group 1: no vascular damage; G2, group 2: mild vascular damage; G3, group 3: moderate vascular damage; G4, group 4: severe vascular damage [32, 35].

Figure 2

Statistical ANOVA interaction among group factors and relative band powers (delta, theta, alpha1, alpha2, and alpha3), on the full scalp region. The groups are based on mean and standard deviations in a normal elderly sample. Group 1: no hippocampal atrophy; group 2: mild hippocampal atrophy; group 3: moderate hippocampal atrophy; group 4: severe hippocampal atrophy. Post hoc results are indicated in the diagram (see [32, 35]).