Electroencephalography-driven approach to prodromal Alzheimer's disease diagnosis: from biomarker integration to network-level comprehension

Abstract

Decay of the temporoparietal cortex is associated with prodromal Alzheimer's disease (AD). Additionally, shrinkage of the temporoparietal cerebral area has been connected with an increase in α3/α2 electroencephalogram (EEG) power ratio in prodromal AD. Furthermore, a lower regional blood perfusion has been exhibited in patients with a higher α3/α2 proportion when contrasted with low α3/α2 proportion. Furthermore, a lower regional blood perfusion and reduced hippocampal volume has been exhibited in patients with higher α3/α2 when contrasted with lower α3/α2 EEG power ratio. Neuropsychological evaluation, EEG recording, and magnetic resonance imaging were conducted in 74 patients with mild cognitive impairment (MCI). Estimation of cortical thickness and α3/α2 frequency power ratio was conducted for each patient. A subgroup of 27 patients also underwent single-photon emission computed tomography evaluation. In view of α3/α2 power ratio, the patients were divided into three groups. The connections among cortical decay, cerebral perfusion, and memory loss were evaluated by Pearson's r coefficient. Results demonstrated that higher α3/α2 frequency power ratio group was identified with brain shrinkage and cutdown perfusion inside the temporoparietal projections. In addition, decay and cutdown perfusion rate were connected with memory shortfalls in patients with MCI. MCI subgroup with higher α3/α2 EEG power ratio are at a greater risk to develop AD dementia.

Keywords: EEG; MRI; SPECT; alpha rhythm; hippocampal atrophy; prodromal AD.

Figure 1

High α3/α2 vs low α3/α2. Notes: Red color represents the brain regions with higher regional cortical thickness in patients with MCI with high α3/α2 ratio compared to patients with MCI with low α3/α2 ratio (P<0.01, uncorrected). The color coding for P-values is on a logarithmic scale. Results are presented on the pial cortical surface of the brain; dark gray regions represent sulci and light gray regions represent gyri. Abbreviation: MCI, mild cognitive impairment.

Figure 2

High α3/α2 vs middle α3/α2. Notes: Red color represents the brain regions with higher regional cortical thickness in patients with MCI with high α3/α2 ratio compared to patients with MCI with middle α3/α2 ratio (P<0.01, uncorrected). The color coding for P-values is on a logarithmic scale. Results are presented on the pial cortical surface of the brain; dark gray regions represent sulci and light gray regions represent gyri. Abbreviation: MCI, mild cognitive impairment.

Figure 3

Correlation results between Babcock memory test (A) and cortical thickness (B). Note: Red color represents the brain regions with higher regional cortical thickness.

Figure 4

Correlation results between AVLT immediate recall (A) and cortical thickness (B). Note: Red color represents the brain regions with higher regional cortical thickness. Abbreviation: AVLT, auditory verbal learning test.

Figure 5

Correlation results between AVLT delay recall (A) and cortical thickness (B). Note: Red color represents the brain regions with higher regional cortical thickness. Abbreviation: AVLT, auditory verbal learning test.

Figure 6

SPECT visual rating. Notes: The output shows a SPECT visual inspection of glucose-uptake metabolism in one of the 17 controls (A), the white ovals denote areas of mild-to-moderate temporoparietal hypometabolism in one of the 14 patients with low-risk MCI (B) and in one of the 13 patients with high-risk MCI (C). Abbreviations: MCI, mild cognitive impairment; SPECT, single-photon emission computed tomography.

Figure 7

Pearson’s r correlations between EEG theta rhythm and hippocampal complex perfusion in patients at low risk (A) and at high risk (B) to develop AD. Abbreviations: AD, Alzheimer’s disease; EEG, electroencephalogram; MCI, mild cognitive impairment.