Abstract
Parkinson’s disease (PD) and Alzheimer’s disease (AD) can coexist in severely affected; elderly patients. Since they have different pathological causes and lesions and consequently require different treatments; it is critical to distinguish PD-related dementia (PD-D) from AD. Conventional electroencephalograph (EEG) analysis has produced poor results. This study investigated the possibility of using relative wavelet energy (RWE) and wavelet coherence (WC) analysis to distinguish between PD-D patients; AD patients and healthy elderly subjects. In EEG signals; we found that low-frequency wavelet energy increased and high-frequency wavelet energy decreased in PD-D patients and AD patients relative to healthy subjects. This result suggests that cognitive decline in both diseases is potentially related to slow EEG activity; which is consistent with previous studies. More importantly; WC values were lower in AD patients and higher in PD-D patients compared with healthy subjects. In particular; AD patients exhibited decreased WC primarily in the γ band and in links related to frontal regions; while PD-D patients exhibited increased WC primarily in the α and β bands and in temporo-parietal links. Linear discriminant analysis (LDA) of RWE produced a maximum accuracy of 79.18% for diagnosing PD-D and 81.25% for diagnosing AD. The discriminant accuracy was 73.40% with 78.78% sensitivity and 69.47% specificity. In distinguishing between the two diseases; the maximum performance of LDA using WC was 80.19%. We suggest that using a wavelet approach to evaluate EEG results may facilitate discrimination between PD-D and AD. In particular; RWE is useful for differentiating individuals with and without dementia and WC is useful for differentiating between PD-D and AD.
Highlights
Parkinson’s disease (PD) is a neurodegenerative disorder that causes motor disabilities including tremors and cognitive impairment
We found that the relative wavelet energy (RWE) values p2 and p3, which were obtained from the high-frequency bands β and γ, were smaller in the PD-related dementia (PD-D) and Alzheimer’s disease (AD) groups compared with the control group
The RWE value p5, which was obtained from the low-frequency band θ, was larger in the posterior channel in the PD-D patients compared with the controls
Summary
Parkinson’s disease (PD) is a neurodegenerative disorder that causes motor disabilities including tremors and cognitive impairment. It has been previously reported that 26% of patients with PD-related dementia (PD-D) exhibit similar symptoms of cognitive impairment to those observed in patients with AD [1]. Mild PD-D is often misdiagnosed and commonly confused with mild AD [5] Additional examinations, such as brain tissue analysis and brain scans, are critically important to increase diagnostic precision. We previously utilized single-photon emission computed tomography (SPECT) scanning to distinguish between PD-D and AD; this neuroimaging method requires considerable time, cost, and effort [4,6,7], compared with the electroencephalography (EEG). The EEG is potentially useful for the early diagnosis of PD-D and AD because the cost, space, and time requirements of this method are lower than those of other neuroimaging techniques
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