Alzheimer disease biomarker based on carotid artery reactivity

Abstract

Alzheimer disease (AD) is a progressive neurodegenerative disorder associated with the disruption of neuronal function. Carotid Artery Reactivity (CAR) is a new biomarker method for AD detection which provides various advantages as compared to existing detection method. Current developed methods have either radiation risk (positron emission tomography [PET] and computed tomography [CT] scanning), high cost and long scanning duration (magnetic resonance imaging [MRI]) or lack accuracy (electroencephalography [EEG]). New AD detection method could be implemented using ultrasound machine by assessing the carotid artery condition since the impairment of this artery leads to brain hypoperfusion, a clinical feature of AD. CAR allows normal functioning artery to dilate in order to permit more bloods flow into the brain. The three different variables utilized to study the CAR were the carotid artery blood flow velocity, its diameter and cross sectional area. Healthy people and Alzheimer patient are believed to have different CAR value. Hence, this study emphasized on finding the normal reactivity value belonging to healthy people and Alzheimer patient. This CAR value could be used to differentiate between healthy people and Alzheimer patient as the new method of detection. The studied subject consisted of 40 healthy people and 20 Alzheimer patients. All subjects had been scanned with ultrasound machine using Doppler and 3D technique before and after performed exercise to achieve 85% of their Maximal Heart Rate (MHR). Readings of each reactivity variables before exercise (rest) and after exercise (stimulated) were recorded to be analyzed to compare its percentage increment value (reactivity). Based on the results, Alzheimer patient recorded very low reactivity value which were 21% (blood flow velocity), 8.1% (diameter changes) and 16.67% (area changes) while normal reactivity recorded high reactivity value which were 109%(blood flow velocity), 22.2% (diameter changes) and 49.59% (area changes).