An investigation of olfactory bulb and entorhinal cortex volumesin both patients with Alzheimer’s disease and healthy individuals,and a comparative analysis of neuropeptides

Abstract

Alzheimer’s Disease (AD) is the most common neurodegenerative disease and is hard to diagnose at the early stages. The pathogenesis of AD is associated with the loss of a sense of smell. Reduction in the volumes of the Olfactory Bulb (OB) and Entorhinal Cortex (EC) is positively correlated with the decline of the smelling function where OB projects to EC. This study aims to detect the early changes in OB and EC volumes in AD patients by comparing them to healthy subjects. This study also aims to make a comparative analysis of plasma levels and the relationship between arginine-vasopressin (AVP) and Oxytocin (OT), which are neuropeptides associated with cognitive functions. The participants comprised 9 AD patients and 12 healthy individuals. We used volumetric methods such as MRICloud and IBASPM to measure the OB and EC volumes with the help of 3D MRI (Magnetic Resonance Imaging) images. We compared the left and right differentiation. Moreover, we investigated the neuropeptide levels in blood samples from the participants. We conducted a correlation analysis for all parameters. Bilateral OB atrophy was discovered in the AD patients in comparison to the control group (p=0.002 for right; p=0.015 for left). The right OB volume was measured to be larger than the left OB volume in the control group,but this asymmetry was not observed in the AD patients. The right and left EC's of the AD patients were atrophic in comparison to the control (p<0.001). The atrophy of the left EC was measured to be higher than that of the right EC (p=0.0008). There was no significant difference between the OT and AVP plasma levels of the AD patients and the control group. The study revealed that the OB and EC volumes of the AD patients were bilaterally reduced in comparison to patients of similar ages. This outcome may indicate that an MRI scan examination of OB and EC volumes may help early AD diagnosis.