Alzheimer's disease and olfaction

Although olfactory disorders are not at the forefront of the clinical description of Alzheimer's disease (AD), they are common and often overlooked by clinicians and by patients who are largely unaware of their deficits. The past 30 years, the literature has shown early olfactory deficits in AD that is spreading across the olfactory spectrum with disease worsening. Partial overlap between brain areas implies both in olfaction and AD especially limbic system - motivating these researches. This study describes olfactory parameters and tests using to investigate peripheral (odor threshold) and central (hedonicity, familiarity, intensity, discrimination, identification, olfactory memory) levels. Besides, this article takes an inventory of olfactory disorders in AD including odor threshold, discrimination, identification and olfactory memory capacities with controversial results observed in literature. At last, we discuss which type of olfactory dysfunction could have a clinical interest.