Functional Representation of Olfactory Impairment in Early Alzheimer's Disease

Article type: Research Article

Authors: Förster, Stefan^{a; *} | Vaitl, Andreas^a | Teipel, Stefan J.^{b; c} | Yakushev, Igor^d | Mustafa, Mona^a | la Fougère, Christian^a | Rominger, Axel^a | Cumming, Paul^a | Bartenstein, Peter^a | Hampel, Harald^{b; e} | Hummel, Thomas^f | Buerger, Katharina^{b; g} | Hundt, Walter^h | Steinbach, Silke^{f; i}

Affiliations: [a] Department of Nuclear Medicine, Ludwig-Maximilian University, Munich, Germany | [b] Dementia Research Section and Memory Clinic, Alzheimer Memorial Center and Geriatric Psychiatry Branch, Department of Psychiatry Ludwig-Maximilian University, Munich, Germany | [c] Department of Psychiatry, University Rostock, Rostock, Germany | [d] Department of Psychiatry, University Mainz, Germany | [e] Department of Psychiatry, University Frankfurt, Germany | [f] Smell & Taste Clinic, Department of Otorhinolaryngology, Technical University, Dresden, Germany | [g] Institute for Stroke and Dementia Research, Klinikum Großhadern, Ludwig-Maximilian University, Munich, Germany | [h] Department of Radiology, Philipps-University, Marburg, Germany | [i] Department of Otorhinolaryngology, Philipps-University, Marburg, Germany

Correspondence: [*] Correspondence to: Stefan Förster, MD, Klinik und Poliklinik für Nuklearmedizin, TU Munich, Ismaninger Str. 22, 81675 Munich, Germany. Tel.: +49 89 4140 2965; Fax: +49 89 4140 4950; E-mail: stefan.foerster@lrz.tum.de.

Note: [] Handling Associate Editor: Valeria Drago

Abstract: We used [18F]fluorodeoxyglucose (FDG) PET analysis to determine performance in different olfactory domains of patients with early AD compared to cognitively healthy subjects, and to map the functional metabolic representation of olfactory impairment in the patient sample. A cohort of patients with early AD (n = 24), consisting of 6 subjects with incipient AD and 18 subjects with mild AD, and a control group of 28 age-matched non-demented individuals were assembled. Patients and controls were tested for olfactory performance using the “Sniffin' Sticks” test battery [odor identification (ID), discrimination (DIS) and threshold (THR)], while patients additionally underwent resting state FDG-PET. Voxel-wise PET results in the patients were correlated with olfaction scores using the general linear model in SPM5. Patients with early AD showed significantly reduced function in all three olfactory subdomains compared to controls. After controlling for effects due to patients' age, gender, cognitive status, and treating scores in the two other olfactory subdomains as nuisance variables, ID scores correlated with normalized FDG uptake in clusters with peaks in the right superior parietal lobule, fusiform gyrus, inferior frontal gyrus, and precuneus, while DIS scores correlated with a single cluster in the left postcentral cortex, and THR scores correlated with clusters in the right thalamus and cerebellum. The subtests employed in the “Sniffin' Sticks” test battery are complementary indicators of different aspects of olfactory dysfunction in early AD, and support the theory of a parallel organized olfactory system, revealed by FDG-PET correlation analysis.

Keywords: Alzheimer's disease, FDG PET, mild cognitive impairment, olfactory system, smell test

DOI: 10.3233/JAD-2010-091549

Journal: Journal of Alzheimer's Disease, vol. 22, no. 2, pp. 581-591, 2010