title: Unirhinal Olfactory Testing for the Diagnostic Workup of Mild Cognitive Impairment.
abstract: BACKGROUND
  Olfactory dysfunction is associated with Alzheimer's disease (AD), and already present at pre-dementia stage.
  
  
  OBJECTIVE
  Based on the assumption that early neurodegeneration in AD is asymmetrical and that olfactory input is primarily processed in the ipsilateral hemisphere, we assessed whether unirhinal psychophysical and electrophysiological assessment of olfactory function can contribute to the diagnostic workup of mild cognitive impairment (MCI).
  
  
  METHODS
  Olfactory function of 13 MCI patients with positive amyloid PET, 13 aged-matched controls (AC) with negative amyloid PET and 13 patients with post-infectious olfactory loss (OD) was assessed unirhinally using (1) psychophysical testing of olfactory detection, discrimination and identification performance and (2) the recording of olfactory event-related brain potentials. Time-frequency analysis was used to enhance the signal-to-noise ratio of the electrophysiological responses. Psychophysical and electrophysiological assessment of auditory and trigeminal chemosensory function served as controls.
  
  
  RESULTS
  As compared to AC and OD, MCI patients exhibited a significant asymmetry of olfactory performance. This asymmetry efficiently discriminated between MCI and AC (sensitivity: 85% , specificity: 77% ), as well as MCI and OD (sensitivity: 85% , specificity: 70% ). There was also an asymmetry of the electrophysiological responses, but not specific for MCI. In both MCI and OD, olfactory stimulation of the best nostril elicited significantly more activity than stimulation of the worse nostril, between 3-7.5 Hz and 1.2-2.0 s after stimulus onset. Trigeminal and auditory psychophysical testing did not show any difference between groups.
  
  
  CONCLUSIONS
  MCI patients exhibit a marked asymmetry of behavioral olfactory function, which could be useful for the diagnostic workup of MCI.
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.|Department of Otorhinolaryngology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Huart
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.|Department of Otorhinolaryngology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Rombaux
authors.affiliation: Department of Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gérard
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.|Department of Neurology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Bernard
authors.initials: B
authors.lastname: Hanseeuw
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.|Department of Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Renaud
authors.initials: R
authors.lastname: Lhommel
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.
authors.forename: Lisa
authors.initials: L
authors.lastname: Quenon
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.|Department of Neurology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: Adrian
authors.initials: A
authors.lastname: Ivanoiu
authors.affiliation: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium.
authors.forename: André
authors.initials: A
authors.lastname: Mouraux
mesh_terms: D000161:Acoustic Stimulation; D016229:Amyloid beta-Peptides / Q000378:metabolism; D058256:Brain Waves / Q000502:physiology; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000150:complications* / Q000175:diagnosis*; D004192:Discrimination, Psychological; D004569:Electroencephalography; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D000857:Olfaction Disorders / Q000209:etiology*; D010775:Photic Stimulation; D049268:Positron-Emission Tomography; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D012903:Smell / Q000502:physiology*; D013997:Time Factors; D014276:Trigeminal Nerve / Q000503:physiopathology
chemical_list: D016229:Amyloid beta-Peptides
keywords: Alzheimer’s disease; EEG; evoked potentials; mild cognitive impairment; olfaction; smell