Distinct patterns of olfactory impairment in Alzheimer's disease, semantic dementia, frontotemporal dementia, and corticobasal degeneration

• Published in: Neuropsychologia Vol. 45; no. 8; pp. 1823 - 1831
• Main Authors: Luzzi, Simona, Snowden, Julie S., Neary, David, Coccia, Michela, Provinciali, Leandro, Lambon Ralph, Matthew A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2007; Elsevier Science
• Subjects: Adult and adolescent clinical studies; Aged; Analysis of Variance; Biological and medical sciences; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dementia - classification; Dementia - complications; Discrimination, Psychological; Female; Humans; Male; Medical sciences; Mental Status Schedule; Middle Aged; Neurodegeneration; Neurodegenerative Diseases - metabolism; Neurology; Neuropsychological Tests; Neuropsychology; Odorants; Odour perception; Odour semantics; Olfaction Disorders - diagnosis; Olfaction Disorders - etiology; Olfactory cortex; Organic mental disorders. Neuropsychology; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Semantics; Smell; Smell - physiology; Odour semantics; Olfactory cortex; SD; AD; CBD; Neurodegeneration; FTD; SPSB; Neuropsychology; Smell; Odour perception; Human; Semantic dementia; Nervous system diseases; Alzheimer disease; Central nervous system; Cerebral disorder; Olfactory pathway; Language; Semantics; Central nervous system disease; Olfaction; Perception; Degenerative disease; Frontotemporal dementia; Neuropsychologia; Odor
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2006.12.008

Performance on tests of odour discrimination, naming, and matching was compared in patients with four distinct forms of neurodegenerative disease: Alzheimer's disease (AD), semantic dementia (SD), frontotemporal dementia (FTD), and corticobasal degeneration (CBD). The SD patients were found to have a severe impairment of identification from olfaction despite having normal discrimination, consistent with the multimodal semantic impairment characteristic of this patient group. The AD patients’ poor odour discrimination suggests that a perceptual impairment is the root of their poor odour identification. Mild impairments in odour identification observed in FTD and CBD are consistent with their generalised executive dysfunction. The findings illustrate that breakdown in olfaction can occur at a perceptual or semantic level, analogous to the distinction between apperceptive and associative forms of deficit in the visual and auditory modalities. The findings add further insights into the nature of the semantic deficit in SD by exploring a hitherto neglected modality and may have relevance in explaining the altered eating habits commonly associated with SD.