Neurodegenerative Dis DOI: 10.1159/000335915
Diseases
Received: June 30, 2011 Accepted after revision: December 18, 2011 Published online: February 16, 2012
Olfactory Deficits and Cognitive Dysfunction in Parkinson’s Disease Teresa Parrao a, b, e Pedro Chana b, c Pablo Venegas a María Isabel Behrens a, b María Luz Aylwin d a
Departamento de Neurología Neurocirugía, Hospital Clínico Universidad de Chile, b Clínica Alemana de Santiago, Centro de Trastornos del Movimiento USACH, and d ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile; e University of Western Australia, Perth, W.A., Australia
c
Key Words Parkinson’s disease ! Olfaction ! Cognition ! Executive functions
Abstract Background: Olfactory deficits and executive dysfunction have been reported in Parkinson’s disease (PD). However, the association between these deficits has not been thoroughly examined. Methods: We studied 44 PD subjects and 17 agematched controls. In PD subjects, symptoms were assessed with the Unified Parkinson’s Disease Rating Scale and the Hoehn and Yahr scale. Cognition in both groups was assessed by a neuropsychological battery. Olfactory identification and sensitivity was evaluated with the Sniffin’ Sticks! test and olfactory detection threshold, respectively. Results: PD subjects showed significant deficits in olfactory function and working memory, executive function, speed of information processing, visuospatial skills and phonological verbal fluency tests when compared with the control group. Moreover, there was a significant correlation between olfactory sensory deficits and executive dysfunction. In PD patients with up to 12 months of motor symptoms, results were equivalent. Conclusion: Our preliminary results suggest a significant association between olfactory deficits and impairments of executive functions in PD. Copyright © 2012 S. Karger AG, Basel
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Introduction
Hyposmia is recognized as a premotor symptom in Parkinson’s disease (PD) [1]. Moreover, cognitive dysfunctions have been described in PD patients [2], some of them occurring at early stages of the disease [3]. One might therefore speculate that cognitive dysfunction is associated with olfactory dysfunction. However, this association has not yet been demonstrated. In this study, we examined the relationship between olfactory impairment and cognitive performance in different stages of PD. Methods Subjects We assessed 44 subjects with idiopathic PD and 17 healthy controls. PD patients met the clinical diagnostic criteria of the UK Parkinson’s Disease Society Brain Bank Research Centre [4]. Exclusion criteria were history of other neurological or psychiatric diseases treated by neuroleptics, history of alcohol or drug abuse and less than 4 years of education. Olfactory Identification All subjects performed the Sniffin’ Sticks! test [5]. Olfactory Detection Threshold We used vanillin and propionic acid to test the olfactory detection threshold in all subjects. Dilution series of the odorants were
Teresa Parrao 16 The Terrace Fremantle, WA 6160 (Australia) Tel. +61 08 9433 0327 E-Mail teresa.parrao @ uwa.edu.au
Table 1. Demographic information and performance on olfactory and cognitive tests of PD and control groups
Age, years Education, years Sniffin’ Sticks test score Threshold vanillin Threshold propionic acid Wechsler Memory Scale III-mental control Wechsler Memory Scale III-digit span forward Wechsler Memory Scale III-digit span backwards Free and Cued Selective Reminding Test-free recall Free and Cued Selective Reminding Test-cued recall Free and Cued Selective Reminding Test-total score Free and Cued Selective Reminding Test-delayed score WCST-numbers of categories Trail Making Test part A Trail Making Test part B Tower of London test-initiation time Tower of London test-total movements Rey-Osterrieth Complex Figure test-copy Semantic verbal fluency Phonologic verbal fluency
PD patients (n = 44)
Controls (n = 17)
63.5810.2 11.283.5 6.083.0 5.381.7 4.181.7 20.785.3 5.981.4 3.381.3 21.686.5 19.383.9 41.086.7 13.583.0 4.181.7 68.4827.9 158.6872.5 92.3866.6 50.9829.3 27.1810.7 15.685.2 10.483.6
63.189.5 13.182.8 10.381.2 7.380.8 6.081.2 22.283.6 5.880.7 4.480.8 25.283.2 20.084.5 45.283.6 18.8810.3 6.080.0 40.087.2 94.4823.7 51.1823.3 30.888.3 35.680.8 20.382.9 16.183.0
p 0.43 0.051
