Prevalence and phenomenology of olfactory hallucinations in Parkinson's disease
- Stephanie Bannier1,2,
- Jean Louis Berdagué3,
- Isabelle Rieu1,2,
- Ingrid de Chazeron2,4,
- Ana Marques1,2,
- Philippe Derost1,2,
- Miguel Ulla1,2,
- Pierre-Michel Llorca2,4,
- Franck Durif1,2
- 1CHU Clermont-Ferrand, Neurology Department, Clermont-Ferrand, France
- 2Univ Clermont 1, UFR Medecine, Clermont-Ferrand, France
- 3INRA, UR454 Microbiologie, Saint-Genès Champanelle, France
- 4CHU Clermont-Ferrand, Department of Psychiatry B, Clermont-Ferrand, France
- Correspondence to Stephanie Bannier, Service neurologie, centre hospitalier de la côte basque, BP8; 64109 Bayonne cedex, France;
Contributors SB is involved from the conception of the study to the drafting of the manuscript. FD is responsible for the design of the study, the analysis and interpretation of data and the revision of the article. MU, AM and PD have participated to the acquisition of data and to the interpretation of the results. IR and IDeC contributed to the design of the study and the statistical analysis of the results.
- Received 31 January 2012
- Revised 4 May 2012
- Accepted 21 May 2012
- Published Online First 29 June 2012
Background Although visual hallucinations in Parkinson's disease (PD) have been described in several major studies, little is known about olfactory hallucinations (OHs).
Methods The authors performed a detailed analysis of OHs in a cohort of 87 Parkinsonian patients to estimate the prevalence of OHs and describe their phenomenology. They also evaluated smelling abilities in terms of detection and identification. Assessment of both, OHs and olfactory function, was also performed using a control group of 40 normal subjects.
Results Nine patients exhibited OHs compared with none of the controls, giving a prevalence of 10% for OHs in patients. OHs were described as rare, short-lasting, unpleasant odours which are not frightening since clearly identified by the patient as hallucinations. Parkinsonian patients with OHs exhibited olfactory impairment of detection and identification compared with controls, but there was no difference in their olfactory abilities from Parkinsonian patients without OHs.
Conclusions In conclusion, OHs should be added to the list of non-motor PD symptoms that can occur early or late in the course of PD. The authors' study did not reveal any significant difference in terms of olfactory abilities between patients with or without OHs. However, olfactory impairment is well documented in Parkinsonian patients and cannot be totally ruled out as a risk factor for OHs. The authors recognise that complex mechanisms are probably involved in this phenomenon.
Competing interests None.
Ethics approval Ethics approval was provided by the regional Medical School Ethics Committee (AU474).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Two posters were selected for the movement disorders congress, Chicago 2008; poster 1080: a new test to evaluate olfaction impairment by S Bannier et al. poster 1081: results of a new test detecting smell impairment in PD by S Bannier et al. One poster has also been selected for the movement disorders congress in Paris 2009: poster 378: olfactory hallucinations, prevalence and phenomenology in Parkinson's disease.