title: Prevalence and phenomenology of olfactory hallucinations in Parkinson's disease.
abstract: 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.
authors: CHU Clermont-Ferrand, Neurology Department, Clermont-Ferrand, France. sbannier@ch-cotebasque.fr
authors: Stephanie
authors: S
authors: Bannier
authors: Jean Louis
authors: JL
authors: Berdagué
authors: Isabelle
authors: I
authors: Rieu
authors: Ingrid
authors: I
authors: de Chazeron
authors: Ana
authors: A
authors: Marques
authors: Philippe
authors: P
authors: Derost
authors: Miguel
authors: M
authors: Ulla
authors: Pierre-Michel
authors: PM
authors: Llorca
authors: Franck
authors: F
authors: Durif
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005602:France / Q000453:epidemiology; D006212:Hallucinations / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D055696:Olfactory Perception; D010300:Parkinson Disease / Q000150:complications* / Q000503:physiopathology*; D015995:Prevalence; D012903:Smell