There is convincing evidence from numerous studies using both psychophysical and electrophysiological approaches that olfaction is markedly reduced in Parkinson´s disease (PD). Data on the prevalence of olfactory dysfunction in PD however, range from 45% and 49% in the pioneering studies of Ansari & Johnson, and Ward, respectively, up to 74% in the work of Hawkes et al., or as high as 90% in a study published by Doty et al. Quality of life, safety, and interpersonal relations, as well as food behavior/nutritional intake are severely altered in a large proportion of patients with olfactory loss. Thus, the same can be assumed in patients with Parkinson's disease. If it was possible to improve olfactory function this would appear as a significant effect in patients with Parkinson's disease. Provided the study would reveal an improvement of olfactory function following therapy with rasagiline, this would have tremendous worldwide impact on the use of this drug. Considering the frequency of PD a very large number of patients would benefit from these findings, especially in terms of quality of life.

Inclusion Criteria:

• Parkinson´s disease, Hoehn & Yahr stage ≤ III
• aged 18-64 yrs
• hyposmia/functional anosmia defined as TDI<30
• written consent

Exclusion Criteria:

• congenital olfactory loss
• significant infections of the nose and nasal sinuses
• diseases/states apart from PD which may significantly affect olfactory function, e.g., asthma, head trauma etc.
• dementia, psychiatric illness, addictive behaviour
• smoker
• severe liver disease
• pregnant or breastfeeding women
• any contraindication for the treatment with Rasagiline
• women without reliable contraception