Olfaction in Parkinson’s Disease – A Clinical Approach

Olfactory loss is one of the major non-motor symptoms of Parkinson’s disease (PD). Olfactory assessment constitutes an important part of PD diagnostic procedures in many clinics. The majority of patients present with severe quantitative olfactory loss, with accompanying qualitative smell disorders being very rare. Olfactory subfunctions are differentially impaired in PD compared with other hyposmic individuals whereby the impairment in odour discrimination turned out to have predictive value in preclinical PD. In terms of PD risk stratification in patients with unexplained smell loss, a clear diagnostic allocation based on an exhaustive clinical assessment and comprehensive chemosensory testing seems to be essential. This brief review summarises relevant information about olfactory dysfunction in PD and discusses the diagnostic utility of olfactory testing for early PD diagnosis.