Spotlight on olfactory dysfunction in Parkinson's disease

Abstract

Olfactory dysfunction is frequent in Parkinson's disease (PD). A correlation between olfactory dysfunction and the pathophysiological process of the disease has been confirmed. On the other hand, olfaction disturbances are also prevalent in other neurodegenerative diseases, and may be related to other factors such as gender, age, smoking, and trauma. Clinically, hyposmia is commonly assessed by smell identification testing. Good diagnostic accuracy has been widely reported, but differences in sensitivity and specificity due to sociocultural factors have also been reported. Since hyposmia may be present before the onset of motor symptoms, it has the potential to serve as a biomarker for the identification of subjects at risk of developing PD. Several studies have been conducted to assess the utility of smell testing as an isolated or combined biomarker for this end. Finally, severe olfactory dysfunction has been associated with faster disease progression and higher risk of cognitive decline in patients with PD. Olfactory dysfunction assessment in PD will continue to be relevant in research and clinical practice.