Diagnostics of olfactory dysfunction in Parkinson's disease - a literature overview and case series

Olfactory dysfunction is increasingly recognised for its predictive value as an early indicator of a number of degenerative neuropathologies including Parkinson's Disease (PD). In this overview, we cover the relationship between PD and olfactory dysfunction (OD). Prodromal premotor symptoms of PD include sleep disturbances, psychiatric disorders, constipation and OD. The latter can precede motor symptoms by several years and its occurrence is frequent in Parkinson s disease with a prevalence that can range from 45%-90%. Olfactory perception in these cases can be tested using subjective and objective methods. Commonly used psychophysical tests in the Czech Republic include Sniffin' Sticks Tests and the Odorized Marker Test but these may be inaccurate and demanding on patients with cognitive deficits in addition to motor symptoms. For these reasons, objective electrophysiological olfactory tests that depend on olfactory/trigeminal event-related potentials (OERPs/TERPs) for example are more useful. In this paper we describe a series of case reports, demonstrating the importance of comprehensive olfactory examination. The significance of objective electrophysiological olfactory/ trigeminal tests in the diagnosis of PD, is underscored given the rising incidence of this condition and the need for early diagnosis.