The impaired ability to smell (also known as olfaction) is increasingly recognized as a consistent feature of the symptomatology of Parkinson's disease (PD). Moreover, the appearance of olfactory dysfunction early in the clinical course of PD makes it an appealing research target as a biomarker. However, very little is known about the progression of olfactory deficits. Demonstration of progression in an early clinical biomarker, that is unaffected by medical therapy, will be very useful in trials of neuroprotective interventions.
A thorough characterization of olfactory dysfunction and progression in early PD is planned.Two groups of patients, one with early PD and another with no evidence of neurological disease will be evaluated with several different measures of olfactory function, anatomy and physiology. At the end of one year, these patients will be re-evaluated to determine the best method for following progression of olfactory dysfunction in PD. It is hoped that this will become a biomarker of disease progression that will allow researchers to determine if novel therapeutic interventions have changed the natural course of the illness.
Final Outcome
Drs. Duda, Doty and Moberg did not detect significant changes in olfactory function associated with disease progression. One reason for the inability to demonstrate a correlation between disease progression and olfactory dysfunction was a high variability in performance on olfactory assessments of many different modalities in PD subjects over time, so that a subset of subjects actually demonstrated improved performance after a one-year delay on any given assessment.
The investigators believe that one possible reason for this was that most of these olfactory assessments were not designed specifically for the assessment of olfactory dysfunction in PD. Therefore, they have attempted to develop a more PD-specific olfactory assessment using the University of Pennsylvania Smell Identification Test. Results from this research were published in abstract form at the 18th World Federation of Neurology World Congress on Parkinson’s Disease and Related Disorders, in Miami, Florida (December 2009). Grant funding to further this research effort are being pursued by Drs. Morley and Duda with the American Academy of Neurology.