The course of olfactory deficits in patients with Parkinson's disease-A study based on psychophysical and electrophysiological measures

Objectives Patients Patients with Parkinson s disease (PD) commonly show olfactory deficits in the early stages of the disease These deficits can be verified psychophysically or electrophysiologically using olfactory event-related potentials (OERP) While psychophysical olfactory function in PD patients can improve over time the course of OERPs in PD has not yet been investigated Methods Olfactory function was investigated twice in 19 patients at 5-year intervals Psychophysical tests Included the Sniffin Sticks test battery In addition OERPs were recorded in response to two odors on each side (phenyl-ethyl-alcohol 40% (v/v) H2S 6 ppm) OERPs were evaluated regarding existence (yes/no) Average disease duration at follow-up was 90 years and the average Hoehn and Yahr score (disease stage) was 2 2 Results Psychophysically 1 patient was normosmic 14 were hyposmic and 4 were functionally anosmic at the initial visit Re-examination revealed 1 normosmic 9 hyposmic and 8 functionally anosmic patients Mean olfactory function decreased significantly in all patients OERPs were initially existent in 3 out of 19 patients At follow-up OERPs were no longer present in these patients but were detectable in 3 other patients Conclusions Overall mean olfactory function decreased although improvements were observed at the individual level We confirmed previous findings regarding psychophysical follow-up results Electrophysiological measures showed a pattern of fluctuation in olfactory function comparable to that of the psychophysical results These fluctuations do not seem to predict the course of the disease (C) 2010 Elsevier Ireland Ltd All rights reserved