A longitudinal study of olfactory function in patients with idiopathic Parkinson's disease

Abstract

Olfactory function is diminished in patients with idiopathic Parkinson disease (IPD). Because previous work almost exclusively relied upon cross-sectional studies, the present investigation aimed to address the correlation between olfactory loss and duration of disease within the context of a longitudinal study, accompanying well-diagnosed patients over an average period of 4.4 years. A group of 27 IPD patients was examined (5 women, 22 men; age range 27-64 years; duration of disease: 0 to 19 years). Psychophysical olfactory testing was performed after 3-6 years (mean 4.4 years) using the "Sniffin' Sticks" test battery which consists of subtests for odor thresholds, odor discrimination, and odor identification. The study yielded the following major results: (1) olfactory function in IPD patients changes in an unpredictable manner, (2) especially when considering results from the second session relatively few IPD patients were completely anosmic; none of the patients, however, were normosmic. One possible explanation for these findings may lie in the hypothesis based on results by Huisman et al. (2004) who reported an increase of dopaminergic neurons in the olfactory bulb in IPD patients. In this scenario, olfactory loss seen early in the disease may be based on an incomplete inhibition of olfactory input at the level of the olfactory bulb.

Premotor Symptoms and Early Diagnosis of Parkinson's Disease

“…[6,7]. One longitudinal study found conflicting results as to whether olfaction worsened over time [8].…”

Association of Olfactory Bulb Volume and Olfactory Sulcus Depth with Olfactory Function in Patients with Parkinson Disease

“…6 The high prevalence of olfactory dysfunction in patients with IPD suggests that IPD may actually be an olfactory disease. 5,6 Recent neuropathologic advances suggest that the olfactory system is among the earliest brain regions involved in PD 7 and olfactory deficits are associated with the presence of incidental Lewy bodies in the brains of decedents without parkinsonism or dementia during life. 8 Results from postmortem studies revealed Lewy bodies in the OB 9 but also in other brain regions related to olfaction, such as the anterior olfactory nucleus, 10 the piriform cortex, 11 the amygdaloid complex, 12 the entorhinal cortex, and the hippocampal formation.…”

“…[1][2][3] Between 70% and 90% of patients with PD have olfactory deficits independent of disease severity and duration. 4,5 Olfactory dysfunction is thus the second most common feature of this disorder, following rigidity and akinesia. 6 The high prevalence of olfactory dysfunction in patients with IPD suggests that IPD may actually be an olfactory disease.…”

The Predictive Role of Hyposmia in Alzheimer's Disease

“…(Kaufmann H et al, 2004;Goldstein D et al, 2010). Once IPD has become clinically manifest, olfaction appears to be already severely compromised, which is in line with the absence of longitudinal changes of olfactory function during IPD progression (Herting et al 2008). In a recent study (Wattendorf E et al, 2009) gray matter atrophy was investigated using morphometric analysis of magnetic resonance images voxel-based morphometry (VBM) and it was related to psychophysically measured scores of olfactory function in early PD patients, moderately advanced PD patients and age-matched healthy controls.…”