Change of olfactory function associated structures in Parkinson's disease: a voxel ⁃ based morphometry study

Abstract

Objective To investigate the structural differences of olfactory associated brain areas between patients with Parkinson's disease (PD) and normal controls, and their relationship to olfactory dysfunction by voxel ⁃ based morphometry (VBM), and to explore the possibility for early diagnosis. Methods Olfactory detection threshold (DT) and olfactory identification threshold (IT) were determined with "five odors olfactory detection arrays" kit provided by Chinese Academy of Sciences on 26 PD patients, and 26 age and gender matched healthy controls. The relationship between olfactory function and age or duration or severity degree [total Unified Parkinson's Disease Rating Scale (UPDRS) scores] was analysed. The analysis of brain structures were performed at a Siemens 3.0T by using magnetization prepared rapid gradient echo imaging (MPRAGE). The data were processed by using SPM5. Results The olfactory thresholds (DT and IT) of PD patients (0.66 ± 0.84, 2.41 ± 0.74) were significantly higher than those of the controls (⁃ 0.64 ± 0.83, 1.08 ± 0.54; Z = 4.455, P = 0.000; t = 4.898, P = 0.000). No significant correlations were seen between olfactory thresholds (DT and IT) and age (DT: rs = 0.199, P = 0.330; IT: rs = 0.256, P = 0.207) or duration (DT: rs = 0.123, P = 0.550; IT: rs = 0.055, P = 0.789) or UPDRS Ⅲ scores (DT: rs = 0.229, P = 0.260; IT: rs = 0.379, P = 0.056) in all PD patients. Compared to controls, significant clusters of increased white matter density were found in bilateral occipital lobes (BA17-19), left posterior cingulate gyrus (BA23, 30, 31) and left paracentral lobule (BA3-5) in PD patients. Significant clusters of increased white matter volume included bilateral occipital lobes (BA17-19), left posterior cingulate gyrus (BA23, 30, 31) and left paracentral lobule (BA3-5). Meanwhile, there were negative relationship between the increase of white matter density in left posterior cingulate gyrus and olfactory IT (rs = 0.496, P = 0.010). Conclusion The olfactory function was found significantly decreased in PD patients, and unrelated to age and duration. Changes of olfactory associated structures, particularly the white matter areas were found by using VBM in early PD with olfactory dysfunction. Our data suggest that early olfactory dysfunction in PD results from changes in the brain areas associated with processing olfaction. VBM can be widely used for the analysis of the diagnosis of PD or neurodegenerative diseases.

DOI：10.3969/j.issn.1672-6731.2011.01.012