Objective: We investigated the possible relationships among olfactory impairment and alterations in diffusion tensor imaging (DTI) of olfactory tracts, comparing a cohort of patients with Parkinson’s disease (PD) and a matched control group.

Background: PD can be better characterized as a multisystem disorder. It is widely accepted that motor features are preceded by a prodromal ‘pre-motor’ phase including a wide range of non-motor disturbances, such as sleep-wake disturbances, mood disorders, autonomic dysfunction and hyposmia [1]. Olfactory dysfunction is recognized as one of the earliest indicators of developing PD and one of the major non-motor symptoms with a significant impact on quality of life [2].

Methods: Olfactory function of each subject was assessed using the Italian Olfactory Identification Test. Motor disability was assessed in all patients using Unified Parkinson’s Disease Rating Scale-III part (UPDRS III) and Hoehn and Yahr rating scale (H&Y). Imaging was performed on a 3T Philips Achieva MR scanner. MRI pre-processing was performed by DTIPrep, DTI reconstruction and fiber tracking by DiffusionToolkit, tractography analyses using TrackVis. The following parameters were used for groupwise comparison: fractional anisotropy (FA), mean diffusivity (MD), tract volume and length.

Results: 17 patients with PD (mean age 64.9±7.6 years, UPDRS III 24.4±11.7, H&Y stage 1.9±0.5) and 9 controls (mean age 60.7±14.2 years) were recruited. Olfactory identification function of all PD patients was decreased. The region of interest analysis of the olfactory tract showed significant FA signal and volume decreases of the PD group when compared with the control group (P<0.05). Significant correlations were found between the MD values and the H&Y stage (r=0.60, P<0.01).

Conclusions: DTI analyses of olfactory structures may be viable as a means of establishing cohorts of subjects with probable pre-clinical PD.

References: [1] Chaudhuri KR, Healy DG, Schapira AH. Non-motor symptoms of Parkinson’s disease: diagnosis and management. Lancet Neurol 2006;5:235–45. [2] Politis M, Wu K, Molloy S, GB P, Chaudhuri KR, Piccini P (2010) Parkinson’s disease symptoms: the patient’s perspective. Mov Disord 25(11):1646–1651.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diffusion-tensor-imaging-of-olfactory-tract-in-parkinsons-disease/