Changes in the olfactory tract of patients with early Parkinson's disease: A DTI tractography study.

Introduction: olfactory impairment is a clinical feature of Parkinson's disease (PD) even in the early phases. Diffusion tensor imaging fiber tracking analysis (DTI-FTA) has been able to highlight changes in the olfactory tract in PD, however in early phases of PD this analysis has not been investigated. We investigated the olfactory tract by DTI-FTA in early stages of PD (ePD). Methods: All patients were assessed using the Italian Olfactory Identification Test (IOIT), the Movement Disorder Society-Unified Parkinson's Disease Rating Scale-Part III (MDS-UPDRS-III) and the Hoehn and Yahr (H&Y) scale. Diffusion imaging was conducted by 3 T MRI. Results: Overall, 26 PD patients and 20 healthy subject were recruited. Hyposmia was observed in all PD patients. DTI-FTA of the olfactory tract showed significant mean diffusivity (MD) increases and a tract volume decrease for PD group. MD and age, only in the PD group, were significant for multiple correlations. Conclusion: DTI-FTA identified microstructural changes in the olfactory tract even in hyposmic ePD patients.