Aberrant nigral diffusion in Parkinson's disease: A longitudinal diffusion tensor imaging study.
Loane C., Politis M., Kefalopoulou Z., Valle-Guzman N., Paul G., Widner H., Foltynie T., Barker RA., Piccini P.
BACKGROUND: Measuring microstructure alterations with diffusion tensor imaging in PD is potentially a valuable tool to use as a biomarker for early diagnosis and to track disease progression. Previous studies have reported a specific decrease of nigral fractional anisotropy in PD. However, to date the effect of disease progression on nigral or striatal diffusion indices has not been fully explored. METHODS: We have conducted a cross-sectional and longitudinal diffusion tensor imaging study in 18 early stage, treated PD patients and 14 age-matched controls. PD patients were scanned on 2 occasions OFF medication, 19.3 months apart (standard deviation = 3.1 months). Longitudinal change of regional nigral and striatal measures of fractional anisotropy and mean diffusivity were calculated using a region-of-interest approach. RESULTS: Region-of-interest analysis demonstrated that at baseline, PD patients and controls did not differ in regard to diffusion indices in any region assessed. A significant difference of nigral fractional anisotropy and mean diffusivity between controls and PD patients at follow-up was detected and confirmed with longitudinal analysis within PD patients. Alterations in striatal regions were not detected in either group or over time. CONCLUSION: Our findings indicate that nigral diffusion measure may be a valuable measure of disease progression. In the future, larger longitudinal studies will confirm whether diffusion indices may serve as sensitive and clinically meaningful measures of disease progression in PD. © 2016 International Parkinson and Movement Disorder Society.