Levodopa responsiveness in Parkinson’s disease patients and white matter alterations in diffusion tensor imaging: a cross-sectional tract-based spatial statistics study

Abstract

This study aimed to investigate the relationship between levodopa responsiveness and white matter alterations in Parkinson's disease patients using diffusion tensor imaging (DTI). Twenty-six recruited Parkinson's disease patients were evaluated using the Mini-Mental State Examination, Hoehn and Yahr scale (H&Y) and Unified Parkinson's Disease Rating Scale (UPDRS). Each patient underwent a DTI scan and an acute levodopa challenge test. The improvement rate of UPDRS-III was calculated, Parkinson's disease patients were grouped into a responsive group (improvement rate ≥30%) and a nonresponsive group (improvement rate <30%). The differences in fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity between the two groups were measured using tract-based spatial statistics. There was no difference in demographic features or baseline evaluations between groups. The UPDRS-III score after the challenge was higher in the nonresponsive group than that in the responsive group. Compared to the responsive group, patients in the nonresponsive group exhibited decreased fractional anisotropy in the corpus callosum; cingulum; left corona radiata; left internal capsule; left middle frontal gyrus; left superior longitudinal fasciculus and right somatosensory cortex. Mean diffusivity and radial diffusivity were increased in wide-ranging areas in the nonresponsive group. No difference was observed in axial diffusivity. White matter alterations in the abovementioned areas may affect the function of the dopaminergic network and thus may be associated with the levodopa response in Parkinson's disease patients. Further studies are needed to analyze the specific mechanism and pathological changes underlying these effects.