Accurate Diagnosis of SWEDD vs. Parkinson Using Microstructural Changes of Cingulum Bundle: Track-Specific Analysis

Abstract

SWEDD (scans without evidence of dopaminergic deficit) patients often are misdiagnosed as having Parkinson disease (PD) but later prove to have distinct features from PD. A commonly found symptom of these patients being focal and unilateral dystonia. SWEDD patients do not respond to dopaminergic therapy and may in turn benefit from management of adult onset dystonia, therefore early differential diagnosis from PD is important in order to avoid over diagnosis of PD and mismanagement of these patients. Along with a different pattern of tremor from PD, SWEDD patients do not show the non-motor symptoms associated with different stages of PD, do not exhibit cognitive deficit and depict a and task specificity of the motor symptoms without any deterioration along time. We hypothesized that the cingulum which is both functional in cognitive control and task set performance and is structurally affected in early stages of PD and is implicated in other non-motor symptoms of PD might be differentially affected in PD and SWEDD group. The diffusion imaging data from 39 PD, 28 SWEDD and 21 normal subjects were reconstructed in the MNI space using q-space diffeomorphic reconstruction (QSDR) to assess association of quantitative anisotropy (QA) and generalized fractional anisotropy (GFA) of left and right cingulum with the PD and SWEDD groups in the baseline level (diagnosis of PD or SWEDD) and age-sex matched controls. We found significant difference between GFA and QA of the left cingulum and QA of the right cingulum in SWEDD and control group versus the PD group. These results suggest a diagnostic value for the cingulum in early PD/SWEDD and also reveal that the diffusion metric parameters of cingulum that are not necessarily sensitive to axonal loss (GFA) might be a better indicator of microstructural changes in early PD/SWEDD.