Effect of istradefylline on postural abnormalities in patients with Parkinson's disease: An association study of baseline postural angle measurements with changes in Unified Dystonia Rating Scale total score

In our previous study, istradefylline treatment in patients with Parkinson's disease (PD) improved postural abnormalities (PAs), as seen from a decrease in the mean Unified Dystonia Rating Scale (UDRS) total score from week 0 to week 24. A subgroup analysis based on baseline clinical characteristics investigated the association between improvement in the UDRS total score and istradefylline treatment. However, the association between an objective assessment of PAs and improvement in the UDRS total score is unclear. This ad hoc analysis investigated the association between improvement in the UDRS total score after istradefylline treatment and baseline trunk and neck angles, objective assessments of PAs, measured from patients' photographs taken in the previous study. The patients (n = 31) were stratified into groups based on the trunk forward flexion angle (TFFA), trunk lateral flexion angle (TLFA), and neck flexion angle (NFA) values at baseline. From week 0 to week 24, significant improvements in the UDRS total score were found in median percent change (−8.33% [interquartile range: −43.97, 0.00], P = 0.039) in patients with equal to or above the median TFFA values, and in median change (−‍1.50 [−9.25, 0.00], P = 0.015) and median percent change (−13.33% [−50.47, 0.00], P = 0.009) in patients with equal to or above the median TLFA values. Patients with more advanced PAs showed more consistent improvements in the UDRS total score with istradefylline. Baseline TFFA and TLFA values, which are objective values, may be useful to assess the istradefylline effectiveness in patients with PD and PAs.