Is reduced arm and leg swing in Parkinson's disease associated with rigidity or bradykinesia?

Background and purpose Arm and leg swings during gait are reduced and asymmetric in Parkinson's disease (PD). Although rigidity and bradykinesia are interconnected with each other, and related with gait hypokinesia including arm and leg swing alteration, it remains uncertain which factor is more responsible for the decrease of arm and leg swings. The study aimed to uncover which factor between rigidity and bradykinesia is more associated with the reduction of arm and leg swings during gait. Methods Patients with PD were selected and divided into a concordance group (21 patients) representing a match of both symptoms and a discordance group (nineteen patients) exhibiting a mismatch of pronounced rigidity and bradykinesia. Visual inspections of video clips for asymmetric features of gait and posture including arm swing, leg swing, shoulder position, external foot rotation were analyzed and accessed by two independent neurologists blindly. Results The side of more pronounced rigidity was significantly and moderately related with the side of more decreased arm and leg swings (p < 0.001, κ = 0.592 in arm swing; p = 0.011, κ = 0.432 in leg swing, respectively), but the side of more dominant bradykinesia was associated with neither arm nor leg swing asymmetry (p = 1, κ = 0.014 in arm swing; p = 1, κ = - 0.036 in leg swing). In addition, asymmetric posturing including shoulder position and a laterally rotated foot showed no relationship with rigidity or bradykinesia. Conclusion The reduction of arm and leg swings during gait in PD was associated with rigidity, but not with bradykinesia.