This study aims to quantify the effects of medication (Med) and deep brain stimulation (DBS) on resting rigidity in patients with Parkinson"s disease. We tested 10 limbs of five patients under each of four treatment conditions: 1) baseline, 2) DBS, 3) Med, 4) DBS + Med. Rigidity at the wrist joint was assessed using the Unified Parkinson"s Disease Rating Scale (UPDRS). The examiner randomly imposed flexion and extension movement on patient"s wrist joint. Resistance to passive movement was quantified by viscoelastic properties. Not only rigidity score but also damping constant showed improvements in rigidity by DBS and Med treatments (p<0.05). This indicates that the viscosity can represent the change in rigidity due to DBS as well as Med, which was manifested by UPDRS score.
