Enhancement of parkinsonian rigidity with contralateral hand activation

Objective: Quantify the enhancement of parkinsonian rigidity associated with a contralateral activation maneuver. Methods: Twelve subjects with PD and eight controls participated in the study protocol. Subjects' tested hand was displaced by a servo-motor throughout wrist flexion and extension motions of 60° without and with a concurrent gripping activation in the contralateral hand, referred to as Passive and Active conditions, respectively. Subjects with PD were tested in both OFF-MED and ON-MED states. Rigidity was quantified by integrating torque with position during both flexion and extension (torque resistance). ANOVA was performed to assess the effect of contralateral activation on rigidity. Results: PD patients had significantly (0.038) enhanced torque resistance in OFF-MED compared to healthy controls and ON-MED. In the Active condition, differences in torque resistance were magnified (p= 0.002). Medication substantially reduced differences in torque resistance between controls and PD patients in the Passive and Active conditions. Conclusions: A contralateral activation maneuver substantially increases rigidity in patients with PD, specifically the OFF-MED state. Rigidity is reduced with the application of dopaminergic medication, even with the presence of a contralateral activation maneuver. Significance: These data support the use of a contralateral activation maneuver as a tool in the diagnosis of PD.