Expectation and the placebo effect in Parkinson's disease patients with subthalamic nucleus deep brain stimulation

To determine whether the degree to which a patient with Parkinson's disease expects therapeutic benefit from sub- thalamic nucleus- deep brain stimulation (STN-DBS) influ- ences the magnitude of his or her improved motor response, 10 patients with idiopathic Parkinson's and bilateral STN- DBS were tested after a 12-hour period off medication and stimulation. Four consecutive UPDRS III scores were per- formed in the following conditions: (a) stimulation OFF, pa- tient aware; (b) stimulation OFF, patient blind; (c) stimulation ON, patient aware; and (d) stimulation ON, patient blind. Statistical significance (P 0.0001) was observed when com- paring main effect ON versus OFF (mean ON: 32.55; mean OFF: 49.15). When the stimulation was OFF, patients aware of this condition had higher UPDRS motor scores than when they were blinded (mean: 50.7 vs. 47.6). With the stimulation ON, UPDRS motor scores were lower when the patients were aware of the stimulation compared with when they were blinded (mean: 30.6 vs. 34.5). The interaction between these levels was significant (P 0.049). This variation was impor- tant for bradykinesia and was not significant for tremor and rigidity. The authors conclude that the information about the condition of the stimulation enhanced the final clinical effect in opposite directions. The results presented support the role of expectation and placebo effects in STN-DBS in Parkinson's disease patients. © 2006 Movement Disorder Society