Preoperative clinical predictors of response to bilateral subthalamic stimulation in patients with Parkinson's disease.

BACKGROUND

Younger age and a response to a supra-threshold levodopa challenge have been reported to predict a favorable response to bilateral subthalamic nucleus (STN) stimulation.

OBJECTIVE

To identify and evaluate clinical factors which predict a positive outcome after bilateral STN stimulation in patients with Parkinson's disease, using each patient's typical doses of antiparkinsonian medication rather than a supra-threshold levodopa challenge.

METHODS

Forty-five Parkinson's disease patients who underwent bilateral STN implantation were included in the study. There were 33 men and 12 women. Mean age and disease duration were 59.4 and 12.7 years, respectively. All patients underwent Unified Parkinson Disease Rating Scale (UPDRS) evaluations in the medication off and on states at baseline and postsurgically with stimulation on at 3, 6 and 12 months. The percentage improvement in UPDRS motor scores at baseline (medication off vs. on) was compared with the percentage improvement after stimulation optimization (baseline medication off vs. follow-up medication off/stimulation on).

RESULTS

The preoperative percentage improvement in UPDRS motor scores with antiparkinsonian medications was predictive of the postoperative percentage improvement in the UPDRS motor scores in the medication off/stimulation on state (r = 0.53, p < 0.001). However, preoperative UPDRS motor scores in the medication on state were more strongly correlated with the postsurgical effect of stimulation (r = 0.64, p < 0.001). The postoperative improvement in UPDRS motor scores with stimulation did not correlate with age, disease duration or time to programming optimization.

CONCLUSIONS

The preoperative percentage improvement in UPDRS motor scores with antiparkinsonian medications and UPDRS motor score in the medication on state at baseline are the strongest clinical predictors of responsiveness to bilateral STN stimulation.