Background: Subthalamic nucleus (STN) deep brain stimulation (DBS) is currently the most common therapeutic surgical procedure for patients with Parkinson's disease (PD) who have failed medical management. However, a summary of clinical evidence on the effectiveness and utilization of STN-DBS has been lacking. We report the results of such a systematic review and meta-analysis.

Methods: A comprehensive review of the literature using MEDLINE and OVID databases from 1965 until 2004 was conducted. Estimates of change in absolute Unified Parkinson's Disease Rating Scale scores after surgery were generated using random effects models. Sources of heterogeneity were explored with meta-regression models, and the possibility of publication bias was evaluated.

Results: Twenty-two studies were included in the meta-analysis. The estimated changes in absolute UPDRS II (motor) and III (activities of daily living) scores after surgery were 13.35 (95% CI 10.85 to 15.85) and 27.55 (95% CI 24.23 to 30.87) respectively. Changes in UPDRS scores were significantly higher in studies with higher baseline UPDRS scores, increasing disease duration prior to surgery, earlier year of publication, and higher baseline levo-dopa responsiveness. Average baseline UPDRS scores were significantly lower (i.e., suggesting milder disease) in later than in earlier studies. No evidence of publication bias was found in the available literature.

Conclusion: Synthesis of the available literature indicates that STN-DBS improves motor activity and activities of daily living in advanced PD. Differences between available studies probably reflect differences in patient populations, rather than surgical technique. Given the apparent effectiveness of this intervention, the wider application of surgery seen in more recent medical literature may be appropriate. Formal evaluation of the cost-utility of this promising technique is a high priority for neurosurgical outcomes research.