Dealing With Side Effects of Deep Brain Stimulation: Lessons Learned From Stimulating the STN

Abstract

Deep brain stimulation (DBS) is increasingly investigated as a therapy for psychiatric disorders. In the ethical evaluation of this novel approach, incidence and impact of side effects (SE) play a key role. In our contribution, we analyze the discussion on SE of DBS of the subthalamic nucleus (STN)—a standard therapy for movement disorders like Parkinson's disease (PD)—based on 66 case reports, 69 review papers, and 347 outcome studies from 1993 to 2009. We show how the DBS community increasingly acknowledged the complexity of STN-DBS side effects. Then we discuss the issue of study quality and the methods used to assess SE. We note that some side effects are the subject of conflicting evaluations by the different stakeholders involved. This complicates the ethical controversy inherent in any novel treatments for diseases that involve psychiatric aspects. We delineate how the lessons from STN-DBS could guide future DBS applications in the field of psychiatry.

Keywords:

• deep brain stimulation
• neuroethics
• Parkinson's disease
• psychiatry
• side effects
• subthalamic nucleus

Acknowledgments

This research has been supported by the Swiss Academy of Medical Sciences (Käthe-Zingg-Schwichtenberg-Fonds) and by the Federal Ministry of Education and Research, Germany (project 01 GP 0804).

Notes

Each study was assigned with points as follows: study was prospective: +1; study was case-controlled with at least 20 participants in each branch: +2 (+1 if less than 20 participants in either branch); study was randomized: +1; test evaluation was blinded: +1; study involved more than one center: +1; the presurgery and postsurgery assessment of the neuropsychiatric tests were made in the “best” (pre: med-on/ post: med-on, stim-on) condition of the patient: +2 (+1 if the assessments were made pre and post); the study involved at least 20 patients: +1; the study had a follow-up time of at least 12 months: +1; the study involved tests of at least three issue classes: +1.

The citation coefficient was construed as follows: We counted the appearance of outcome studies in the analytic part of reviews that either performed a meta-analysis following established standards (e.g., Cochrane) or were at least systematically evaluated (i.e., we excluded merely narrative reviews; thus, we considered 23 reviews). The citation of outcome papers is weighted with the probability of being able to be cited due to the year of publication to take into account, such that a paper, e.g., published in 2006 cannot be cited in a review published in 2004. Thus, each outcome paper received a citation coefficient value between 0 and 1. For the correlation analysis, only outcomes with nonzero citation coefficient have been analyzed.