Stimulation-induced side effects after deep brain stimulation - a systematic review

Objective: Deep brain stimulation (DBS) was approved by Food and Drug Administration for Parkinson's disease, essential tremor, primary generalised or segmental dystonia and obsessive-compulsive disorder (OCD) treatment. The exact mechanism of DBS remains unclear which causes side effects. The aim of this review was to assess variables causing stimulation-induced chronic psychiatric/personality-changing side effects. Methods: The analysis of scientific database (PubMed, Cochrane Library, EMBASE) was conducted. The included articles had to be research study or case report and DBS to be conducted in therapeutic purposes. The researches with mental disorders in patients' medical histories were excluded. Results: Seventeen articles were used in the review. In the group of movement disorders the characteristic of side effects was strongly related to the placement of the electrode implantation. Tiredness/fatigue was correlated with DBS in thalamus. Implantations in subthalamic nucleus were mostly followed by affective side effects such as depression or suicide. The higher voltage of electrode was connected with more severe depression after implantation. The analysis of affective disorder contained only three articles - two about OCD and one about depression. Forgetfulness and word-finding problems as activities connected with cognition may be an inevitable side effect if obsessive thoughts are to be inhibited. Conclusion: DBS of subthalamic nucleus should be seen as the most hazardous place of implantation. As a result there is a strong need of 'gold standards' based on the connectivity research and closer cooperation of scientists and clinicians.