Deep brain stimulation for movement disorders: update on recent discoveries and outlook on future developments.

Modern deep brain stimulation (DBS) has become a routine therapy for patients with movement disorders such as Parkinson's disease, generalized or segmental dystonia and for multiple forms of tremor. Growing numbers of publications also report beneficial effects in other movement disorders such as Tourette's syndrome, various forms of chorea and DBS is even being studied for Parkinson's-related dementia. While exerting remarkable effects on many motor symptoms, DBS does not restore normal neurophysiology and therefore may also have undesirable side effects including speech and gait deterioration. Furthermore, its efficacy might be compromised in the long term, due to progression of the underlying disease. Various programming strategies have been studied to try and address these issues, e.g., the use of low-frequency rather than high-frequency stimulation or the targeting of alternative brain structures such as the pedunculopontine nucleus. In addition, further technical developments will soon provide clinicians with an expanded choice of hardware such as segmented electrodes allowing for a steering of the current to optimize beneficial effects and reduce side effects as well as the possibility of adaptive stimulation systems based on closed-loop concepts with or without accompanying advances in programming and imaging software. In the present article, we will provide an update on the most recent achievements and discoveries relevant to the application of DBS in the treatment of movement disorder patients and give an outlook on future clinical and technical developments.