Steering technology for deep brain stimulation

This scientific commentary refers to ‘Directional deep brain stimulation: an intraoperative double-blind pilot study', by Pollo et al ., (doi:10.1093/brain/awu102). Over the last two decades, deep brain stimulation has become widely accepted as a treatment for Parkinson’s disease, dystonia and tremor, and its use is increasing in disorders such as obsessive-compulsive disorder, depression and pain. The primary objective is always to achieve symptom suppression with few or no side effects; in other words, to attain as wide a therapeutic window as possible. In the past, efforts to achieve this were focused largely on ensuring accurate electrode placement, be it with the help of imaging and/or with microelectrode recordings. Excellent results can be obtained in this way, but unwanted side effects still occur in ∼13% of patients (Deuschl et al. , 2006). Today, a number of new technologies are under development to address this problem. In this issue of Brain , Pollo et al. present data from a randomized clinical trial in which one of these approaches—directional stimulation—produces a wider therapeutic window than traditional methods (Pollo et al. , 2014).To put this result into context, it is worth reviewing, albeit briefly, some of the other strategies that are under development with the aim of maximizing therapeutic benefit while minimizing side effects. Demand pacemakersCurrently, most pacemakers deliver stimulation continuously at a fixed rate, in what is a rather simple but nevertheless effective therapy. However, constant stimulation can incur unwanted side effects by spreading to other fibre tracts or by disrupting normal brain signals embedded in pathological activity. Alteration of such ‘normal’ signals may affect emotion or cognition, for example. By targeting stimulation specifically …