For some dystonic patients, it remains difficult to know whether they represent good candidates for DBS. Therefore, despite the difficulties in conducting controlled trials for rare forms of dystonia, in the future, it is crucial to classify dystonia according to their response to DBS. In addition, the respective location of the different potential targets of DBS will have to be more clearly defined. More precisely, the choice of one specific target of stimulation will have to be based on the etiology of dystonia but also on the individual clinical presentation. In the same vein, multiple targets of stimulation could be used depending on the clinical features (e.g., the association between motor and behavioral signs, which could indicate the need to stimulate both the motor and limbic parts of the GPi). This will again need well-designed and controlled studies before any generalization. The exact interest in cortical stimulation, either direct or magnetic, should also be clarified in the next few years.
Finally, as for DBS in other disorders, the use of a more anatomically precise stimulation device and of tailored stimulation parameters based on individual electrophysiological recordings could improve its efficacy and reduce side effects. This is the case, for example, with the use of DBS electrode with a segmented design, allowing a more selective activation of the target structure. In addition, the use of biophysical models could allow for the calculation of the volume of tissue stimulated and adaption of the stimulation parameters in order to minimize the spread of current to surrounding areas. We could also speculate that coordinated reset neuromodulation designed for effective control of synchronization by multisite stimulation of neuronal target populations will be proposed in the future in order to more effectively counteract pathological neuronal synchrony characteristic of several neurological disorders, and to increase life expectancy of the pulse generator.[91,92] In the same vein, the use of closed-loop stimulation, which, until now, has only been tested in Parkinson's disease, could be interesting for treating dystonia with tailored stimulation parameters, depending on the patient condition and electrophysiological activity, instead of permanent stimulation parameters.[93–95] This, however, remains speculative in dystonia.
Future Neurology. 2014;9(1):77-87. © 2014 Future Medicine Ltd.