Deep Brain Stimulation for Epilepsy: Biomarkers for Optimization

Two large-scale controlled clinical trials have provided Class I evidence for the benefit of deep brain stimulation (DBS) as a therapy for refractory epilepsy. However, the efficacy has been variable, with some patients not achieving any improvement in their seizure control. This disparity could be the result of suboptimal stimulation parameters/electrodes or alternatively a difference in the type of seizures being treated. This review presents the most recent clinical results with a focus on two major targets for DBS, the anterior nucleus of the thalamus (ANT) and the hippocampus. We detail the etiologies where DBS might work best, and provide evidence for the use of recorded neural responses for the optimization of stimulation parameters and closed-loop control of devices.

Stimulation of the hippocampus may work well for both focal and generalized seizures, whereas ANT stimulation may be best for focal seizures only. Studies have demonstrated that changes in stimulation-evoked response shape can be used as a biomarker for stimulation efficacy. Furthermore, new biomarkers have been identified that could be used for closed-loop stimulation. Improvements in patient screening and stimulation optimization are needed for patients to achieve optimal seizure control. Furthermore, therapy should be adjusted to suit individual patient needs. Recording evoked responses during the application of DBS could be used to measure the effectiveness of DBS and titrate stimulation as needed.