Cognitive change after DBS in refractory epilepsy: A randomized-controlled trial

Deep brain stimulation of the anterior thalamic nucleus (ANT-DBS) reduces seizure frequency in patients with refractory epilepsy. There are, however, few studies on treatment-related changes in cognitive functions. The main objective of this study was to investigate cognitive changes in patients receiving ANT-DBS. We also explored whether possible effects were related to stimulation duration and whether change in seizure frequency was associated with cognitive changes.

Bilateral ANT electrodes were implanted in 18 patients with refractory epilepsy, aged 18-52 years. Immediately after implantation, patients were randomized to stimulation ON (n = 8) or OFF (n = 10) for the first 6 months (blinded phase). During the following 6-month open phase, both groups received stimulation. Neuropsychological assessments were conducted before implantation (T1), at the end of the blinded period (T2), and 1 year after implantation (T3).

Groupwise comparisons across the three time points revealed changes in performance in two of 22 cognitive test scores: motor speed and sustained attention. We found no significant group differences in cognitive change from T1 to T2. Patients reported fewer symptoms of executive dysfunction after 12 months of stimulation. Patients showing significant improvement in seizure frequency had better performance in a measure of verbal learning.

Our results indicate that ANT-DBS has very limited effects on cognitive functioning, as measured by formal tests after 6- or 12-month stimulation. ANT-DBS may have a positive influence on executive function. Our findings provide limited support for an association between change in seizure frequency and cognitive functioning.