Cognitive improvement after long-term electrical stimulation of bilateral anterior thalamic nucleus in refractory epilepsy patients

INTRODUCTION The cognitive and behavioral effect of deep brain stimulation (DBS) administered to the deep cerebral nuclei for epilepsy treatment is unknown. We investigated the cognitive outcomes at least 12 months after DBS to the bilateral anterior thalamic nucleus (ATN) for controlling intractable epilepsy. METHODS Nine patients with intractable epilepsy who were not candidates for resective surgery, but who were treated by bilateral ATN DBS underwent cognitive and behavioral assessments before implantation and more than 1 year after DBS surgery. Postoperative cognitive assessments were carried out under a continuous stimulation mode. RESULTS The mean seizure-reduction rate of these patients after ATN DBS was 57.9% (35.6-90.4%). Cognitive testing showed favorable results for verbal fluency tasks (letter and category, p<0.05), and a significant improvement in delayed verbal memory was observed (p=0.017). However, we did not observe any significant changes in general abilities (IQ, MMSE), information processing (digit forward and backward, Trail A, and Digit Symbol), or executive function (Trail B and WCST). Interestingly, we did not observe any significant cognitive decline approximately 1 year (mean, 15.9 months) after ATN DBS surgery. CONCLUSIONS We showed that ATN DBS not only resulted in promising clinical effects but was also associated with improvements in both verbal recall and oral information processing, which may be related to the bilateral activation of the fronto-limbic circuit following DBS surgery. Further controlled, long-term studies with larger populations are warranted for elucidating the clinical effects of ATN DBS.